ios: nearbyConnections: Move source to //third_party.

PiperOrigin-RevId: 408046875

cpp/core/BUILD

@@ -24,7 +24,7 @@ cc_library(
     compatible_with = ["//buildenv/target:non_prod"],
     copts = ["-DCORE_ADAPTER_DLL"],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
+        "//platform/impl/ios:__subpackages__",
         "//third_party/nearby_connections/windows:__subpackages__",
     ],
     deps = [
@@ -58,9 +58,9 @@ cc_library(
     compatible_with = ["//buildenv/target:non_prod"],
     copts = ["-DCORE_ADAPTER_DLL"],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
         "//analytics:__subpackages__",
         "//core:__subpackages__",
+        "//platform/impl/ios:__subpackages__",
     ],
     deps = [
         "//absl/strings",

cpp/platform/api/BUILD

@@ -37,7 +37,6 @@ cc_library(
     ],
     compatible_with = ["//buildenv/target:non_prod"],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
         "//platform/base:__pkg__",
         "//platform/impl:__subpackages__",
         "//platform/public:__pkg__",

cpp/platform/base/BUILD

@@ -44,7 +44,6 @@ cc_library(
     compatible_with = ["//buildenv/target:non_prod"],
     copts = ["-DCORE_ADAPTER_DLL"],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
         "//analytics:__subpackages__",
         "//third_party/nearby_connections/cpp/cal:__subpackages__",
         "//core:__subpackages__",

cpp/platform/impl/ios/BUILD

@@ -0,0 +1,52 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+licenses(["notice"])
+
+package(default_visibility = ["//visibility:public"])
+
+objc_library(
+    name = "Connections",
+    srcs = [
+        "Source/Internal/GNCAdvertiser.mm",
+        "Source/Internal/GNCCore.mm",
+        "Source/Internal/GNCCoreConnection.mm",
+        "Source/Internal/GNCDiscoverer.mm",
+        "Source/Internal/GNCPayload.m",
+        "Source/Internal/GNCPayloadListener.mm",
+        "Source/Internal/GNCUtils.mm",
+        "Source/Internal/platform.mm",
+    ],
+    hdrs = [
+        "Source/GNCAdvertiser.h",
+        "Source/GNCConnection.h",
+        "Source/GNCConnections.h",
+        "Source/GNCDiscoverer.h",
+        "Source/GNCPayload.h",
+        "Source/Internal/GNCCore.h",
+        "Source/Internal/GNCCoreConnection.h",
+        "Source/Internal/GNCPayload+Internal.h",
+        "Source/Internal/GNCPayloadListener.h",
+        "Source/Internal/GNCUtils.h",
+    ],
+    deps = [
+        "//base",
+        "//absl/functional:bind_front",
+        "//core",
+        "//core:core_types",
+        "//platform/impl/ios/Source/Mediums",
+        "//platform/impl/ios/Source/Platform",
+        "//platform/impl/ios/Source/Shared",
+        "//third_party/objective_c/google_toolbox_for_mac:GTM_Logger",
+    ],
+)

cpp/platform/impl/ios/Source/GNCAdvertiser.h

@@ -0,0 +1,84 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "GNCConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** This contains info about a discoverer endpoint intitiating a connection with an advertiser. */
+@protocol GNCAdvertiserConnectionInfo <NSObject>
+/** This is a human readable name of the discoverer. */
+@property(nonatomic, readonly, copy) NSString *name;
+/** This token can be used to verify the identity of the discoverer. */
+@property(nonatomic, readonly, copy) NSString *authToken;
+@end
+
+/** This class contains success and failure handlers for the connection request. */
+@interface GNCConnectionResultHandlers : NSObject
+
+/**
+ * This factory method creates a pair of handlers for a successful or failed connection.
+ *
+ * @param successHandler This handler is called if both endpoints accept the connection.
+ *                       A @c GNCConnection object is passed, meaning that the connection has
+ *                       been established and you may start sending and receiving payloads.
+ * @param failureHandler This handler is called if either endpoint rejects the connection.
+ */
++ (instancetype)successHandler:(GNCConnectionHandler)successHandler
+                failureHandler:(GNCConnectionFailureHandler)failureHandler;
+
+@end
+
+/**
+ * This handler is called when a discoverer requests a connection with an advertiser. In
+ * response, the advertiser should accept or reject via @c responseHandler.
+ *
+ * @param endpointId The ID of the endpoint.
+ * @param connectionInfo Information about the discoverer.
+ * @param responseHandler Handler for the connection response, which is either an acceptance or
+ *                        rejection of the connection request.
+ * @return Handlers for the final connection result. This will be called as soon as the final
+ *         connection result is known, when either side rejects or both sides accept.
+ */
+typedef GNCConnectionResultHandlers *_Nonnull (^GNCAdvertiserConnectionInitiationHandler)(
+    GNCEndpointId endpointId, id<GNCAdvertiserConnectionInfo> connectionInfo,
+    GNCConnectionResponseHandler responseHandler);
+
+/**
+ *  An advertiser broadcasts a service that can be seen by discoverers, which can then make
+ *  requests to connect to it. Release the advertiser object to stop advertising.
+ */
+@interface GNCAdvertiser : NSObject
+
+/**
+ * Factory method that creates an advertiser.
+ *
+ * @param endpointInfo A data for endpoint info which contains readable name of this endpoint,
+ *                     to be displayed on other endpoints.
+ * @param serviceId A string that uniquely identifies the advertised service.
+ * @param strategy The connection topology to use.
+ * @param connectionInitiationHandler A handler that is called when a discoverer requests a
+ *                                    connection with this endpoint.
+ */
++ (instancetype)advertiserWithEndpointInfo:(NSData *)endpointInfo
+                                 serviceId:(NSString *)serviceId
+                                  strategy:(GNCStrategy)strategy
+               connectionInitiationHandler:
+                   (GNCAdvertiserConnectionInitiationHandler)connectionInitiationHandler;
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/GNCConnection.h

@@ -0,0 +1,167 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class GNCBytesPayload, GNCStreamPayload, GNCFilePayload;
+
+/** Response to a connection request. */
+typedef NS_ENUM(NSInteger, GNCConnectionResponse) {
+  GNCConnectionResponseReject,  // reject the connection request
+  GNCConnectionResponseAccept,  // accept the connection request
+};
+
+/** Reason for a failed connection request. */
+typedef NS_ENUM(NSInteger, GNCConnectionFailure) {
+  GNCConnectionFailureRejected,  // an endpoint rejected the connection request
+  GNCConnectionFailureUnknown,   // there was an error while attempting to make the connection
+};
+
+/** Handler for a @c GNCConnectionFailure value. */
+typedef void (^GNCConnectionFailureHandler)(GNCConnectionFailure);
+
+/** Reasons that a connection can be severed by either endpoint. */
+typedef NS_ENUM(NSInteger, GNCDisconnectedReason) {
+  GNCDisconnectedReasonUnknown,  // the endpoint can no longer be reached
+};
+
+/** Handler for a @c GNCDisconnectedReason value. */
+typedef void (^GNCDisconnectedHandler)(GNCDisconnectedReason);
+
+/** Result of a payload transfer. */
+typedef NS_ENUM(NSInteger, GNCPayloadResult) {
+  GNCPayloadResultSuccess,   // Payload delivery was successful.
+  GNCPayloadResultFailure,   // An error occurred during payload delivery.
+  GNCPayloadResultCanceled,  // Payload delivery was canceled.
+};
+
+/** Handler for a @c GNCPayloadResult value. */
+typedef void (^GNCPayloadResultHandler)(GNCPayloadResult);
+
+/** Connection topology. See https://developers.google.com/nearby/connections/strategies. */
+typedef NS_ENUM(NSInteger, GNCStrategy) {
+  GNCStrategyCluster,       // M-to-N
+  GNCStrategyStar,          // 1-to-N
+  GNCStrategyPointToPoint,  // 1-to-1
+};
+
+/** Every endpoint has a unique identifier. */
+typedef NSString *GNCEndpointId;
+
+/** This handler receives a Bytes payload.  It is called when the payload data is fully received. */
+typedef void (^GNCBytesPayloadHandler)(GNCBytesPayload *payload);
+
+/**
+ * This handler receives a Stream payload, signifying the start of receipt of a stream. The payload
+ * data should be read from the supplied input stream. The progress object can be used to monitor
+ * progress or cancel the operation. This handler must return a completion handler, which is
+ * called when the operation is finished.
+ */
+typedef GNCPayloadResultHandler _Nonnull (^GNCStreamPayloadHandler)(GNCStreamPayload *payload,
+                                                                    NSProgress *progress);
+
+/**
+ * This handler receives a File payload, signifying the start of receipt of a file. The
+ * progress object can be used to monitor progress or cancel the operation. This handler must
+ * return a completion handler, which is called when the operation finishes successfully or if
+ * there is an error. The file will be stored in a temporary location. If an error occurs or the
+ * operation is canceled, the file will contain all data that was received. It is the client's
+ * responsibility to delete the file when it is no longer needed.
+ */
+typedef GNCPayloadResultHandler _Nonnull (^GNCFilePayloadHandler)(GNCFilePayload *payload,
+                                                                  NSProgress *progress);
+
+/** This class contains optional handlers for a connection. */
+@interface GNCConnectionHandlers : NSObject
+
+/**
+ * This handler receives Bytes payloads. It is optional; apps that don't send and receive Bytes
+ * payloads need not supply this handler.
+ */
+@property(nonatomic, nullable) GNCBytesPayloadHandler bytesPayloadHandler;
+
+/**
+ * This handler receives a stream that delivers a payload in chunks. It is optional; apps that
+ * don't send and receive Stream payloads need not supply this handler.
+ */
+@property(nonatomic, nullable) GNCStreamPayloadHandler streamPayloadHandler;
+
+/**
+ * This handler receives a File payload. It is optional; apps that don't send and receive File
+ * payloads need not supply this handler.
+ * Note: File payloads are not yet supported.
+ */
+@property(nonatomic, nullable) GNCFilePayloadHandler filePayloadHandler;
+
+/**
+ * This handler is called when the connection is ended, whether due to the endpoint disconnecting
+ * or moving out of range.  It is optional.
+ */
+@property(nonatomic, nullable) GNCDisconnectedHandler disconnectedHandler;
+
+/**
+ * This factory method lets you specify a subset of the connection handlers in a single expression.
+ *
+ * @param builderBlock Set up the handlers in this block.
+ */
++ (instancetype)handlersWithBuilder:(void (^)(GNCConnectionHandlers *))builderBlock;
+
+@end
+
+/**
+ * This represents a connection with an endpoint. Use it to send payloads to the endpoint, and
+ * release it to disconnect.
+ */
+@protocol GNCConnection <NSObject>
+
+/**
+ * Send a Bytes payload. A progress object is returned, which can be used to monitor
+ * progress or cancel the operation. |completion| will be called when the operation completes
+ * (in all cases, even if failed or was canceled).
+ */
+- (NSProgress *)sendBytesPayload:(GNCBytesPayload *)payload
+                      completion:(GNCPayloadResultHandler)completion;
+
+/**
+ * Send a Stream payload. A progress object is returned, which can be used to monitor
+ * progress or cancel the operation. The stream data is read from the supplied NSInputStream.
+ * |completion| will be called when the operation completes.
+ */
+- (NSProgress *)sendStreamPayload:(GNCStreamPayload *)payload
+                       completion:(GNCPayloadResultHandler)completion;
+
+/**
+ * Send a File payload. A progress object is returned, which can be used to monitor progress or
+ * cancel the operation. |completion| will be called when the operation completes.
+ * Note: File payloads are not yet supported.
+ */
+- (NSProgress *)sendFilePayload:(GNCFilePayload *)payload
+                     completion:(GNCPayloadResultHandler)completion;
+@end
+
+/**
+ * This handler takes a @c GNCConnection object and returns a @c GNCConnectionHandlers
+ * object containing the desired payload and connection-ended handlers.
+ */
+typedef GNCConnectionHandlers *_Nonnull (^GNCConnectionHandler)(id<GNCConnection> connection);
+
+/**
+ * This handler takes a response to a connection request. Pass @c GNCConnectionResponseAccept to
+ * accept the request and @c GNCConnectionResponseReject to reject it.
+ */
+typedef void (^GNCConnectionResponseHandler)(GNCConnectionResponse response);
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/GNCConnections.h

@@ -0,0 +1,20 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Umbrella header file for Nearby Connections library.
+
+#import "GNCAdvertiser.h"
+#import "GNCConnection.h"
+#import "GNCDiscoverer.h"
+#import "GNCPayload.h"

cpp/platform/impl/ios/Source/GNCDiscoverer.h

@@ -0,0 +1,92 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "GNCConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** This is info about an advertiser endpoint with which the discoverer has requested a connection.
+ */
+@protocol GNCDiscovererConnectionInfo <NSObject>
+/** This token can be used to verify the identity of the advertiser. */
+@property(nonatomic, readonly, copy) NSString *authToken;
+@end
+
+/**
+ * This handler is called to establish authorization with the advertiser. In response,
+ * @c responseHandler should be called to accept or reject the connection.
+ *
+ * @param connectionInfo Information about the advertiser.
+ * @param responseHandler Handler for the connection response, which is either an acceptance or
+ *                        rejection of the connection request.
+ * @return Handler for the connection if it was successful.
+ */
+typedef GNCConnectionHandler _Nonnull (^GNCDiscovererConnectionInitializationHandler)(
+    id<GNCDiscovererConnectionInfo> connectionInfo, GNCConnectionResponseHandler responseHandler);
+
+/**
+ * This handler should be called to request a connection with an advertiser.
+ *
+ * @param name A human readable name of this endpoint, to be displayed on the other endpoint.
+ * @param authorizationHandler This handler is called to establish authorization.
+ * @param failureHandler This handler is called if there was an error making the connection.
+ */
+typedef void (^GNCConnectionRequester)(
+    NSString *name, GNCDiscovererConnectionInitializationHandler connectionAuthorizationHandler,
+    GNCConnectionFailureHandler failureHandler);
+
+/** This contains info about a discovered advertiser endpoint. */
+@protocol GNCDiscoveredEndpointInfo <NSObject>
+/** This is a human readable name of the advertiser. */
+@property(nonatomic, readonly, copy) NSString *name;
+/** Call this block to request a connection with the advertiser. */
+@property(nonatomic, readonly) GNCConnectionRequester requestConnection;
+@end
+
+/** This handler is called when a previously discovered advertiser endpoint is lost. */
+typedef void (^GNCEndpointLostHandler)(void);
+
+/**
+ * This handler is called when an advertiser endpoint is discovered.
+ *
+ * @param endpointId The ID of the endpoint.
+ * @param connectionInfo Information about the endpoint.
+ * @return Block that is called when the endpoint is lost.
+ */
+typedef GNCEndpointLostHandler _Nonnull (^GNCEndpointFoundHandler)(
+    GNCEndpointId endpointId, id<GNCDiscoveredEndpointInfo> endpointInfo);
+
+/**
+ * A discoverer searches for endpoints advertising the specified service, and allows connection
+ * requests to be sent to them. Release the discoverer object to stop discovering.
+ */
+@interface GNCDiscoverer : NSObject
+
+/**
+ * Factory method that creates a discoverer.
+ *
+ * @param serviceId A string that uniquely identifies the advertised service to search for.
+ * @param strategy The connection topology to use.
+ * @param endpointFoundHandler This handler is called when an endpoint advertising the service is
+ *                              discovered.
+ */
++ (instancetype)discovererWithServiceId:(NSString *)serviceId
+                               strategy:(GNCStrategy)strategy
+                   endpointFoundHandler:(GNCEndpointFoundHandler)endpointFoundHandler;
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/GNCPayload.h

@@ -0,0 +1,62 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** This class encapsulates a Bytes payload. */
+@interface GNCBytesPayload : NSObject
+
+/** The unique identifier of the payload. */
+@property(nonatomic, readonly) int64_t identifier;
+
+/** The content of the payload. */
+@property(nonatomic, readonly) NSData *bytes;
+
+/**
+ * Creates a Bytes payload object.
+ * Note: To maximize performance, @c bytes is strongly referenced, not copied.
+ */
++ (instancetype)payloadWithBytes:(NSData *)bytes;
+
+@end
+
+/** This class encapsulates a Stream payload. */
+@interface GNCStreamPayload : NSObject
+
+/** The unique identifier of the payload. */
+@property(nonatomic, readonly) int64_t identifier;
+
+/** The payload data is read from this input stream. */
+@property(nonatomic, readonly) NSInputStream *stream;
+
++ (instancetype)payloadWithStream:(NSInputStream *)stream;
+
+@end
+
+/** This class encapsulates a File payload. */
+@interface GNCFilePayload : NSObject
+
+/** The unique identifier of the payload. */
+@property(nonatomic, readonly) int64_t identifier;
+
+/** A URL that identifies the file. */
+@property(nonatomic, readonly, copy) NSURL *fileURL;
+
++ (instancetype)payloadWithFileURL:(NSURL *)fileURL;
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCAdvertiser.mm

@@ -0,0 +1,313 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCAdvertiser.h"
+
+#include <string>
+
+#include "third_party/absl/functional/bind_front.h"
+#include "third_party/nearby_connections/cpp/core/core.h"
+#include "third_party/nearby_connections/cpp/core/listeners.h"
+#include "third_party/nearby_connections/cpp/core/options.h"
+#include "third_party/nearby_connections/cpp/core/params.h"
+#include "third_party/nearby_connections/cpp/core/status.h"
+#include "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCoreConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCPayloadListener.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCUtils.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+using ::location::nearby::ByteArrayFromNSData;
+using ::location::nearby::CppStringFromObjCString;
+using ::location::nearby::ObjCStringFromCppString;
+using ::location::nearby::connections::ConnectionListener;
+using ::location::nearby::connections::ConnectionOptions;
+using ::location::nearby::connections::ConnectionRequestInfo;
+using ::location::nearby::connections::ConnectionResponseInfo;
+using ::location::nearby::connections::GNCStrategyToStrategy;
+using ::location::nearby::connections::Medium;
+using ResultListener = ::location::nearby::connections::ResultCallback;
+using ::location::nearby::connections::Status;
+
+/** This is a GNCAdvertiserConnectionInfo that provides storage for its properties. */
+@interface GNCAdvertiserConnectionInfo : NSObject
+
+@property(nonatomic, readonly) NSString *name;
+@property(nonatomic, readonly) NSString *authToken;
+
+- (instancetype)initWithName:(NSString *)name authToken:(NSString *)authToken;
+
+@end
+
+@implementation GNCAdvertiserConnectionInfo
+
+- (instancetype)initWithName:(NSString *)name authToken:(NSString *)authToken {
+  self = [super init];
+  if (self) {
+    _name = [name copy];
+    _authToken = [authToken copy];
+  }
+  return self;
+}
+
+@end
+
+/** Information retained about an endpoint before and after requesting a connection. */
+@interface GNCAdvertiserEndpointInfo : NSObject
+@property(nonatomic) GNCAdvertiserConnectionInfo *connectionInfo;
+@property(nonatomic) GNCConnectionResponse clientResponse;
+@property(nonatomic) BOOL clientResponseReceived;  // whether the client response has been received
+@property(nonatomic, nullable) GNCConnectionResultHandlers *connectionResultHandlers;
+@property(nonatomic, weak) GNCCoreConnection *connection;
+@property(nonatomic) GNCConnectionHandlers *connectionHandlers;
+@end
+
+@implementation GNCAdvertiserEndpointInfo
+
++ (instancetype)infoWithEndpointConnectionInfo:(GNCAdvertiserConnectionInfo *)connInfo {
+  GNCAdvertiserEndpointInfo *info = [[GNCAdvertiserEndpointInfo alloc] init];
+  info.connectionInfo = connInfo;
+  return info;
+}
+
+@end
+
+/** GNCAdvertiser members. */
+@interface GNCAdvertiser ()
+@property(nonatomic) GNCCore *core;
+@property(nonatomic) GNCAdvertiserConnectionInitiationHandler initiationHandler;
+@property(nonatomic, assign) Status status;
+@property(nonatomic) NSMutableDictionary<GNCEndpointId, GNCAdvertiserEndpointInfo *> *endpoints;
+@end
+
+/** C++ classes passed to the core library by GNCAdvertiser. */
+namespace location {
+namespace nearby {
+namespace connections {
+
+/** This class contains the callbacks for establishing and severing a connection. */
+class GNCAdvertiserConnectionListener {
+ public:
+  explicit GNCAdvertiserConnectionListener(GNCAdvertiser *advertiser) : advertiser_(advertiser) {}
+
+  void OnInitiated(const std::string &endpoint_id, const ConnectionResponseInfo &info) {
+    GNCAdvertiser *advertiser = advertiser_;  // strongify
+    if (!advertiser) return;
+
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCAdvertiserEndpointInfo *endpointInfo = advertiser.endpoints[endpointId];
+    if (endpointInfo) {
+      GTMLoggerError(@"Connection already initiated for endpoint: %@", endpointId);
+    } else {
+      // TODO(b/169292092): endpointInfo is an advertisement byte array. Need to implement to
+      // extract the endpoint name not just force to cast string.
+      NSString *name = ObjCStringFromCppString(std::string(info.remote_endpoint_info));
+      NSString *authToken = ObjCStringFromCppString(info.authentication_token);
+      GNCAdvertiserConnectionInfo *connInfo =
+          [[GNCAdvertiserConnectionInfo alloc] initWithName:name authToken:authToken];
+      endpointInfo = [GNCAdvertiserEndpointInfo infoWithEndpointConnectionInfo:connInfo];
+
+      // Call the connection initiation handler. Synchronous because it returns the connection
+      // result handlers.
+      dispatch_sync(dispatch_get_main_queue(), ^{
+        __weak __typeof__(advertiser) weakAdvertiser = advertiser;
+        endpointInfo.connectionResultHandlers = advertiser.initiationHandler(
+            endpointId, (id<GNCAdvertiserConnectionInfo>)connInfo,
+            ^(GNCConnectionResponse response) {
+              __strong __typeof__(advertiser) strongAdvertiser = weakAdvertiser;
+              endpointInfo.clientResponse = response;
+              endpointInfo.clientResponseReceived = YES;
+              if (response == GNCConnectionResponseAccept) {
+                // The connection was accepted by the client.
+                if (payload_listener_ == nullptr) {
+                  payload_listener_ = std::make_unique<GNCPayloadListener>(
+                      advertiser.core,
+                      ^{
+                        return endpointInfo.connectionHandlers;
+                      },
+                      ^{
+                        return endpointInfo.connection.payloads;
+                      });
+                }
+                advertiser.core->_core->AcceptConnection(
+                    CppStringFromObjCString(endpointId),
+                    PayloadListener{
+                        .payload_cb = absl::bind_front(&GNCPayloadListener::OnPayload,
+                                                       payload_listener_.get()),
+                        .payload_progress_cb = absl::bind_front(
+                            &GNCPayloadListener::OnPayloadProgress, payload_listener_.get()),
+                    },
+                    ResultListener{});
+              } else {
+                // The connection was rejected by the client.
+                advertiser.core->_core->RejectConnection(CppStringFromObjCString(endpointId),
+                                                         ResultListener{});
+              }
+            });
+      });
+      advertiser.endpoints[endpointId] = endpointInfo;
+    }
+  }
+
+  void OnAccepted(const std::string &endpoint_id) {
+    GNCAdvertiser *advertiser = advertiser_;  // strongify
+    if (!advertiser) return;
+
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCAdvertiserEndpointInfo *endpointInfo = advertiser.endpoints[endpointId];
+    if (!endpointInfo) {
+      GTMLoggerInfo(@"Connection result for unknown endpoint: %@", endpointId);
+      return;
+    }
+
+    // The connection has been accepted by both endpoints, so create the GNCConnection object
+    // and pass it to |successHandler| for the client to use. It will be removed from |endpoints|
+    // when the client disconnects (on dealloc of GNCConnection).
+    // Note: Use a local strong reference to the connection object; don't just assign to
+    // |endpointInfo.connection|. Without a strong reference, the connection object can be
+    // deallocated before |successHandler| is called in the Release build.
+    __weak __typeof__(advertiser) weakAdvertiser = advertiser;
+    id<GNCConnection> connection = [GNCCoreConnection
+        connectionWithEndpointId:endpointId
+                            core:advertiser.core
+                  deallocHandler:^{
+                    __strong __typeof__(advertiser) strongAdvertiser = weakAdvertiser;
+                    if (!strongAdvertiser) return;
+                    [strongAdvertiser.endpoints removeObjectForKey:endpointId];
+                  }];
+    endpointInfo.connection = connection;
+
+    // Callback is synchronous because it returns the connection handlers.
+    dispatch_sync(dispatch_get_main_queue(), ^{
+      endpointInfo.connectionHandlers =
+          endpointInfo.connectionResultHandlers.successHandler(connection);
+    });
+  }
+
+  void OnRejected(const std::string &endpoint_id, Status status) {
+    GNCAdvertiser *advertiser = advertiser_;  // strongify
+    if (!advertiser) return;
+
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCAdvertiserEndpointInfo *endpointInfo = advertiser.endpoints[endpointId];
+    if (!endpointInfo) {
+      GTMLoggerInfo(@"Connection result for unknown endpoint: %@", endpointId);
+      return;
+    }
+
+    // One side rejected, so call failureHandler with the connection status (we do this in all
+    // cases), and forget the endpoint.
+    dispatch_async(dispatch_get_main_queue(), ^{
+      endpointInfo.connectionResultHandlers.failureHandler(GNCConnectionFailureRejected);
+    });
+    [advertiser.endpoints removeObjectForKey:endpointId];
+  }
+
+  void OnDisconnected(const std::string &endpoint_id) {
+    GNCAdvertiser *advertiser = advertiser_;  // strongify
+    if (!advertiser) return;
+
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCAdvertiserEndpointInfo *endpointInfo = advertiser.endpoints[endpointId];
+    if (endpointInfo) {
+      if (endpointInfo.connection) {
+        GNCDisconnectedHandler disconnectedHandler =
+            endpointInfo.connectionHandlers.disconnectedHandler;
+        dispatch_async(dispatch_get_main_queue(), ^{
+          if (disconnectedHandler) disconnectedHandler(GNCDisconnectedReasonUnknown);
+        });
+      } else {
+        GTMLoggerInfo(@"Disconnect for unconnected endpoint: %@", endpointId);
+      }
+      [advertiser.endpoints removeObjectForKey:endpointId];
+    } else {
+      GTMLoggerInfo(@"Disconnect for unknown endpoint: %@", endpointId);
+    }
+  }
+
+  void OnBandwidthChanged(const std::string &endpoint_id, Medium medium) {
+    GNCAdvertiser *advertiser = advertiser_;  // strongify
+    if (!advertiser) return;
+
+    // TODO(b/169292092): Implement.
+  }
+
+ private:
+  __weak GNCAdvertiser *advertiser_;
+  std::unique_ptr<GNCPayloadListener> payload_listener_;
+};
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+using ::location::nearby::connections::GNCAdvertiserConnectionListener;
+
+@interface GNCAdvertiser () {
+  std::unique_ptr<GNCAdvertiserConnectionListener> advertiserListener;
+};
+
+@end
+
+@implementation GNCAdvertiser
+
++ (instancetype)advertiserWithEndpointInfo:(NSData *)endpointInfo
+                                 serviceId:(NSString *)serviceId
+                                  strategy:(GNCStrategy)strategy
+               connectionInitiationHandler:
+                   (GNCAdvertiserConnectionInitiationHandler)initiationHandler {
+  GNCAdvertiser *advertiser = [[GNCAdvertiser alloc] init];
+  advertiser.initiationHandler = initiationHandler;
+  advertiser.endpoints = [[NSMutableDictionary alloc] init];
+  advertiser.core = GNCGetCore();
+  advertiser->advertiserListener = std::make_unique<GNCAdvertiserConnectionListener>(advertiser);
+
+  ConnectionListener listener = {
+      .initiated_cb = absl::bind_front(&GNCAdvertiserConnectionListener::OnInitiated,
+                                       advertiser->advertiserListener.get()),
+      .accepted_cb = absl::bind_front(&GNCAdvertiserConnectionListener::OnAccepted,
+                                      advertiser->advertiserListener.get()),
+      .rejected_cb = absl::bind_front(&GNCAdvertiserConnectionListener::OnRejected,
+                                      advertiser->advertiserListener.get()),
+      .disconnected_cb = absl::bind_front(&GNCAdvertiserConnectionListener::OnDisconnected,
+                                          advertiser->advertiserListener.get()),
+  };
+
+  advertiser.core->_core->StartAdvertising(CppStringFromObjCString(serviceId),
+                                           ConnectionOptions{
+                                               .strategy = GNCStrategyToStrategy(strategy),
+                                               .auto_upgrade_bandwidth = true,
+                                               .enforce_topology_constraints = true,
+                                           },
+                                           ConnectionRequestInfo{
+                                               .endpoint_info = ByteArrayFromNSData(endpointInfo),
+                                               .listener = std::move(listener),
+                                           },
+                                           ResultListener{});
+  return advertiser;
+}
+
+- (void)dealloc {
+  GTMLoggerInfo(@"GNCAdvertiser deallocated");
+  _core->_core->StopAdvertising(ResultListener{});
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCCore.h

@@ -0,0 +1,55 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#include <memory>
+
+#include "core/core.h"
+#include "core/internal/service_controller_router.h"
+#include "platform/base/payload_id.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** This class contains the C++ Core object. */
+@interface GNCCore : NSObject {
+ @public
+  std::unique_ptr<::location::nearby::connections::Core> _core;
+  std::unique_ptr<::location::nearby::connections::ServiceControllerRouter>
+      _service_controller_router;
+}
+
+/**
+ * These functions are the utilities to manipulate the InputFile in ImplementationPlatform for
+ * sending File payload.
+ *
+ * Inserts the URL to the map, keyed by payloadID. The element will not be inserted if there
+ * already is an element with the key in the map.
+ */
+- (void)insertURLToMapWithPayloadID:(::location::nearby::PayloadId)payloadId urlToSend:(NSURL *)url;
+
+/**
+ * Returns the URL with the payloadID and removes the entry from the map. Returns nil if
+ * payloadID is not found.
+ */
+- (nullable NSURL *)extractURLWithPayloadID:(::location::nearby::PayloadId)payloadId;
+
+- (void)clearSendingURLMaps;
+
+@end
+
+/** This function returns the Core singleton, wrapped in an Obj-C object for lifetime management. */
+GNCCore *GNCGetCore();
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCCore.mm

@@ -0,0 +1,94 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+
+#include <utility>
+
+#include "third_party/absl/container/flat_hash_map.h"
+#include "third_party/absl/container/internal/common.h"
+#include "third_party/nearby_connections/cpp/core/core.h"
+#include "third_party/nearby_connections/cpp/core/internal/service_controller_router.h"
+#include "third_party/nearby_connections/cpp/platform/base/payload_id.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+using ::location::nearby::connections::Core;
+using ::location::nearby::PayloadId;
+using ::location::nearby::connections::ServiceControllerRouter;
+
+@implementation GNCCore {
+  // A map to store the NSURL object with PayloadId for sendFilePayload in GNCConnection.
+  // This is the place to store the NSURL for InputFile creation in ImplementationPlatform.
+  absl::flat_hash_map<PayloadId, NSURL *> _sending_urls;
+}
+
+- (instancetype)init {
+  GTMLoggerInfo(@"GNCCore created");
+  self = [super init];
+  if (self) {
+    _service_controller_router = std::make_unique<ServiceControllerRouter>();
+    _core = std::make_unique<Core>(_service_controller_router.get());
+  }
+  return self;
+}
+
+- (void)dealloc {
+  _core.reset();
+  _service_controller_router.reset();
+  GTMLoggerInfo(@"GNCCore deallocated");
+}
+
+- (void)insertURLToMapWithPayloadID:(PayloadId)payloadId urlToSend:(NSURL *)url {
+  _sending_urls.emplace(payloadId, url);
+}
+
+- (nullable NSURL *)extractURLWithPayloadID:(PayloadId)payloadId {
+  NSURL *url;
+  auto it = _sending_urls.find(payloadId);
+  if (it != _sending_urls.end()) {
+    auto pair = _sending_urls.extract(it);
+    url = pair.mapped();
+  }
+  return url;
+}
+
+- (void)clearSendingURLMaps {
+  _sending_urls.clear();
+}
+
+@end
+
+GNCCore *GNCGetCore() {
+  static NSObject *syncSingleton;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    syncSingleton = [[NSObject alloc] init];
+  });
+
+  // The purpose of keeping a weak reference to the GNCCore object is to ensure that it will be
+  // released when all external strong references are gone. I.e., when the app is no longer doing
+  // any NC operations, the core will be released.
+  static __weak GNCCore *core;
+
+  // Strongly reference the GNCCore object for the duration of this function to ensure it isn't
+  // prematurely deallocated by ARC after being created (which can happen in optimized builds).
+  GNCCore *strongCore = core;
+  @synchronized(syncSingleton) {
+    if (!strongCore) {
+      strongCore = [[GNCCore alloc] init];
+      core = strongCore;
+    }
+  }
+  return strongCore;
+}

cpp/platform/impl/ios/Source/Internal/GNCCoreConnection.h

@@ -0,0 +1,44 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** This holds the progress and completion for a pending payload. */
+@interface GNCPayloadInfo : NSObject
+@property(nonatomic, nullable) NSProgress *progress;
+@property(nonatomic, nullable) GNCPayloadResultHandler completion;
+
++ (instancetype)infoWithProgress:(nullable NSProgress *)progress
+                      completion:(GNCPayloadResultHandler)completion;
+- (void)callCompletion:(GNCPayloadResult)result;
+@end
+
+/** GNCConnection that interfaces with the Core library. */
+@interface GNCCoreConnection : NSObject <GNCConnection>
+@property(nonatomic) GNCCore *core;
+@property(nonatomic, copy) GNCEndpointId endpointId;
+@property(nonatomic) dispatch_block_t deallocHandler;
+@property(nonatomic) NSMutableDictionary<NSNumber *, GNCPayloadInfo *> *payloads;
+
++ (instancetype)connectionWithEndpointId:(GNCEndpointId)endpointId
+                                    core:(GNCCore *)core
+                          deallocHandler:(dispatch_block_t)deallocHandler;
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCCoreConnection.mm

@@ -0,0 +1,188 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCoreConnection.h"
+
+#include "third_party/nearby_connections/cpp/core/core.h"
+#include "third_party/nearby_connections/cpp/core/payload.h"
+#include "third_party/nearby_connections/cpp/platform/api/input_file.h"
+#import "third_party/nearby_connections/cpp/platform/base/exception.h"
+#include "third_party/nearby_connections/cpp/platform/base/input_stream.h"
+#import "third_party/nearby_connections/cpp/platform/base/payload_id.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCPayload.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#include "third_party/nearby_connections/cpp/platform/public/file.h"
+
+using ::location::nearby::ByteArrayFromNSData;
+using ::location::nearby::CppStringFromObjCString;
+using ::location::nearby::InputFile;
+using ::location::nearby::InputStream;
+using ::location::nearby::connections::Payload;
+using ::location::nearby::PayloadId;
+using ResultListener = ::location::nearby::connections::ResultCallback;
+
+namespace location {
+namespace nearby {
+namespace connections {
+
+/**
+ * This InputStream subclass takes input from an NSInputStream. The update handler is called for
+ * each chunk of data sent, giving the client an opportunity to handle cancelation.
+ */
+class GNCInputStreamFromNSStream : public InputStream {
+ public:
+  explicit GNCInputStreamFromNSStream(NSInputStream *nsStream) : nsStream_(nsStream) {
+    [nsStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
+    [nsStream open];
+  }
+
+  ~GNCInputStreamFromNSStream() override { Close(); }
+
+  ExceptionOr<ByteArray> Read() { return Read(kMaxChunkSize); }
+
+  ExceptionOr<ByteArray> Read(std::int64_t size) override {
+    uint8_t *bytesRead = new uint8_t[size];
+    NSUInteger numberOfBytesToRead = [[NSNumber numberWithLongLong:size] unsignedIntegerValue];
+    NSInteger numberOfBytesRead = [nsStream_ read:bytesRead maxLength:numberOfBytesToRead];
+    if (numberOfBytesRead == 0) {
+      // Reached end of stream.
+      return ExceptionOr<ByteArray>();
+    } else if (numberOfBytesRead < 0) {
+      // Stream error.
+      return ExceptionOr<ByteArray>{Exception::kIo};
+    }
+    return ExceptionOr<ByteArray>(ByteArrayFromNSData([NSData dataWithBytes:bytesRead
+                                                                     length:numberOfBytesRead]));
+  }
+
+  Exception Close() override {
+    [nsStream_ close];
+    return {Exception::kSuccess};
+  }
+
+ private:
+  static const size_t kMaxChunkSize = 32 * 1024;
+  NSInputStream *nsStream_;
+  // dispatch_block_t update_handler_;
+};
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+@implementation GNCPayloadInfo
+
++ (instancetype)infoWithProgress:(nullable NSProgress *)progress
+                      completion:(GNCPayloadResultHandler)completion {
+  GNCPayloadInfo *info = [[GNCPayloadInfo alloc] init];
+  info.progress = progress;
+  info.completion = completion;
+  return info;
+}
+
+- (void)callCompletion:(GNCPayloadResult)result {
+  if (_completion) _completion(result);
+  _completion = nil;
+}
+
+@end
+
+@implementation GNCCoreConnection
+
++ (instancetype)connectionWithEndpointId:(GNCEndpointId)endpointId
+                                    core:(GNCCore *)core
+                          deallocHandler:(dispatch_block_t)deallocHandler {
+  GNCCoreConnection *connection = [[GNCCoreConnection alloc] init];
+  connection.endpointId = endpointId;
+  connection.core = core;
+  connection.deallocHandler = deallocHandler;
+  connection.payloads = [[NSMutableDictionary alloc] init];
+  return connection;
+}
+
+- (void)dealloc {
+  _core->_core->DisconnectFromEndpoint(CppStringFromObjCString(_endpointId), ResultListener{});
+  _deallocHandler();
+}
+
+- (NSProgress *)sendBytesPayload:(GNCBytesPayload *)payload
+                      completion:(GNCPayloadResultHandler)completion {
+  Payload corePayload(ByteArrayFromNSData(payload.bytes));
+  NSUInteger length = payload.bytes.length;
+  PayloadId payloadId = corePayload.GetId();
+  NSProgress *progress = [NSProgress progressWithTotalUnitCount:length];
+  __weak __typeof__(self) weakSelf = self;
+  progress.cancellationHandler = ^{
+    [weakSelf cancelPayloadWithId:payloadId];
+  };
+  return [self sendPayload:std::move(corePayload)
+                      size:length
+                  progress:progress
+                completion:completion];
+}
+
+- (NSProgress *)sendStreamPayload:(GNCStreamPayload *)payload
+                       completion:(GNCPayloadResultHandler)completion {
+  NSProgress *progress = [NSProgress progressWithTotalUnitCount:-1];
+
+  PayloadId payloadId = Payload::GenerateId();
+  Payload corePayload(payloadId, [payload]() -> InputStream & {
+    location::nearby::connections::GNCInputStreamFromNSStream *stream =
+        new location::nearby::connections::GNCInputStreamFromNSStream(payload.stream);
+    return *stream;
+  });
+  return [self sendPayload:std::move(corePayload) size:-1 progress:progress completion:completion];
+}
+
+- (NSProgress *)sendFilePayload:(GNCFilePayload *)payload
+                     completion:(GNCPayloadResultHandler)completion {
+  NSProgress *progress = [NSProgress progressWithTotalUnitCount:0];
+
+  std::int64_t fileSize = 0;
+  NSURL *fileURL = payload.fileURL;
+  NSNumber *fileSizeValue = nil;
+  BOOL result = [fileURL getResourceValue:&fileSizeValue forKey:NSURLFileSizeKey error:nil];
+  if (result == YES) {
+    fileSize = fileSizeValue.longValue;
+  }
+  PayloadId payloadId = Payload::GenerateId();
+  // Add the pair of payloadId and fileURL to the map in the GNCCore.
+  [_core insertURLToMapWithPayloadID:payloadId urlToSend:fileURL];
+  Payload corePayload(payloadId, InputFile(payloadId, fileSize));
+  progress.totalUnitCount = fileSize;
+  return [self sendPayload:std::move(corePayload)
+                      size:fileSize
+                  progress:progress
+                completion:completion];
+}
+
+#pragma mark Private
+
+- (NSProgress *)sendPayload:(Payload)payload
+                       size:(uint64_t)size
+                   progress:(NSProgress *)progress
+                 completion:(GNCPayloadResultHandler)completion {
+  _payloads[@(payload.GetId())] = [GNCPayloadInfo infoWithProgress:progress completion:completion];
+  _core->_core->SendPayload(std::vector<std::string>(1, CppStringFromObjCString(_endpointId)),
+                            std::move(payload), ResultListener{});
+  return progress;
+}
+
+- (void)cancelPayloadWithId:(PayloadId)payloadId {
+  _core->_core->CancelPayload(payloadId, ResultListener{});
+}
+
+@end

cpp/platform/impl/ios/Source/Internal/GNCDiscoverer.mm

@@ -0,0 +1,394 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCDiscoverer.h"
+
+#include <string>
+#include <utility>
+
+#include "third_party/absl/functional/bind_front.h"
+#include "third_party/nearby_connections/cpp/core/core.h"
+#include "third_party/nearby_connections/cpp/core/listeners.h"
+#include "third_party/nearby_connections/cpp/core/options.h"
+#include "third_party/nearby_connections/cpp/core/status.h"
+#include "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCoreConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCPayloadListener.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCUtils.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+using ::location::nearby::ByteArray;
+using ::location::nearby::CppStringFromObjCString;
+using ::location::nearby::connections::ConnectionOptions;
+using ::location::nearby::connections::DiscoveryListener;
+using ::location::nearby::connections::DistanceInfo;
+using ::location::nearby::connections::GNCStrategyToStrategy;
+using ResultListener = ::location::nearby::connections::ResultCallback;
+using ::location::nearby::connections::Status;
+
+/** This is a GNCDiscovererConnectionInfo that provides storage for its properties. */
+@interface GNCDiscovererConnectionInfo : NSObject <GNCDiscovererConnectionInfo>
+@property(nonatomic, copy) NSString *authToken;
+
+/** Creates a GNCDiscovererConnectionInfo object. */
++ (instancetype)infoWithAuthToken:(NSString *)authToken;
+@end
+
+@implementation GNCDiscovererConnectionInfo
+
++ (instancetype)infoWithAuthToken:(NSString *)authToken {
+  GNCDiscovererConnectionInfo *info = [[GNCDiscovererConnectionInfo alloc] init];
+  info.authToken = authToken;
+  return info;
+}
+
+@end
+
+/** This is a GNCDiscoveredEndpointInfo that provides storage for its properties. */
+@interface GNCDiscoveredEndpointInfo : NSObject <GNCDiscoveredEndpointInfo>
+@property(nonatomic, copy) NSString *name;
+@end
+
+@implementation GNCDiscoveredEndpointInfo
+
+@synthesize requestConnection = _requestConnection;
+
++ (instancetype)infoWithName:(NSString *)name
+           requestConnection:(GNCConnectionRequester)requestConnection {
+  GNCDiscoveredEndpointInfo *info = [[GNCDiscoveredEndpointInfo alloc] init];
+  info.name = name;
+  info->_requestConnection = requestConnection;
+  return info;
+}
+
+@end
+
+/** Information retained by the discoverer about each discovered endpoint. */
+@interface GNCDiscovererEndpointInfo : NSObject
+
+/** Handles lostHandler once |onEndpointLost| has been callback. */
+@property(nonatomic) GNCEndpointLostHandler lostHandler;
+
+/** The connInitHandler is stored after requestConnection. */
+@property(nonatomic, nullable) GNCDiscovererConnectionInitializationHandler connInitHandler;
+
+/** The connFailureHandler is stored after requestConnection. */
+@property(nonatomic, nullable) GNCConnectionFailureHandler connFailureHandler;
+
+/** Client responses Accept or Reject. */
+@property(nonatomic) GNCConnectionResponse clientResponse;
+
+/** Whether the client response has been received. */
+@property(nonatomic) BOOL clientResponseReceived;
+
+/**
+ * The connectionhandler returned by connInitHandler. Stored here if the connection is accepted.
+ */
+@property(nonatomic, nullable) GNCConnectionHandler connectionHandler;
+
+/** @c GNCCoreConnection is created and stored if connection is accepted. */
+@property(nonatomic, weak) GNCCoreConnection *connection;
+
+/** @c GNCConnectionHandlers object is returned by connectionHandler and stored here. */
+@property(nonatomic) GNCConnectionHandlers *connectionHandlers;
+@end
+
+@implementation GNCDiscovererEndpointInfo
+@end
+
+/** GNCDiscoverer members. */
+@interface GNCDiscoverer ()
+@property(nonatomic) GNCCore *core;
+@property(nonatomic) GNCEndpointFoundHandler endpointFoundHandler;
+@property(nonatomic, assign) Status status;
+@property(nonatomic) NSMapTable<GNCEndpointId, GNCDiscovererEndpointInfo *> *endpoints;
+@end
+
+/** C++ classes passed to the core library by GNCDiscoverer. */
+namespace location {
+namespace nearby {
+namespace connections {
+
+/** This class contains the discoverer callbacks related to a connection. */
+class GNCDiscovererConnectionListener {
+ public:
+  GNCDiscovererConnectionListener(GNCCore *core,
+                                  NSMapTable<GNCEndpointId, GNCDiscovererEndpointInfo *> *endpoints)
+      : core_(core), endpoints_(endpoints) {}
+
+  void OnInitiated(const std::string &endpoint_id, const ConnectionResponseInfo &info) {
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCDiscovererEndpointInfo *endpointInfo = [endpoints_ objectForKey:endpointId];
+    if (!endpointInfo) {
+      return;
+    }
+
+    // Call the connection initiation handler. Synchronous because it returns the connection
+    // handler.
+    NSString *authToken = ObjCStringFromCppString(info.authentication_token);
+    GNCCore *core = core_;  // don't capture |this|
+    dispatch_sync(dispatch_get_main_queue(), ^{
+      endpointInfo.connectionHandler = endpointInfo.connInitHandler(
+          [GNCDiscovererConnectionInfo infoWithAuthToken:authToken],
+          ^(GNCConnectionResponse response) {
+            endpointInfo.clientResponse = response;
+            endpointInfo.clientResponseReceived = YES;
+            if (response == GNCConnectionResponseAccept) {
+              // The connect was accepted by the client.
+              if (payload_listener_ == nullptr) {
+                payload_listener_ = std::make_unique<GNCPayloadListener>(
+                    core,
+                    ^{
+                      return endpointInfo.connectionHandlers;
+                    },
+                    ^{
+                      return endpointInfo.connection.payloads;
+                    });
+              }
+              core->_core->AcceptConnection(
+                  CppStringFromObjCString(endpointId),
+                  PayloadListener{
+                      .payload_cb =
+                          absl::bind_front(&GNCPayloadListener::OnPayload, payload_listener_.get()),
+                      .payload_progress_cb = absl::bind_front(
+                          &GNCPayloadListener::OnPayloadProgress, payload_listener_.get()),
+                  },
+                  ResultListener{});
+            } else {
+              // The connect was rejected by the client.
+              core->_core->RejectConnection(CppStringFromObjCString(endpointId), ResultListener{});
+            }
+          });
+    });
+  }
+
+  void OnAccepted(const std::string &endpoint_id) {
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCDiscovererEndpointInfo *endpointInfo = [endpoints_ objectForKey:endpointId];
+    if (!endpointInfo) {
+      return;
+    }
+
+    // The connection has been accepted by both endpoints, so create the GNCConnection object
+    // and pass it to |successHandler| for the client to use.
+    // Note: Use a local strong reference to the connection object; don't just assign to
+    // |endpointInfo.connection|. Without a strong reference, the connection object can be
+    // deallocated before |successHandler| is called in the Release build.
+    id<GNCConnection> connection = [GNCCoreConnection
+        connectionWithEndpointId:endpointId
+                            core:core_
+                  deallocHandler:^{
+                      // Don't remove the remote endpoint (like GNCAdvertiser does) because that's
+                      // done when the endpoint is lost.
+                  }];
+    endpointInfo.connection = connection;
+
+    // Callback is synchronous because it returns the connection handlers.
+    dispatch_sync(dispatch_get_main_queue(), ^{
+      endpointInfo.connectionHandlers = endpointInfo.connectionHandler(endpointInfo.connection);
+    });
+    endpointInfo.clientResponseReceived = NO;  // support reconnection after disconnection
+  }
+
+  void OnRejected(const std::string &endpoint_id, Status status) {
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCDiscovererEndpointInfo *endpointInfo = [endpoints_ objectForKey:endpointId];
+    if (!endpointInfo) {
+      return;
+    }
+
+    // If either side rejected, call failureHandler with the connection status.
+    dispatch_async(dispatch_get_main_queue(), ^{
+      endpointInfo.connFailureHandler(GNCConnectionFailureRejected);
+    });
+    endpointInfo.clientResponseReceived = NO;  // support reconnection after disconnection
+  }
+
+  void OnDisconnected(const std::string &endpoint_id) {
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCDiscovererEndpointInfo *endpointInfo = [endpoints_ objectForKey:endpointId];
+    if (!endpointInfo) {
+      return;
+    }
+
+    if (endpointInfo.connection) {
+      GNCDisconnectedHandler disconnectedHandler =
+          endpointInfo.connectionHandlers.disconnectedHandler;
+      dispatch_async(dispatch_get_main_queue(), ^{
+        if (disconnectedHandler) disconnectedHandler(GNCDisconnectedReasonUnknown);
+      });
+    }
+  }
+
+  void OnBandwidthChanged(const std::string &endpoint_id, Medium medium) {
+    // TODO(b/169292092): Implement.
+  }
+
+ private:
+  GNCCore *core_;
+  NSMapTable<GNCEndpointId, GNCDiscovererEndpointInfo *> *endpoints_;
+  std::unique_ptr<GNCPayloadListener> payload_listener_;
+};
+
+class GNCDiscoveryListener {
+ public:
+  explicit GNCDiscoveryListener(GNCDiscoverer *discoverer) : discoverer_(discoverer) {}
+
+  void OnEndpointFound(const std::string &endpoint_id, const ByteArray &endpoint_info,
+                       const std::string &service_id) {
+    GNCDiscoverer *discoverer = discoverer_;  // strongify
+    if (!discoverer) {
+      return;
+    }
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+
+    if ([discoverer.endpoints objectForKey:endpointId] != nil) {
+      GTMLoggerError(@"Endpoint already discovered: %@", endpointId);
+    } else {
+      // The GNCDiscoveredEndpointInfo object created here lives as long as the client has strong
+      // reference to it. Here's the chain of strong references maintained here:
+      // client -> GNCDiscoveredEndpointInfo -> RequestConnection block ->
+      //   GNCDiscovererEndpointInfo (stored weakly in the |endpoints| map table)
+      GNCDiscovererEndpointInfo *endpointInfo = [[GNCDiscovererEndpointInfo alloc] init];
+      [discoverer.endpoints setObject:endpointInfo forKey:endpointId];
+
+      // TODO(b/169292092): endpointInfo is an advertisement byte array. Need to implement to
+      // extract the endpoint name not just force to cast string.
+      NSString *name = ObjCStringFromCppString(std::string(endpoint_info));
+      GNCCore *core = discoverer.core;  // don't capture |this| or |discoverer|
+      NSMapTable<GNCEndpointId, GNCDiscovererEndpointInfo *> *endpoints = discoverer.endpoints;
+      GNCDiscoveredEndpointInfo *discEndpointInfo = [GNCDiscoveredEndpointInfo
+               infoWithName:name
+          requestConnection:^(NSString *name,
+                              GNCDiscovererConnectionInitializationHandler connInitHandler,
+                              GNCConnectionFailureHandler connFailureHandler) {
+            endpointInfo.connInitHandler = connInitHandler;
+            endpointInfo.connFailureHandler = connFailureHandler;
+            if (discoverer_connection_listener_ == nullptr) {
+              discoverer_connection_listener_ =
+                  std::make_unique<GNCDiscovererConnectionListener>(core, endpoints);
+            }
+
+            ConnectionListener listener = {
+                .initiated_cb = absl::bind_front(&GNCDiscovererConnectionListener::OnInitiated,
+                                                 discoverer_connection_listener_.get()),
+                .accepted_cb = absl::bind_front(&GNCDiscovererConnectionListener::OnAccepted,
+                                                discoverer_connection_listener_.get()),
+                .rejected_cb = absl::bind_front(&GNCDiscovererConnectionListener::OnRejected,
+                                                discoverer_connection_listener_.get()),
+                .disconnected_cb =
+                    absl::bind_front(&GNCDiscovererConnectionListener::OnDisconnected,
+                                     discoverer_connection_listener_.get()),
+            };
+
+            core->_core->RequestConnection(
+                CppStringFromObjCString(endpointId),
+                ConnectionRequestInfo{.endpoint_info = std::move(endpoint_info),
+                                      .listener = std::move(listener)},
+                ConnectionOptions{},
+                ResultListener{.result_cb = [&connFailureHandler](Status status) {
+                  if (!status.Ok()) {
+                    dispatch_sync(dispatch_get_main_queue(), ^{
+                      connFailureHandler(GNCConnectionFailureUnknown);
+                    });
+                  }
+                }});
+          }];
+
+      // Call the client endpoint-found handler.  Tail call for reentrancy.
+      dispatch_sync(dispatch_get_main_queue(), ^{
+        endpointInfo.lostHandler = discoverer.endpointFoundHandler(endpointId, discEndpointInfo);
+      });
+    }
+  }
+
+  void OnEndpointLost(const std::string &endpoint_id) {
+    GNCDiscoverer *discoverer = discoverer_;  // strongify
+    if (!discoverer) {
+      return;
+    }
+
+    NSString *endpointId = ObjCStringFromCppString(endpoint_id);
+    GNCDiscovererEndpointInfo *info = [discoverer.endpoints objectForKey:endpointId];
+    if (!info) {
+      GTMLoggerError(@"Endpoint already lost: %@", endpointId);
+    } else {
+      dispatch_async(dispatch_get_main_queue(), ^{
+        info.lostHandler();
+      });
+    }
+    [discoverer.endpoints removeObjectForKey:endpointId];
+  }
+
+  void OnEndpointDistanceChanged_cb(const std::string &endpoint_id, DistanceInfo info) {
+    // TODO(b/169292092): Implement.
+  }
+
+ private:
+  __weak GNCDiscoverer *discoverer_;
+  std::unique_ptr<GNCDiscovererConnectionListener> discoverer_connection_listener_;
+};
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+using ::location::nearby::connections::GNCDiscoveryListener;
+
+@interface GNCDiscoverer () {
+  std::unique_ptr<GNCDiscoveryListener> discoveryListener;
+};
+
+@end
+
+@implementation GNCDiscoverer
+
++ (instancetype)discovererWithServiceId:(NSString *)serviceId
+                               strategy:(GNCStrategy)strategy
+                   endpointFoundHandler:(GNCEndpointFoundHandler)endpointFoundHandler {
+  GNCDiscoverer *discoverer = [[GNCDiscoverer alloc] init];
+  discoverer.endpointFoundHandler = endpointFoundHandler;
+  discoverer.endpoints = [NSMapTable strongToWeakObjectsMapTable];
+  discoverer.core = GNCGetCore();
+  discoverer->discoveryListener = std::make_unique<GNCDiscoveryListener>(discoverer);
+
+  DiscoveryListener listener = {
+      .endpoint_found_cb = absl::bind_front(&GNCDiscoveryListener::OnEndpointFound,
+                                            discoverer->discoveryListener.get()),
+      .endpoint_lost_cb = absl::bind_front(&GNCDiscoveryListener::OnEndpointLost,
+                                           discoverer->discoveryListener.get()),
+  };
+
+  discoverer.core->_core->StartDiscovery(CppStringFromObjCString(serviceId),
+                                         ConnectionOptions{
+                                             .strategy = GNCStrategyToStrategy(strategy),
+                                         },
+                                         std::move(listener), ResultListener{});
+
+  return discoverer;
+}
+
+- (void)dealloc {
+  GTMLoggerInfo(@"GNCDiscoverer deallocated");
+  _core->_core->StopDiscovery(ResultListener{});
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCPayload+Internal.h

@@ -0,0 +1,36 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCPayload.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** This category adds the ability to specify a payload ID. */
+@interface GNCBytesPayload (Internal)
++ (instancetype)payloadWithBytes:(NSData *)bytes identifier:(int64_t)identifier;
+@end
+
+
+/** This category adds the ability to specify a payload ID. */
+@interface GNCStreamPayload (Internal)
++ (instancetype)payloadWithStream:(NSInputStream *)stream identifier:(int64_t)identifier;
+@end
+
+
+/** This category adds the ability to specify a payload ID. */
+@interface GNCFilePayload (Internal)
++ (instancetype)payloadWithFileURL:(NSURL *)fileURL identifier:(int64_t)identifier;
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCPayload.m

@@ -0,0 +1,88 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCPayload.h"
+
+#include <stdlib.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+uint64_t GNCRandom64() {
+  return ((uint64_t)arc4random() << 32) + arc4random();
+}
+
+@implementation GNCBytesPayload
+
+- (instancetype)initWithBytes:(NSData *)bytes identifier:(int64_t)identifier {
+  self = [super init];
+  if (self) {
+    _identifier = identifier;
+    _bytes = bytes;
+  }
+  return self;
+}
+
++ (instancetype)payloadWithBytes:(NSData *)bytes {
+  return [[self alloc] initWithBytes:bytes identifier:GNCRandom64()];
+}
+
++ (instancetype)payloadWithBytes:(NSData *)bytes identifier:(int64_t)identifier {
+  return [[self alloc] initWithBytes:bytes identifier:identifier];
+}
+
+@end
+
+@implementation GNCStreamPayload
+
+- (instancetype)initWithStream:(NSInputStream *)stream identifier:(int64_t)identifier {
+  self = [super init];
+  if (self) {
+    _identifier = identifier;
+    _stream = stream;
+  }
+  return self;
+}
+
++ (instancetype)payloadWithStream:(NSInputStream *)stream {
+  return [[self alloc] initWithStream:stream identifier:GNCRandom64()];
+}
+
++ (instancetype)payloadWithStream:(NSInputStream *)stream identifier:(int64_t)identifier {
+  return [[self alloc] initWithStream:stream identifier:identifier];
+}
+
+@end
+
+@implementation GNCFilePayload
+
+- (instancetype)initWithFileURL:(NSURL *)fileURL identifier:(int64_t)identifier {
+  self = [super init];
+  if (self) {
+    _identifier = identifier;
+    _fileURL = [fileURL copy];
+  }
+  return self;
+}
+
++ (instancetype)payloadWithFileURL:(NSURL *)fileURL {
+  return [[self alloc] initWithFileURL:fileURL identifier:GNCRandom64()];
+}
+
++ (instancetype)payloadWithFileURL:(NSURL *)fileURL identifier:(int64_t)identifier {
+  return [[self alloc] initWithFileURL:fileURL identifier:identifier];
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCPayloadListener.h

@@ -0,0 +1,55 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class GNCPayloadInfo;
+
+namespace location {
+namespace nearby {
+namespace connections {
+
+/** This fetches a GNCConnectionHandlers object. */
+typedef GNCConnectionHandlers *_Nonnull (^GNCConnectionHandlersProvider)();
+
+/** This fetches a payload dictionary. */
+typedef NSMutableDictionary<NSNumber *, GNCPayloadInfo *> *_Nonnull (^GNCPayloadsProvider)();
+
+/** This is the payload handler for an advertiser or discoverer. */
+class GNCPayloadListener : public PayloadListener {
+ public:
+  GNCPayloadListener(GNCCore *core, GNCConnectionHandlersProvider handlersProvider,
+                     GNCPayloadsProvider payloadsProvider)
+      : core_(core), handlers_provider_(handlersProvider), payloads_provider_(payloadsProvider) {}
+
+  void OnPayload(const std::string& endpoint_id, Payload payload);
+  void OnPayloadProgress(const std::string& endpoint_id,
+                         const PayloadProgressInfo& info);
+
+ private:
+  GNCCore *core_;
+  GNCConnectionHandlersProvider handlers_provider_;
+  GNCPayloadsProvider payloads_provider_;
+};
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCPayloadListener.mm

@@ -0,0 +1,218 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCPayloadListener.h"
+
+#include <string>
+
+#include "third_party/nearby_connections/cpp/core/core.h"
+#include "third_party/nearby_connections/cpp/core/listeners.h"
+#include "third_party/nearby_connections/cpp/core/payload.h"
+#include "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+#include "third_party/nearby_connections/cpp/platform/base/exception.h"
+#include "third_party/nearby_connections/cpp/platform/base/input_stream.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCPayload.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCoreConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCPayload+Internal.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#include "third_party/nearby_connections/cpp/platform/public/file.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+namespace location {
+namespace nearby {
+namespace connections {
+
+void GNCPayloadListener::OnPayload(const std::string &endpoint_id, Payload payload) {
+  GNCConnectionHandlers *handlers = handlers_provider_();
+  int64_t payloadId = payload.GetId();
+
+  // Note:  The payload must be destroyed by each individual payload type handler below, because in
+  // the Stream payload case, it runs an asynchronous read-write loop, which needs the payload
+  // and its stream to live until the stream ends.
+  NSMutableDictionary<NSNumber *, GNCPayloadInfo *> *payloads = payloads_provider_();
+
+  switch (payload.GetType()) {
+    case Payload::Type::kBytes: {
+      NSData *data = NSDataFromByteArray(payload.AsBytes());  // don't capture C++ object
+
+      // Wait for the payload transfer update to arrive before calling the Bytes payload handler.
+      GNCPayloadInfo *info = [GNCPayloadInfo
+          infoWithProgress:nil
+                completion:^(GNCPayloadResult result) {
+                  NSCAssert(result == GNCPayloadResultSuccess, @"Expected success");
+                  if (handlers.bytesPayloadHandler) {
+                    // Call the Bytes payload handler.
+                    dispatch_async(dispatch_get_main_queue(), ^{
+                      handlers.bytesPayloadHandler([GNCBytesPayload payloadWithBytes:data
+                                                                          identifier:payloadId]);
+                    });
+                  }
+                }];
+      payloads[@(payloadId)] = info;
+      break;
+    }
+
+    case Payload::Type::kStream:
+      if (handlers.streamPayloadHandler) {
+        // Make a pair of bound streams so data pumped into the output stream becomes
+        // available for reading from the input stream.
+        NSInputStream *clientInputStream;
+        NSOutputStream *clientOutputStream;
+        // TODO(b/169292092): Base on medium's bandwidth?
+        [NSStream getBoundStreamsWithBufferSize:1024
+                                    inputStream:&clientInputStream
+                                   outputStream:&clientOutputStream];
+
+        NSProgress *progress = [NSProgress progressWithTotalUnitCount:-1];  // indeterminate
+        progress.cancellable = YES;
+
+        // Pass the payload to the stream payload handler, receiving the completion handler from it.
+        // Since it returns a value, it must be called synchronously.
+        __block GNCPayloadResultHandler completion;
+        dispatch_sync(dispatch_get_main_queue(), ^{
+          completion = handlers.streamPayloadHandler(
+              [GNCStreamPayload payloadWithStream:clientInputStream identifier:payloadId],
+              progress);
+        });
+        GNCPayloadInfo *info = [GNCPayloadInfo infoWithProgress:progress completion:completion];
+        payloads[@(payloadId)] = info;
+
+        // This is a loop that reads data from the C++ input stream and writes it to the output
+        // stream that feeds it to the client input stream.
+        __block InputStream *payloadInputStream = payload.AsStream();
+        dispatch_queue_t queue =
+            dispatch_queue_create("StreamReceiverQueue", DISPATCH_QUEUE_SERIAL);
+        dispatch_async(queue, ^{
+          [clientOutputStream open];
+          while (true) {
+            if (progress.isCancelled) {
+              // Payload was canceled by the client.
+              core_->_core->CancelPayload(payloadId, ResultCallback{.result_cb = [](Status status) {
+                                            // TODO(b/148640962): Implement.
+                                          }});
+              break;
+            }
+
+            ExceptionOr<ByteArray> readResult = payloadInputStream->Read(1024);
+            if (!readResult.ok()) {
+              // Error reading from stream.
+              // TODO(b/169292092): Tell core an error has occurred?
+              dispatch_async(dispatch_get_main_queue(), ^{
+                [info callCompletion:GNCPayloadResultFailure];
+              });
+              break;
+            }
+            ByteArray byteArray = readResult.GetResult();
+            if (byteArray.Empty()) {
+              // End of stream.
+              break;
+            }
+
+            // Loop until it's all been consumed by the client output stream.
+            NSData *data = NSDataFromByteArray(byteArray);
+            NSUInteger totalLength = data.length;
+            NSUInteger totalNumberWritten = 0;
+            while (totalNumberWritten < totalLength) {
+              NSInteger numberWritten =
+                  [clientOutputStream write:&((const uint8_t *)data.bytes)[totalNumberWritten]
+                                  maxLength:totalLength - totalNumberWritten];
+              if (numberWritten <= 0) {  // stream error or reached end of stream
+                // TODO(b/169292092): Tell core an error has occurred?
+                dispatch_async(dispatch_get_main_queue(), ^{
+                  [info callCompletion:GNCPayloadResultFailure];
+                });
+                break;
+              }
+              totalNumberWritten += numberWritten;
+            }
+          }
+        });
+      }
+      break;
+
+    case Payload::Type::kFile:
+      if (handlers.filePayloadHandler) {
+        InputFile *payloadInputFile = payload.AsFile();
+        NSURL *fileURL =
+            [NSURL URLWithString:ObjCStringFromCppString(payloadInputFile->GetFilePath())];
+        int64_t fileSize = payloadInputFile->GetTotalSize();
+        NSProgress *progress = [NSProgress progressWithTotalUnitCount:fileSize];
+        progress.cancellable = YES;
+        progress.cancellationHandler = ^{
+          // Payload was canceled by the client.
+          core_->_core->CancelPayload(payloadId, ResultCallback{.result_cb = [](Status status) {
+                                        // TODO(b/148640962): Implement.
+                                      }});
+        };
+
+        // Pass the payload to the file payload handler, receiving the completion handler from it.
+        // Since it returns a value, it must be called synchronously.
+        __block GNCPayloadResultHandler completion;
+        void (^passPayloadBlock)(void) = ^{
+          completion = handlers.filePayloadHandler(
+              [GNCFilePayload payloadWithFileURL:fileURL identifier:payloadId], progress);
+        };
+        if ([NSThread isMainThread]) {
+          passPayloadBlock();
+        } else {
+          dispatch_sync(dispatch_get_main_queue(), passPayloadBlock);
+        }
+        GNCPayloadInfo *info = [GNCPayloadInfo infoWithProgress:progress completion:completion];
+        payloads[@(payloadId)] = info;
+      }
+      break;
+
+    default:
+      ;// fall through
+  }
+}
+
+void GNCPayloadListener::OnPayloadProgress(const std::string &endpoint_id,
+                                           const PayloadProgressInfo &info) {
+  // Note: The logic in this callback for handling progress updates and payload completion is
+  // identical for Bytes, Stream and File payloads.
+  NSMutableDictionary<NSNumber *, GNCPayloadInfo *> *payloads = payloads_provider_();
+  NSNumber *payloadId = @(info.payload_id);
+  GNCPayloadInfo *payloadInfo = payloads[payloadId];
+  if (payloadInfo) {
+    // Update the progress.
+    if (payloadInfo.progress) {
+      payloadInfo.progress.completedUnitCount = info.bytes_transferred;
+    }
+
+    // Call the completion handler for success/failure/canceled, but not in-progress.
+    if (info.status == PayloadProgressInfo::Status::kInProgress) {
+      return;
+    }
+    GNCPayloadResult result =
+        (info.status == PayloadProgressInfo::Status::kSuccess)    ? GNCPayloadResultSuccess
+        : (info.status == PayloadProgressInfo::Status::kCanceled) ? GNCPayloadResultCanceled
+                                                                  : GNCPayloadResultFailure;
+    dispatch_async(dispatch_get_main_queue(), ^{
+      payloadInfo.completion(result);
+    });
+
+    // Release the payload info.
+    [payloads removeObjectForKey:payloadId];
+  }
+}
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCUtils.h

@@ -0,0 +1,43 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#include <string>
+
+#include "core/listeners.h"
+#include "core/options.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCAdvertiser.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+namespace location {
+namespace nearby {
+namespace connections {
+
+/** Converts GNCStrategy to Strategy. */
+const Strategy& GNCStrategyToStrategy(GNCStrategy strategy);
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+/** Internal-only properties of the connection result handlers class. */
+@interface GNCConnectionResultHandlers ()
+@property(nonatomic) GNCConnectionHandler successHandler;
+@property(nonatomic) GNCConnectionFailureHandler failureHandler;
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/GNCUtils.mm

@@ -0,0 +1,77 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCUtils.h"
+
+#include "third_party/nearby_connections/cpp/core/strategy.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCAdvertiser.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/GNCConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+namespace location {
+namespace nearby {
+namespace connections {
+
+const Strategy& GNCStrategyToStrategy(GNCStrategy strategy) {
+  switch (strategy) {
+    case GNCStrategyCluster:
+      return Strategy::kP2pCluster;
+    case GNCStrategyStar:
+      return Strategy::kP2pStar;
+    case GNCStrategyPointToPoint:
+      return Strategy::kP2pPointToPoint;
+  }
+}
+
+}  // namespace connections
+}  // namespace nearby
+}  // namespace location
+
+@implementation GNCConnectionHandlers
+
+- (instancetype)initWithBuilderBlock:(void (^)(GNCConnectionHandlers*))builderBlock {
+  self = [super init];
+  if (self) {
+    builderBlock(self);
+  }
+  return self;
+}
+
++ (instancetype)handlersWithBuilder:(void (^)(GNCConnectionHandlers * _Nonnull))builderBlock {
+  return [[self alloc] initWithBuilderBlock:builderBlock];
+}
+
+@end
+
+@implementation GNCConnectionResultHandlers
+
+- (instancetype)initWithSuccessHandler:(GNCConnectionHandler)successHandler
+                        failureHandler:(GNCConnectionFailureHandler)failureHandler {
+  self = [super init];
+  if (self) {
+    _successHandler = successHandler;
+    _failureHandler = failureHandler;
+  }
+  return self;
+}
+
++ (instancetype)successHandler:(GNCConnectionHandler)successHandler
+                failureHandler:(GNCConnectionFailureHandler)failureHandler {
+  return [[self alloc] initWithSuccessHandler:successHandler failureHandler:failureHandler];
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Internal/platform.mm

@@ -0,0 +1,151 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "third_party/nearby_connections/cpp/platform/api/platform.h"
+
+#include <string>
+
+#include "third_party/nearby_connections/cpp/platform/api/mutex.h"
+#include "third_party/nearby_connections/cpp/platform/base/payload_id.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Internal/GNCCore.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/atomic_boolean.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/atomic_uint32.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/condition_variable.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/count_down_latch.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/input_file.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/log_message.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/multi_thread_executor.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/mutex.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/scheduled_executor.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/single_thread_executor.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/wifi_lan.h"
+#include "third_party/nearby_connections/cpp/platform/impl/shared/file.h"
+
+namespace location {
+namespace nearby {
+namespace api {
+
+namespace {
+std::string GetPayloadPath(PayloadId payload_id) {
+  // This is to get a file path, e.g. /tmp/[payload_id], for the storage of payload file.
+  // NOTE: Per
+  // https://developer.apple.com/library/content/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/FileSystemOverview/FileSystemOverview.html
+  // Files saved in the /tmp directory will be deleted by the system. Callers should be responsible
+  // for copying the files to the permanent storage.
+  NSString *payloadIdString = ObjCStringFromCppString(std::to_string(payload_id));
+  return CppStringFromObjCString(
+      [NSTemporaryDirectory() stringByAppendingPathComponent:payloadIdString]);
+}
+}  // namespace
+
+// Atomics:
+std::unique_ptr<AtomicBoolean> ImplementationPlatform::CreateAtomicBoolean(bool initial_value) {
+  return std::make_unique<ios::AtomicBoolean>(initial_value);
+}
+
+std::unique_ptr<AtomicUint32> ImplementationPlatform::CreateAtomicUint32(
+    std::uint32_t initial_value) {
+  return std::make_unique<ios::AtomicUint32>(initial_value);
+}
+
+std::unique_ptr<CountDownLatch> ImplementationPlatform::CreateCountDownLatch(std::int32_t count) {
+  return std::make_unique<ios::CountDownLatch>(count);
+}
+
+std::unique_ptr<Mutex> ImplementationPlatform::CreateMutex(Mutex::Mode mode) {
+  // iOS does not support unchecked Mutex in debug mode, therefore
+  // ios::Mutex is used for both kRegular and kRegularNoCheck.
+  if (mode == Mutex::Mode::kRecursive) {
+    return absl::make_unique<ios::RecursiveMutex>();
+  } else {
+    return absl::make_unique<ios::Mutex>();
+  }
+}
+
+std::unique_ptr<ConditionVariable> ImplementationPlatform::CreateConditionVariable(Mutex* mutex) {
+  return std::make_unique<ios::ConditionVariable>(static_cast<ios::Mutex*>(mutex));
+}
+
+std::unique_ptr<InputFile> ImplementationPlatform::CreateInputFile(PayloadId payload_id,
+                                                                   std::int64_t total_size) {
+  // Extract the NSURL object with payload_id from |GNCCore| which stores the maps. If the retrieved
+  // NSURL object is not nil, we create InputFile by ios::InputFile. The difference is
+  // that ios::InputFile implements to read bytes from local real file for sending.
+  GNCCore* core = GNCGetCore();
+  NSURL* url = [core extractURLWithPayloadID:payload_id];
+  if (url != nil) {
+    return absl::make_unique<ios::InputFile>(url);
+  } else {
+    return absl::make_unique<shared::InputFile>(GetPayloadPath(payload_id), total_size);
+  }
+}
+
+std::unique_ptr<OutputFile> ImplementationPlatform::CreateOutputFile(PayloadId payload_id) {
+  return absl::make_unique<shared::OutputFile>(GetPayloadPath(payload_id));
+}
+
+std::unique_ptr<LogMessage> ImplementationPlatform::CreateLogMessage(
+    const char* file, int line, LogMessage::Severity severity) {
+  return absl::make_unique<ios::LogMessage>(file, line, severity);
+}
+
+// Java-like Executors
+std::unique_ptr<SubmittableExecutor> ImplementationPlatform::CreateSingleThreadExecutor() {
+  return std::make_unique<ios::SingleThreadExecutor>();
+}
+
+std::unique_ptr<SubmittableExecutor> ImplementationPlatform::CreateMultiThreadExecutor(
+    int max_concurrency) {
+  return std::make_unique<ios::MultiThreadExecutor>(max_concurrency);
+}
+
+std::unique_ptr<ScheduledExecutor> ImplementationPlatform::CreateScheduledExecutor() {
+  return std::make_unique<ios::ScheduledExecutor>();
+}
+
+// Mediums
+std::unique_ptr<BluetoothAdapter> ImplementationPlatform::CreateBluetoothAdapter() {
+  return nullptr;
+}
+
+std::unique_ptr<BluetoothClassicMedium> ImplementationPlatform::CreateBluetoothClassicMedium(
+    api::BluetoothAdapter& adapter) {
+  return nullptr;
+}
+
+std::unique_ptr<BleMedium> ImplementationPlatform::CreateBleMedium(api::BluetoothAdapter& adapter) {
+  return nullptr;
+}
+
+std::unique_ptr<ble_v2::BleMedium> ImplementationPlatform::CreateBleV2Medium(
+    api::BluetoothAdapter& adapter) {
+  return nullptr;
+}
+
+std::unique_ptr<ServerSyncMedium> ImplementationPlatform::CreateServerSyncMedium() {
+  return nullptr;
+}
+
+std::unique_ptr<WifiMedium> ImplementationPlatform::CreateWifiMedium() { return nullptr; }
+
+std::unique_ptr<WifiLanMedium> ImplementationPlatform::CreateWifiLanMedium() {
+  return std::make_unique<ios::WifiLanMedium>();
+}
+
+std::unique_ptr<WebRtcMedium> ImplementationPlatform::CreateWebRtcMedium() { return nullptr; }
+
+}  // namespace api
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Mediums/BUILD

@@ -0,0 +1,57 @@
+load("//tools/build_defs/apple:objc.bzl", "objc_proto_library")
+
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+licenses(["notice"])
+
+package(default_visibility = ["//platform/impl/ios:__subpackages__"])
+
+objc_library(
+    name = "Mediums",
+    srcs = [
+        "GNCLeaks.m",
+        "GNCMConnection.m",
+        "WifiLan/GNCMBonjourBrowser.m",
+        "WifiLan/GNCMBonjourConnection.m",
+        "WifiLan/GNCMBonjourService.m",
+        "WifiLan/GNCMBonjourUtils.m",
+    ],
+    hdrs = [
+        "GNCLeaks.h",
+        "GNCMConnection.h",
+        "WifiLan/GNCMBonjourBrowser.h",
+        "WifiLan/GNCMBonjourConnection.h",
+        "WifiLan/GNCMBonjourService.h",
+        "WifiLan/GNCMBonjourUtils.h",
+    ],
+    deps = [
+        ":ObjCProtos",
+        "//base",
+        "//absl/numeric:int128",
+        "//platform/impl/ios/Source/Shared",
+        "//third_party/objective_c/google_toolbox_for_mac:GTM_Logger",
+    ],
+)
+
+objc_proto_library(
+    name = "ObjCProtos",
+    deps = [":Protos"],
+)
+
+proto_library(
+    name = "Protos",
+    deps = [
+        "//proto/connections:offline_wire_formats_proto",
+    ],
+)

cpp/platform/impl/ios/Source/Mediums/GNCLeaks.h

@@ -0,0 +1,18 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+// Verifies that an object has been deallocated after the given time period.
+void GNCVerifyDealloc(id object, NSTimeInterval timeInterval);

cpp/platform/impl/ios/Source/Mediums/GNCLeaks.m

@@ -0,0 +1,27 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCLeaks.h"
+
+void GNCVerifyDealloc(id object, NSTimeInterval timeInterval) {
+#if DEBUG
+  __weak id weakObj = object;
+  NSCAssert(weakObj != nil, @"Pointer to %@ is already nil", weakObj);
+  NSLog(@"Verifying deallocation of %@", NSStringFromClass([weakObj class]));
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(timeInterval * NSEC_PER_SEC)),
+                 dispatch_get_main_queue(), ^{
+                   NSCAssert(weakObj == nil, @"%@ not deallocated.", weakObj);
+                 });
+#endif
+}

cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h

@@ -0,0 +1,101 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** Result of a medium payload transfer. */
+typedef NS_ENUM(NSInteger, GNCMPayloadResult) {
+  GNCMPayloadResultSuccess,   // Payload delivery was successful.
+  GNCMPayloadResultFailure,   // An error occurred during payload delivery.
+  GNCMPayloadResultCanceled,  // Payload delivery was canceled.
+};
+
+/** Handler for a @c GNCMPayloadResult value. */
+typedef void (^GNCMPayloadResultHandler)(GNCMPayloadResult);
+
+/**
+ * A progress handler is periodically called during payload delivery. It is passed a value
+ * ranging from 0 (when the operation has just started) to the total size (when the operation is
+ * finished).
+ */
+typedef void (^GNCMProgressHandler)(size_t count);
+
+/** This handler is called when data is received from a remote endpoint. */
+typedef void (^GNCMPayloadHandler)(NSData *data);
+
+/**
+ * This represents a connection with a remote endpoint at the medium level. Use it to send
+ * payloads to the remote endpoint, and release it to disconnect.
+ */
+@protocol GNCMConnection <NSObject>
+
+/**
+ * Sends data to the remote endpoint. Wait for the completion to be called before sending another
+ * payload.
+ *
+ * @param payload         The data to send.
+ * @param progressHandler Called repeatedly for progress feedback while the data is being sent.
+ * @param completion      Callback called when the data has been fully sent,
+ *                        or it has failed to be sent (not connected or disconnected).
+ */
+- (void)sendData:(NSData *)payload
+    progressHandler:(GNCMProgressHandler)progressHandler
+         completion:(GNCMPayloadResultHandler)completion;
+
+@end
+
+/** This class contains optional handlers for a connection. */
+@interface GNCMConnectionHandlers : NSObject
+
+/** This handler is called when data is sent from the remote endpoint. */
+@property(nonatomic) GNCMPayloadHandler payloadHandler;
+
+/** This handler is called when the connection is ended. */
+@property(nonatomic) dispatch_block_t disconnectedHandler;
+
+/** This method creates a GNCMConnectionHandlers object from payload and disconnect handlers. */
++ (instancetype)payloadHandler:(GNCMPayloadHandler)payloadHandler
+           disconnectedHandler:(dispatch_block_t)disconnectedHandler;
+
+@end
+
+/**
+ * This handler takes a GNCMConnection object and returns a GNCMConnectionHandlers object. It is
+ * called when a connection is successfully made with a remote endpoint. If |connection| is nil,
+ * the connection couldn't be established; in this case, return nil.
+ */
+typedef GNCMConnectionHandlers *_Nullable (^GNCMConnectionHandler)(
+    id<GNCMConnection> __nullable connection);
+
+/**
+ * This handler is called by a discovering endpoint to request a connection with an an advertising
+ * endpoint.
+ */
+typedef void (^GNCMConnectionRequester)(GNCMConnectionHandler connectionHandler);
+
+/** This handler is called when a previously discovered advertising endpoint is lost. */
+typedef void (^GNCMEndpointLostHandler)(void);
+
+/**
+ * This handler is called on a discoverer when a nearby advertising endpoint is
+ * discovered. Calls |requestConnection| to request a connection with the advertiser.
+ */
+typedef GNCMEndpointLostHandler _Nonnull (^GNCMEndpointFoundHandler)(
+    NSString *endpointId, NSString *serviceType, NSString *serviceName,
+    NSDictionary<NSString *, NSData *> *_Nullable TXTRecordData,
+    GNCMConnectionRequester requestConnection);
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Mediums/GNCMConnection.m

@@ -0,0 +1,31 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@implementation GNCMConnectionHandlers
+
++ (instancetype)payloadHandler:(GNCMPayloadHandler)payloadHandler
+           disconnectedHandler:(dispatch_block_t)disconnectedHandler {
+  GNCMConnectionHandlers *handlers = [[GNCMConnectionHandlers alloc] init];
+  handlers.payloadHandler = payloadHandler;
+  handlers.disconnectedHandler = disconnectedHandler;
+  return handlers;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourBrowser.h

@@ -0,0 +1,42 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * GNCMBonjourBrowser browses mDNS services publishing the specified mDNS type and domain. The mDNS
+ * type is a string formatted as "_[serviceIdHash]._tcp." in which [serviceIdHash] is generated as
+ * a SHA-256 hash from the service ID and taken the 6 first bytes of string in upper case.
+ * Calls the specififed endpoint found handler when one is found. The endpoint found handler
+ * supplies a requester block, which can be called to establish a socket to the service found.
+ *
+ * Don't hold the strong reference of caller self in endpointFoundHandler to ensure there is no
+ * retain cycle between them.
+ *
+ * @param serviceType An mDNS type that uniquely identifies the published service to search for.
+ * @param endpointFoundHandler The handler that is called when an endpoint publishing the service
+ *                             ID is discovered.
+ */
+@interface GNCMBonjourBrowser : NSObject
+
+- (instancetype)initWithServiceType:(NSString *)serviceType
+               endpointFoundHandler:(GNCMEndpointFoundHandler)handler;
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourBrowser.m

@@ -0,0 +1,176 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourBrowser.h"
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourUtils.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+typedef NSString *GNCEndpointId;
+
+@interface GNCMNetServiceInfo : NSObject
+@property(nonatomic) NSNetService *service;
+@property(nonatomic, copy) GNCMEndpointLostHandler endpointLostHandler;
+@property(nonatomic, copy, nullable) GNCMConnectionHandler connectionHandler;
+@end
+
+@implementation GNCMNetServiceInfo
+
++ (instancetype)infoWithService:(NSNetService *)service {
+  GNCMNetServiceInfo *info = [[GNCMNetServiceInfo alloc] init];
+  info.service = service;
+  return info;
+}
+
+- (BOOL)isEqual:(GNCMNetServiceInfo *)object {
+  return [_service isEqual:object.service];
+}
+
+- (NSUInteger)hash {
+  return [_service hash];
+}
+
+@end
+
+@interface GNCMBonjourBrowser () <NSNetServiceBrowserDelegate, NSNetServiceDelegate>
+
+@property(nonatomic, copy) GNCMEndpointFoundHandler endpointFoundHandler;
+
+@property(nonatomic) NSNetServiceBrowser *netBrowser;
+@property(nonatomic) NSMutableDictionary<GNCEndpointId, GNCMNetServiceInfo *> *endpoints;
+
+@end
+
+@implementation GNCMBonjourBrowser
+
+- (instancetype)initWithServiceType:(NSString *)serviceType
+               endpointFoundHandler:(GNCMEndpointFoundHandler)handler {
+  self = [super init];
+  if (self) {
+    _endpointFoundHandler = handler;
+
+    _netBrowser = [[NSNetServiceBrowser alloc] init];
+    _netBrowser.delegate = self;
+    [_netBrowser scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
+    [_netBrowser searchForServicesOfType:serviceType inDomain:GNCMBonjourDomain];
+    _endpoints = [NSMutableDictionary dictionary];
+  }
+  return self;
+}
+
+#pragma mark NSNetServiceBrowserDelegate
+
+- (void)netServiceBrowserWillSearch:(NSNetServiceBrowser *)browser {
+  GTMLoggerDebug(@"Browsing");
+}
+
+- (void)netServiceBrowserDidStopSearch:(NSNetServiceBrowser *)browser {
+  GTMLoggerDebug(@"Stop browsing");
+}
+
+- (void)netServiceBrowser:(NSNetServiceBrowser *)browser
+             didNotSearch:(NSDictionary<NSString *, NSNumber *> *)errorDict {
+  GTMLoggerDebug(@"Not browsing with errorDict: %@", errorDict);
+}
+
+- (void)netServiceBrowser:(NSNetServiceBrowser *)browser
+           didFindService:(NSNetService *)service
+               moreComing:(BOOL)moreComing {
+  GTMLoggerDebug(@"Found service: %@", service);
+
+  GNCMNetServiceInfo *info = [GNCMNetServiceInfo infoWithService:service];
+
+  // Just to be safe, check if the service is already known and deal with it accordingly.
+  NSArray<GNCEndpointId> *endpointIds = [_endpoints allKeysForObject:info];
+  if (endpointIds.count > 0) return;
+
+  // Add the newly discovered service to the list of services.
+  GNCEndpointId endpointId = [[NSUUID UUID] UUIDString];
+  _endpoints[endpointId] = info;
+
+  service.delegate = self;
+  [service resolveWithTimeout:0];
+}
+
+- (void)netServiceBrowser:(NSNetServiceBrowser *)browser
+         didRemoveService:(NSNetService *)service
+               moreComing:(BOOL)moreComing {
+  GTMLoggerDebug(@"Lost service: %@", service);
+  NSArray<GNCEndpointId> *endpointIds =
+      [_endpoints allKeysForObject:[GNCMNetServiceInfo infoWithService:service]];
+  NSAssert(endpointIds.count <= 1, @"Unexpected duplicate service");
+  if (endpointIds.count > 0) {
+    GNCEndpointId endpointId = endpointIds[0];
+    GNCMNetServiceInfo *info = _endpoints[endpointId];
+    [_endpoints removeObjectForKey:endpointId];
+    // Tail call to preserve reentrancy.
+    if (info.endpointLostHandler) {
+      info.endpointLostHandler();
+    }
+  }
+}
+
+#pragma mark NSNetServiceDelegate
+
+- (void)netServiceDidResolveAddress:(NSNetService *)service {
+  GTMLoggerDebug(@"Resolved service: %@ addresses: %@", service, service.addresses);
+
+  GNCMNetServiceInfo *info = [GNCMNetServiceInfo infoWithService:service];
+
+  NSArray<GNCEndpointId> *endpointIds = [_endpoints allKeysForObject:info];
+  if (endpointIds.count > 0) {
+    // Get TXTRecord data.
+    NSData *data = [service TXTRecordData];
+    NSDictionary<NSString *, NSData *> *TXTRecordData =
+        [NSNetService dictionaryFromTXTRecordData:data];
+
+    // The endpointLostHandler is returned from the endpointFoundHandler. The main benefit of this
+    // is that it allows rejection from the remote endpoint to be received by the local endpoint
+    // before the local endpoint has accepted or rejected.
+    info.endpointLostHandler = _endpointFoundHandler(
+        endpointIds[0], service.type, service.name, TXTRecordData,
+        ^(GNCMConnectionHandler connectionHandler) {
+          // A connection is requested, so resolve the service to get the I/O streams.
+          info.connectionHandler = connectionHandler;
+          if (info.connectionHandler) {
+            dispatch_sync(dispatch_get_main_queue(), ^{
+              NSInputStream *inputStream;
+              NSOutputStream *outputStream;
+              [info.service scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
+              [info.service getInputStream:&inputStream outputStream:&outputStream];
+              GNCMBonjourConnection *connection =
+                  [[GNCMBonjourConnection alloc] initWithInputStream:inputStream
+                                                        outputStream:outputStream
+                                                               queue:nil];
+              connection.connectionHandlers = info.connectionHandler(connection);
+            });
+          }
+        });
+    _endpoints[endpointIds[0]] = info;
+  }
+}
+
+- (void)netService:(NSNetService *)service
+     didNotResolve:(NSDictionary<NSString *, NSNumber *> *)errorDict {
+  GTMLoggerDebug(@"Did not resolve service: %@", service);
+  NSArray<GNCEndpointId> *endpointIds =
+      [_endpoints allKeysForObject:[GNCMNetServiceInfo infoWithService:service]];
+  if (endpointIds.count > 0) {
+    _endpoints[endpointIds[0]].connectionHandler = nil;
+  }
+}
+
+@end

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourConnection.h

@@ -0,0 +1,38 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * This medium connection sends and receives payloads over the NSInputStream and NSOutputStream
+ * passed to it.
+ *
+ * @param inputStream The input stream to read from.
+ * @param outputStream The output stream to write to.
+ * @param queue The queue on which the GNCMConnection callbacks will be called. If nil, the main
+ *              queue is used.
+ */
+@interface GNCMBonjourConnection : NSObject <GNCMConnection>
+@property(nonatomic) GNCMConnectionHandlers *connectionHandlers;
+
+- (instancetype)initWithInputStream:(NSInputStream *)inputStream
+                       outputStream:(NSOutputStream *)outputStream
+                              queue:(nullable dispatch_queue_t)queue;
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourConnection.m

@@ -0,0 +1,207 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourConnection.h"
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+enum { kMaxPacketSize = 32 * 1024 };
+
+@interface GNCMBonjourConnection () <NSStreamDelegate>
+@property(nonatomic) NSInputStream *inputStream;
+@property(nonatomic) NSOutputStream *outputStream;
+@property(nonatomic) dispatch_queue_t callbackQueue;
+
+@property(nonatomic, copy, nullable) NSData *dataBeingWritten;
+@property(nonatomic) NSInteger numberOfBytesLeftToWrite;
+@property(nonatomic, copy, nullable) GNCMProgressHandler progressHandler;
+@property(nonatomic, copy, nullable) GNCMPayloadResultHandler completion;
+@end
+
+@implementation GNCMBonjourConnection
+
+- (instancetype)initWithInputStream:(NSInputStream *)inputStream
+                       outputStream:(NSOutputStream *)outputStream
+                              queue:(nullable dispatch_queue_t)queue {
+  self = [super init];
+  if (self) {
+    _inputStream = inputStream;
+    _inputStream.delegate = self;
+    [_inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
+    [_inputStream open];
+
+    _outputStream = outputStream;
+    _outputStream.delegate = self;
+    [_outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
+    [_outputStream open];
+
+    _callbackQueue = queue;
+  }
+  return self;
+}
+
+- (void)dealloc {
+  [self closeStreams];
+}
+
+- (void)sendData:(NSData *)payload
+    progressHandler:(GNCMProgressHandler)progressHandler
+         completion:(GNCMPayloadResultHandler)completion {
+  if (_dataBeingWritten) {
+    GTMLoggerInfo(@"Attempting to send payload while one is already in flight");
+    [self dispatchCallback:^{
+      completion(GNCMPayloadResultFailure);
+    }];
+    return;
+  }
+
+  self.dataBeingWritten = payload;
+  self.numberOfBytesLeftToWrite = payload.length;
+  self.progressHandler = progressHandler;
+  self.completion = completion;
+  [self writeChunk];
+}
+
+#pragma mark NSStreamDelegate
+
+- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)event {
+  switch (event) {
+    case NSStreamEventHasBytesAvailable: {
+      // Data has arrived on the input stream.
+      NSAssert(stream == _inputStream, @"Error: Expected input stream");
+
+      if (_connectionHandlers.payloadHandler) {
+        uint8_t bytesRead[kMaxPacketSize];
+        NSInteger numberOfBytesRead;
+        @synchronized(self.inputStream) {
+          numberOfBytesRead = [self.inputStream read:bytesRead maxLength:kMaxPacketSize];
+        }
+        NSData *data = nil;
+        if (numberOfBytesRead > 0) {
+          GTMLoggerInfo(@"Read %lu bytes", (u_long)numberOfBytesRead);
+          data = [NSData dataWithBytes:bytesRead length:numberOfBytesRead];
+        }
+        [self dispatchCallback:^{
+          self.connectionHandlers.payloadHandler(data ?: [NSData data]);
+        }];
+      }
+      break;
+    }
+
+    case NSStreamEventHasSpaceAvailable:
+      // There is space available on the output stream.
+      NSAssert(stream == _outputStream, @"Error: Expected output stream");
+
+      // Schedule this in a future runloop cycle because -writeChunk, which can cause this event
+      // to be received synchronously, is not reentrant.
+      [self performSelector:@selector(writeChunk) withObject:nil afterDelay:0.0];
+      break;
+
+    case NSStreamEventErrorOccurred:
+      GTMLoggerInfo(@"Stream error: %@", [stream streamError]);
+      // Fall through.
+    case NSStreamEventEndEncountered: {
+      GTMLoggerInfo(@"Stream closing");
+      [self closeStreams];
+      if (_connectionHandlers.disconnectedHandler) {
+        [self dispatchCallback:^{
+          self.connectionHandlers.disconnectedHandler();
+        }];
+      }
+      break;
+    }
+
+    case NSStreamEventOpenCompleted:
+    case NSStreamEventNone:
+    default:
+      break;
+  }
+}
+
+#pragma mark Private
+
+// Calls a block on the callback queue.
+- (void)dispatchCallback:(dispatch_block_t)block {
+  dispatch_async(_callbackQueue ?: dispatch_get_main_queue(), block);
+}
+
+// Writes a chunk of the outgoing data to the output stream, calling the progress and completion
+// handlers as needed.
+- (void)writeChunk {
+  void (^reportProgress)(size_t) = ^(size_t count) {
+    // Captures the progress handler because the property is nilled out below.
+    GNCMProgressHandler progressHandler = _progressHandler;
+    if (progressHandler != nil) {
+      [self dispatchCallback:^{
+        progressHandler(count);
+      }];
+    }
+  };
+
+  void (^completed)(GNCMPayloadResult) = ^(GNCMPayloadResult result) {
+    reportProgress(_dataBeingWritten.length);
+    _progressHandler = nil;
+    _dataBeingWritten = nil;
+
+    // Captures the completion because the property is nilled out below.
+    GNCMPayloadResultHandler completion = _completion;
+    if (completion != nil) {
+      [self dispatchCallback:^{
+        completion(result);
+      }];
+    }
+    _completion = nil;
+  };
+
+  @synchronized(_outputStream) {
+    if (_numberOfBytesLeftToWrite) {
+      NSUInteger dataLength = (UInt32)_dataBeingWritten.length;
+      if (_numberOfBytesLeftToWrite == dataLength) {
+        GTMLoggerInfo(@"Starting a write operation of length %lu", (u_long)dataLength);
+      }
+      NSInteger numberOfPayloadBytesWritten =
+          [_outputStream write:&_dataBeingWritten.bytes[dataLength - _numberOfBytesLeftToWrite]
+                     maxLength:_numberOfBytesLeftToWrite];
+
+      GTMLoggerInfo(@"Wrote %lu bytes", (u_long)numberOfPayloadBytesWritten);
+      if (numberOfPayloadBytesWritten >= 0) {
+        _numberOfBytesLeftToWrite -= numberOfPayloadBytesWritten;
+        reportProgress(_dataBeingWritten.length - _numberOfBytesLeftToWrite);
+        if (_numberOfBytesLeftToWrite < 0) {
+          GTMLoggerInfo(@"Unexpected number of bytes written");
+          _numberOfBytesLeftToWrite = 0;
+        }
+        if (_numberOfBytesLeftToWrite == 0) completed(GNCMPayloadResultSuccess);
+      } else {
+        GTMLoggerInfo(@"Error writing to output stream");
+        completed(GNCMPayloadResultFailure);
+      }
+    }
+  }
+}
+
+- (void)closeStreams {
+  @synchronized(_inputStream) {
+    [_inputStream close];
+    _inputStream = nil;
+  }
+
+  @synchronized(_outputStream) {
+    [_outputStream close];
+    _outputStream = nil;
+  }
+}
+
+@end

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourService.h

@@ -0,0 +1,49 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * GNCMBonjourService publishes mDNS type and domain with the specified service ID via Apple
+ * Bonjour service. The mDNS type is a string formatted as "_[serviceIdHash]._tcp." in which
+ * [serviceIdHash] is generated as a SHA-256 hash from the service ID and taken the 6 first bytes
+ * of string in upper case.
+ * When the service connects, the specified |endpointConnectedHandler| is called, which establishes
+ * a connection to the browser.
+ *
+ * Don't hold the strong reference of caller self in endpointConnectedHandler to ensure there is no
+ * retain cycle between them.
+ *
+ * @param serviceName A service name that embeds the |WifiLanServiceInfo| information.
+ * @param serviceType An mDNS type that uniquely identifies the published service to search for.
+ * @param port The requesting socket port number.
+ * @param txtRecordData The TXTRecord data.
+ * @param endpointConnectedHandler The handler that is called when a browser connects.
+ */
+@interface GNCMBonjourService : NSObject
+
+- (instancetype)initWithServiceName:(NSString *)serviceName
+                        serviceType:(NSString *)serviceType
+                               port:(NSInteger)port
+                      TXTRecordData:(NSDictionary<NSString *, NSData *> *)TXTRecordData
+           endpointConnectedHandler:(GNCMConnectionHandler)handler;
+
+@end
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourService.m

@@ -0,0 +1,88 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourService.h"
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourUtils.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+@interface GNCMBonjourService () <NSNetServiceDelegate>
+
+@property(nonatomic, copy) NSString *serviceName;
+@property(nonatomic, copy) NSString *serviceType;
+@property(nonatomic, copy) GNCMConnectionHandler endpointConnectedHandler;
+
+@property(nonatomic) NSNetService *netService;
+
+@end
+
+@implementation GNCMBonjourService
+
+- (instancetype)initWithServiceName:(NSString *)serviceName
+                        serviceType:(NSString *)serviceType
+                               port:(NSInteger)port
+                      TXTRecordData:(NSDictionary<NSString *, NSData *> *)TXTRecordData
+           endpointConnectedHandler:(GNCMConnectionHandler)handler {
+  self = [super init];
+  if (self) {
+    _serviceName = [serviceName copy];
+    _serviceType = [serviceType copy];
+    _endpointConnectedHandler = handler;
+
+    _netService = [[NSNetService alloc] initWithDomain:GNCMBonjourDomain
+                                                  type:_serviceType
+                                                  name:_serviceName
+                                                  port:port];
+    [_netService setTXTRecordData:[NSNetService dataFromTXTRecordDictionary:TXTRecordData]];
+
+    _netService.delegate = self;
+    [_netService scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
+    [_netService publishWithOptions:NSNetServiceListenForConnections];
+  }
+  return self;
+}
+
+- (void)dealloc {
+  [_netService stop];
+}
+
+#pragma mark NSNetServiceDelegate
+
+- (void)netServiceDidPublish:(NSNetService *)service {
+  GTMLoggerDebug(@"Did publish service: %@", service);
+}
+
+- (void)netService:(NSNetService *)service
+     didNotPublish:(NSDictionary<NSString *, NSNumber *> *)errorDict {
+  GTMLoggerDebug(@"Error publishing: service: %@, errorDic: %@", service, errorDict);
+}
+
+- (void)netServiceDidStop:(NSNetService *)service {
+  GTMLoggerDebug(@"Stopped publishing service: %@", service);
+}
+
+- (void)netService:(NSNetService *)service
+    didAcceptConnectionWithInputStream:(NSInputStream *)inputStream
+                          outputStream:(NSOutputStream *)outputStream {
+  GTMLoggerDebug(@"Accepted connection, service: %@", service);
+  GNCMBonjourConnection *connection =
+      [[GNCMBonjourConnection alloc] initWithInputStream:inputStream
+                                            outputStream:outputStream
+                                                   queue:nil];
+  connection.connectionHandlers = _endpointConnectedHandler(connection);
+}
+
+@end

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourUtils.h

@@ -0,0 +1,18 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+// mDNS domain.
+FOUNDATION_EXPORT NSString *_Nonnull const GNCMBonjourDomain;

cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourUtils.m

@@ -0,0 +1,17 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourUtils.h"
+
+NSString *const GNCMBonjourDomain = @"local";

cpp/platform/impl/ios/Source/Platform/BUILD

@@ -0,0 +1,93 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+licenses(["notice"])
+
+package(default_visibility = ["//platform/impl/ios:__subpackages__"])
+
+objc_library(
+    name = "Platform",
+    srcs = [
+        "crypto.mm",
+        "input_file.mm",
+        "log_message.mm",
+        "multi_thread_executor.mm",
+        "scheduled_executor.mm",
+        "utils.mm",
+        "wifi_lan.mm",
+    ],
+    hdrs = [
+        "input_file.h",
+        "log_message.h",
+        "multi_thread_executor.h",
+        "scheduled_executor.h",
+        "single_thread_executor.h",
+        "utils.h",
+        "wifi_lan.h",
+    ],
+    sdk_frameworks = [
+        "CoreBluetooth",
+        "CoreFoundation",
+    ],
+    deps = [
+        ":Platform_cc",
+        "//platform/api:platform",
+        "//platform/api:types",
+        "//platform/impl/ios/Source/Mediums",
+        "//platform/impl/ios/Source/Shared",
+        "//platform/impl/shared:file",
+        "//third_party/objective_c/google_toolbox_for_mac:GTM_Logger",
+    ],
+)
+
+cc_library(
+    name = "Platform_cc",
+    srcs = [
+        "condition_variable.cc",
+        "count_down_latch.cc",
+        "system_clock.cc",
+    ],
+    hdrs = [
+        "atomic_boolean.h",
+        "atomic_uint32.h",
+        "condition_variable.h",
+        "count_down_latch.h",
+        "mutex.h",
+    ],
+    deps = [
+        "//absl/strings:str_format",
+        "//absl/synchronization",
+        "//absl/time",
+        "//platform/api:platform",
+        "//platform/api:types",
+    ],
+)
+
+cc_test(
+    name = "Platform_cc_test",
+    srcs = [
+        "atomic_boolean_test.cc",
+        "atomic_uint32_test.cc",
+        "condition_variable_test.cc",
+        "count_down_latch_test.cc",
+        "mutex_test.cc",
+    ],
+    shard_count = 16,
+    deps = [
+        ":Platform_cc",
+        "//testing/base/public:gunit_main",
+        "//absl/synchronization",
+        "//absl/time",
+        "//thread/fiber",
+    ],
+)

cpp/platform/impl/ios/Source/Platform/atomic_boolean.h

@@ -0,0 +1,46 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_ATOMIC_BOOLEAN_H_
+#define PLATFORM_IMPL_IOS_ATOMIC_BOOLEAN_H_
+
+#include <atomic>
+
+#include "platform/api/atomic_boolean.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete AtomicBoolean implementation.
+class AtomicBoolean : public api::AtomicBoolean {
+ public:
+  explicit AtomicBoolean(bool initial_value) : value_(initial_value) {}
+  ~AtomicBoolean() override = default;
+
+  AtomicBoolean(const AtomicBoolean&) = delete;
+  AtomicBoolean& operator=(const AtomicBoolean&) = delete;
+
+  bool Get() const override { return value_.load(); }
+  bool Set(bool value) override { return value_.exchange(value); }
+
+ private:
+  std::atomic_bool value_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_ATOMIC_BOOLEAN_H_

cpp/platform/impl/ios/Source/Platform/atomic_boolean_test.cc

@@ -0,0 +1,78 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/atomic_boolean.h"
+
+#include "gtest/gtest.h"
+#include "thread/fiber/fiber.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+namespace {
+
+TEST(AtomicBooleanTest, SetOnSameThread) {
+  AtomicBoolean atomic_boolean_{false};
+
+  EXPECT_EQ(false, atomic_boolean_.Get());
+
+  atomic_boolean_.Set(true);
+  EXPECT_EQ(true, atomic_boolean_.Get());
+}
+
+TEST(AtomicBooleanTest, MultipleSetGetOnSameThread) {
+  AtomicBoolean atomic_boolean_{false};
+
+  EXPECT_EQ(false, atomic_boolean_.Get());
+
+  atomic_boolean_.Set(true);
+  EXPECT_EQ(true, atomic_boolean_.Get());
+
+  atomic_boolean_.Set(true);
+  EXPECT_EQ(true, atomic_boolean_.Get());
+
+  atomic_boolean_.Set(false);
+  EXPECT_EQ(false, atomic_boolean_.Get());
+
+  atomic_boolean_.Set(true);
+  EXPECT_EQ(true, atomic_boolean_.Get());
+}
+
+TEST(AtomicBooleanTest, SetOnNewThread) {
+  AtomicBoolean atomic_boolean_{false};
+
+  EXPECT_EQ(false, atomic_boolean_.Get());
+
+  thread::Fiber f([&] { atomic_boolean_.Set(true); });
+  f.Join();
+
+  EXPECT_EQ(true, atomic_boolean_.Get());
+}
+
+TEST(AtomicBooleanTest, GetOnNewThread) {
+  AtomicBoolean atomic_boolean_{false};
+
+  EXPECT_EQ(false, atomic_boolean_.Get());
+
+  atomic_boolean_.Set(true);
+  EXPECT_EQ(true, atomic_boolean_.Get());
+
+  thread::Fiber f([&] { EXPECT_EQ(true, atomic_boolean_.Get()); });
+  f.Join();
+}
+
+}  // namespace
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/atomic_uint32.h

@@ -0,0 +1,47 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_ATOMIC_UINT32_H_
+#define PLATFORM_IMPL_IOS_ATOMIC_UINT32_H_
+
+#include <atomic>
+#include <cstdint>
+
+#include "platform/api/atomic_reference.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete AtomicUint32 implementation.
+class AtomicUint32 : public api::AtomicUint32 {
+ public:
+  explicit AtomicUint32(std::uint32_t initial_value) : value_(initial_value) {}
+  ~AtomicUint32() override = default;
+
+  AtomicUint32(const AtomicUint32&) = delete;
+  AtomicUint32& operator=(const AtomicUint32&) = delete;
+
+  std::uint32_t Get() const override { return value_; }
+  void Set(std::uint32_t value) override { value_ = value; }
+
+ private:
+  std::atomic<std::uint32_t> value_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_ATOMIC_UINT32_H_

cpp/platform/impl/ios/Source/Platform/atomic_uint32_test.cc

@@ -0,0 +1,64 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/atomic_uint32.h"
+
+#include "gtest/gtest.h"
+#include "thread/fiber/fiber.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+namespace {
+
+TEST(AtomicUint32Test, GetOnSameThread) {
+  std::uint32_t initial_value = 1450;
+  AtomicUint32 atomic_reference_{initial_value};
+
+  EXPECT_EQ(initial_value, atomic_reference_.Get());
+}
+
+TEST(AtomicUint32Test, SetGetOnSameThread) {
+  std::uint32_t initial_value_ = 1450;
+  AtomicUint32 atomic_reference_{initial_value_};
+
+  std::uint32_t new_value = 28;
+  atomic_reference_.Set(new_value);
+  EXPECT_EQ(new_value, atomic_reference_.Get());
+}
+
+TEST(AtomicUint32Test, SetOnNewThread) {
+  std::uint32_t initial_value_ = 1450;
+  AtomicUint32 atomic_reference_{initial_value_};
+
+  std::uint32_t new_thread_value = 28;
+  thread::Fiber f([&] { atomic_reference_.Set(new_thread_value); });
+  f.Join();
+  EXPECT_EQ(new_thread_value, atomic_reference_.Get());
+}
+
+TEST(AtomicUint32Test, GetOnNewThread) {
+  std::uint32_t initial_value_ = 1450;
+  AtomicUint32 atomic_reference_{initial_value_};
+
+  std::uint32_t new_value = 28;
+  atomic_reference_.Set(new_value);
+  thread::Fiber f([&] { EXPECT_EQ(new_value, atomic_reference_.Get()); });
+  f.Join();
+}
+
+}  // namespace
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/condition_variable.cc

@@ -0,0 +1,37 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/condition_variable.h"
+
+#include "platform/impl/ios/Source/Platform/mutex.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+Exception ConditionVariable::Wait() {
+  condition_variable_.Wait(mutex_);
+  return {Exception::kSuccess};
+}
+
+Exception ConditionVariable::Wait(absl::Duration timeout) {
+  condition_variable_.WaitWithTimeout(mutex_, timeout);
+  return {Exception::kSuccess};
+}
+
+void ConditionVariable::Notify() { condition_variable_.SignalAll(); }
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/condition_variable.h

@@ -0,0 +1,48 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_CONDITION_VARIABLE_H_
+#define PLATFORM_IMPL_IOS_CONDITION_VARIABLE_H_
+
+#include "absl/synchronization/mutex.h"
+#include "platform/api/condition_variable.h"
+#include "platform/impl/ios/Source/Platform/mutex.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete ConditionVariable implementation.
+class ConditionVariable : public api::ConditionVariable {
+ public:
+  explicit ConditionVariable(ios::Mutex* mutex) : mutex_(&mutex->mutex_) {}
+  ~ConditionVariable() override = default;
+
+  ConditionVariable(const ConditionVariable&) = delete;
+  ConditionVariable& operator=(const ConditionVariable&) = delete;
+
+  Exception Wait() override;
+  Exception Wait(absl::Duration timeout) override;
+  void Notify() override;
+
+ private:
+  absl::Mutex* mutex_;
+  absl::CondVar condition_variable_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_CONDITION_VARIABLE_H_

cpp/platform/impl/ios/Source/Platform/condition_variable_test.cc

@@ -0,0 +1,84 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/condition_variable.h"
+
+#include "gtest/gtest.h"
+#include "absl/time/clock.h"
+#include "platform/impl/ios/Source/Platform/mutex.h"
+#include "thread/fiber/fiber.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+namespace {
+
+TEST(ConditionVariableTest, CanCreate) {
+  Mutex mutex{};
+  ConditionVariable cond{&mutex};
+}
+
+TEST(ConditionVariableTest, CanWakeupWaiter) {
+  Mutex mutex{};
+  ConditionVariable cond{&mutex};
+  bool done = false;
+  bool waiting = false;
+  {
+    thread::Fiber f([&cond, &mutex, &done, &waiting] {
+      mutex.Lock();
+      waiting = true;
+      cond.Wait();
+      waiting = false;
+      done = true;
+      mutex.Unlock();
+    });
+    while (true) {
+      {
+        mutex.Lock();
+        if (waiting) {
+          mutex.Unlock();
+          break;
+        }
+        mutex.Unlock();
+      }
+      absl::SleepFor(absl::Milliseconds(100));
+    }
+    {
+      mutex.Lock();
+      cond.Notify();
+      EXPECT_FALSE(done);
+      mutex.Unlock();
+    }
+    f.Join();
+  }
+  EXPECT_TRUE(done);
+}
+
+TEST(ConditionVariableTest, WaitTerminatesOnTimeoutWithoutNotify) {
+  Mutex mutex{};
+  ConditionVariable cond{&mutex};
+  mutex.Lock();
+
+  const absl::Duration kWaitTime = absl::Milliseconds(100);
+  absl::Time start = absl::Now();
+  cond.Wait(kWaitTime);
+  absl::Duration duration = absl::Now() - start;
+  EXPECT_GE(duration, kWaitTime);
+  mutex.Unlock();
+}
+
+}  // namespace
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/count_down_latch.cc

@@ -0,0 +1,40 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/count_down_latch.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+Exception CountDownLatch::Await() {
+  absl::MutexLock lock(&mutex_, absl::Condition(IsZeroOrNegative, &count_));
+  return {Exception::kSuccess};
+}
+
+ExceptionOr<bool> CountDownLatch::Await(absl::Duration timeout) {
+  bool condition = mutex_.LockWhenWithTimeout(
+      absl::Condition(IsZeroOrNegative, &count_), timeout);
+  mutex_.Unlock();
+  return ExceptionOr<bool>(condition);
+}
+
+void CountDownLatch::CountDown() {
+  absl::MutexLock lock(&mutex_);
+  count_--;
+}
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/count_down_latch.h

@@ -0,0 +1,49 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_COUNT_DOWN_LATCH_H_
+#define PLATFORM_IMPL_IOS_COUNT_DOWN_LATCH_H_
+
+#include "absl/synchronization/mutex.h"
+#include "platform/api/count_down_latch.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete CountDownLatch implementation.
+class CountDownLatch : public api::CountDownLatch {
+ public:
+  explicit CountDownLatch(int count) : count_(count) {}
+  ~CountDownLatch() override = default;
+
+  CountDownLatch(const CountDownLatch&) = delete;
+  CountDownLatch& operator=(const CountDownLatch&) = delete;
+
+  Exception Await() override;
+  ExceptionOr<bool> Await(absl::Duration timeout) override;
+  void CountDown() override;
+
+ private:
+  static bool IsZeroOrNegative(int* count) { return 0 >= *count; }
+
+  absl::Mutex mutex_;
+  int count_ ABSL_GUARDED_BY(mutex_);
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_COUNT_DOWN_LATCH_H_

cpp/platform/impl/ios/Source/Platform/count_down_latch_test.cc

@@ -0,0 +1,83 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/count_down_latch.h"
+
+#include "gtest/gtest.h"
+#include "thread/fiber/fiber.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+namespace {
+
+TEST(CountDownLatchTest, LatchAwaitCanWait) {
+  CountDownLatch latch(1);
+  std::atomic_bool done = false;
+
+  thread::Fiber f([&done, &latch] {
+    done = true;
+    latch.CountDown();
+  });
+  f.Join();
+
+  latch.Await();
+  EXPECT_TRUE(done);
+}
+
+TEST(CountDownLatchTest, LatchExtraCountDownIgnored) {
+  CountDownLatch latch(1);
+  std::atomic_bool done = false;
+
+  thread::Fiber f([&done, &latch] {
+    done = true;
+    latch.CountDown();
+    latch.CountDown();
+    latch.CountDown();
+  });
+  f.Join();
+
+  latch.Await();
+  EXPECT_TRUE(done);
+}
+
+TEST(CountDownLatchTest, LatchAwaitWithTimeoutCanExpire) {
+  CountDownLatch latch(1);
+
+  auto response = latch.Await(absl::Milliseconds(100));
+
+  EXPECT_TRUE(response.ok());
+  EXPECT_FALSE(response.result());
+}
+
+TEST(CountDownLatchTest, InitialCountZero_AwaitDoesNotBlock) {
+  CountDownLatch latch(0);
+
+  auto response = latch.Await();
+
+  EXPECT_TRUE(response.Ok());
+}
+
+TEST(CountDownLatchTest, InitialCountNegative_AwaitDoesNotBlock) {
+  CountDownLatch latch(-1);
+
+  auto response = latch.Await();
+
+  EXPECT_TRUE(response.Ok());
+}
+
+}  // namespace
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/crypto.mm

@@ -0,0 +1,39 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "third_party/nearby_connections/cpp/platform/api/crypto.h"
+
+#import "third_party/absl/strings/string_view.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Shared/GNCUtils.h"
+
+namespace location {
+namespace nearby {
+
+void Crypto::Init() {}
+
+ByteArray Crypto::Md5(absl::string_view input) {
+  if (input.empty()) return ByteArray();
+
+  return ByteArrayFromNSData(GNCMd5String(ObjCStringFromCppString(input)));
+}
+
+ByteArray Crypto::Sha256(absl::string_view input) {
+  if (input.empty()) return ByteArray();
+
+  return ByteArrayFromNSData(GNCSha256String(ObjCStringFromCppString(input)));
+}
+
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/input_file.h

@@ -0,0 +1,48 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_INPUT_FILE_H_
+#define PLATFORM_IMPL_IOS_INPUT_FILE_H_
+
+#import <Foundation/Foundation.h>
+
+#include "platform/api/input_file.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+/** This InputFile subclass takes input from an NSURL. */
+class InputFile : public api::InputFile {
+ public:
+  explicit InputFile(NSURL *nsURL);
+  ~InputFile() override = default;
+  InputFile(InputFile &&) = default;
+  InputFile &operator=(InputFile &&) = default;
+
+  ExceptionOr<ByteArray> Read(std::int64_t size) override;
+  std::string GetFilePath() const override;
+  std::int64_t GetTotalSize() const override;
+  Exception Close() override;
+
+ private:
+  NSURL *nsURL_;
+  NSInputStream *nsStream_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_INPUT_FILE_H_

cpp/platform/impl/ios/Source/Platform/input_file.mm

@@ -0,0 +1,69 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/input_file.h"
+
+#include <string>
+
+#import "third_party/nearby_connections/cpp/platform/base/exception.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+InputFile::InputFile(NSURL *nsURL) : nsURL_(nsURL) {
+  std::string string = CppStringFromObjCString([nsURL_ absoluteString]);
+  nsStream_ = [NSInputStream inputStreamWithURL:nsURL_];
+  [nsStream_ scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
+  [nsStream_ open];
+}
+
+ExceptionOr<ByteArray> InputFile::Read(std::int64_t size) {
+  uint8_t *bytes_read = new uint8_t[size];
+  NSUInteger numberOfBytesToRead = [[NSNumber numberWithLongLong:size] unsignedIntegerValue];
+  NSInteger numberOfBytesRead = [nsStream_ read:bytes_read maxLength:numberOfBytesToRead];
+  if (numberOfBytesRead == 0) {
+    // Reached end of stream.
+    return ExceptionOr<ByteArray>();
+  } else if (numberOfBytesRead < 0) {
+    // Stream error.
+    return ExceptionOr<ByteArray>(Exception::kIo);
+  }
+  return ExceptionOr<ByteArray>(ByteArrayFromNSData([NSData dataWithBytes:bytes_read
+                                                                   length:numberOfBytesRead]));
+}
+
+std::string InputFile::GetFilePath() const {
+  return CppStringFromObjCString([nsURL_ absoluteString]);
+}
+
+std::int64_t InputFile::GetTotalSize() const {
+  NSNumber *fileSizeValue = nil;
+  BOOL result = [nsURL_ getResourceValue:&fileSizeValue forKey:NSURLFileSizeKey error:nil];
+  if (result) {
+    return fileSizeValue.longValue;
+  } else {
+    return 0;
+  }
+}
+
+Exception InputFile::Close() {
+  [nsStream_ close];
+  return {Exception::kSuccess};
+}
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/log_message.h

@@ -0,0 +1,47 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_LOG_MESSAGE_H_
+#define PLATFORM_IMPL_IOS_LOG_MESSAGE_H_
+
+#include "base/check.h"
+#include "platform/api/log_message.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete LogMessage implementation
+class LogMessage : public api::LogMessage {
+ public:
+  LogMessage(const char* file, int line, Severity severity);
+  ~LogMessage() override = default;
+
+  LogMessage(const LogMessage&) = delete;
+  LogMessage& operator=(const LogMessage&) = delete;
+
+  void Print(const char* format, ...) override;
+
+  std::ostream& Stream() override;
+
+ private:
+  absl::LogStreamer log_streamer_;
+  api::LogMessage::Severity severity_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // IPHONE_SHARED_NEARBY_CONNECTIONS_SOURCE_PLATFORM_LOG_MESSAGE_H_

cpp/platform/impl/ios/Source/Platform/log_message.mm

@@ -0,0 +1,87 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/log_message.h"
+
+#include "base/logging.h"
+#include "third_party/nearby_connections/cpp/platform/api/log_message.h"
+#include "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+api::LogMessage::Severity gMinLogSeverity = api::LogMessage::Severity::kInfo;
+
+GTMLoggerLevel ConvertSeverity(api::LogMessage::Severity severity) {
+  switch (severity) {
+    case api::LogMessage::Severity::kVerbose:
+      return kGTMLoggerLevelDebug;
+    case api::LogMessage::Severity::kInfo:
+      return kGTMLoggerLevelInfo;
+    case api::LogMessage::Severity::kWarning:
+      return kGTMLoggerLevelInfo;
+    case api::LogMessage::Severity::kError:
+      return kGTMLoggerLevelError;
+    case api::LogMessage::Severity::kFatal:
+      return kGTMLoggerLevelAssert;
+  }
+}
+
+LogMessage::LogMessage(const char* file, int line, Severity severity)
+    : log_streamer_(ConvertSeverity(severity), file, line), severity_(severity) {}
+
+void LogMessage::Print(const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  switch (ConvertSeverity(severity_)) {
+    case kGTMLoggerLevelDebug:
+      [[GTMLogger sharedLogger] logDebug:[NSString stringWithUTF8String:format], ap];
+      break;
+    case kGTMLoggerLevelInfo:
+      [[GTMLogger sharedLogger] logInfo:[NSString stringWithUTF8String:format], ap];
+      break;
+    case kGTMLoggerLevelError:
+      [[GTMLogger sharedLogger] logError:[NSString stringWithUTF8String:format], ap];
+      break;
+    case kGTMLoggerLevelAssert:
+      [[GTMLogger sharedLogger] logAssert:[NSString stringWithUTF8String:format], ap];
+      break;
+    case kGTMLoggerLevelUnknown:
+        // no-op
+        break;
+  }
+}
+
+// TODO(b/169292092): GTMLogger doesn't support stream. Temporarily use absl LogStreamer to make
+// build pass.
+std::ostream& LogMessage::Stream() { return log_streamer_.stream(); }
+
+}  // namespace ios
+
+namespace api {
+
+// static
+void LogMessage::SetMinLogSeverity(Severity severity) { ios::gMinLogSeverity = severity; }
+
+// static
+bool LogMessage::ShouldCreateLogMessage(Severity severity) {
+  // TODO(b/169292092): GTMLogger doesn't support stream which cause crash. Temporarily turn off
+  // LogMessage.
+  return false;
+}
+
+}  // namespace api
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/multi_thread_executor.h

@@ -0,0 +1,47 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_MULTI_THREAD_EXECUTOR_H_
+#define PLATFORM_IMPL_IOS_MULTI_THREAD_EXECUTOR_H_
+
+#include "platform/api/submittable_executor.h"
+#import "third_party/nearby_connections/cpp/platform/base/runnable.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/scheduled_executor.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+class MultiThreadExecutor : public api::SubmittableExecutor {
+ public:
+  explicit MultiThreadExecutor(int max_concurrency);
+  ~MultiThreadExecutor() override = default;
+
+  MultiThreadExecutor(const MultiThreadExecutor&) = delete;
+  MultiThreadExecutor& operator=(const MultiThreadExecutor&) = delete;
+
+  // api::SubmittableExecutor:
+  void Shutdown() override;
+  void Execute(Runnable&& runnable) override;
+  bool DoSubmit(Runnable&& runnable) override;
+
+ private:
+  std::unique_ptr<ScheduledExecutor> scheduled_executor_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_MULTI_THREAD_EXECUTOR_H_

cpp/platform/impl/ios/Source/Platform/multi_thread_executor.mm

@@ -0,0 +1,40 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/multi_thread_executor.h"
+
+#include "third_party/nearby_connections/cpp/platform/base/runnable.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/scheduled_executor.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+MultiThreadExecutor::MultiThreadExecutor(int max_concurrency) {
+  scheduled_executor_ = std::make_unique<ScheduledExecutor>(max_concurrency);
+}
+
+void MultiThreadExecutor::Shutdown() { scheduled_executor_->Shutdown(); }
+
+void MultiThreadExecutor::Execute(Runnable&& runnable) {
+  scheduled_executor_->Execute(std::move(runnable));
+}
+
+bool MultiThreadExecutor::DoSubmit(Runnable&& runnable) {
+  return scheduled_executor_->DoSubmit(std::move(runnable));
+}
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/mutex.h

@@ -0,0 +1,84 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_MUTEX_H_
+#define PLATFORM_IMPL_IOS_MUTEX_H_
+
+#include "absl/synchronization/mutex.h"
+#include "platform/api/mutex.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete Mutex implementation.
+class ABSL_LOCKABLE Mutex : public api::Mutex {
+ public:
+  explicit Mutex() {}
+  ~Mutex() override = default;
+
+  Mutex(const Mutex&) = delete;
+  Mutex& operator=(const Mutex&) = delete;
+
+  void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION() override {
+    mutex_.Lock();
+    mutex_.ForgetDeadlockInfo();
+  }
+  void Unlock() ABSL_UNLOCK_FUNCTION() override { mutex_.Unlock(); }
+
+ private:
+  friend class ConditionVariable;
+  absl::Mutex mutex_;
+};
+
+class ABSL_LOCKABLE RecursiveMutex : public api::Mutex {
+ public:
+  RecursiveMutex() = default;
+  ~RecursiveMutex() override = default;
+
+  RecursiveMutex(RecursiveMutex&&) = delete;
+  RecursiveMutex& operator=(RecursiveMutex&&) = delete;
+
+  void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION() override {
+    intptr_t thread_id = ThreadId();
+    if (thread_id_.load(std::memory_order_acquire) != thread_id) {
+      mutex_.Lock();
+      thread_id_.store(thread_id, std::memory_order_release);
+    }
+    ++count_;
+  }
+
+  void Unlock() ABSL_UNLOCK_FUNCTION() override {
+    if (--count_ == 0) {
+      thread_id_.store(0, std::memory_order_release);
+      mutex_.Unlock();
+    }
+  }
+
+ private:
+  static inline intptr_t ThreadId() {
+    ABSL_CONST_INIT thread_local int per_thread = 0;
+    return reinterpret_cast<intptr_t>(&per_thread);
+  }
+
+  std::atomic<intptr_t> thread_id_{0};
+  int count_{0};
+  absl::Mutex mutex_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_MUTEX_H_

cpp/platform/impl/ios/Source/Platform/mutex_test.cc

@@ -0,0 +1,92 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/impl/ios/Source/Platform/mutex.h"
+
+#include "gtest/gtest.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/synchronization/notification.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "thread/fiber/fiber.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+namespace {
+
+static const absl::Duration kTimeToWait = absl::Milliseconds(500);
+
+TEST(MutexTest, LockOnce_UnlockOnce) {
+  Mutex test_mutex_1{};
+  test_mutex_1.Lock();
+  test_mutex_1.Unlock();
+
+  RecursiveMutex test_mutex_2;
+  test_mutex_2.Lock();
+  test_mutex_2.Unlock();
+}
+
+TEST(MutexTest, BasicLockingWorks) {
+  absl::Notification lock_obtained;
+  Mutex test_mutex{};
+  test_mutex.Lock();
+  thread::Fiber f([&test_mutex, &lock_obtained] {
+    test_mutex.Lock();
+    test_mutex.Unlock();
+    lock_obtained.Notify();
+  });
+  EXPECT_FALSE(lock_obtained.WaitForNotificationWithTimeout(kTimeToWait));
+  test_mutex.Unlock();
+  EXPECT_TRUE(lock_obtained.WaitForNotificationWithTimeout(kTimeToWait));
+  f.Join();
+}
+
+TEST(MutexTest, RecursiveLockingWorks) {
+  absl::Notification lock_obtained;
+  RecursiveMutex test_mutex;
+  test_mutex.Lock();
+  thread::Fiber f([&test_mutex, &lock_obtained] {
+    test_mutex.Lock();
+    test_mutex.Unlock();
+    lock_obtained.Notify();
+  });
+  EXPECT_FALSE(lock_obtained.WaitForNotificationWithTimeout(kTimeToWait));
+  test_mutex.Unlock();
+  EXPECT_TRUE(lock_obtained.WaitForNotificationWithTimeout(kTimeToWait));
+  f.Join();
+}
+
+TEST(MutexTest, RecursiveLockingForNestedWorks) {
+  absl::Notification lock_obtained;
+  RecursiveMutex test_mutex;
+  test_mutex.Lock();
+  thread::Fiber f([&test_mutex, &lock_obtained]()
+                      ABSL_NO_THREAD_SAFETY_ANALYSIS {
+                        test_mutex.Lock();
+                        test_mutex.Lock();
+                        test_mutex.Unlock();
+                        test_mutex.Unlock();
+                        lock_obtained.Notify();
+                      });
+  EXPECT_FALSE(lock_obtained.WaitForNotificationWithTimeout(kTimeToWait));
+  test_mutex.Unlock();
+  EXPECT_TRUE(lock_obtained.WaitForNotificationWithTimeout(kTimeToWait));
+  f.Join();
+}
+
+}  // namespace
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/scheduled_executor.h

@@ -0,0 +1,68 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_SCHEDULED_EXECUTOR_H_
+#define PLATFORM_IMPL_IOS_SCHEDULED_EXECUTOR_H_
+
+#import <Foundation/Foundation.h>
+
+#include <functional>
+#include <memory>
+
+#include "platform/api/scheduled_executor.h"
+#include "platform/base/runnable.h"
+
+/**
+ * The impl class is an Obj-C class so that
+ *  (a) the dispatch block can strongly retain it, and
+ *  (b) for ease of declaring an atomic property.
+ */
+@interface GNCOperationQueueImpl : NSObject
+@property(nonatomic) NSOperationQueue* queue;
+@property(atomic) BOOL shuttingDown;
+@end
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+// Concrete ScheduledExecutor implementation.
+class ScheduledExecutor : public api::ScheduledExecutor {
+ public:
+  // The max_concurrency = 1 for default constructor.
+  ScheduledExecutor();
+  explicit ScheduledExecutor(int max_concurrency);
+  ~ScheduledExecutor() override;
+
+  ScheduledExecutor(const ScheduledExecutor&) = delete;
+  ScheduledExecutor& operator=(const ScheduledExecutor&) = delete;
+
+  // api::ScheduledExecutor:
+  void Shutdown() override;
+  std::shared_ptr<api::Cancelable> Schedule(Runnable&& runnable, absl::Duration duration) override;
+  void Execute(Runnable&& runnable) override;
+
+  bool DoSubmit(Runnable&& runnable);
+
+ private:
+  void Shutdown(std::int64_t timeout_millis);
+
+  GNCOperationQueueImpl* impl_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_SCHEDULED_EXECUTOR_H_

cpp/platform/impl/ios/Source/Platform/scheduled_executor.mm

@@ -0,0 +1,144 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/scheduled_executor.h"
+
+#import <Foundation/Foundation.h>
+
+#include "third_party/absl/time/time.h"
+#include "third_party/nearby_connections/cpp/platform/base/runnable.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/atomic_boolean.h"
+
+// This wraps the C++ Runnable in an Obj-C object for memory management. It is retained by the
+// dispatch block below, and deleted when the block is released.
+@interface GNCRunnableWrapper : NSObject {
+ @public
+  location::nearby::Runnable _runnable;
+  std::unique_ptr<location::nearby::ios::AtomicBoolean> _canceled;
+}
+@end
+
+@implementation GNCRunnableWrapper
+
++ (instancetype)wrapperWithRunnable:(location::nearby::Runnable)runnable {
+  GNCRunnableWrapper *wrapper = [[GNCRunnableWrapper alloc] init];
+  wrapper->_runnable = runnable;
+  wrapper->_canceled = std::make_unique<location::nearby::ios::AtomicBoolean>(false);
+  return wrapper;
+}
+
+@end
+
+@implementation GNCOperationQueueImpl
+
++ (instancetype)implWithMaxConcurrency:(int)maxConcurrency {
+  GNCOperationQueueImpl *impl = [[GNCOperationQueueImpl alloc] init];
+  impl.queue = [[NSOperationQueue alloc] init];
+  impl.queue.maxConcurrentOperationCount = maxConcurrency;
+  return impl;
+}
+
+@end
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+static const std::int64_t kExecutorShutdownDefaultTimeout = 500;  // 0.5 seconds
+
+// This Cancelable references a Runnable and a cancel method that sets its canceled boolean to true.
+class CancelableForRunnable : public api::Cancelable {
+ public:
+  explicit CancelableForRunnable(GNCRunnableWrapper *runnable) : runnable_(runnable) {}
+  CancelableForRunnable() = default;
+  ~CancelableForRunnable() override = default;
+  CancelableForRunnable(const CancelableForRunnable &) = delete;
+  CancelableForRunnable &operator=(const CancelableForRunnable &) = delete;
+
+  // api::Cancelable:
+  bool Cancel() override {
+    runnable_->_canceled->Set(true);
+    return true;
+  }
+
+ private:
+  GNCRunnableWrapper *runnable_;
+};
+
+ScheduledExecutor::ScheduledExecutor() { impl_ = [GNCOperationQueueImpl implWithMaxConcurrency:1]; }
+
+ScheduledExecutor::ScheduledExecutor(int max_concurrency) {
+  impl_ = [GNCOperationQueueImpl implWithMaxConcurrency:max_concurrency];
+}
+
+ScheduledExecutor::~ScheduledExecutor() { impl_ = nil; }
+
+void ScheduledExecutor::Shutdown() { Shutdown(kExecutorShutdownDefaultTimeout); }
+
+std::shared_ptr<api::Cancelable> ScheduledExecutor::Schedule(Runnable &&runnable,
+                                                             absl::Duration duration) {
+  if (impl_.shuttingDown) return std::shared_ptr<api::Cancelable>(nullptr);
+
+  // Wrap the runnable in an Obj-C object so it can be referenced by the delayed block.
+  GNCRunnableWrapper *wrapper = [GNCRunnableWrapper wrapperWithRunnable:std::move(runnable)];
+  CancelableForRunnable *cancelable = new CancelableForRunnable(wrapper);
+  GNCOperationQueueImpl *impl = impl_;  // don't capture |this|
+  dispatch_after(
+      dispatch_time(DISPATCH_TIME_NOW, absl::ToInt64Milliseconds(duration) * NSEC_PER_MSEC),
+      dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0), ^{
+        [impl.queue addOperationWithBlock:^{
+          // Execute the runnable only if the executor is not shutting down, and the runnable isn't
+          // canceled.
+          // Warning: This block should reference only Obj-C objects, and never C++ objects.
+          if (!impl.shuttingDown &&  !wrapper->_canceled->Get()) {
+            wrapper->_runnable();
+          }
+        }];
+      });
+
+  return std::shared_ptr<api::Cancelable>(cancelable);
+}
+
+void ScheduledExecutor::Execute(Runnable &&runnable) {
+  DoSubmit(std::move(runnable));
+}
+
+bool ScheduledExecutor::DoSubmit(Runnable &&runnable) {
+  if (impl_.shuttingDown) {
+    return false;
+  }
+
+  // Submit the runnable to the queue.
+  Runnable local_runnable = std::move(runnable);
+  [impl_.queue addOperationWithBlock:^{
+    local_runnable();
+  }];
+  return true;
+}
+
+void ScheduledExecutor::Shutdown(std::int64_t timeout_millis) {
+  // Prevent new/delayed operations from being queued/executed.
+  impl_.shuttingDown = YES;
+
+  // Block until either (a) all currently executing operations finish, or (b) the timeout expires.
+  dispatch_group_t group = dispatch_group_create();
+  dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0), ^{
+    [impl_.queue waitUntilAllOperationsAreFinished];
+  });
+  dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, timeout_millis * NSEC_PER_MSEC));
+}
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/single_thread_executor.h

@@ -0,0 +1,35 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_SINGLE_THREAD_EXECUTOR_H_
+#define PLATFORM_IMPL_IOS_SINGLE_THREAD_EXECUTOR_H_
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/multi_thread_executor.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+class SingleThreadExecutor : public MultiThreadExecutor {
+ public:
+  SingleThreadExecutor() : MultiThreadExecutor(1) {}
+  ~SingleThreadExecutor() override = default;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_SINGLE_THREAD_EXECUTOR_H_
+

cpp/platform/impl/ios/Source/Platform/system_clock.cc

@@ -0,0 +1,33 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "platform/api/system_clock.h"
+
+#include "absl/time/clock.h"
+
+namespace location {
+namespace nearby {
+
+void SystemClock::Init() {}
+
+absl::Time SystemClock::ElapsedRealtime() { return absl::Now(); }
+
+// TODO(b/169292092): Check the iOS primitive implementation for SystemClock.
+Exception SystemClock::Sleep(absl::Duration duration) {
+  absl::SleepFor(duration);
+  return {Exception::kSuccess};
+}
+
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Platform/utils.h

@@ -0,0 +1,74 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <CoreBluetooth/CoreBluetooth.h>
+#import <Foundation/Foundation.h>
+
+#include <set>
+#include <string>
+
+#include "absl/container/flat_hash_map.h"
+#include "absl/strings/string_view.h"
+#include "platform/base/byte_array.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+namespace location {
+namespace nearby {
+
+/// Converts an Obj-C BOOL to a C++ bool.
+bool CppBoolFromObjCBool(BOOL b);
+
+/// Converts NSNumber to a char.
+char CharFromNSNumber(NSNumber *n);
+
+/// Converts a C++ string to an Obj-C string.
+NSString *ObjCStringFromCppString(absl::string_view s);
+
+/// Converts an Obj-C string to a C++ string.
+std::string CppStringFromObjCString(NSString *s);
+
+/// Converts ByteArray to NSData.
+NSData *NSDataFromByteArray(ByteArray byteArray);
+
+/// Converts NSData to ByteArray.
+ByteArray ByteArrayFromNSData(NSData *data);
+
+/// Converts NSUUID to a C++ string (representing a UUID).
+std::string UUIDStringFromNSUUID(NSUUID *uuid);
+
+/// Converts a C++ string (representing a Bluetooth UUID) to CBUUID.
+CBUUID *CBUUIDFromBluetoothUUIDString(absl::string_view bluetoothUUID);
+
+/// Converts CBUUID to a C++ string (representing a Bluetooth UUID).
+std::string BluetoothUUIDStringFromCBUUID(CBUUID *bluetoothUUID);
+
+/// Converts a C++ set of strings (representing Bluetooth UUIDs) to an NSSet of CBUUID.
+NSSet<CBUUID *> *CBUUIDSetFromBluetoothUUIDStringSet(const std::set<std::string> &bluetoothUUIDSet);
+
+/// Converts an NSSet of CBUUID to a C++ set of strings (representing Bluetooth UUIDs).
+std::set<std::string> BluetoothUUIDStringSetFromCBUUIDSet(NSSet<CBUUID *> *bluetoothUUIDSet);
+
+/// Converts a C++ TxtRecord to an Obj-C TxtRecord.
+NSDictionary<NSString *, NSData *> *NSDictionaryFromCppTxtRecords(
+    const absl::flat_hash_map<std::string, std::string> &txt_records);
+
+/// Converts an Obj-C TxtRecord to a C++ TxtRecord.
+absl::flat_hash_map<std::string, std::string> AbslHashMapFromObjCTxtRecords(
+    NSDictionary<NSString *, NSData *> *txtRecords);
+
+}  // namespace nearby
+}  // namespace location
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Platform/utils.mm

@@ -0,0 +1,104 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+
+#import "third_party/absl/container/flat_hash_map.h"
+#include "third_party/absl/strings/string_view.h"
+#include "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+namespace location {
+namespace nearby {
+
+bool CppBoolFromObjCBool(BOOL b) { return b ? true : false; }
+
+char CharFromNSNumber(NSNumber* n) { return n.charValue; }
+
+NSString* ObjCStringFromCppString(absl::string_view s) {
+  return [NSString stringWithUTF8String:s.data()];
+}
+
+std::string CppStringFromObjCString(NSString* s) {
+  return std::string([s UTF8String], [s lengthOfBytesUsingEncoding:NSUTF8StringEncoding]);
+}
+
+NSData* NSDataFromByteArray(ByteArray byteArray) {
+  return [NSData dataWithBytes:byteArray.data() length:byteArray.size()];
+}
+
+ByteArray ByteArrayFromNSData(NSData* data) {
+  return ByteArray((const char*)data.bytes, data.length);
+}
+
+std::string UUIDStringFromNSUUID(NSUUID* uuid) { return CppStringFromObjCString(uuid.UUIDString); }
+
+CBUUID* CBUUIDFromBluetoothUUIDString(absl::string_view bluetoothUUID) {
+  return [CBUUID UUIDWithString:ObjCStringFromCppString(bluetoothUUID)];
+}
+
+std::string BluetoothUUIDStringFromCBUUID(CBUUID* bluetoothUUID) {
+  return CppStringFromObjCString(bluetoothUUID.UUIDString);
+}
+
+NSSet<CBUUID*>* CBUUIDSetFromBluetoothUUIDStringSet(const std::set<std::string>& bluetoothUUIDSet) {
+  NSMutableSet<CBUUID*>* objcBluetoothUUIDSet = [NSMutableSet set];
+  for (std::set<std::string>::const_iterator it = bluetoothUUIDSet.begin();
+       it != bluetoothUUIDSet.end(); ++it) {
+    [objcBluetoothUUIDSet addObject:CBUUIDFromBluetoothUUIDString(*it)];
+  }
+  return objcBluetoothUUIDSet;
+}
+
+std::set<std::string> BluetoothUUIDStringSetFromCBUUIDSet(NSSet<CBUUID*>* bluetoothUUIDSet) {
+  std::set<std::string> cppBluetoothUUIDSet;
+  for (CBUUID* bluetoothUUID in bluetoothUUIDSet) {
+    cppBluetoothUUIDSet.insert(BluetoothUUIDStringFromCBUUID(bluetoothUUID));
+  }
+  return cppBluetoothUUIDSet;
+}
+
+NSDictionary<NSString*, NSData*>* NSDictionaryFromCppTxtRecords(
+    const absl::flat_hash_map<std::string, std::string>& txt_records) {
+  NSMutableArray<NSString*>* keyArray = [[NSMutableArray alloc] init];
+  NSMutableArray<NSData*>* valueArray = [[NSMutableArray alloc] init];
+  for (auto it = txt_records.begin(); it != txt_records.end(); it++) {
+    NSString* key = @(it->first.c_str());
+    NSString* value = @(it->second.c_str());
+    [keyArray addObject:key];
+    [valueArray addObject:[value dataUsingEncoding:NSUTF8StringEncoding]];
+  }
+
+  NSDictionary<NSString*, NSData*>* dict = [[NSDictionary alloc] initWithObjects:valueArray
+                                                                         forKeys:keyArray];
+  return dict;
+}
+
+absl::flat_hash_map<std::string, std::string> AbslHashMapFromObjCTxtRecords(
+    NSDictionary<NSString*, NSData*>* txtRecords) {
+  absl::flat_hash_map<std::string, std::string> txt_record;
+
+  for (NSString* key in txtRecords) {
+    NSString* value = [[NSString alloc] initWithData:[txtRecords objectForKey:key]
+                                            encoding:NSUTF8StringEncoding];
+    txt_record.insert({CppStringFromObjCString(key), CppStringFromObjCString(value)});
+  }
+  return txt_record;
+}
+
+}  // namespace nearby
+}  // namespace location
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Platform/wifi_lan.h

@@ -0,0 +1,198 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_IOS_WIFI_LAN_H_
+#define PLATFORM_IMPL_IOS_WIFI_LAN_H_
+
+#import <Foundation/Foundation.h>
+#include <string>
+
+#include "absl/base/thread_annotations.h"
+#include "absl/container/flat_hash_map.h"
+#include "platform/api/wifi_lan.h"
+#include "platform/base/nsd_service_info.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"  // IWYU pragma: export
+
+@class GNCMBonjourBrowser;
+@class GNCMBonjourService;
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+/** InputStream that reads from GNCMConnection. */
+class WifiLanInputStream : public InputStream {
+ public:
+  WifiLanInputStream();
+  ~WifiLanInputStream() override;
+
+  ExceptionOr<ByteArray> Read(std::int64_t size) override;
+  Exception Close() override;
+
+  GNCMConnectionHandlers* GetConnectionHandlers() { return connectionHandlers_; }
+
+ private:
+  GNCMConnectionHandlers* connectionHandlers_;
+  NSMutableArray<NSData*>* newDataPackets_;
+  NSMutableData* accumulatedData_;
+  NSCondition* condition_;
+};
+
+/** OutputStream that writes to GNCMConnection. */
+class WifiLanOutputStream : public OutputStream {
+ public:
+  explicit WifiLanOutputStream(id<GNCMConnection> connection)
+      : connection_(connection), condition_([[NSCondition alloc] init]) {}
+  ~WifiLanOutputStream() override;
+
+  Exception Write(const ByteArray& data) override;
+  Exception Flush() override;
+  Exception Close() override;
+
+ private:
+  id<GNCMConnection> connection_;
+  NSCondition* condition_;
+};
+
+/** Concrete WifiLanSocket implementation. */
+class WifiLanSocket : public api::WifiLanSocket {
+ public:
+  WifiLanSocket() = default;
+  explicit WifiLanSocket(id<GNCMConnection> connection);
+  ~WifiLanSocket() override;
+
+  // api::WifiLanSocket:
+  InputStream& GetInputStream() override { return *input_stream_; }
+  OutputStream& GetOutputStream() override { return *output_stream_; }
+  Exception Close() override ABSL_LOCKS_EXCLUDED(mutex_);
+
+  bool IsClosed() const ABSL_LOCKS_EXCLUDED(mutex_);
+
+ private:
+  void DoClose() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  mutable absl::Mutex mutex_;
+  bool closed_ ABSL_GUARDED_BY(mutex_) = false;
+  std::unique_ptr<WifiLanInputStream> input_stream_;
+  std::unique_ptr<WifiLanOutputStream> output_stream_;
+};
+
+/** Concrete WifiLanServerSocket implementation. */
+class WifiLanServerSocket : public api::WifiLanServerSocket {
+ public:
+  static std::string GetName(const std::string& ip_address, int port);
+
+  ~WifiLanServerSocket() override;
+
+  // api::WifiLanServerSocket:
+  std::string GetIPAddress() const override ABSL_LOCKS_EXCLUDED(mutex_) {
+    absl::MutexLock lock(&mutex_);
+    return ip_address_;
+  }
+  void SetIPAddress(const std::string& ip_address) ABSL_LOCKS_EXCLUDED(mutex_) {
+    absl::MutexLock lock(&mutex_);
+    ip_address_ = ip_address;
+  }
+  int GetPort() const override ABSL_LOCKS_EXCLUDED(mutex_) {
+    absl::MutexLock lock(&mutex_);
+    return port_;
+  }
+  void SetPort(int port) ABSL_LOCKS_EXCLUDED(mutex_) {
+    absl::MutexLock lock(&mutex_);
+    port_ = port;
+  }
+  std::unique_ptr<api::WifiLanSocket> Accept() override ABSL_LOCKS_EXCLUDED(mutex_);
+  Exception Close() override ABSL_LOCKS_EXCLUDED(mutex_);
+
+  bool Connect(std::unique_ptr<WifiLanSocket> socket) ABSL_LOCKS_EXCLUDED(mutex_);
+  void SetCloseNotifier(std::function<void()> notifier) ABSL_LOCKS_EXCLUDED(mutex_);
+
+ private:
+  Exception DoClose() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  mutable absl::Mutex mutex_;
+  std::string ip_address_ ABSL_GUARDED_BY(mutex_);
+  int port_ ABSL_GUARDED_BY(mutex_);
+  absl::CondVar cond_;
+  absl::flat_hash_set<std::unique_ptr<WifiLanSocket>> pending_sockets_ ABSL_GUARDED_BY(mutex_);
+  std::function<void()> close_notifier_ ABSL_GUARDED_BY(mutex_);
+  bool closed_ ABSL_GUARDED_BY(mutex_) = false;
+};
+
+/** Concrete WifiLanMedium implementation. */
+class WifiLanMedium : public api::WifiLanMedium {
+ public:
+  WifiLanMedium() = default;
+  ~WifiLanMedium() override;
+
+  WifiLanMedium(const WifiLanMedium&) = delete;
+  WifiLanMedium& operator=(const WifiLanMedium&) = delete;
+
+  // api::WifiLanMedium:
+  bool StartAdvertising(const NsdServiceInfo& nsd_service_info) override
+      ABSL_LOCKS_EXCLUDED(mutex_);
+  bool StopAdvertising(const NsdServiceInfo& nsd_service_info) override ABSL_LOCKS_EXCLUDED(mutex_);
+
+  bool StartDiscovery(const std::string& service_type, DiscoveredServiceCallback callback) override
+      ABSL_LOCKS_EXCLUDED(mutex_);
+  bool StopDiscovery(const std::string& service_type) override ABSL_LOCKS_EXCLUDED(mutex_);
+
+  std::unique_ptr<api::WifiLanSocket> ConnectToService(
+      const NsdServiceInfo& remote_service_info, CancellationFlag* cancellation_flag) override;
+  std::unique_ptr<api::WifiLanSocket> ConnectToService(
+      const std::string& ip_address, int port, CancellationFlag* cancellation_flag) override;
+  std::unique_ptr<api::WifiLanServerSocket> ListenForService(int port) override
+      ABSL_LOCKS_EXCLUDED(mutex_);
+
+ private:
+  struct AdvertisingInfo {
+    bool Empty() const { return services.empty(); }
+    void Clear() { services.clear(); }
+    void Add(const std::string& service_type, GNCMBonjourService* service) {
+      services.insert({service_type, service});
+    }
+    void Remove(const std::string& service_type) { services.erase(service_type); }
+    bool Existed(const std::string& service_type) const { return services.contains(service_type); }
+
+    absl::flat_hash_map<std::string, GNCMBonjourService*> services;
+  };
+  struct DiscoveringInfo {
+    bool Empty() const { return services.empty(); }
+    void Clear() { services.clear(); }
+    void Add(const std::string& service_type, GNCMBonjourBrowser* browser) {
+      services.insert({service_type, browser});
+    }
+    void Remove(const std::string& service_type) { services.erase(service_type); }
+    bool Existed(const std::string& service_type) const { return services.contains(service_type); }
+
+    absl::flat_hash_map<std::string, GNCMBonjourBrowser*> services;
+  };
+
+  std::string GetFakeIPAddress() const;
+  int GetFakePort() const;
+
+  absl::Mutex mutex_;
+  AdvertisingInfo advertising_info_ ABSL_GUARDED_BY(mutex_);
+  int requesting_port_ = 0;
+  DiscoveringInfo discovering_info_ ABSL_GUARDED_BY(mutex_);
+  absl::flat_hash_map<std::string, WifiLanServerSocket*> server_sockets_ ABSL_GUARDED_BY(mutex_);
+  absl::flat_hash_map<std::string, GNCMConnectionRequester> connection_requesters_
+      ABSL_GUARDED_BY(mutex_);
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_IOS_WIFI_LAN_H_

cpp/platform/impl/ios/Source/Platform/wifi_lan.mm

@@ -0,0 +1,497 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/wifi_lan.h"
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "third_party/absl/container/flat_hash_map.h"
+#include "third_party/absl/container/internal/common.h"
+#include "third_party/absl/memory/memory.h"
+#include "third_party/absl/strings/str_cat.h"
+#include "third_party/absl/strings/str_format.h"
+#include "third_party/absl/synchronization/mutex.h"
+#include "third_party/nearby_connections/cpp/platform/api/wifi_lan.h"
+#include "third_party/nearby_connections/cpp/platform/base/cancellation_flag.h"
+#include "third_party/nearby_connections/cpp/platform/base/exception.h"
+#include "third_party/nearby_connections/cpp/platform/base/nsd_service_info.h"
+#include "third_party/nearby_connections/cpp/platform/base/prng.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/GNCMConnection.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourBrowser.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Mediums/WifiLan/GNCMBonjourService.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMLogger.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+/** WifiLanInputStream implementation. */
+WifiLanInputStream::WifiLanInputStream()
+    : newDataPackets_([NSMutableArray array]),
+      accumulatedData_([NSMutableData data]),
+      condition_([[NSCondition alloc] init]) {
+  // Create the handlers of incoming data from the remote endpoint.
+  connectionHandlers_ = [GNCMConnectionHandlers
+      payloadHandler:^(NSData* data) {
+        [condition_ lock];
+        // Add the incoming data to the data packet array to be processed in Read() below.
+        [newDataPackets_ addObject:data];
+        [condition_ signal];
+        [condition_ unlock];
+      }
+      disconnectedHandler:^{
+        [condition_ lock];
+        // Release the data packet array, meaning the stream has been closed or severed.
+        newDataPackets_ = nil;
+        [condition_ signal];
+        [condition_ unlock];
+      }];
+}
+
+WifiLanInputStream::~WifiLanInputStream() {
+  NSCAssert(!newDataPackets_, @"WifiLanInputStream not closed before destruction");
+}
+
+ExceptionOr<ByteArray> WifiLanInputStream::Read(std::int64_t size) {
+  // Block until either (a) the connection has been closed, or (b) enough data to return.
+  NSData* dataToReturn;
+  [condition_ lock];
+  while (true) {
+    // Check if the stream has been closed or severed.
+    if (!newDataPackets_) break;
+
+    if (newDataPackets_.count > 0) {
+      // Add the packet data to the accumulated data.
+      for (NSData* data in newDataPackets_) {
+        if (data.length > 0) {
+          [accumulatedData_ appendData:data];
+        }
+      }
+      [newDataPackets_ removeAllObjects];
+    }
+
+    if ((size == -1) && (accumulatedData_.length > 0)) {
+      // Return all of the data.
+      dataToReturn = accumulatedData_;
+      accumulatedData_ = [NSMutableData data];
+      break;
+    } else if (accumulatedData_.length > 0) {
+      // Return up to |size| bytes of the data.
+      std::int64_t sizeToReturn = accumulatedData_.length < size ? accumulatedData_.length : size;
+      NSRange range = NSMakeRange(0, (NSUInteger)sizeToReturn);
+      dataToReturn = [accumulatedData_ subdataWithRange:range];
+      [accumulatedData_ replaceBytesInRange:range withBytes:nil length:0];
+      break;
+    }
+
+    [condition_ wait];
+  }
+  [condition_ unlock];
+
+  if (dataToReturn) {
+    GTMLoggerInfo(@"[NEARBY] Input stream: Received data of size: %lu",
+                  (unsigned long)dataToReturn.length);
+    return ExceptionOr<ByteArray>(ByteArrayFromNSData(dataToReturn));
+  } else {
+    return ExceptionOr<ByteArray>{Exception::kIo};
+  }
+}
+
+Exception WifiLanInputStream::Close() {
+  // Unblock pending read operation.
+  [condition_ lock];
+  newDataPackets_ = nil;
+  [condition_ signal];
+  [condition_ unlock];
+  return {Exception::kSuccess};
+}
+
+/** WifiLanOutputStream implementation. */
+WifiLanOutputStream::~WifiLanOutputStream() {
+  NSCAssert(!connection_, @"WifiLanOutputStream not closed before destruction");
+}
+
+Exception WifiLanOutputStream::Write(const ByteArray& data) {
+  [condition_ lock];
+  GTMLoggerDebug(@"[NEARBY] Sending data of size: %lu",
+                 (unsigned long)NSDataFromByteArray(data).length);
+
+  NSMutableData* packet = [NSMutableData dataWithData:NSDataFromByteArray(data)];
+
+  // Send the data, blocking until the completion handler is called.
+  __block GNCMPayloadResult sendResult = GNCMPayloadResultFailure;
+  __block bool isComplete = NO;
+  NSCondition* condition = condition_;  // don't capture |this| in completion
+  // Check if connection_ is nil, then just don't wait and return as failure.
+  if (connection_ != nil) {
+    [connection_ sendData:packet
+        progressHandler:^(size_t count) {
+        }
+        completion:^(GNCMPayloadResult result) {
+          // Make sure we haven't already reported completion before. This prevents a crash
+          // where we try leaving a dispatch group more times than we entered it.
+          // b/79095653.
+          if (isComplete) {
+            return;
+          }
+          isComplete = YES;
+          sendResult = result;
+          [condition lock];
+          [condition signal];
+          [condition unlock];
+        }];
+    [condition_ wait];
+    [condition_ unlock];
+  } else {
+    sendResult = GNCMPayloadResultFailure;
+    [condition_ unlock];
+  }
+
+  if (sendResult == GNCMPayloadResultSuccess) {
+    return {Exception::kSuccess};
+  } else {
+    return {Exception::kIo};
+  }
+}
+
+Exception WifiLanOutputStream::Flush() {
+  // The Write() function block until the data is received by the remote endpoint, so there's
+  // nothing to do here.
+  return {Exception::kSuccess};
+}
+
+Exception WifiLanOutputStream::Close() {
+  // Unblock pending write operation.
+  [condition_ lock];
+  connection_ = nil;
+  [condition_ signal];
+  [condition_ unlock];
+  return {Exception::kSuccess};
+}
+
+/** WifiLanSocket implementation. */
+WifiLanSocket::WifiLanSocket(id<GNCMConnection> connection)
+    : input_stream_(new WifiLanInputStream()),
+      output_stream_(new WifiLanOutputStream(connection)) {}
+
+WifiLanSocket::~WifiLanSocket() {
+  absl::MutexLock lock(&mutex_);
+  DoClose();
+}
+
+bool WifiLanSocket::IsClosed() const {
+  absl::MutexLock lock(&mutex_);
+  return closed_;
+}
+
+Exception WifiLanSocket::Close() {
+  absl::MutexLock lock(&mutex_);
+  DoClose();
+  return {Exception::kSuccess};
+}
+
+void WifiLanSocket::DoClose() {
+  if (!closed_) {
+    input_stream_->Close();
+    output_stream_->Close();
+    closed_ = true;
+  }
+}
+
+/** WifiLanServerSocket implementation. */
+std::string WifiLanServerSocket::GetName(const std::string& ip_address, int port) {
+  std::string dot_delimited_string;
+  if (!ip_address.empty()) {
+    for (auto byte : ip_address) {
+      if (!dot_delimited_string.empty()) absl::StrAppend(&dot_delimited_string, ".");
+      absl::StrAppend(&dot_delimited_string, absl::StrFormat("%d", byte));
+    }
+  }
+  std::string out = absl::StrCat(dot_delimited_string, ":", port);
+  return out;
+}
+
+WifiLanServerSocket::~WifiLanServerSocket() {
+  absl::MutexLock lock(&mutex_);
+  DoClose();
+}
+
+std::unique_ptr<api::WifiLanSocket> WifiLanServerSocket::Accept() {
+  absl::MutexLock lock(&mutex_);
+  while (!closed_ && pending_sockets_.empty()) {
+    cond_.Wait(&mutex_);
+  }
+  // Return early if closed.
+  if (closed_) return {};
+
+  auto remote_socket = std::move(pending_sockets_.extract(pending_sockets_.begin()).value());
+  return std::move(remote_socket);
+}
+
+bool WifiLanServerSocket::Connect(std::unique_ptr<WifiLanSocket> socket) {
+  absl::MutexLock lock(&mutex_);
+  if (closed_) {
+    return false;
+  }
+  // add client socket to the pending list
+  pending_sockets_.insert(std::move(socket));
+  cond_.SignalAll();
+  if (closed_) {
+    return false;
+  }
+  return true;
+}
+
+void WifiLanServerSocket::SetCloseNotifier(std::function<void()> notifier) {
+  absl::MutexLock lock(&mutex_);
+  close_notifier_ = std::move(notifier);
+}
+
+Exception WifiLanServerSocket::Close() {
+  absl::MutexLock lock(&mutex_);
+  return DoClose();
+}
+
+Exception WifiLanServerSocket::DoClose() {
+  bool should_notify = !closed_;
+  closed_ = true;
+  if (should_notify) {
+    cond_.SignalAll();
+    if (close_notifier_) {
+      auto notifier = std::move(close_notifier_);
+      mutex_.Unlock();
+      // Notifier may contain calls to public API, and may cause deadlock, if
+      // mutex_ is held during the call.
+      notifier();
+      mutex_.Lock();
+    }
+  }
+  return {Exception::kSuccess};
+}
+
+/** WifiLanMedium implementation. */
+WifiLanMedium::~WifiLanMedium() {
+  advertising_info_.Clear();
+  discovering_info_.Clear();
+}
+
+bool WifiLanMedium::StartAdvertising(const NsdServiceInfo& nsd_service_info) {
+  std::string service_type = nsd_service_info.GetServiceType();
+  NSString* serviceType = ObjCStringFromCppString(service_type);
+  {
+    absl::MutexLock lock(&mutex_);
+    if (advertising_info_.Existed(service_type)) {
+      GTMLoggerInfo(@"[NEARBY] WifiLan StartAdvertising: Can't start advertising because "
+                    @"service_type=%@, has started already",
+                    serviceType);
+      return false;
+    }
+  }
+
+  // Retrieve service name.
+  NSString* serviceName = ObjCStringFromCppString(nsd_service_info.GetServiceName());
+  // Retrieve TXTRecord and convert it to NSDictionary type.
+  NSDictionary<NSString*, NSData*>* TXTRecordData =
+      NSDictionaryFromCppTxtRecords(nsd_service_info.GetTxtRecords());
+  // Get ip address and port to retrieve the server_socket, if not, then return nil.
+  std::string ip_address = nsd_service_info.GetIPAddress();
+  int port = nsd_service_info.GetPort();
+  __block std::string socket_name = WifiLanServerSocket::GetName(ip_address, port);
+  GNCMBonjourService* service = [[GNCMBonjourService alloc]
+           initWithServiceName:serviceName
+                   serviceType:serviceType
+                          port:requesting_port_
+                 TXTRecordData:TXTRecordData
+      endpointConnectedHandler:^GNCMConnectionHandlers*(id<GNCMConnection> connection) {
+        auto item = server_sockets_.find(socket_name);
+        WifiLanServerSocket* server_socket = item != server_sockets_.end() ? item->second : nullptr;
+        if (!server_socket) {
+          return nil;
+        }
+        auto socket = absl::make_unique<WifiLanSocket>(connection);
+        GNCMConnectionHandlers* connectionHandlers =
+            static_cast<WifiLanInputStream&>(socket->GetInputStream()).GetConnectionHandlers();
+        server_socket->Connect(std::move(socket));
+        return connectionHandlers;
+      }];
+  {
+    absl::MutexLock lock(&mutex_);
+    advertising_info_.Add(service_type, service);
+  }
+  return true;
+}
+
+bool WifiLanMedium::StopAdvertising(const NsdServiceInfo& nsd_service_info) {
+  std::string service_type = nsd_service_info.GetServiceType();
+  {
+    absl::MutexLock lock(&mutex_);
+    if (!advertising_info_.Existed(service_type)) {
+      GTMLoggerInfo(@"[NEARBY] WifiLan StopAdvertising: Can't stop advertising because we never "
+                    @"started advertising for service_type=%@",
+                    ObjCStringFromCppString(service_type));
+      return false;
+    }
+    advertising_info_.Remove(service_type);
+  }
+  return true;
+}
+
+bool WifiLanMedium::StartDiscovery(const std::string& service_type,
+                                   DiscoveredServiceCallback callback) {
+  NSString* serviceType = ObjCStringFromCppString(service_type);
+  {
+    absl::MutexLock lock(&mutex_);
+    if (discovering_info_.Existed(service_type)) {
+      GTMLoggerInfo(@"[NEARBY] WifiLan StartAdvertising: Can't start discovery because "
+                    @"service_type=%@, has started already",
+                    serviceType);
+      return false;
+    }
+  }
+  GNCMBonjourBrowser* browser = [[GNCMBonjourBrowser alloc]
+       initWithServiceType:serviceType
+      endpointFoundHandler:^GNCMEndpointLostHandler(
+          NSString* endpointId, NSString* serviceType, NSString* serviceName,
+          NSDictionary<NSString*, NSData*>* _Nullable txtRecordData,
+          GNCMConnectionRequester requestConnection) {
+        __block NsdServiceInfo nsd_service_info = {};
+        nsd_service_info.SetServiceName(CppStringFromObjCString(serviceName));
+        nsd_service_info.SetServiceType(CppStringFromObjCString(serviceType));
+        // Set TXTRecord converted from NSDictionary to hash map.
+        if (txtRecordData != nil) {
+          auto txt_records = AbslHashMapFromObjCTxtRecords(txtRecordData);
+          nsd_service_info.SetTxtRecords(txt_records);
+        }
+        connection_requesters_.insert({CppStringFromObjCString(serviceType), requestConnection});
+        callback.service_discovered_cb(nsd_service_info);
+        return ^{
+          callback.service_lost_cb(nsd_service_info);
+        };
+      }];
+  {
+    absl::MutexLock lock(&mutex_);
+    discovering_info_.Add(service_type, browser);
+  }
+  return true;
+}
+
+bool WifiLanMedium::StopDiscovery(const std::string& service_type) {
+  {
+    absl::MutexLock lock(&mutex_);
+    if (!discovering_info_.Existed(service_type)) {
+      GTMLoggerInfo(@"[NEARBY] WifiLan StopDiscovery: Can't stop discovering because "
+                     "we never started discovering.");
+      return false;
+    }
+    discovering_info_.Remove(service_type);
+  }
+  return true;
+}
+
+std::unique_ptr<api::WifiLanSocket> WifiLanMedium::ConnectToService(
+    const NsdServiceInfo& remote_service_info, CancellationFlag* cancellation_flag) {
+  std::string service_type = remote_service_info.GetServiceType();
+  GTMLoggerInfo(@"[NEARBY] WifiLan ConnectToService, service_type=%@",
+                ObjCStringFromCppString(service_type));
+
+  GNCMConnectionRequester connection_requester = nil;
+  {
+    absl::MutexLock lock(&mutex_);
+    const auto& it = connection_requesters_.find(service_type);
+    if (it == connection_requesters_.end()) {
+      return {};
+    }
+    connection_requester = it->second;
+  }
+
+  dispatch_group_t group = dispatch_group_create();
+  dispatch_group_enter(group);
+  __block std::unique_ptr<WifiLanSocket> socket;
+  if (connection_requester != nil) {
+    if (cancellation_flag->Cancelled()) {
+      GTMLoggerError(@"[NEARBY] WifiLan Connect: Has been cancelled: service_type=%@",
+                     ObjCStringFromCppString(service_type));
+      dispatch_group_leave(group);  // unblock
+      return {};
+    }
+
+    connection_requester(^(id<GNCMConnection> connection) {
+      // If the connection wasn't successfully established, return a NULL socket.
+      if (connection) {
+        socket = absl::make_unique<WifiLanSocket>(connection);
+      }
+
+      dispatch_group_leave(group);  // unblock
+      return socket != nullptr ? static_cast<WifiLanInputStream&>(socket->GetInputStream())
+                                     .GetConnectionHandlers()
+                               : nullptr;
+    });
+  }
+  dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
+
+  return std::move(socket);
+}
+
+std::unique_ptr<api::WifiLanSocket> WifiLanMedium::ConnectToService(
+    const std::string& ip_address, int port, CancellationFlag* cancellation_flag) {
+  // Not implemented.
+  return {};
+}
+
+std::unique_ptr<api::WifiLanServerSocket> WifiLanMedium::ListenForService(int port) {
+  auto server_socket = std::make_unique<WifiLanServerSocket>();
+  // The fake ip address and port need to be set here since they can't be retrieved before
+  // StartAadvertising begins. Furthermore, NSNetService can't resolve ip address when finding
+  // service. Try to fake them and make it socket name as a key of server_sockets_ which acts
+  // the same socket binding.
+  server_socket->SetIPAddress(GetFakeIPAddress());
+  requesting_port_ = port;
+  server_socket->SetPort(requesting_port_ == 0 ? GetFakePort() : requesting_port_);
+  std::string socket_name =
+      WifiLanServerSocket::GetName(server_socket->GetIPAddress(), server_socket->GetPort());
+  server_socket->SetCloseNotifier([this, socket_name]() {
+    absl::MutexLock lock(&mutex_);
+    server_sockets_.erase(socket_name);
+  });
+  GTMLoggerInfo(@"[NEARBY] WifiLan Adding server socket, socket_name=%@",
+                ObjCStringFromCppString(socket_name));
+  absl::MutexLock lock(&mutex_);
+  server_sockets_.insert({socket_name, server_socket.get()});
+  return server_socket;
+}
+
+std::string WifiLanMedium::GetFakeIPAddress() const {
+  std::string ip_address;
+  ip_address.resize(4);
+  uint32_t raw_ip_addr = Prng().NextUint32();
+  ip_address[0] = static_cast<char>(raw_ip_addr >> 24);
+  ip_address[1] = static_cast<char>(raw_ip_addr >> 16);
+  ip_address[2] = static_cast<char>(raw_ip_addr >> 8);
+  ip_address[3] = static_cast<char>(raw_ip_addr >> 0);
+
+  return ip_address;
+}
+
+int WifiLanMedium::GetFakePort() const {
+  uint16_t port = Prng().NextUint32();
+
+  return port;
+}
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/ios/Source/Shared/BUILD

@@ -0,0 +1,30 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+licenses(["notice"])
+
+package(default_visibility = ["//platform/impl/ios:__subpackages__"])
+
+objc_library(
+    name = "Shared",
+    srcs = [
+        "GNCUtils.m",
+    ],
+    hdrs = [
+        "GNCUtils.h",
+    ],
+    deps = [
+        "//third_party/objective_c/google_toolbox_for_mac:GTM_StringEncoding",
+        "//smhasher:libmurmur3",
+    ],
+)

cpp/platform/impl/ios/Source/Shared/GNCUtils.h

@@ -0,0 +1,50 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+// Current version of socket protocol.
+extern const int GNCSocketVersion;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/// Generates a SHA-256 hash (32 bytes) from a data object.
+NSData *_Nullable GNCSha256Data(NSData *data);
+
+/// Generates a SHA-256 hash (32 bytes) from a string.
+NSData *_Nullable GNCSha256String(NSString *string);
+
+
+/// Generates an MD5 hash (16 bytes) from a data object.
+NSData *_Nullable GNCMd5Data(NSData *data);
+
+/// Generates an MD5 hash (16 bytes) from a string.
+NSData *_Nullable GNCMd5String(NSString *string);
+
+
+/// Base64-encode.
+NSString *GNCBase64Encode(NSData *data);
+
+/// Base64-decode.
+NSData *GNCBase64Decode(NSString *string);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Source/Shared/GNCUtils.m

@@ -0,0 +1,65 @@
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Shared/GNCUtils.h"
+
+#import <CommonCrypto/CommonDigest.h>
+
+#import "third_party/objective_c/google_toolbox_for_mac/Foundation/GTMStringEncoding.h"
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+
+NS_ASSUME_NONNULL_BEGIN
+
+const int GNCSocketVersion = 2;
+
+NSData *GNCSha256Data(NSData *data) {
+  unsigned char output[CC_SHA256_DIGEST_LENGTH];
+  CC_LONG length = (CC_LONG)data.length;
+  if (!CC_SHA256(data.bytes, length, output)) return nil;
+  return [NSData dataWithBytes:output length:CC_SHA256_DIGEST_LENGTH];
+}
+
+NSData *GNCSha256String(NSString *string) {
+  return GNCSha256Data([string dataUsingEncoding:NSUTF8StringEncoding]);
+}
+
+NSData *GNCMd5Data(NSData *data) {
+  unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];
+  CC_MD5(data.bytes, (CC_LONG)data.length, md5Buffer);
+  return [NSData dataWithBytes:md5Buffer length:CC_MD5_DIGEST_LENGTH];
+}
+
+NSData *GNCMd5String(NSString *string) {
+  return GNCMd5Data([string dataUsingEncoding:NSUTF8StringEncoding]);
+}
+
+static GTMStringEncoding *GNCBase64WebSafeEncodingNoPadding() {
+  static dispatch_once_t onceToken;
+  static GTMStringEncoding *encoding;
+  dispatch_once(&onceToken, ^{
+    encoding = [GTMStringEncoding stringEncodingWithString:
+        @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"];
+    [encoding setDoPad:NO];
+  });
+  return encoding;
+}
+
+NSString *GNCBase64Encode(NSData *data) {
+  return [GNCBase64WebSafeEncodingNoPadding() encode:data error:nil];
+}
+
+NSData *GNCBase64Decode(NSString *string) {
+  return [GNCBase64WebSafeEncodingNoPadding() decode:string error:nil];
+}
+
+NS_ASSUME_NONNULL_END

cpp/platform/impl/ios/Tests/BUILD

@@ -0,0 +1,64 @@
+load("//tools/build_defs/apple:ios.bzl", "ios_unit_test")
+
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+licenses(["notice"])
+
+package(default_visibility = ["//visibility:public"])
+
+objc_library(
+    name = "PlatformTestslib",
+    testonly = 1,
+    srcs = [
+        "Platform/GNCCryptoTest.mm",
+        "Platform/GNCInputFileTest.mm",
+        "Platform/GNCMultiThreadExecutorTest.mm",
+        "Platform/GNCScheduledExecutorTest.mm",
+        "Platform/GNCSingleThreadExecutorTest.mm",
+    ],
+    deps = [
+        "//base",
+        "//platform/impl/ios:Connections",
+    ],
+)
+
+ios_unit_test(
+    name = "PlatformTests",
+    minimum_os_version = "12.0",
+    runner = "//testing/utp/ios:IOS_12",
+    deps = [
+        ":PlatformTestslib",
+    ],
+)
+
+objc_library(
+    name = "SharedTestslib",
+    testonly = 1,
+    srcs = [
+        "Shared/GNCUtilsTest.mm",
+    ],
+    deps = [
+        "//platform/impl/ios/Source/Platform",
+        "//platform/impl/ios/Source/Shared",
+    ],
+)
+
+ios_unit_test(
+    name = "SharedTests",
+    minimum_os_version = "12.0",
+    runner = "//testing/utp/ios:IOS_12",
+    deps = [
+        ":SharedTestslib",
+    ],
+)

cpp/platform/impl/ios/Tests/Platform/GNCCryptoTest.mm

@@ -0,0 +1,52 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <XCTest/XCTest.h>
+
+#include "third_party/nearby_connections/cpp/platform/api/crypto.h"
+#include "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+
+@interface GNCCryptoTest : XCTestCase
+@end
+
+@implementation GNCCryptoTest
+
+// Tests that the hash functions return the expected values.
+- (void)testHashValues {
+  std::string string("com.google.location.nearby");
+
+  // SHA-256 test.
+  {
+    const uint8_t sha256ExpectedHash[] = {
+        0x09, 0x8e, 0x3c, 0x54, 0x2d, 0xee, 0x9e, 0x35,
+        0x1d, 0xe7, 0x5b, 0xcf, 0xda, 0xb5, 0x62, 0xd3,
+        0xde, 0xba, 0x14, 0x49, 0xbd, 0xf5, 0x95, 0x04,
+        0x1f, 0x1d, 0x99, 0x84, 0x87, 0xc3, 0xcb, 0x8a, };
+    location::nearby::ByteArray sha256Hash = location::nearby::Crypto::Sha256(string);
+    XCTAssert(sha256Hash.size() == sizeof(sha256ExpectedHash) &&
+              memcmp(sha256Hash.data(), sha256ExpectedHash, sizeof(sha256ExpectedHash)) == 0);
+  }
+
+  // MD5 test.
+  {
+    const uint8_t md5ExpectedHash[] = {
+        0x97, 0x78, 0x1d, 0x3d, 0xee, 0xd7, 0xdc, 0x5a,
+        0x6e, 0xee, 0x50, 0x08, 0xce, 0xd1, 0xb2, 0xe8 };
+    location::nearby::ByteArray md5Hash = location::nearby::Crypto::Md5(string);
+    XCTAssert(md5Hash.size() == sizeof(md5ExpectedHash) &&
+              memcmp(md5Hash.data(), md5ExpectedHash, sizeof(md5ExpectedHash)) == 0);
+  }
+}
+
+@end

cpp/platform/impl/ios/Tests/Platform/GNCInputFileTest.mm

@@ -0,0 +1,56 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <XCTest/XCTest.h>
+
+#import "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+#import "third_party/nearby_connections/cpp/platform/base/exception.h"
+#import "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/input_file.h"
+
+using ::location::nearby::ios::InputFile;
+using ::location::nearby::ByteArray;
+using ::location::nearby::ExceptionOr;
+
+@interface GNCInputFileTest : XCTestCase
+@end
+
+@implementation GNCInputFileTest
+
+// TODO(b/169292092): Find more tools (e.g. file/util/TempPath) to test fake file.
+- (void)testNonExistentPath {
+  std::string cc_path("/foo/bar/test.ext");
+  NSString* objcPath = [NSString stringWithUTF8String:cc_path.c_str()];
+  NSURL *testURL = [NSURL URLWithString:objcPath];
+
+  auto input_file = std::make_unique<InputFile>(testURL);
+  XCTAssert(input_file != nullptr);
+
+  XCTAssertEqual(input_file->GetTotalSize(), 0);
+  ExceptionOr<ByteArray> read_result = input_file->Read(3);
+  XCTAssertFalse(read_result.ok());
+}
+
+- (void)testGetFilePath {
+  std::string cc_path("/foo/bar/test.ext");
+  NSString* objcPath = [NSString stringWithUTF8String:cc_path.c_str()];
+  NSURL *testURL = [NSURL URLWithString:objcPath];
+
+  auto input_file = std::make_unique<InputFile>(testURL);
+  XCTAssert(input_file != nullptr);
+
+  std::string input_file_path = input_file->GetFilePath();
+  XCTAssertTrue([objcPath isEqualToString:[NSString stringWithUTF8String:input_file_path.c_str()]]);
+}
+
+@end

cpp/platform/impl/ios/Tests/Platform/GNCMultiThreadExecutorTest.mm

@@ -0,0 +1,114 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <XCTest/XCTest.h>
+
+#include "third_party/absl/time/time.h"
+#include "third_party/nearby_connections/cpp/platform/api/cancelable.h"
+#include "third_party/nearby_connections/cpp/platform/api/executor.h"
+#include "third_party/nearby_connections/cpp/platform/api/platform.h"
+#include "third_party/nearby_connections/cpp/platform/api/submittable_executor.h"
+#include "third_party/nearby_connections/cpp/platform/base/runnable.h"
+
+using location::nearby::Runnable;
+using location::nearby::api::ImplementationPlatform;
+using MultiThreadExecutor = location::nearby::api::SubmittableExecutor;
+
+@interface GNCMultiThreadExecutorTest : XCTestCase
+@property(atomic) int counter;
+@property(atomic) int otherCounter;
+@end
+
+@implementation GNCMultiThreadExecutorTest
+
+// Creates a MultiThreadExecutor.
+- (std::unique_ptr<MultiThreadExecutor>)executor {
+  std::unique_ptr<MultiThreadExecutor> executor =
+      ImplementationPlatform::CreateMultiThreadExecutor(4);
+  XCTAssert(executor != nullptr);
+  return executor;
+}
+
+// Tests that the executor executes runnables as expected.
+- (void)testExecute {
+  std::unique_ptr<MultiThreadExecutor> executor([self executor]);
+
+  // Execute two runnables that increment the counter.
+  const int kIncrements = 13;
+  Runnable incrementer = [self]() { self.counter++; };
+  for (int i = 0; i < kIncrements; i++) {
+    executor->Execute(std::move(incrementer));
+  }
+
+  // Check that the counter has the expected value after giving the runnables time to run.
+  [NSThread sleepForTimeInterval:0.01];
+  XCTAssertEqual(self.counter, kIncrements);
+}
+
+// Tests that the executor submits runnables as expected.
+- (void)testSubmit {
+  std::unique_ptr<MultiThreadExecutor> executor([self executor]);
+
+  // Submit two runnables that increment the counter.
+  const int kIncrements = 13;
+  Runnable incrementer = [self]() { self.counter++; };
+  for (int i = 0; i < kIncrements; i++) {
+    executor->DoSubmit(std::move(incrementer));
+  }
+
+  // Check that the counter has the expected value after giving the runnables time to run.
+  [NSThread sleepForTimeInterval:0.01];
+  XCTAssertEqual(self.counter, kIncrements);
+}
+
+// Tests that fails to submit when the executor is shut down.
+- (void)testFailtoSubmitAfterShutdown {
+  std::unique_ptr<MultiThreadExecutor> executor([self executor]);
+
+  executor->Shutdown();
+
+  XCTAssertFalse(executor->DoSubmit([self]() { self.counter++; }));
+
+  // Check that the counter has the expected value after giving the runnables time to run.
+  [NSThread sleepForTimeInterval:0.01];
+  XCTAssertEqual(self.counter, 0);
+}
+
+// Tests that when the executor is shut down, it waits for pending operations to finish, and no new
+// operations will be executed.
+- (void)testShutdownToAllowExistingTaskComplete {
+  std::unique_ptr<MultiThreadExecutor> executor([self executor]);
+
+  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0);
+  XCTestExpectation *expectation = [self expectationWithDescription:@"finished"];
+
+  const int kRunnableCount = 1000;
+  for (int i = 0; i < kRunnableCount; i++) {
+    executor->Execute([self]() { self.counter++; });
+  }
+
+  executor->Shutdown();
+
+  executor->Execute([self]() { self.otherCounter++; });
+
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), queue, ^{
+    XCTAssertLessThanOrEqual(self.counter, kRunnableCount);
+    XCTAssertEqual(self.otherCounter, 0);
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:0.5 handler:nil];
+}
+
+@end

cpp/platform/impl/ios/Tests/Platform/GNCScheduledExecutorTest.mm

@@ -0,0 +1,139 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <XCTest/XCTest.h>
+
+#include "third_party/absl/time/time.h"
+#include "third_party/nearby_connections/cpp/platform/api/cancelable.h"
+#include "third_party/nearby_connections/cpp/platform/api/executor.h"
+#include "third_party/nearby_connections/cpp/platform/api/platform.h"
+#include "third_party/nearby_connections/cpp/platform/api/scheduled_executor.h"
+#include "third_party/nearby_connections/cpp/platform/base/runnable.h"
+
+using location::nearby::Runnable;
+using location::nearby::api::ImplementationPlatform;
+using location::nearby::api::ScheduledExecutor;
+
+@interface GNCScheduledExecutorTest : XCTestCase
+@property(atomic) int counter;
+@end
+
+@implementation GNCScheduledExecutorTest
+
+// Creates a ScheduledExecutor.
+- (std::unique_ptr<ScheduledExecutor>)executor {
+  std::unique_ptr<ScheduledExecutor> executor = ImplementationPlatform::CreateScheduledExecutor();
+  XCTAssert(executor != nullptr);
+  return executor;
+}
+
+// Tests that the executor schedules operation at the specified time.
+- (void)testScheduling {
+  std::unique_ptr<ScheduledExecutor> executor([self executor]);
+
+  XCTestExpectation *expectation = [self expectationWithDescription:@"finished"];
+
+  Runnable incrementer = [self]() { self.counter++; };
+
+  void (^checkCounter)(int, NSTimeInterval, dispatch_block_t) =
+      ^(int expectedCount, NSTimeInterval delay, dispatch_block_t finalBlock) {
+        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC)),
+                       dispatch_get_main_queue(), ^{
+                         XCTAssertEqual(self.counter, expectedCount);
+                         finalBlock();
+                       });
+      };
+
+  // Schedule two runnables that increment the counter, at 0.4 and 0.8 seconds.
+  executor->Schedule(std::move(incrementer), absl::Seconds(0.4));
+  executor->Schedule(std::move(incrementer), absl::Seconds(0.8));
+
+  // Check that the counter contains the expected values at 0.2, 0.6, and 1.0 seconds.
+  checkCounter(0, 0.2, ^{});
+  checkCounter(1, 0.6, ^{});
+  checkCounter(2, 1.0, ^{ [expectation fulfill]; });
+
+  [self waitForExpectationsWithTimeout:1.2 handler:nil];
+}
+
+// Tests that fails to schedule when the executor is shut down.
+- (void)testFailtoScheduleAfterShutdown {
+  std::unique_ptr<ScheduledExecutor> executor([self executor]);
+
+  executor->Shutdown();
+
+  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0);
+  XCTestExpectation *expectation = [self expectationWithDescription:@"finished"];
+
+  const NSTimeInterval delay = 0.1;
+  executor->Schedule([self]() { self.counter++; }, absl::Milliseconds(delay));
+
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * 2 * NSEC_PER_SEC)), queue, ^{
+    XCTAssertEqual(self.counter, 0);
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:delay * 5 handler:nil];
+}
+
+// Tests that fails to cancel when the executor is shut down.
+- (void)testFailToCancelAfterShutdown {
+  std::unique_ptr<ScheduledExecutor> executor([self executor]);
+
+  executor->Shutdown();
+
+  auto cancelable = executor->Schedule([self]() { self.counter++; }, absl::Seconds(0.1));
+
+  XCTAssert(cancelable.get() == nullptr);
+}
+
+// Tests that shutting down an existing task fails to complete.
+- (void)testShutdownToFailExistingTask {
+  std::unique_ptr<ScheduledExecutor> executor([self executor]);
+
+  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0);
+  XCTestExpectation *expectation = [self expectationWithDescription:@"finished"];
+
+  const NSTimeInterval delay = 0.1;
+  executor->Schedule([self]() { self.counter++; }, absl::Milliseconds(delay));
+
+  executor->Shutdown();
+
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * 2 * NSEC_PER_SEC)), queue, ^{
+    XCTAssertEqual(self.counter, 0);
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:delay * 5 handler:nil];
+}
+
+// Tests that a canceled runnable doesn't run.
+- (void)testCancelable {
+  std::unique_ptr<ScheduledExecutor> executor([self executor]);
+
+  // This runnable should run but not increment the counter because it sleeps for longer than the
+  // cancel below.
+  const NSTimeInterval delay = 0.1;
+  auto cancelable = executor->Schedule([self]() { self.counter++; }, absl::Seconds(delay));
+  XCTAssert(cancelable.get() != nullptr);
+
+  // Cancel the runnable.
+  cancelable->Cancel();
+
+  // Wait for the time interval to pass and verify that it didn't run.
+  [NSThread sleepForTimeInterval:delay * 1.1];
+  XCTAssertEqual(self.counter, 0);
+}
+
+@end

cpp/platform/impl/ios/Tests/Platform/GNCSingleThreadExecutorTest.mm

@@ -0,0 +1,95 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <XCTest/XCTest.h>
+
+#include "third_party/absl/time/time.h"
+#include "third_party/nearby_connections/cpp/platform/api/cancelable.h"
+#include "third_party/nearby_connections/cpp/platform/api/executor.h"
+#include "third_party/nearby_connections/cpp/platform/api/platform.h"
+#include "third_party/nearby_connections/cpp/platform/api/submittable_executor.h"
+#include "third_party/nearby_connections/cpp/platform/base/runnable.h"
+
+using location::nearby::Runnable;
+using location::nearby::api::ImplementationPlatform;
+using SingleThreadExecutor = location::nearby::api::SubmittableExecutor;
+
+@interface GNCSingleThreadExecutorTest : XCTestCase
+@property(atomic) int counter;
+@end
+
+@implementation GNCSingleThreadExecutorTest
+
+// Creates a SingleThreadExecutor.
+- (std::unique_ptr<SingleThreadExecutor>)executor {
+  std::unique_ptr<SingleThreadExecutor> executor =
+      ImplementationPlatform::CreateSingleThreadExecutor();
+  XCTAssert(executor != nullptr);
+  return executor;
+}
+
+// Tests that the executor executes runnables as expected.
+- (void)testRunnables {
+  std::unique_ptr<SingleThreadExecutor> executor([self executor]);
+
+  Runnable incrementer = [self]() { self.counter++; };
+
+  // Schedule two runnables that increment the counter.
+  executor->Execute(std::move(incrementer));
+  executor->Execute(std::move(incrementer));
+
+  // Check that the counter has the expected value after a moment.
+  [NSThread sleepForTimeInterval:0.01];
+  XCTAssertEqual(self.counter, 2);
+}
+
+// Tests that fails to execute when the executor is shut down.
+- (void)testShutdownBeforeInvokeTask {
+  std::unique_ptr<SingleThreadExecutor> executor([self executor]);
+
+  executor->Shutdown();
+
+  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0);
+  XCTestExpectation *expectation = [self expectationWithDescription:@"finished"];
+
+  executor->Execute([self]() { self.counter++; });
+
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), queue, ^{
+    XCTAssertEqual(self.counter, 0);
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:0.5 handler:nil];
+}
+
+// Tests that shutting down an existing task allows to complete.
+- (void)testShutdownToAllowExistingTaskComplete {
+  std::unique_ptr<SingleThreadExecutor> executor([self executor]);
+
+  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0);
+  XCTestExpectation *expectation = [self expectationWithDescription:@"finished"];
+
+  executor->Execute([self]() { self.counter++; });
+
+  executor->Shutdown();
+
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), queue, ^{
+    XCTAssertEqual(self.counter, 1);
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:0.5 handler:nil];
+}
+
+@end

cpp/platform/impl/ios/Tests/Shared/GNCUtilsTest.mm

@@ -0,0 +1,46 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <XCTest/XCTest.h>
+
+#include "third_party/nearby_connections/cpp/platform/base/byte_array.h"
+#include "third_party/nearby_connections/cpp/platform/impl/ios/Source/Platform/utils.h"
+
+using location::nearby::ByteArray;
+using location::nearby::ByteArrayFromNSData;
+using location::nearby::CppStringFromObjCString;
+using location::nearby::ObjCStringFromCppString;
+
+@interface GNCUtilsTest : XCTestCase
+@end
+
+@implementation GNCUtilsTest
+
+// Tests that strings can be converted between C++ and Obj-C.
+- (void)testStrings {
+  XCTAssert([ObjCStringFromCppString(std::string("Hey")) isEqual:@"Hey"]);
+  XCTAssert(CppStringFromObjCString(@"Dude") == std::string("Dude"));
+}
+
+// Tests that data objects can be converted between C++ and Obj-C.
+- (void)testDataObjects {
+  uint8_t bytes[] = {0xfe, 0xed, 0xfa, 0xce, 0xde, 0xad, 0xbe, 0xef};
+  ByteArray byteArray = ByteArray{(const char *)bytes, sizeof(bytes)};
+  NSData *nsData = [NSData dataWithBytes:bytes length:sizeof(bytes)];
+
+  XCTAssert([NSDataFromByteArray(byteArray) isEqual:nsData]);
+  XCTAssert(memcmp(ByteArrayFromNSData(nsData).data(), bytes, sizeof(bytes)) == 0);
+}
+
+@end

cpp/platform/impl/shared/BUILD

@@ -49,7 +49,6 @@ cc_library(
     hdrs = ["file.h"],
     compatible_with = ["//buildenv/target:non_prod"],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
         "//platform/impl:__subpackages__",
     ],
     deps = [

cpp/platform/public/BUILD

@@ -52,10 +52,10 @@ cc_library(
     ],
     compatible_with = ["//buildenv/target:non_prod"],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
         "//analytics:__subpackages__",
         "//core:__subpackages__",
         "//platform/base:__pkg__",
+        "//platform/impl/ios:__subpackages__",
         "//platform/impl/windows:__subpackages__",
         "//platform/public:__pkg__",
     ],

proto/connections/BUILD

@@ -26,7 +26,7 @@ proto_library(
         "//buildenv/target:non_prod",
     ],
     visibility = [
-        "//googlemac/iPhone/Shared/Nearby/Connections:__subpackages__",
+        "//platform/impl/ios:__subpackages__",
     ],
 )