Weave port [3/n]: Introduce weave packet counter generator

PiperOrigin-RevId: 523189849

Package.swift

@@ -547,6 +547,7 @@ let package = Package(
         "internal/test/fake_device_info_test.cc",
         "internal/test/fake_task_runner_test.cc",
         "internal/weave/packet_test.cc",
+        "internal/weave/packet_sequence_number_generator_test.cc",
         "internal/weave/packetizer_test.cc",
         // simulation
         "connections/implementation/offline_simulation_user.cc",

internal/weave/BUILD

@@ -2,15 +2,18 @@ cc_library(
     name = "weave",
     srcs = [
         "packet.cc",
+        "packet_sequence_number_generator.cc",
         "packetizer.cc",
     ],
     hdrs = [
         "packet.h",
+        "packet_sequence_number_generator.h",
         "packetizer.h",
     ],
     deps = [
         "//internal/platform:base",
         "//internal/platform:types",
+        "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/status",
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
@@ -33,6 +36,19 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "packet_sequence_number_generator_test",
+    srcs = [
+        "packet_sequence_number_generator_test.cc",
+    ],
+    deps = [
+        ":weave",
+        "//internal/platform/implementation/g3",  # build_cleaner: keep
+        "@com_github_protobuf_matchers//protobuf-matchers",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_test(
     name = "packetizer_test",
     srcs = [

internal/weave/packet_sequence_number_generator.cc

@@ -0,0 +1,39 @@
+// Copyright 2023 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 "internal/weave/packet_sequence_number_generator.h"
+
+#include "internal/platform/mutex_lock.h"
+#include "internal/weave/packet.h"
+
+namespace nearby {
+namespace weave {
+
+int PacketSequenceNumberGenerator::Next() {
+  MutexLock lock(&mutex_);
+  int next_packet_counter = packet_counter_;
+  if (next_packet_counter == Packet::kMaxPacketCounter) {
+    packet_counter_ = 0;
+  } else {
+    ++packet_counter_;
+  }
+  return next_packet_counter;
+}
+
+void PacketSequenceNumberGenerator::Reset() {
+  MutexLock lock(&mutex_);
+  packet_counter_ = 0;
+}
+}  // namespace weave
+}  // namespace nearby

internal/weave/packet_sequence_number_generator.h

@@ -0,0 +1,45 @@
+// Copyright 2023 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 THIRD_PARTY_NEARBY_INTERNAL_WEAVE_PACKET_SEQUENCE_NUMBER_GENERATOR_H_
+#define THIRD_PARTY_NEARBY_INTERNAL_WEAVE_PACKET_SEQUENCE_NUMBER_GENERATOR_H_
+
+#include "absl/base/thread_annotations.h"
+#include "internal/platform/mutex.h"
+
+namespace nearby {
+namespace weave {
+
+// Keeps a counter of the next Weave packet to set the new Weave packet sequence
+// number in a connection. This counter automatically rolls over once it hits 7,
+// since 3 bits are allocated in the packet to the counter, making its max value
+// 0b111, or 7.
+class PacketSequenceNumberGenerator {
+ public:
+  // Returns the next counter in the sequence, incrementing the counter
+  // internally.
+  int Next();
+
+  // Resets the counter to 0.
+  void Reset();
+
+ private:
+  Mutex mutex_;
+  int packet_counter_ ABSL_GUARDED_BY(mutex_) = 0;
+};
+
+}  // namespace weave
+}  // namespace nearby
+
+#endif  // THIRD_PARTY_NEARBY_INTERNAL_WEAVE_PACKET_SEQUENCE_NUMBER_GENERATOR_H_

internal/weave/packet_sequence_number_generator_test.cc

@@ -0,0 +1,60 @@
+// Copyright 2023 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 "internal/weave/packet_sequence_number_generator.h"
+
+#include "gmock/gmock.h"
+#include "protobuf-matchers/protocol-buffer-matchers.h"
+#include "gtest/gtest.h"
+
+namespace nearby {
+namespace weave {
+namespace {
+
+TEST(PacketSequenceNumberGeneratorTest, TestNext) {
+  PacketSequenceNumberGenerator generator;
+  EXPECT_EQ(generator.Next(), 0);
+  EXPECT_EQ(generator.Next(), 1);
+  EXPECT_EQ(generator.Next(), 2);
+  EXPECT_EQ(generator.Next(), 3);
+}
+
+TEST(PacketSequenceNumberGeneratorTest, TestNextWrapping) {
+  PacketSequenceNumberGenerator generator;
+  EXPECT_EQ(generator.Next(), 0);
+  EXPECT_EQ(generator.Next(), 1);
+  EXPECT_EQ(generator.Next(), 2);
+  EXPECT_EQ(generator.Next(), 3);
+  EXPECT_EQ(generator.Next(), 4);
+  EXPECT_EQ(generator.Next(), 5);
+  EXPECT_EQ(generator.Next(), 6);
+  EXPECT_EQ(generator.Next(), 7);
+  EXPECT_EQ(generator.Next(), 0);
+  EXPECT_EQ(generator.Next(), 1);
+}
+
+TEST(PacketSequenceNumberGeneratorTest, TestReset) {
+  PacketSequenceNumberGenerator generator;
+  EXPECT_EQ(generator.Next(), 0);
+  EXPECT_EQ(generator.Next(), 1);
+  EXPECT_EQ(generator.Next(), 2);
+  generator.Reset();
+  EXPECT_EQ(generator.Next(), 0);
+  EXPECT_EQ(generator.Next(), 1);
+  EXPECT_EQ(generator.Next(), 2);
+}
+
+}  // namespace
+}  // namespace weave
+}  // namespace nearby