[Nearby] Optimize NWFramework socket reads and writes for performance and memory. III

PiperOrigin-RevId: 894930585

internal/platform/implementation/apple/Mediums/WiFiCommon/GNCNWFrameworkError.h

@@ -26,4 +26,5 @@ typedef NS_ERROR_ENUM(GNCNWFrameworkErrorDomain, GNCNWFrameworkError){
     GNCNWFrameworkErrorUnknown,
     GNCNWFrameworkErrorTimedOut,
     GNCNWFrameworkErrorDuplicateDiscovererForServiceType,
+    GNCNWFrameworkErrorNotConnected,
 };

internal/platform/implementation/apple/Mediums/WiFiCommon/GNCNWFrameworkSocket.h

@@ -75,6 +75,17 @@
  */
 - (BOOL)write:(NSData *)data error:(NSError **_Nullable)error;
 
+/**
+ * Writes raw bytes to the connection.
+ *
+ * @param bytes The buffer to write.
+ * @param length The number of bytes to write.
+ * @param error Error that will be populated on failure.
+ */
+- (BOOL)writeBytes:(const void *)bytes 
+            length:(NSUInteger)length 
+             error:(NSError **_Nullable)error;
+
 /**
  * Gracefully closes the connection to remote endpoint.
  *

internal/platform/implementation/apple/Mediums/WiFiCommon/GNCNWFrameworkSocket.mm

@@ -92,7 +92,7 @@ static const NSTimeInterval kConnectionWriteTimeout = 5.0;  // 5 seconds timeout
   if (!self.connection) {
     if (error) {
       *error = [NSError errorWithDomain:GNCNWFrameworkErrorDomain
-                                   code:GNCNWFrameworkErrorUnknown
+                                   code:GNCNWFrameworkErrorNotConnected
                                userInfo:nil];
     }
     return std::nullopt;
@@ -185,6 +185,50 @@ static const NSTimeInterval kConnectionWriteTimeout = 5.0;  // 5 seconds timeout
   return signaled && blockSuccess;
 }
 
+- (BOOL)writeBytes:(const void *)bytes length:(NSUInteger)length error:(NSError **)error {
+  if (!self.connection) {
+    if (error) {
+      *error = [NSError errorWithDomain:GNCNWFrameworkErrorDomain
+                                   code:GNCNWFrameworkErrorNotConnected
+                               userInfo:nil];
+    }
+    return NO;
+  }
+
+  dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
+
+  __block NSError *blockError = nil;
+
+  // OPTIMIZATION: Use DISPATCH_DATA_DESTRUCTOR_DEFAULT to perform a
+  // single copy into a GCD-managed buffer. No NSData required.
+  // TODO: edwinwu - Investigate to see if it is worth to make it zero-copy by replacing
+  // DISPATCH_DATA_DESTRUCTOR_DEFAULT with a custom empty destructor:
+  //     dispatch_data_t dispatchData = dispatch_data_create(bytes, length, nil, ^{
+  //         // Zero-copy: ownership remains with the caller.
+  //     });
+  dispatch_data_t dispatchData =
+      dispatch_data_create(bytes, length, nil, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+
+  [self.connection sendData:dispatchData
+                    context:NW_CONNECTION_DEFAULT_MESSAGE_CONTEXT
+                 isComplete:NO
+          completionHandler:^(nw_error_t _Nullable sendError) {
+            if (sendError) {
+              blockError = (__bridge_transfer NSError *)nw_error_copy_cf_error(sendError);
+            }
+            dispatch_semaphore_signal(semaphore);
+          }];
+
+  // Wait until signaled or the 5-second timeout passes
+  intptr_t waitResult = dispatch_semaphore_wait(
+      semaphore,
+      dispatch_time(DISPATCH_TIME_NOW, (int64_t)(kConnectionWriteTimeout * NSEC_PER_SEC)));
+  if (error != nil) {
+    *error = blockError;
+  }
+  return (waitResult == 0) && (blockError == nil);
+}
+
 - (void)close {
   [_connection cancel];
   _connection = nil;

internal/platform/implementation/apple/Mediums/WiFiCommon/Tests/GNCNWFrameworkSocketTest.mm

@@ -132,6 +132,28 @@ NS_ASSUME_NONNULL_BEGIN
   XCTAssertFalse(result);
 }
 
+- (void)testWriteBytes_Success {
+  NSError *error = nil;
+  NSString *testString = @"testData";
+  NSData *testData = [testString dataUsingEncoding:NSUTF8StringEncoding];
+
+  BOOL result = [_socket writeBytes:testData.bytes length:testData.length error:&error];
+
+  XCTAssertTrue(result);
+  XCTAssertNil(error);
+}
+
+- (void)testWriteBytes_Error {
+  NSError *error = nil;
+  NSString *testString = @"testData";
+  NSData *testData = [testString dataUsingEncoding:NSUTF8StringEncoding];
+  _fakeConnection.simulateSendFailure = YES;
+
+  BOOL result = [_socket writeBytes:testData.bytes length:testData.length error:&error];
+
+  XCTAssertFalse(result);
+}
+
 - (void)testClose {
   XCTAssertFalse(_fakeConnection.cancelCalled);
   [_socket close];
@@ -140,6 +162,7 @@ NS_ASSUME_NONNULL_BEGIN
   NSError *error = nil;
   XCTAssertNil([_socket readMaxLength:10 error:&error]);
   XCTAssertFalse([_socket write:[NSData data] error:&error]);
+  XCTAssertFalse([_socket writeBytes:"test" length:4 error:&error]);
 }
 
 @end