Allow multiple pending reads

src/objective-c/GRPCClient/GRPCCall.h

@@ -265,7 +265,7 @@ extern NSString *const kGRPCTrailersKey;
  */
 - (void)finish;
 
-- (void)receiveNextMessage;
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages;
 
 /**
  * Get a copy of the original call options.

src/objective-c/GRPCClient/GRPCCall.m

@@ -70,7 +70,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
                  callOptions:(GRPCCallOptions *)callOptions
                    writeDone:(void (^)(void))writeDone;
 
-- (void)receiveNextMessage;
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages;
 
 @end
 
@@ -123,7 +123,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
   /** Flags whether call has been finished. */
   BOOL _finished;
   /** The number of pending messages receiving requests. */
-  NSUInteger _pendingReceiveNextMessage;
+  NSUInteger _pendingReceiveNextMessages;
 }
 
 - (instancetype)initWithRequestOptions:(GRPCRequestOptions *)requestOptions
@@ -212,9 +212,9 @@ const char *kCFStreamVarName = "grpc_cfstream";
     if (_callOptions.initialMetadata) {
       [_call.requestHeaders addEntriesFromDictionary:_callOptions.initialMetadata];
     }
-    if (_pendingReceiveNextMessage) {
+    if (_pendingReceiveNextMessages > 0) {
-      [_call receiveNextMessage];
+      [_call receiveNextMessages:_pendingReceiveNextMessages];
-      _pendingReceiveNextMessage = NO;
+      _pendingReceiveNextMessages = 0;
     }
     copiedCall = _call;
   }
@@ -399,16 +399,16 @@ const char *kCFStreamVarName = "grpc_cfstream";
   }
 }
 
-- (void)receiveNextMessage {
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages {
   GRPCCall *copiedCall = nil;
   @synchronized(self) {
     copiedCall = _call;
     if (copiedCall == nil) {
-      _pendingReceiveNextMessage = YES;
+      _pendingReceiveNextMessages += numberOfMessages;
       return;
     }
   }
-  [copiedCall receiveNextMessage];
+  [copiedCall receiveNextMessages:numberOfMessages];
 }
 
 @end
@@ -481,8 +481,8 @@ const char *kCFStreamVarName = "grpc_cfstream";
   // Indicate a read request to core is pending.
   BOOL _pendingCoreRead;
 
-  // Indicate a read message request from user.
+  // Indicate pending read message request from user.
-  BOOL _pendingReceiveNextMessage;
+  NSUInteger _pendingReceiveNextMessages;
 }
 
 @synthesize state = _state;
@@ -591,7 +591,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
     _responseQueue = dispatch_get_main_queue();
 
     // do not start a read until initial metadata is received
-    _pendingReceiveNextMessage = NO;
+    _pendingReceiveNextMessages = 0;
     _pendingCoreRead = YES;
   }
   return self;
@@ -669,11 +669,11 @@ const char *kCFStreamVarName = "grpc_cfstream";
     if (_state != GRXWriterStateStarted) {
       return;
     }
-    if (_callOptions.enableFlowControl && (_pendingCoreRead || !_pendingReceiveNextMessage)) {
+    if (_callOptions.enableFlowControl && (_pendingCoreRead || _pendingReceiveNextMessages == 0)) {
       return;
     }
     _pendingCoreRead = YES;
-    _pendingReceiveNextMessage = NO;
+    _pendingReceiveNextMessages--;
   }
 
   dispatch_async(_callQueue, ^{
@@ -696,7 +696,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
         // that's on the hands of any server to have. Instead we finish and ask
         // the server to cancel.
         @synchronized(strongSelf) {
-          strongSelf->_pendingReceiveNextMessage = NO;
+          strongSelf->_pendingReceiveNextMessages--;
           [strongSelf
               finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
                                                   code:GRPCErrorCodeResourceExhausted
@@ -764,13 +764,13 @@ const char *kCFStreamVarName = "grpc_cfstream";
   });
 }
 
-- (void)receiveNextMessage {
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages {
-  @synchronized(self) {
+  if (numberOfMessages == 0) {
-    // Duplicate invocation of this method. Return
-    if (_pendingReceiveNextMessage) {
     return;
   }
-    _pendingReceiveNextMessage = YES;
+  @synchronized(self) {
+    _pendingReceiveNextMessages += numberOfMessages;
+
     [self maybeStartNextRead];
   }
 }
@@ -793,7 +793,6 @@ const char *kCFStreamVarName = "grpc_cfstream";
       }
     }
   };
-
   GRPCOpSendMessage *op =
       [[GRPCOpSendMessage alloc] initWithMessage:message handler:resumingHandler];
   if (!_unaryCall) {

src/objective-c/ProtoRPC/ProtoRPC.h

@@ -136,8 +136,20 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)finish;
 
+/**
+ * Tell gRPC to receive the next message. If flow control is enabled, the messages received from the
+ * server are buffered in gRPC until the user want to receive the next message. If flow control is
+ * not enabled, messages will be automatically received after the previous one is delivered.
+ */
 - (void)receiveNextMessage;
 
+/**
+ * Tell gRPC to receive the next N message. If flow control is enabled, the messages received from
+ * the server are buffered in gRPC until the user want to receive the next message. If flow control
+ * is not enabled, messages will be automatically received after the previous one is delivered.
+ */
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages;
+
 @end
 
 NS_ASSUME_NONNULL_END

src/objective-c/ProtoRPC/ProtoRPC.m

@@ -72,6 +72,7 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 
 - (void)start {
   [_call start];
+  [_call receiveNextMessage];
   [_call writeMessage:_message];
   [_call finish];
 }
@@ -198,11 +199,14 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 }
 
 - (void)receiveNextMessage {
+  [self receiveNextMessages:1];
+}
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages {
   GRPCCall2 *copiedCall;
   @synchronized(self) {
     copiedCall = _call;
   }
-  [copiedCall receiveNextMessage];
+  [copiedCall receiveNextMessages:numberOfMessages];
 }
 
 - (void)didReceiveInitialMetadata:(NSDictionary *)initialMetadata {

src/objective-c/tests/APIv2Tests/APIv2Tests.m

@@ -502,7 +502,7 @@ static const NSTimeInterval kInvertedTimeout = 2;
   [self waitForExpectationsWithTimeout:kTestTimeout handler:nil];
 }
 
-- (void)testWriteFlowControl {
+- (void)testFlowControlWrite {
   __weak XCTestExpectation *expectWriteData =
       [self expectationWithDescription:@"Reported write data"];
 
@@ -531,7 +531,7 @@ static const NSTimeInterval kInvertedTimeout = 2;
                                     callOptions:options];
 
   [call start];
-  [call receiveNextMessage];
+  [call receiveNextMessages:1];
   [call writeData:[request data]];
 
   // Wait for 3 seconds and make sure we do not receive the response
@@ -540,7 +540,7 @@ static const NSTimeInterval kInvertedTimeout = 2;
   [call finish];
 }
 
-- (void)testReadFlowControl {
+- (void)testFlowControlRead {
   __weak __block XCTestExpectation *expectBlockedMessage =
       [self expectationWithDescription:@"Message not delivered without recvNextMessage"];
   __weak __block XCTestExpectation *expectPassedMessage = nil;
@@ -593,29 +593,31 @@ static const NSTimeInterval kInvertedTimeout = 2;
   expectPassedClose = [self expectationWithDescription:@"Close delivered after receiveNextMessage"];
 
   unblocked = YES;
-  [call receiveNextMessage];
+  [call receiveNextMessages:1];
 
   [self waitForExpectationsWithTimeout:kTestTimeout handler:nil];
 }
 
-- (void)testReadFlowControlMultipleMessages {
+- (void)testFlowControlMultipleMessages {
-  XCTestExpectation *expectPassedMessage =
+  __weak XCTestExpectation *expectPassedMessage =
       [self expectationWithDescription:@"two messages delivered with receiveNextMessage"];
   expectPassedMessage.expectedFulfillmentCount = 2;
-  XCTestExpectation *expectBlockedMessage =
+  __weak XCTestExpectation *expectBlockedMessage =
       [self expectationWithDescription:@"Message 3 not delivered"];
   expectBlockedMessage.inverted = YES;
+  __weak XCTestExpectation *expectWriteTwice =
+      [self expectationWithDescription:@"Write 2 messages done"];
+  expectWriteTwice.expectedFulfillmentCount = 2;
 
   RMTStreamingOutputCallRequest *request = [RMTStreamingOutputCallRequest message];
   RMTResponseParameters *parameters = [RMTResponseParameters message];
   parameters.size = kSimpleDataLength;
   [request.responseParametersArray addObject:parameters];
-  [request.responseParametersArray addObject:parameters];
   request.payload.body = [NSMutableData dataWithLength:kSimpleDataLength];
 
   GRPCRequestOptions *callRequest =
   [[GRPCRequestOptions alloc] initWithHost:(NSString *)kHostAddress
-                                      path:kOutputStreamingCallMethod.HTTPPath
+                                      path:kFullDuplexCallMethod.HTTPPath
                                     safety:GRPCCallSafetyDefault];
   GRPCMutableCallOptions *options = [[GRPCMutableCallOptions alloc] init];
   options.transportType = GRPCTransportTypeInsecure;
@@ -628,25 +630,26 @@ static const NSTimeInterval kInvertedTimeout = 2;
                                       messageCallback:^(NSData *message) {
                                         if (messageId <= 1) {
                                           [expectPassedMessage fulfill];
-                                          if (messageId < 1) {
-                                            [call receiveNextMessage];
-                                          }
                                         } else {
                                           [expectBlockedMessage fulfill];
                                         }
                                         messageId++;
                                       }
-                                      closeCallback:nil]
+                                      closeCallback:nil
+                                      writeDataCallback:^{
+                                        [expectWriteTwice fulfill];
+                                      }]
                      callOptions:options];
 
-  [call receiveNextMessage];
+  [call receiveNextMessages:2];
   [call start];
   [call writeData:[request data]];
+  [call writeData:[request data]];
 
   [self waitForExpectationsWithTimeout:kInvertedTimeout handler:nil];
 }
 
-- (void)testReadFlowControlReadyBeforeStart {
+- (void)testFlowControlReadReadyBeforeStart {
   __weak XCTestExpectation *expectPassedMessage =
       [self expectationWithDescription:@"Message delivered with receiveNextMessage"];
   __weak XCTestExpectation *expectPassedClose =
@@ -678,7 +681,7 @@ static const NSTimeInterval kInvertedTimeout = 2;
                               }]
                  callOptions:options];
 
-  [call receiveNextMessage];
+  [call receiveNextMessages:1];
   [call start];
   [call writeData:[request data]];
   [call finish];
@@ -686,7 +689,7 @@ static const NSTimeInterval kInvertedTimeout = 2;
   [self waitForExpectationsWithTimeout:kInvertedTimeout handler:nil];
 }
 
-- (void)testReadFlowControlReadyAfterStart {
+- (void)testFlowControlReadReadyAfterStart {
   __weak XCTestExpectation *expectPassedMessage =
       [self expectationWithDescription:@"Message delivered with receiveNextMessage"];
   __weak XCTestExpectation *expectPassedClose =
@@ -720,14 +723,14 @@ static const NSTimeInterval kInvertedTimeout = 2;
                  callOptions:options];
 
   [call start];
-  [call receiveNextMessage];
+  [call receiveNextMessages:1];
   [call writeData:[request data]];
   [call finish];
 
   [self waitForExpectationsWithTimeout:kTestTimeout handler:nil];
 }
 
-- (void)testReadFlowControlNonBlockingFailure {
+- (void)testFlowControlReadNonBlockingFailure {
   __weak XCTestExpectation *completion = [self expectationWithDescription:@"RPC completed."];
 
   GRPCRequestOptions *requestOptions =