第2月第1天 GCDAsyncSocket dispatch_source_set_event_handler

+ (void)startCFStreamThreadIfNeeded
{
	LogTrace();

	static dispatch_once_t predicate;
	dispatch_once(&predicate, ^{

		cfstreamThreadRetainCount = 0;
		cfstreamThreadSetupQueue = dispatch_queue_create("GCDAsyncSocket-CFStreamThreadSetup", DISPATCH_QUEUE_SERIAL);
	});

	dispatch_sync(cfstreamThreadSetupQueue, ^{ @autoreleasepool {

		if (++cfstreamThreadRetainCount == 1)
		{
			cfstreamThread = [[NSThread alloc] initWithTarget:self
			                                         selector:@selector(cfstreamThread)
			                                           object:nil];
			[cfstreamThread start];
		}
	}});
}

+ (void)cfstreamThread { @autoreleasepool
{
	[[NSThread currentThread] setName:GCDAsyncSocketThreadName];

	LogInfo(@"CFStreamThread: Started");

	// We can't run the run loop unless it has an associated input source or a timer.
	// So we'll just create a timer that will never fire - unless the server runs for decades.
	[NSTimer scheduledTimerWithTimeInterval:[[NSDate distantFuture] timeIntervalSinceNow]
	                                 target:self
	                               selector:@selector(ignore:)
	                               userInfo:nil
	                                repeats:YES];

	NSThread *currentThread = [NSThread currentThread];
	NSRunLoop *currentRunLoop = [NSRunLoop currentRunLoop];

	BOOL isCancelled = [currentThread isCancelled];

	while (!isCancelled && [currentRunLoop runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]])
	{
		isCancelled = [currentThread isCancelled];
	}

	LogInfo(@"CFStreamThread: Stopped");
}}

- (BOOL)addStreamsToRunLoop
{
	LogTrace();

	NSAssert(dispatch_get_specific(IsOnSocketQueueOrTargetQueueKey), @"Must be dispatched on socketQueue");
	NSAssert((readStream != NULL && writeStream != NULL), @"Read/Write stream is null");

	if (!(flags & kAddedStreamsToRunLoop))
	{
		LogVerbose(@"Adding streams to runloop...");

		[[self class] startCFStreamThreadIfNeeded];
		[[self class] performSelector:@selector(scheduleCFStreams:)
		                     onThread:cfstreamThread
		                   withObject:self
		                waitUntilDone:YES];

		flags |= kAddedStreamsToRunLoop;
	}

	return YES;
}

　　

一、GCDAsyncSocket的核心就是dispatch_source_set_event_handler

1.accpet回调

            accept4Source = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socket4FD, , socketQueue);

            int socketFD = socket4FD;
            dispatch_source_t acceptSource = accept4Source;

            dispatch_source_set_event_handler(accept4Source, ^{ @autoreleasepool {

                LogVerbose(@"event4Block");

                unsigned long i = ;
                unsigned long numPendingConnections = dispatch_source_get_data(acceptSource);

                LogVerbose(@"numPendingConnections: %lu", numPendingConnections);

                while ([self doAccept:socketFD] && (++i < numPendingConnections));
            }});

2.read,write回调

    readSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socketFD, , socketQueue);
    writeSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_WRITE, socketFD, , socketQueue);

    // Setup event handlers

    dispatch_source_set_event_handler(readSource, ^{ @autoreleasepool {

        LogVerbose(@"readEventBlock");

        socketFDBytesAvailable = dispatch_source_get_data(readSource);
        LogVerbose(@"socketFDBytesAvailable: %lu", socketFDBytesAvailable);

        if (socketFDBytesAvailable > )
            [self doReadData];
        else
            [self doReadEOF];
    }});

    dispatch_source_set_event_handler(writeSource, ^{ @autoreleasepool {

        LogVerbose(@"writeEventBlock");

        flags |= kSocketCanAcceptBytes;
        [self doWriteData];
    }});

二，缓存区

1.创建

GCDAsyncReadPacket没有传入buffer，则readpacket没有缓冲区，socket可读时会放入preBuffer

- (void)readDataToData:(NSData *)data withTimeout:(NSTimeInterval)timeout tag:(long)tag
{
    [self readDataToData:data withTimeout:timeout buffer:nil bufferOffset: maxLength: tag:tag];
}

- (void)readDataToData:(NSData *)data
           withTimeout:(NSTimeInterval)timeout
                buffer:(NSMutableData *)buffer
          bufferOffset:(NSUInteger)offset
                   tag:(long)tag
{
    [self readDataToData:data withTimeout:timeout buffer:buffer bufferOffset:offset maxLength: tag:tag];
}

- (void)readDataToData:(NSData *)data withTimeout:(NSTimeInterval)timeout maxLength:(NSUInteger)length tag:(long)tag
{
    [self readDataToData:data withTimeout:timeout buffer:nil bufferOffset: maxLength:length tag:tag];
}

- (void)readDataToData:(NSData *)data
           withTimeout:(NSTimeInterval)timeout
                buffer:(NSMutableData *)buffer
          bufferOffset:(NSUInteger)offset
             maxLength:(NSUInteger)maxLength
                   tag:(long)tag
{
    if ([data length] == ) {
        LogWarn(@"Cannot read: [data length] == 0");
        return;
    }
    if (offset > [buffer length]) {
        LogWarn(@"Cannot read: offset > [buffer length]");
        return;
    }
    if (maxLength >  && maxLength < [data length]) {
        LogWarn(@"Cannot read: maxLength > 0 && maxLength < [data length]");
        return;
    }

    GCDAsyncReadPacket *packet = [[GCDAsyncReadPacket alloc] initWithData:buffer
                                                              startOffset:offset
                                                                maxLength:maxLength
                                                                  timeout:timeout
                                                               readLength:
                                                               terminator:data
                                                                      tag:tag];

    dispatch_async(socketQueue, ^{ @autoreleasepool {

        LogTrace();

        if ((flags & kSocketStarted) && !(flags & kForbidReadsWrites))
        {
            [readQueue addObject:packet];
            [self maybeDequeueRead];
        }
    }});

    // Do not rely on the block being run in order to release the packet,
    // as the queue might get released without the block completing.
}

三、面向对象封装

1.socket可读的时候先用preBuffer接收，拷贝到currentRead->buffer中,为生产者－消费者模式.

    GCDAsyncReadPacket *currentRead;
    GCDAsyncWritePacket *currentWrite;

    GCDAsyncSocketPreBuffer *preBuffer;

        uint8_t *buffer;

        if (readIntoPreBuffer)
        {
            [preBuffer ensureCapacityForWrite:bytesToRead];

            buffer = [preBuffer writeBuffer];
        }

。。。

            int socketFD = (socket4FD == SOCKET_NULL) ? socket6FD : socket4FD;

            ssize_t result = read(socketFD, buffer, (size_t)bytesToRead);
            LogVerbose(@"read from socket = %i", (int)result);

。。。

                if (readIntoPreBuffer)
                {
                    // We just read a big chunk of data into the preBuffer

                    [preBuffer didWrite:bytesRead];
                    LogVerbose(@"read data into preBuffer - preBuffer.length = %zu", [preBuffer availableBytes]);

                    // Search for the terminating sequence

                    bytesToRead = [currentRead readLengthForTermWithPreBuffer:preBuffer found:&done];
                    LogVerbose(@"copying %lu bytes from preBuffer", (unsigned long)bytesToRead);

                    // Ensure there's room on the read packet's buffer

                    [currentRead ensureCapacityForAdditionalDataOfLength:bytesToRead];

                    // Copy bytes from prebuffer into read buffer

                    uint8_t *readBuf = (uint8_t *)[currentRead->buffer mutableBytes] + currentRead->startOffset
                                                                                     + currentRead->bytesDone;

                    memcpy(readBuf, [preBuffer readBuffer], bytesToRead);

                    // Remove the copied bytes from the prebuffer
                    [preBuffer didRead:bytesToRead];
                    LogVerbose(@"preBuffer.length = %zu", [preBuffer availableBytes]);

                    // Update totals
                    currentRead->bytesDone += bytesToRead;
                    totalBytesReadForCurrentRead += bytesToRead;

                    // Our 'done' variable was updated via the readLengthForTermWithPreBuffer:found: method above
                }

4.runloop