accept4Source = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socket4FD, 0, socketQueue);                        int socketFD = socket4FD;            dispatch_source_t acceptSource = accept4Source;                        dispatch_source_set_event_handler(accept4Source, ^{ @autoreleasepool {                                LogVerbose(@"event4Block");                                unsigned long i = 0;                unsigned long numPendingConnections = dispatch_source_get_data(acceptSource);                                LogVerbose(@"numPendingConnections: %lu", numPendingConnections);                                while ([self doAccept:socketFD] && (++i < numPendingConnections));            }});

    readSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socketFD, 0, socketQueue);    writeSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_WRITE, socketFD, 0, 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 > 0)            [self doReadData];        else            [self doReadEOF];    }});        dispatch_source_set_event_handler(writeSource, ^{ @autoreleasepool {                LogVerbose(@"writeEventBlock");                flags |= kSocketCanAcceptBytes;        [self doWriteData];    }});

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

    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                }