使用cfnetwork写入输出流时，exc_bad_access

我正在开发iPhone应用程序。我正在尝试通过gmail服务器使用smtp发送带有一个URL的消息。我使用CFNetwork框架。有时邮件发送没有问题，但很多时候，如果在行exc_bad_access处出现异常exc_bad_access，如果

(CFWriteStreamCanAcceptBytes(outputStream))

1类：HSK_CFUtilities

CFIndex CFWriteStreamWriteFully(CFWriteStreamRef outputStream, const uint8_t* buffer, CFIndex length)
{
    CFIndex bufferOffset = 0;
    CFIndex bytesWritten;

    while (bufferOffset < length)
    {
        if (CFWriteStreamCanAcceptBytes(outputStream))
        {
            bytesWritten = CFWriteStreamWrite(outputStream, &(buffer[bufferOffset]), length - bufferOffset);
            if (bytesWritten < 0)
            {
                // Bail!                
                return bytesWritten;
            }
            bufferOffset += bytesWritten;
        }
        else if (CFWriteStreamGetStatus(outputStream) == kCFStreamStatusError)
        {
            return -1;
        }
        else
        {
            // Pump the runloop
            CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0.0, true);
        }
    }

    return bufferOffset;
}

2类：方法中的SKPSMTPMessage parseBuffer

 case kSKPSMTPWaitingSendSuccess:
                {
                    if ([tmpLine hasPrefix:@"250 "])
                    {
                        sendState = kSKPSMTPWaitingQuitReply;

                        NSString *quitString = @"QUIT\r\n";
                        DEBUGLOG(@"C: %@", quitString);
                        if (CFWriteStreamWriteFully((CFWriteStreamRef)outputStream, (const uint8_t *)[quitString UTF8String], [quitString lengthOfBytesUsingEncoding:NSUTF8StringEncoding]) < 0)
                        {
                            error =  [outputStream streamError];
                            encounteredError = YES;
                        }
                        else
                        {
                            [self startShortWatchdog];
                        }
                    }

我想知道您是否可以给我一个提示？我将不胜感激任何帮助 。预先谢谢您，最好的问候。