我正在开发一个 iPhone 应用程序,该应用程序涉及将相机中的完整照片(通常每张照片在 1.5 到 2.0 MB 之间)及其缩略图(小得多)上传到 Amazon S3。
缩略图总是成功上传,但是有时完整图像则不然,当它们失败时,它们会失败并显示 POSIX 错误代码 12(又名 ENOMEM)。不过,我添加了调试代码来在错误发生时打印可用内存量,并且总是有相当多的可用内存,通常超过 100 MB。
此外,当通过 3G 上传时,错误会更频繁地出现,而通过 wifi 上传时,错误会更少出现——这看起来很奇怪,因为请求没有下载太多,并且上传的文件已经在内存中(我也尝试过)从磁盘流式传输,没有任何改进)。
我尝试使用 NSURLConnection、Foundation CFHTTP* 函数和 ASIHTTPRequest 库上传文件,但无论如何,错误发生的频率相同。更奇怪的是,我的谷歌搜索显示,最终用户有时会从 Safari 收到错误代码 12——我还没有看到任何 iOS 开发人员提到过这一点。我正在使用继承的代码库,因此它可能有问题,但我什至不确定要寻找什么。任何见解将不胜感激!
我能够解决这个问题的唯一方法是直接使用套接字并手动形成 HTTP 标头。所以我的上传代码目前如下所示:
- (void)socketClose
{
[_inputStream setDelegate:nil];
[_inputStream close];
[_inputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
SCR_RELEASE_SAFELY(_inputStream);
[_outputStream setDelegate:nil];
[_outputStream close];
[_outputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
SCR_RELEASE_SAFELY(_outputStream);
SCR_RELEASE_SAFELY(_headerBuffer);
}
- (void)sendRequest
{
[self socketClose];
SCR_RELEASE_SAFELY(_headerBuffer);
if (!_shouldCancel)
{
NSString *httpMessage = [NSString stringWithFormat:@"POST upload.php HTTP/1.1\r\n"
"Host:"
#ifndef TESTBED
" %@"
#endif
"\r\n"
"User-Agent: MyApp/3.0.0 CFNetwork/534 Darwin/10.7.0\r\n"
"Content-Length: %d\r\n"
"Accept: */*\r\n"
"Accept-Language: en-us\r\n"
"Accept-Encoding: gzip, deflate\r\n"
"Content-Type: application/x-www-form-urlencoded\r\n"
"Connection: keep-alive\r\n\r\n"
"data="
#ifndef TESTBED
, [self.serverUrl host]
#endif
, _bytesToUpload];
NSString *key = @"data=";
NSData *keyData = [key dataUsingEncoding:NSASCIIStringEncoding];
_bytesToUpload -= [keyData length];
_bytesToUpload = MAX(0, _bytesToUpload);
_headerBuffer = [[NSMutableData alloc] initWithData:[httpMessage dataUsingEncoding:NSUTF8StringEncoding]];
_writtenDataBytes = 0;
CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault
, (CFStringRef)[self.serverUrl host]
#ifdef TESTBED
, 8888
#else
, 80
#endif
, (CFReadStreamRef *)(&_inputStream)
, (CFWriteStreamRef *)(&_outputStream));
[_inputStream setDelegate:self];
[_outputStream setDelegate:self];
[_inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[_outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[_inputStream open];
[_outputStream open];
}
}
- (void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent
{
if (_outputStream == theStream)
{
switch (streamEvent)
{
case NSStreamEventOpenCompleted:
{
[self regenerateTimeoutTimer];
break;
}
case NSStreamEventHasSpaceAvailable:
{
SCR_RELEASE_TIMER(_timeoutTimer);
NSInteger length = _headerBuffer.length;
if (length > 0)
{
NSInteger written = [_outputStream write:(const uint8_t *)[_headerBuffer bytes] maxLength:length];
NSInteger rest = length - written;
if (rest > 0)
{
memmove([_headerBuffer mutableBytes], (const uint8_t *)[_headerBuffer mutableBytes] + written, rest);
}
[_headerBuffer setLength:rest];
}
else
{
const uint8_t *dataBytes = [_data bytes];
while ([_outputStream hasSpaceAvailable] && (_writtenDataBytes < _bytesToUpload))
{
NSInteger written = [_outputStream write:dataBytes
maxLength:MIN(_dataLength, _bytesToUpload - _writtenDataBytes)];
if (written > 0)
{
_writtenDataBytes += written;
}
}
}
[self regenerateTimeoutTimer];
break;
}
case NSStreamEventErrorOccurred:
{
SCR_RELEASE_TIMER(_timeoutTimer);
[self reportError:[theStream streamError]];
break;
}
case NSStreamEventEndEncountered:
{
SCR_RELEASE_TIMER(_timeoutTimer);
[self socketClose];
break;
}
}
}
else if (_inputStream == theStream)
{
switch (streamEvent)
{
case NSStreamEventHasBytesAvailable:
{
SCR_RELEASE_TIMER(_timeoutTimer);
/* Read server response here if you wish */
[self socketClose];
break;
}
case NSStreamEventErrorOccurred:
{
SCR_RELEASE_TIMER(_timeoutTimer);
[self reportError:[theStream streamError]];
break;
}
case NSStreamEventEndEncountered:
{
SCR_RELEASE_TIMER(_timeoutTimer);
[self socketClose];
break;
}
}
}
}
尽管 ASIHTTPRequest 可以在这里工作,但我们决定放弃这种依赖关系,以便获得性能并让一切都在我们自己的准确控制之下。您可以使用 Wireshark 工具来调试此类事情。
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