当NSOutputStream完成时关闭连接

Question

当NSOutputStream完成发送数据时，如何关闭连接?

搜索后，我发现事件NSStreamEventEndEncountered只在服务器断开连接时调用。如果OutputStream已经完成了要发送的数据，则不会。

StreamStatus总是返回0(连接关闭)或2(连接打开)，但从不返回4(写入数据)。

因为上面提到的两种方法都没有告诉我足够的写过程，我无法找到一种方法来确定流是否仍在写，或者它是否已经完成，我现在可以关闭连接。

经过5天的谷歌搜索和尝试，我完全没有主意了…感谢任何帮助。由于

按要求添加代码:

- (void)startSend:(NSString *)filePath
{
BOOL                    success;
NSURL *                 url;

assert(filePath != nil);
assert([[NSFileManager defaultManager] fileExistsAtPath:filePath]);
assert( [filePath.pathExtension isEqual:@"png"] || [filePath.pathExtension isEqual:@"jpg"] );

assert(self.networkStream == nil);      // don't tap send twice in a row!
assert(self.fileStream == nil);         // ditto

// First get and check the URL.
...
....
.....

// If the URL is bogus, let the user know.  Otherwise kick off the connection.
...
....
.....

if ( ! success) {
    self.statusLabel.text = @"Invalid URL";
} else {

    // Open a stream for the file we're going to send.  We do not open this stream; 
    // NSURLConnection will do it for us.

    self.fileStream = [NSInputStream inputStreamWithFileAtPath:filePath];
    assert(self.fileStream != nil);

    [self.fileStream open];

    // Open a CFFTPStream for the URL.

    self.networkStream = CFBridgingRelease(
        CFWriteStreamCreateWithFTPURL(NULL, (__bridge CFURLRef) url)
    );
    assert(self.networkStream != nil);

    if ([self.usernameText.text length] != 0) {
        success = [self.networkStream setProperty:self.usernameText.text forKey:(id)kCFStreamPropertyFTPUserName];
        assert(success);
        success = [self.networkStream setProperty:self.passwordText.text forKey:(id)kCFStreamPropertyFTPPassword];
        assert(success);
    }

    self.networkStream.delegate = self;
    [self.networkStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    ///////******** LINE ADDED BY ME TO DISONNECT FROM FTP AFTER CLOSING CONNECTION *********////////////
    [self.networkStream setProperty:(id)kCFBooleanFalse forKey:(id)kCFStreamPropertyFTPAttemptPersistentConnection];
    ///////******** END LINE ADDED BY ME *********//////////// 
    [self.networkStream open];

    // Tell the UI we're sending.

    [self sendDidStart];
}
}

- (void)stopSendWithStatus:(NSString *)statusString
{
if (self.networkStream != nil) {
    [self.networkStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    self.networkStream.delegate = nil;
    [self.networkStream close];
    self.networkStream = nil;
}
if (self.fileStream != nil) {
    [self.fileStream close];
    self.fileStream = nil;
}
[self sendDidStopWithStatus:statusString];
}

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
// An NSStream delegate callback that's called when events happen on our 
// network stream.
{
#pragma unused(aStream)
assert(aStream == self.networkStream);

switch (eventCode) {
    case NSStreamEventOpenCompleted: {
        [self updateStatus:@"Opened connection"];
    } break;
    case NSStreamEventHasBytesAvailable: {
        assert(NO);     // should never happen for the output stream
    } break;
    case NSStreamEventHasSpaceAvailable: {
        [self updateStatus:@"Sending"];

        // If we don't have any data buffered, go read the next chunk of data.

        if (self.bufferOffset == self.bufferLimit) {
            NSInteger   bytesRead;

            bytesRead = [self.fileStream read:self.buffer maxLength:kSendBufferSize];

            if (bytesRead == -1) {
                [self stopSendWithStatus:@"File read error"];
            } else if (bytesRead == 0) {
                [self stopSendWithStatus:nil];
            } else {
                self.bufferOffset = 0;
                self.bufferLimit  = bytesRead;
            }
        }

        // If we're not out of data completely, send the next chunk.

        if (self.bufferOffset != self.bufferLimit) {
            NSInteger   bytesWritten;
            bytesWritten = [self.networkStream write:&self.buffer[self.bufferOffset] maxLength:self.bufferLimit - self.bufferOffset];
            assert(bytesWritten != 0);
            if (bytesWritten == -1) {
                [self stopSendWithStatus:@"Network write error"];
            } else {
                self.bufferOffset += bytesWritten;
            }
        }
    } break;
    case NSStreamEventErrorOccurred: {
        [self stopSendWithStatus:@"Stream open error"];
    } break;
    case NSStreamEventEndEncountered: {
        // FOR WHATEVER REASON THIS IS NEVER CALLED!!!!
    } break;
    default: {
        assert(NO);
    } break;
}
}

Answer 1

你的问题可以有两种解释。如果你问的是"我有一个NSOutputStream，我已经完成了对它的写入，我该如何发出信号?"那么答案就像调用close方法一样简单。

或者，如果你真正说的是"我有一个NSInputStream，我想知道我什么时候到达了流结束"，那么你可以看看hasBytesAvailable或streamStatus == NSStreamStatusAtEnd。

对于你的信息，要实际获得状态NSStreamStatusWriting，你需要从另一个线程调用streamStatus方法，而这个线程正在调用write:maxLength:。

—编辑:代码建议

您永远不会得到通知的原因是输出流永远不会完成(除非它是固定大小的流，而FTP流不是)。它是"完成"的输入流，此时您可以关闭输出流。这就是你最初问题的答案。

作为进一步的建议，除了处理输出流上的错误外，我将跳过运行循环调度和"事件处理"。然后我会把读/写代码放入一个NSOperation子类并把它发送到一个NSOperationQueue。通过在那个队列中保持对NSOperations的引用，你将能够很容易地取消它们，甚至通过添加一个percentComplete属性来显示一个进度条。我已经测试了下面的代码，它可以工作。用你的FTP输出流替换我的内存输出流。您将注意到我跳过了验证，当然您应该保留这些验证。它们应该在NSOperation之外完成以便更容易查询用户。

@interface NSSendFileOperation : NSOperation<NSStreamDelegate> {
    NSInputStream  *_inputStream;
    NSOutputStream *_outputStream;
    uint8_t *_buffer;
}
@property (copy) NSString* sourceFilePath;
@property (copy) NSString* targetFilePath;
@property (copy) NSString* username;
@property (copy) NSString* password;
@end

@implementation NSSendFileOperation
- (void) main
{
    static int kBufferSize = 4096;
    _inputStream  = [NSInputStream inputStreamWithFileAtPath:self.sourceFilePath];
    _outputStream = [NSOutputStream outputStreamToMemory];
    _outputStream.delegate = self;
    [_inputStream open];
    [_outputStream open];
    _buffer = calloc(1, kBufferSize);
    while (_inputStream.hasBytesAvailable) {
        NSInteger bytesRead = [_inputStream read:_buffer maxLength:kBufferSize];
        if (bytesRead > 0) {
            [_outputStream write:_buffer maxLength:bytesRead];
            NSLog(@"Wrote %ld bytes to output stream",bytesRead);
        }
    }
    NSData *outputData = [_outputStream propertyForKey:NSStreamDataWrittenToMemoryStreamKey];
    NSLog(@"Wrote a total of %lu bytes to output stream.", outputData.length);
    free(_buffer);
    _buffer = NULL;
    [_outputStream close];
    [_inputStream close];
}
- (void) stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
    // Handle output stream errors such as disconnections here
}
@end

int main (int argc, const char * argv[])
{
    @autoreleasepool {
        NSOperationQueue *sendQueue = [[NSOperationQueue alloc] init];
        NSSendFileOperation *sendOp = [[NSSendFileOperation alloc] init];
        sendOp.username = @"test";
        sendOp.password = @"test";
        sendOp.sourceFilePath = @"/Users/eric/bin/data/english-words.txt";
        sendOp.targetFilePath = @"/Users/eric/Desktop/english-words.txt";
        [sendQueue addOperation:sendOp];
        [sendQueue waitUntilAllOperationsAreFinished];
    }
    return 0;
}