objective-c - NSOutputStream 完成后关闭连接

Question

当 NSOutputStream 发送完数据时，如何关闭连接？

四处搜索后，我发现只有在服务器断开连接时才会调用事件 NSStreamEventEndEncountered。如果 OutputStream 已完成要发送的数据，则不会。

StreamStatus 始终返回 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关于写入过程的足够信息，所以我无法找到一种方法来确定 Stream 是否仍在写入或者它是否已经完成并且我现在可以关闭连接。

经过 5 天的谷歌搜索和尝试后，我完全没有想法......感谢任何帮助。谢谢

根据要求编辑添加的代码:

- (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

您的问题可以有两种解释。如果你问的是“我有一个 NSOutputStream，我已经写完了，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，如果您真正想说的是“我有一个 NSInputStream，我想知道我何时到达流的末尾”，那么您可以查看 hasBytesAvailable 或 streamStatus == NSStreamStatusAtEnd。

请注意，要实际获取状态 NSStreamStatusWriting，您需要在该线程调用 write:maxLength: 时从另一个线程调用 streamStatus 方法。

--- 编辑:代码建议

您永远不会收到通知的原因是输出流从未完成(除非它是固定大小的流，而 FTP 流不是)。这是“完成”的输入流，此时您可以关闭输出流。这就是你原来问题的答案。

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”。然后我将读/写代码放入 NSOperation 子类并将其发送到 NSOperationQueue。通过在该队列中保留对 NSOperations 的引用，您可以轻松取消它们，甚至可以通过添加 percentComplete 属性来显示进度条。我已经测试了下面的代码并且它有效。将我的内存输出流替换为您的 FTP 输出流。您会注意到我已经跳过了验证，您当然应该保留这些验证。它们可能应该在 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;
}