流式获取数据 - NSInputStream

Question

所有，

我有一个服务器，它有一个用于通信的 TCP 套接字流。我需要访问该流并读取它需要发送给我的初始数据。

我当前的代码如下。老实说，我完全是盲目的。我不确定这是否正确，更不用说是否适合这份工作了。

-(void) initNetworkCommunication
{
    //input stream
    NSInputStream *iStream;
    NSURL *url = [url initWithString:@"192.168.17.1:2004"];

    [iStream initWithURL:url];
    [iStream setDelegate:self];
    [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [iStream open];

}

所以从我看来，这段代码初始化了流，但是如何从流中读取数据呢？

谢谢

Answer 1

从流中获取数据有两种方法：轮询和使用流事件。

轮询更简单，但会阻塞正在运行的线程。如果使用此方法，则不需要执行 setDelegate: 或 scheduleInRunLoop:forMode: 调用。轮询是通过重复调用read:maxLength:来执行的。

NSInteger result;
uint8_t buffer[BUFFER_LEN]; // BUFFER_LEN can be any positive integer
while((result = [iStream read:buffer maxLength:BUFFER_LEN]) != 0) {
    if(result > 0) {
        // buffer contains result bytes of data to be handled
    } else {
        // The stream had an error. You can get an NSError object using [iStream streamError]
    }
}
// Either the stream ran out of data or there was an error

使用流事件需要设置委托并将流添加到运行循环。当某些事件发生时（包括接收数据时），流不会阻塞线程，而是向其委托发送一条 stream:handleEvent: 消息。然后委托可以从流中检索数据。下面是一个 stream:handleEvent: 方法示例：

- (void)stream:(NSInputStream *)iStream handleEvent:(NSStreamEvent)event {
    BOOL shouldClose = NO;
    switch(event) {
        case  NSStreamEventEndEncountered:
            shouldClose = YES;
            // If all data hasn't been read, fall through to the "has bytes" event
            if(![iStream hasBytesAvailable]) break;
        case NSStreamEventHasBytesAvailable: ; // We need a semicolon here before we can declare local variables
            uint8_t *buffer;
            NSUInteger length;
            BOOL freeBuffer = NO;
            // The stream has data. Try to get its internal buffer instead of creating one
            if(![iStream getBuffer:&buffer length:&length]) {
                // The stream couldn't provide its internal buffer. We have to make one ourselves
                buffer = malloc(BUFFER_LEN * sizeof(uint8_t));
                freeBuffer = YES;
                NSInteger result = [iStream read:buffer maxLength:BUFFER_LEN];
                if(result < 0) {
                    // error copying to buffer
                    break;
                }
                length = result;
            }
            // length bytes of data in buffer
            if(freeBuffer) free(buffer);
            break;
        case NSStreamEventErrorOccurred:
            // some other error
            shouldClose = YES;
            break;
    }
    if(shouldClose) [iStream close];
}

Answer 2

我根据其他一些答案想出了这个。

public enum StreamError: Error {
    case Error(error: Error?, partialData: [UInt8])
}

extension InputStream {

    public func readData(bufferSize: Int = 1024) throws -> Data {
        var buffer = [UInt8](repeating: 0, count: bufferSize)
        var data: [UInt8] = []

        open()

        while true {
            let count = read(&buffer, maxLength: buffer.capacity)

            guard count >= 0 else {
                close()
                throw StreamError.Error(error: streamError, partialData: data)
            }

            guard count != 0 else {
                close()
                return Data(bytes: data)
            }

            data.append(contentsOf: (buffer.prefix(count)))
        }

    }
}