Stream to Get Data - NSInputStream

Question

All,

I have a server that has a tcp socket stream for communication. I need to get to that stream and read the initial data that it needs to send me.

My cur

Answer 1

I came up with this, based on some other answers.

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)))
        }

    }
}

Answer 2

There are two ways to get data from a stream: polling and using stream events.

Polling is simpler, but will block the thread it is running in. If you use this method, you don't need to perform the setDelegate: or scheduleInRunLoop:forMode: calls. Polling is performed by repeatedly calling read:maxLength:.

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

Using stream events requires setting the delegate and adding the stream to a run loop. Instead of blocking the thread, the stream will send a stream:handleEvent: message to its delegate when certain events occur, including when it receives data. The delegate can then retrieve the data from the stream. Here is an example stream:handleEvent: method:

- (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];
}