如何通过 NSOutputStream 发送整数？

Question

因此，我正在制作一个通过 NSStream 不断发送点数组的 iOS 应用程序，但因为有时发送方会在接收方收到一个数组之前写入两个数组，所以我决定首先写入长度，然后写入数组数据本身，以便接收者知道要处理多少字节。

发送者：

if (_outStream && [_outStream hasSpaceAvailable]){
    const uint8_t *buffer = [data bytes];
    uint64_t length = CFSwapInt64HostToLittle([data length]);
    NSLog(@"Sending bytes with length: %llu", length);
    int er1 = [_outStream write:(const uint8_t *)&length maxLength:sizeof(length)];
    int er2 = [_outStream write:buffer maxLength:length];  
    if (er1 < 0 || er2 < 0) {
        [self _showAlert:@"Failed sending data to peer"];
    }
}

接收者：

case NSStreamEventHasBytesAvailable:
    {
        if (stream == _inStream) {
            uint8_t *b;
            int len = 0;
            len = [_inStream read:b maxLength:8];
            uint64_t dataLength = CFSwapInt64LittleToHost(*b);
            NSLog(@"Received bytes with length: %llu", dataLength);
            if(len < 0) {
                if ([stream streamStatus] != NSStreamStatusAtEnd)
                    [self _showAlert:@"Failed reading data from peer"];
            } else if (len > 0){
                uint8_t bytes[dataLength];
                int length = [_inStream read:bytes maxLength:dataLength];

                [currentDownload appendBytes:bytes length:length]; 
                 id pointsArray = [NSKeyedUnarchiver unarchiveObjectWithData:currentDownload];
                [currentDownload release];
                currentDownload = [[NSMutableData alloc] init];
                if ([pointsArray isKindOfClass:[NSArray class]]) {
                    [drawScene addNewPoint:[[pointsArray objectAtIndex:0] CGPointValue] previousPoint:[[pointsArray objectAtIndex:1] CGPointValue]];
                }

            }
        }
        break;
    }

问题是接收者接收到不正确的整数，因此它读取了不正确的字节数。

谁能帮我解决这个问题吗？

Answer 1

难道当您读取数据时，您是从旨在传达长度的介绍性位开始，而不是从实际数据开始？

对于：

[currentDownload appendBytes:bytes length:length];

尝试替换如下内容：

NSRange rangeLeftover = NSMakeRange(sizeof(uint8_t), [currentDownload length] - sizeof(uint8_t));
NSData *dataLeftover = [currentDownload subdataWithRange:rangeLeftover];
uint8_t bytesLeftover[[dataLeftover length]];
[dataLeftover getBytes:&bytesLeftover length:[dataLeftover length]];
currentDownload = [NSMutableData data]; // clear
[currentDownload appendBytes:bytesLeftover length:[dataLeftover length]];