How to send integer through NSOutputStream? - iphone

Question

So I'm making an iOS app that constantly sends and array of points through NSStreams, but because sometimes the sender writes two arrays before the receiver receives one, I decided to first write the length, then the array data itself, so that the receiver knows how many bytes to process.
sender:
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"];
}
}
receiver:
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;
}
The problem is that the receiver receives an incorrect integer, hence it reads an incorrect amount of bytes.
Can anyone help me with this?

Answer 1

Could it be that when you read the data, you're starting with the introductory bits intended to convey length, rather than starting with the actual data?
For:
[currentDownload appendBytes:bytes length:length];
try substituting something like this:
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]];