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Re: Cocoa-dev Digest, Vol 6, Issue 1522
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Re: Cocoa-dev Digest, Vol 6, Issue 1522


  • Subject: Re: Cocoa-dev Digest, Vol 6, Issue 1522
  • From: Greg Guerin <email@hidden>
  • Date: Thu, 22 Oct 2009 10:28:17 -0700

Ashley Perrien wrote:

uint8_t *readBuffer;
NSUInteger bufferLength;
BOOL gotBuffer = [readStream getBuffer: &readBuffer length: &bufferLength];


if (gotBuffer) {
int len = [readStream read: readBuffer maxLength: bufferLength];
if (len <= 0)
NSLog(@"nothing read");
else
NSLog(@"Read: %@", [[[NSString alloc] initWithBytes: readBuffer length: bufferLength encoding:NSUTF8StringEncoding] autorelease]);
}
else {
NSLog(@"Did not get a buffer");
}
}
// Output: No Bytes , Did not get a buffer


This code is mis-designed.

First, if gotBuffer is YES, then the available data is already present in the returned-by-reference readBuffer. Calling read:maxLength: will return the NEXT series of bytes. It will block in doing this, unlike the non-blocking getBuffer:length: call.

Second, if you're expecting a buffer to be available immediately, your expectation is misplaced. It takes time for the first packet to arrive and be processed. If you call read:maxLength:, however, then that is a blocking method, and it will suspend the calling thread until sufficient data has arrived.

I agree with Jens Alfke: you should read the stream programming guide, and look at a working example.


I'm not entirely sure why you mention the null character.


I misread what you were doing with the data. I thought it was being treated as a C string in UTF8 encoding.

  -- GG
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