title: Convert unsigned char array to NSData and back
body: <p>How do you convert an unsigned char array to an NSData in objective c?</p>
  
  <p>This is what I am trying to do, but it doesn't work.
  Buffer is my unsigned char array.</p>
  
  <pre><code>NSData *data = [NSData dataWithBytes:message length:length];
  </code></pre>