title: iPhone: fast hash function for storing web images (url) as files (hashed filenames)
body: <p>What is a fast hash function available for the iPhone to hash web urls (images)? </p>
  
  <p>I'd like to store the cached web image as a file with a hash as the filename, because I suppose the raw web url could contain strange characters that could cause problems on the file system. </p>
  
  <p>The hash function doesn't need to be cryptographic, but it definitely needs to be fast.</p>
  
  <p><strong>Example:</strong> </p>
  
  <p>Input: <code>http://www.calumetphoto.com/files/iccprofiles/icc-test-image.jpg</code></p>
  
  <p>Output: <code>3573ed9c4d3a5b093355b2d8a1468509</code></p>
  
  <p>This was done by using MD5(), but since I don't know much about that topic I don't know if it is overkill (-> slow).</p>