murmurhash2_gc.js

/**
 * JS Implementation of MurmurHash2
 * 
 * @author <a href="mailto:gary.court@gmail.com">Gary Court</a>
 * @see http://github.com/garycourt/murmurhash-js
 * @author <a href="mailto:aappleby@gmail.com">Austin Appleby</a>
 * @see http://sites.google.com/site/murmurhash/
 * 
 * @param {string} str ASCII only
 * @param {number} seed Positive integer only
 * @return {number} 32-bit positive integer hash
 */

function murmurhash2_32_gc(str, seed) {
  var
    l = str.length,
    h = seed ^ l,
    i = 0,
    k;
  
  while (l >= 4) {
  	k = 
  	  ((str.charCodeAt(i) & 0xff)) |
  	  ((str.charCodeAt(++i) & 0xff) << 8) |
  	  ((str.charCodeAt(++i) & 0xff) << 16) |
  	  ((str.charCodeAt(++i) & 0xff) << 24);
    
    k = (((k & 0xffff) * 0x5bd1e995) + ((((k >>> 16) * 0x5bd1e995) & 0xffff) << 16));
    k ^= k >>> 24;
    k = (((k & 0xffff) * 0x5bd1e995) + ((((k >>> 16) * 0x5bd1e995) & 0xffff) << 16));

	h = (((h & 0xffff) * 0x5bd1e995) + ((((h >>> 16) * 0x5bd1e995) & 0xffff) << 16)) ^ k;

    l -= 4;
    ++i;
  }
  
  switch (l) {
  case 3: h ^= (str.charCodeAt(i + 2) & 0xff) << 16;
  case 2: h ^= (str.charCodeAt(i + 1) & 0xff) << 8;
  case 1: h ^= (str.charCodeAt(i) & 0xff);
          h = (((h & 0xffff) * 0x5bd1e995) + ((((h >>> 16) * 0x5bd1e995) & 0xffff) << 16));
  }

  h ^= h >>> 13;
  h = (((h & 0xffff) * 0x5bd1e995) + ((((h >>> 16) * 0x5bd1e995) & 0xffff) << 16));
  h ^= h >>> 15;

  return h >>> 0;
}