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1/* eslint no-fallthrough: 0 */2/**3 * Mnemonist MurmurHash 34 * =======================5 *6 * Straightforward implementation of the third version of MurmurHash.7 *8 * Note: this piece of code belong to haschisch.9 */10 11/**12 * Various helpers.13 */14function mul32(a, b) {15  return (a & 0xffff) * b + (((a >>> 16) * b & 0xffff) << 16) & 0xffffffff;16}17 18function sum32(a, b) {19  return (a & 0xffff) + (b >>> 16) + (((a >>> 16) + b & 0xffff) << 16) & 0xffffffff;20}21 22function rotl32(a, b) {23  return (a << b) | (a >>> (32 - b));24}25 26/**27 * MumurHash3 function.28 *29 * @param  {number}    seed - Seed.30 * @param  {ByteArray} data - Data.31 */32module.exports = function murmurhash3(seed, data) {33  var c1 = 0xcc9e2d51,34      c2 = 0x1b873593,35      r1 = 15,36      r2 = 13,37      m = 5,38      n = 0x6b64e654;39 40  var hash = seed,41      k1,42      i,43      l;44 45  for (i = 0, l = data.length - 4; i <= l; i += 4) {46    k1 = (47      data[i] |48      (data[i + 1] << 8) |49      (data[i + 2] << 16) |50      (data[i + 3] << 24)51    );52 53    k1 = mul32(k1, c1);54    k1 = rotl32(k1, r1);55    k1 = mul32(k1, c2);56 57    hash ^= k1;58    hash = rotl32(hash, r2);59    hash = mul32(hash, m);60    hash = sum32(hash, n);61  }62 63  k1 = 0;64 65  switch (data.length & 3) {66    case 3:67      k1 ^= data[i + 2] << 16;68    case 2:69      k1 ^= data[i + 1] << 8;70    case 1:71      k1 ^= data[i];72      k1 = mul32(k1, c1);73      k1 = rotl32(k1, r1);74      k1 = mul32(k1, c2);75      hash ^= k1;76    default:77  }78 79  hash ^= data.length;80  hash ^= hash >>> 16;81  hash = mul32(hash, 0x85ebca6b);82  hash ^= hash >>> 13;83  hash = mul32(hash, 0xc2b2ae35);84  hash ^= hash >>> 16;85 86  return hash >>> 0;87};88