MurmurHash2.java

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package rlpark.plugin.rltoys.algorithms.representations.tilescoding.hashing;

//Ported by Derek Young from the C version (specifically the endian-neutral
//version) from:
//http://murmurhash.googlepages.com/
//
//released to the public domain - dmy999@gmail.com
public class MurmurHash2 {
  @SuppressWarnings("fallthrough")
  public static int hash(byte[] data, int seed) {
    // 'm' and 'r' are mixing constants generated offline.
    // They're not really 'magic', they just happen to work well.
    int m = 0x5bd1e995;
    int r = 24;

    // Initialize the hash to a 'random' value
    int len = data.length;
    int h = seed ^ len;

    int i = 0;
    while (len >= 4) {
      int k = data[i + 0] & 0xFF;
      k |= (data[i + 1] & 0xFF) << 8;
      k |= (data[i + 2] & 0xFF) << 16;
      k |= (data[i + 3] & 0xFF) << 24;

      k *= m;
      k ^= k >>> r;
      k *= m;

      h *= m;
      h ^= k;

      i += 4;
      len -= 4;
    }

    switch (len) {
    case 3:
      h ^= (data[i + 2] & 0xFF) << 16;
    case 2:
      h ^= (data[i + 1] & 0xFF) << 8;
    case 1:
      h ^= data[i + 0] & 0xFF;
      h *= m;
    }
    h ^= h >>> 13;
    h *= m;
    h ^= h >>> 15;
    return h;
  }
}