Returns the MurmurHash3_x86_32 hash. - Java java.lang

Java examples for java.lang:String Hash

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Description

Returns the MurmurHash3_x86_32 hash.

Demo Code

public class Main {
  /**/*from  w w w  .j a v a2  s .c  o  m*/
   * Returns the MurmurHash3_x86_32 hash. Original source/tests at
   * https://github.com/yonik/java_util/
   */
  @SuppressWarnings("fallthrough")
  public static int murmurhash3_x86_32(byte[] data, int offset, int len, int seed) {

    final int c1 = 0xcc9e2d51;
    final int c2 = 0x1b873593;

    int h1 = seed;
    int roundedEnd = offset + (len & 0xfffffffc); // round down to 4 byte block

    for (int i = offset; i < roundedEnd; i += 4) {
      // little endian load order
      int k1 = (data[i] & 0xff) | ((data[i + 1] & 0xff) << 8) | ((data[i + 2] & 0xff) << 16) | (data[i + 3] << 24);
      k1 *= c1;
      k1 = Integer.rotateLeft(k1, 15);
      k1 *= c2;

      h1 ^= k1;
      h1 = Integer.rotateLeft(h1, 13);
      h1 = h1 * 5 + 0xe6546b64;
    }

    // tail
    int k1 = 0;

    switch (len & 0x03) {
    case 3:
      k1 = (data[roundedEnd + 2] & 0xff) << 16;
      // fallthrough
    case 2:
      k1 |= (data[roundedEnd + 1] & 0xff) << 8;
      // fallthrough
    case 1:
      k1 |= (data[roundedEnd] & 0xff);
      k1 *= c1;
      k1 = Integer.rotateLeft(k1, 15);
      k1 *= c2;
      h1 ^= k1;
    }

    // finalization
    h1 ^= len;

    // fmix(h1);
    h1 ^= h1 >>> 16;
    h1 *= 0x85ebca6b;
    h1 ^= h1 >>> 13;
    h1 *= 0xc2b2ae35;
    h1 ^= h1 >>> 16;

    return h1;
  }
}

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