MurmurHash

时间:2023-03-09 15:31:20
MurmurHash

public int hash(byte[] data, int length, int seed) {

    int m = 0x5bd1e995;

    int r = 24;



    int h = seed ^ length;



    int len_4 = length >> 2;



    for (int i = 0; i < len_4; i++) {

      int i_4 = i << 2;

      int k = data[i_4 + 3];

      k = k << 8;

      k = k | (data[i_4 + 2] & 0xff);

      k = k << 8;

      k = k | (data[i_4 + 1] & 0xff);

      k = k << 8;

      k = k | (data[i_4 + 0] & 0xff);

      k *= m;

      k ^= k >>> r;

      k *= m;

      h *= m;

      h ^= k;

    }



    // avoid calculating modulo

    int len_m = len_4 << 2;

    int left = length - len_m;



    if (left != 0) {

      if (left >= 3) {

        h ^= (int) data[length - 3] << 16;

      }

      if (left >= 2) {

        h ^= (int) data[length - 2] << 8;

      }

      if (left >= 1) {

        h ^= (int) data[length - 1];

      }



      h *= m;

    }



    h ^= h >>> 13;

    h *= m;

    h ^= h >>> 15;



    return h;

  }