module Object::Cassandra::Murmur3

Public Class Methods

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static VALUE
rb_murmur3_hash(VALUE self, VALUE rb_string)
{
  char*   bytes;
  int64_t length;

  Check_Type(rb_string, T_STRING);

  bytes  = RSTRING_PTR(rb_string);
  length = RSTRING_LEN(rb_string);

  const int nblocks = length / 16;
  int i;

  int64_t h1 = 0;
  int64_t h2 = 0;

  int64_t c1 = BIG_CONSTANT(0x87c37b91114253d5);
  int64_t c2 = BIG_CONSTANT(0x4cf5ad432745937f);

  //----------
  // body

  const int64_t* blocks = (const int64_t*)(bytes);

  for(i = 0; i < nblocks; i++)
  {
    int64_t k1 = getblock(blocks, i * 2 + 0);
    int64_t k2 = getblock(blocks, i * 2 + 1);

    k1 *= c1;
    k1  = rotl(k1, 31);
    k1 *= c2;
    h1 ^= k1;

    h1  = rotl(h1, 27);
    h1 += h2;
    h1  = h1 * 5 + 0x52dce729;

    k2 *= c2;
    k2  = rotl(k2, 33);
    k2 *= c1;
    h2 ^= k2;

    h2  = rotl(h2, 31);
    h2 += h1;
    h2  = h2 * 5 + 0x38495ab5;
  }

  //----------
  // tail

  const int8_t* tail = (const int8_t*) (bytes + nblocks * 16);

  int64_t k1 = 0;
  int64_t k2 = 0;

  switch(length & 15)
  {
    case 15: k2 ^= ((int64_t) tail[14]) << 48;
    case 14: k2 ^= ((int64_t) tail[13]) << 40;
    case 13: k2 ^= ((int64_t) tail[12]) << 32;
    case 12: k2 ^= ((int64_t) tail[11]) << 24;
    case 11: k2 ^= ((int64_t) tail[10]) << 16;
    case 10: k2 ^= ((int64_t) tail[ 9]) << 8;
    case  9: k2 ^= ((int64_t) tail[ 8]) << 0;
             k2 *= c2;
             k2  = rotl(k2, 33);
             k2 *= c1;
             h2 ^= k2;
    case  8: k1 ^= ((int64_t) tail[7]) << 56;
    case  7: k1 ^= ((int64_t) tail[6]) << 48;
    case  6: k1 ^= ((int64_t) tail[5]) << 40;
    case  5: k1 ^= ((int64_t) tail[4]) << 32;
    case  4: k1 ^= ((int64_t) tail[3]) << 24;
    case  3: k1 ^= ((int64_t) tail[2]) << 16;
    case  2: k1 ^= ((int64_t) tail[1]) << 8;
    case  1: k1 ^= ((int64_t) tail[0]) << 0;
             k1 *= c1;
             k1  = rotl(k1, 31);
             k1 *= c2;
             h1 ^= k1;
  };

  //----------
  // finalization

  h1 ^= length;
  h2 ^= length;

  h1 += h2;
  h2 += h1;

  h1 = fmix(h1);
  h2 = fmix(h2);

  h1 += h2;
  h2 += h1;

  return LL2NUM(h1);
}