Function Hash32

tensorflow/core/lib/hash/hash.cc:35–82

static inline uint64 ByteAs64(char c) { return static_cast<uint64>(c) & 0xff; }

uint32 Hash32(const char* data, size_t n, uint32 seed) {
  // 'm' and 'r' are mixing constants generated offline.
  // They're not really 'magic', they just happen to work well.

  const uint32 m = 0x5bd1e995;
  const int r = 24;

  // Initialize the hash to a 'random' value
  uint32 h = seed ^ n;

  // Mix 4 bytes at a time into the hash
  while (n >= 4) {
    uint32 k = core::DecodeFixed32(data);

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

    h *= m;
    h ^= k;

    data += 4;
    n -= 4;
  }

  // Handle the last few bytes of the input array

  switch (n) {
    case 3:
      h ^= ByteAs32(data[2]) << 16;
      TF_FALLTHROUGH_INTENDED;
    case 2:
      h ^= ByteAs32(data[1]) << 8;
      TF_FALLTHROUGH_INTENDED;
    case 1:
      h ^= ByteAs32(data[0]);
      h *= m;
  }

  // Do a few final mixes of the hash to ensure the last few
  // bytes are well-incorporated.

  h ^= h >> 13;
  h *= m;
  h ^= h >> 15;

  return h;
}

uint64 SDBMHash64(const char *key, size_t len) {
  register uint64 hash_value = 0;