MurmurHash3_x86_32 in TypeScript

murmur3a.ts

// Inspired by: https://github.com/levitation/murmurhash-js

function murmur3a(data: string, seed: number = 0): number {
  const len = data.length;
  const nBlocks = len >>> 2;
  const tailOffset = nBlocks << 2;
  let k1;

  /* Body */

  let i = 0;
  for (; i < tailOffset; ++i) {
    k1 =
      (data.charCodeAt(i) & 0xff) |
      ((data.charCodeAt(++i) & 0xff) << 8) |
      ((data.charCodeAt(++i) & 0xff) << 16) |
      ((data.charCodeAt(++i) & 0xff) << 24);
    k1 =
      // Math.imul(k1, 0xcc9e2d51):
      ((k1 * 0xcc9e) << 16) + k1 * 0x2d51;
    k1 =
      // rotl32(k1, 15):
      (k1 << 15) | (k1 >>> 17);

    seed ^=
      // Math.imul(k1, 0x1b873593):
      ((k1 * 0x1b87) << 16) + k1 * 0x3593;
    seed =
      0xe6546b64 +
      5 *
        // rotl32(seed, 13):
        ((seed << 13) | (seed >>> 19));
  }

  /* Tail */

  if (tailOffset < len) {
    k1 = 0;
    for (i = len; i & 3; ) {
      k1 <<= 8;
      k1 |= data.charCodeAt(--i) & 0xff;
    }

    k1 =
      // Math.imul(k1, 0xcc9e2d51):
      ((k1 * 0xcc9e) << 16) + k1 * 0x2d51;
    k1 =
      // rotl32(k1, 15):
      (k1 << 15) | (k1 >>> 17);
    seed ^=
      // Math.imul(k1, 0x1b873593):
      ((k1 * 0x1b87) << 16) + k1 * 0x3593;
  }

  /* Finalization */

  seed ^= len;

  seed ^= seed >>> 16;
  seed =
    // Math.imul(seed, 0x85ebca6b):
    ((seed * 0x85eb) << 16) + seed * 0xca6b;
  seed ^= seed >>> 13;
  seed =
    // Math.imul(seed, 0xc2b2ae35):
    ((seed * 0xc2b2) << 16) + seed * 0xae35;
  return (seed ^ (seed >>> 16)) >>> 0;
}

// Source: https://stackoverflow.com/a/31929528
const tests = [
  { data: "", seed: 0, hash: 0 },
  { data: "", seed: 1, hash: 0x514e28b7 },
  { data: "", seed: 0xffffffff, hash: 0x81f16f39 },
  { data: "\xFF\xFF\xFF\xFF", seed: 0, hash: 0x76293b50 },
  { data: "\x21\x43\x65\x87", seed: 0, hash: 0xf55b516b },
  { data: "\x21\x43\x65\x87", seed: 0x5082edee, hash: 0x2362f9de },
  { data: "\x21\x43\x65", seed: 0, hash: 0x7e4a8634 },
  { data: "\x21\x43", seed: 0, hash: 0xa0f7b07a },
  { data: "\x21", seed: 0, hash: 0x72661cf4 },
  { data: "\x00\x00\x00\x00", seed: 0, hash: 0x2362f9de },
  { data: "\x00\x00\x00", seed: 0, hash: 0x85f0b427 },
  { data: "\x00\x00", seed: 0, hash: 0x30f4c306 },
  { data: "\x00", seed: 0, hash: 0x514e28b7 },
  { data: "a".repeat(256), seed: 0x9747b28c, hash: 0x37405bdc },
  {
    data: unescape(encodeURIComponent("ππππππππ")),
    seed: 0x9747b28c,
    hash: 0xd58063c1
  }
];

tests.forEach(test => {
  console.log(murmur3a(test.data, test.seed) === test.hash);
});