murmurhash32-node/lib/murmurhash64Av2.js

JavaScript implementation of the murmurhash algorithm - 32bit

"use strict";

/* global BigInt */

const { stringToBuffer, toUInt64 } = require("./utils");

const MURMURHASH_M = BigInt("0xc6a4a7935bd1e995");
const MURMURHASH_R = BigInt(47);

function murmurhash64Av2(key, seed = 0) {
  key = stringToBuffer(key);

  let len = key.length;
  seed = BigInt(seed);

  let h = seed ^ (BigInt(len) * MURMURHASH_M);
  let remainder = len & 7;
  let bytes = len - remainder;

  let i = 0;
  while (i < bytes) {
    let k =
      BigInt(key[i++]) |
      (BigInt(key[i++]) << BigInt(8)) |
      (BigInt(key[i++]) << BigInt(16)) |
      (BigInt(key[i++]) << BigInt(24)) |
      (BigInt(key[i++]) << BigInt(32)) |
      (BigInt(key[i++]) << BigInt(40)) |
      (BigInt(key[i++]) << BigInt(48)) |
      (BigInt(key[i++]) << BigInt(56));

    k = k * MURMURHASH_M;
    k = toUInt64(k);
    k ^= k >> MURMURHASH_R;
    k *= MURMURHASH_M;

    h ^= k;
    h *= MURMURHASH_M;
  }

  switch (remainder) {
    case 7:
      h ^= BigInt(key[i + 6]) << BigInt(48);
    case 6:
      h ^= BigInt(key[i + 5]) << BigInt(40);
    case 5:
      h ^= BigInt(key[i + 4]) << BigInt(32);
    case 4:
      h ^= BigInt(key[i + 3]) << BigInt(24);
    case 3:
      h ^= BigInt(key[i + 2]) << BigInt(16);
    case 2:
      h ^= BigInt(key[i + 1]) << BigInt(8);
    case 1:
      h ^= BigInt(key[i]);

      h *= MURMURHASH_M;
  }

  h = toUInt64(h);
  h ^= h >> MURMURHASH_R;
  h *= MURMURHASH_M;
  h = toUInt64(h);
  h ^= h >> MURMURHASH_R;

  return "0x" + h.toString(16);
}

module.exports = murmurhash64Av2;