cyrb53.js

/*
    cyrb53 (c) 2018 bryc (github.com/bryc)
    License: Public domain (or MIT if needed). Attribution appreciated.
    A fast and simple 53-bit string hash function with decent collision resistance.
    Largely inspired by MurmurHash2/3, but with a focus on speed/simplicity.
*/
const cyrb53 = function(str, seed = 0) {
  let h1 = 0xdeadbeef ^ seed, h2 = 0x41c6ce57 ^ seed;
  for(let i = 0, ch; i < str.length; i++) {
    ch = str.charCodeAt(i);
    h1 = Math.imul(h1 ^ ch, 2654435761);
    h2 = Math.imul(h2 ^ ch, 1597334677);
  }
  h1  = Math.imul(h1 ^ (h1 >>> 16), 2246822507);
  h1 ^= Math.imul(h2 ^ (h2 >>> 13), 3266489909);
  h2  = Math.imul(h2 ^ (h2 >>> 16), 2246822507);
  h2 ^= Math.imul(h1 ^ (h1 >>> 13), 3266489909);
  return 4294967296 * (2097151 & h2) + (h1 >>> 0);
};

/*
    cyrb53a beta (c) 2023 bryc (github.com/bryc)
    License: Public domain (or MIT if needed). Attribution appreciated.
    This is a work-in-progress, and changes to the algorithm are expected.
    The original cyrb53 has a slight mixing bias in the low bits of h1.
    This doesn't affect collision rate, but I want to try to improve it.
    This new version has preliminary improvements in avalanche behavior.
*/
const cyrb53a_beta = function(str, seed = 0) {
  let h1 = 0xdeadbeef ^ seed, h2 = 0x41c6ce57 ^ seed;
  for(let i = 0, ch; i < str.length; i++) {
    ch = str.charCodeAt(i);
    h1 = Math.imul(h1 ^ ch, 0x85ebca77);
    h2 = Math.imul(h2 ^ ch, 0xc2b2ae3d);
  }
  h1 ^= Math.imul(h1 ^ (h2 >>> 15), 0x735a2d97);
  h2 ^= Math.imul(h2 ^ (h1 >>> 15), 0xcaf649a9);
  h1 ^= h2 >>> 16; h2 ^= h1 >>> 16;
    return 2097152 * (h2 >>> 0) + (h1 >>> 11);
};