SukkaSurge/Build/lib/string-hash.ts

/**
 * FNV-1a Hash implementation
 * @author Travis Webb (tjwebb) <me@traviswebb.com>
 *
 * Ported from https://github.com/tjwebb/fnv-plus/blob/master/index.js
 *
 * Simplified, optimized and add modified for 52 bit, which provides a larger hash space
 * and still making use of Javascript's 53-bit integer space.
 */
export function fnv1a52(str: string) {
  const len = str.length;
  let i = 0,
    t0 = 0,
    v0 = 0x2325,
    t1 = 0,
    v1 = 0x8422,
    t2 = 0,
    v2 = 0x9CE4,
    t3 = 0,
    v3 = 0xCBF2;

  while (i < len) {
    v0 ^= str.charCodeAt(i++);
    t0 = v0 * 435;
    t1 = v1 * 435;
    t2 = v2 * 435;
    t3 = v3 * 435;
    t2 += v0 << 8;
    t3 += v1 << 8;
    t1 += t0 >>> 16;
    v0 = t0 & 65535;
    t2 += t1 >>> 16;
    v1 = t1 & 65535;
    v3 = (t3 + (t2 >>> 16)) & 65535;
    v2 = t2 & 65535;
  }

  return (
    (v3 & 15) * 281_474_976_710_656
    + v2 * 4_294_967_296
    + v1 * 65536
    + (v0 ^ (v3 >> 4))
  );
}

export function fnv1a(s: string) {
  let h = 0x81_1C_9D_C5;

  for (let i = 0, l = s.length; i < l; i++) {
    h ^= s.charCodeAt(i);
    h += (h << 1) + (h << 4) + (h << 7) + (h << 8) + (h << 24);
  }

  return (h >>> 0);
}

export const stringHash = (payload: string) => fnv1a52(payload).toString(36) + payload.length.toString(36);