reign/lib/hash-functions/buffer/index.js

A persistent, typed-objects implementation.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = hashBuffer;
exports.fnv = fnv;
exports.djb = djb;
exports.murmur3 = murmur3;


/**
 * Hash a Buffer or Uint8Array and return the value.
 */
function hashBuffer(input) {
  let hash = 0;
  const length = input.length;
  for (let i = 0; i < length; i++) {
    hash = (hash << 5) - hash + input[i];
  }
  return hash >>> 0;
}

/**
 * Calculate a 32 bit FNV-1a hash
 */
function fnv(input) {
  let hash = 0x811c9dc5;

  for (let i = 0; i < input.length; i++) {
    hash ^= input[i];
    hash += (hash << 1) + (hash << 4) + (hash << 7) + (hash << 8) + (hash << 24);
  }
  return hash >>> 0;
}

/**
 * Calculate a 32 bit DJB hash.
 */
function djb(input) {
  let hash = 5381;
  for (let i = 0; i < input.length; i++) {
    hash = (hash << 5) + hash + input[i];
  }
  return hash >>> 0;
}

/**
 * Calculate a 32 bit Murmur3 hash.
 */
function murmur3(key) {
  let seed = arguments.length <= 1 || arguments[1] === undefined ? 0 : arguments[1];

  let h1b, k1;

  const remainder = key.length & 3; // key.length % 4
  const bytes = key.length - remainder;
  let h1 = seed;
  let c1 = 0xcc9e2d51;
  let c2 = 0x1b873593;
  let i = 0;

  while (i < bytes) {
    k1 = key[i] & 0xff | (key[++i] & 0xff) << 8 | (key[++i] & 0xff) << 16 | (key[++i] & 0xff) << 24;
    ++i;

    k1 = (k1 & 0xffff) * c1 + (((k1 >>> 16) * c1 & 0xffff) << 16) & 0xffffffff;
    k1 = k1 << 15 | k1 >>> 17;
    k1 = (k1 & 0xffff) * c2 + (((k1 >>> 16) * c2 & 0xffff) << 16) & 0xffffffff;

    h1 ^= k1;
    h1 = h1 << 13 | h1 >>> 19;
    h1b = (h1 & 0xffff) * 5 + (((h1 >>> 16) * 5 & 0xffff) << 16) & 0xffffffff;
    h1 = (h1b & 0xffff) + 0x6b64 + (((h1b >>> 16) + 0xe654 & 0xffff) << 16);
  }

  k1 = 0;

  switch (remainder) {
    case 3:
      k1 ^= (key[i + 2] & 0xff) << 16;
    case 2:
      k1 ^= (key[i + 1] & 0xff) << 8;
    case 1:
      k1 ^= key[i] & 0xff;

      k1 = (k1 & 0xffff) * c1 + (((k1 >>> 16) * c1 & 0xffff) << 16) & 0xffffffff;
      k1 = k1 << 15 | k1 >>> 17;
      k1 = (k1 & 0xffff) * c2 + (((k1 >>> 16) * c2 & 0xffff) << 16) & 0xffffffff;
      h1 ^= k1;
  }

  h1 ^= key.length;

  h1 ^= h1 >>> 16;
  h1 = (h1 & 0xffff) * 0x85ebca6b + (((h1 >>> 16) * 0x85ebca6b & 0xffff) << 16) & 0xffffffff;
  h1 ^= h1 >>> 13;
  h1 = (h1 & 0xffff) * 0xc2b2ae35 + (((h1 >>> 16) * 0xc2b2ae35 & 0xffff) << 16) & 0xffffffff;
  h1 ^= h1 >>> 16;

  return h1 >>> 0;
}