@ardatan/relay-compiler/util/murmurHash.js.flow

A compiler tool for building GraphQL-driven applications.

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict
 * @format
 */

// flowlint ambiguous-object-type:error

/**
 * Based on implementations by Gary Court and Austin Appleby, 2011, MIT.
 * @preserve-header
 */

'use strict';

const BASE62 = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

/**
 * @param {string} key A UTF-16 or ASCII string
 * @return {string} a base62 murmur hash
 */
function murmurHash(str: string): string {
  /* eslint-disable no-bitwise */
  const length = str.length;
  const rem = length & 3;
  const len = length ^ rem;

  let h = 0;
  let i = 0;
  let k;

  while (i !== len) {
    const ch4 = str.charCodeAt(i + 3);

    k =
      str.charCodeAt(i) ^
      (str.charCodeAt(i + 1) << 8) ^
      (str.charCodeAt(i + 2) << 16) ^
      ((ch4 & 0xff) << 24) ^
      ((ch4 & 0xff00) >> 8);

    i += 4;

    k = (k * 0x2d51 + (k & 0xffff) * 0xcc9e0000) >>> 0;
    k = (k << 15) | (k >>> 17);
    k = (k * 0x3593 + (k & 0xffff) * 0x1b870000) >>> 0;
    h ^= k;
    h = (h << 13) | (h >>> 19);
    h = (h * 5 + 0xe6546b64) >>> 0;
  }

  k = 0;
  switch (rem) {
    /* eslint-disable no-fallthrough */
    case 3:
      k ^= str.charCodeAt(len + 2) << 16;
    case 2:
      k ^= str.charCodeAt(len + 1) << 8;
    case 1:
      k ^= str.charCodeAt(len);

      k = (k * 0x2d51 + (k & 0xffff) * 0xcc9e0000) >>> 0;
      k = (k << 15) | (k >>> 17);
      k = (k * 0x3593 + (k & 0xffff) * 0x1b870000) >>> 0;
      h ^= k;
  }

  h ^= length;
  h ^= h >>> 16;
  h = (h * 0xca6b + (h & 0xffff) * 0x85eb0000) >>> 0;
  h ^= h >>> 13;
  h = (h * 0xae35 + (h & 0xffff) * 0xc2b20000) >>> 0;
  h ^= h >>> 16;

  h >>>= 0;

  if (!h) {
    return '0';
  }

  let s = '';
  while (h) {
    const d = h % 62;
    s = BASE62[d] + s;
    h = (h - d) / 62;
  }
  return s;
}

module.exports = murmurHash;