js-crc-update/src/crc.js

Simple CRC checksum functions for JavaScript(CRC-16 and CRC-32).

(function () {
  'use strict';

  var root = typeof window === 'object' ? window : {};
  var NODE_JS = !root.JS_CRC_NO_NODE_JS && typeof process === 'object' && process.versions && process.versions.node;
  if (NODE_JS) {
    root = global;
  }
  var COMMON_JS = !root.JS_CRC_NO_COMMON_JS && typeof module === 'object' && module.exports;
  var AMD = typeof define === 'function' && define.amd;
  var ARRAY_BUFFER = !root.JS_CRC_NO_ARRAY_BUFFER && typeof ArrayBuffer !== 'undefined';
  var HEX_CHARS = '0123456789abcdef'.split('');

  var Modules = [
    {
        name: 'crc128',
        polynom: 0xEDB88320,
        initValue: -1,
        bytes: 10
    },
    {
        name: 'crc64',
        polynom: 0xEDB88320,
        initValue: -1,
        bytes: 6
    },
    {
      name: 'crc32',
      polynom: 0xEDB88320,
      initValue: -1,
      bytes: 4
    },
    {
      name: 'crc16',
      polynom: 0xA001,
      initValue: 0,
      bytes: 2
    }
  ];

  var i, j, k, b;
  for (i = 0; i < Modules.length; ++i) {
    var m = Modules[i];
    m.method = (function (m) {
      return function (message) {
        return crc(message, m);
      };
    })(m);
    m.table = [];
    for (j = 0; j < 256; ++j) {
      b = j;
      for (k = 0; k < 8; ++k) {
        b = b & 1 ? m.polynom ^ (b >>> 1) : b >>> 1;
      }
      m.table[j] = b >>> 0;
    }
  }

  var crc = function (message, module) {
    var notString = typeof message !== 'string';
    if (notString && ARRAY_BUFFER && message instanceof ArrayBuffer) {
      message = new Uint8Array(message);
    }

    var crc = module.initValue, code, i, length = message.length, table = module.table;
    if (notString) {
      for (i = 0; i < length; ++i) {
        crc = table[(crc ^ message[i]) & 0xFF] ^ (crc >>> 8);
      }
    } else {
      for (i = 0; i < length; ++i) {
        code = message.charCodeAt(i);
        if (code < 0x80) {
          crc = table[(crc ^ code) & 0xFF] ^ (crc >>> 8);
        } else if (code < 0x800) {
          crc = table[(crc ^ (0xc0 | (code >> 6))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
        } else if (code < 0xd800 || code >= 0xe000) {
          crc = table[(crc ^ (0xe0 | (code >> 12))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | ((code >> 6) & 0x3f))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
        } else {
          code = 0x10000 + (((code & 0x3ff) << 10) | (message.charCodeAt(++i) & 0x3ff));
          crc = table[(crc ^ (0xf0 | (code >> 18))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | ((code >> 12) & 0x3f))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | ((code >> 6) & 0x3f))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
        }
      }
    }
    crc ^= module.initValue;

    var hex = '';
    if (module.bytes > 2) {
      hex += HEX_CHARS[(crc >> 28) & 0x0F] + HEX_CHARS[(crc >> 24) & 0x0F] +
             HEX_CHARS[(crc >> 20) & 0x0F] + HEX_CHARS[(crc >> 16) & 0x0F];
    }
    hex += HEX_CHARS[(crc >> 12) & 0x0F] + HEX_CHARS[(crc >> 8) & 0x0F] +
           HEX_CHARS[(crc >> 4) & 0x0F] + HEX_CHARS[crc & 0x0F];
    return hex;
  };

  var exports = {};
  for (i = 0;i < Modules.length;++i) {
    var m = Modules[i];
    exports[m.name] = m.method;
  }
  if (COMMON_JS) {
    module.exports = exports;
  } else {
    for (i = 0;i < Modules.length;++i) {
      var m = Modules[i];
      root[m.name] = m.method;
    }
    if (AMD) {
      define(function() {
        return exports;
      });
    }
  }
})();