مشاهدة ملف: crc.js

"use strict";

let crcTable = [];

(function () {
  for (let i = 0; i < 256; i++) {
    let currentCrc = i;
    for (let j = 0; j < 8; j++) {
      if (currentCrc & 1) {
        currentCrc = 0xedb88320 ^ (currentCrc >>> 1);
      } else {
        currentCrc = currentCrc >>> 1;
      }
    }
    crcTable[i] = currentCrc;
  }
})();

let CrcCalculator = (module.exports = function () {
  this._crc = -1;
});

CrcCalculator.prototype.write = function (data) {
  for (let i = 0; i < data.length; i++) {
    this._crc = crcTable[(this._crc ^ data[i]) & 0xff] ^ (this._crc >>> 8);
  }
  return true;
};

CrcCalculator.prototype.crc32 = function () {
  return this._crc ^ -1;
};

CrcCalculator.crc32 = function (buf) {
  let crc = -1;
  for (let i = 0; i < buf.length; i++) {
    crc = crcTable[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
  }
  return crc ^ -1;
};