nyks/string/crc32.js

nodejs exupery style

"use strict";

/**
* from  crc32.js (C) 2014-2015 SheetJS -- http://sheetjs.com
*/

var use_in32 = typeof Int32Array !== 'undefined';

/* istanbul ignore next */
var table = (function() {
  var c     = 0;
  var table = new Array(256);

  for(var n = 0; n != 256; ++n) {
    c = n;
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    c = ((c & 1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
    table[n] = c;
  }
  return use_in32 ? new Int32Array(table) : table;
}());

/* much much faster to intertwine utf8 and crc */
/* istanbul ignore next */
function crc32_str(str) {
  for(var crc = -1, i = 0, L = str.length, c, d; i < L;) {
    c = str.charCodeAt(i++);
    if(c < 0x80) {
      crc = (crc >>> 8) ^ table[(crc ^ c) & 0xFF];
    } else if(c < 0x800) {
      crc = (crc >>> 8) ^ table[(crc ^ (192 | ((c >> 6) & 31))) & 0xFF];
      crc = (crc >>> 8) ^ table[(crc ^ (128 | (c & 63))) & 0xFF];
    } else if(c >= 0xD800 && c < 0xE000) {
      c = (c & 1023) + 64; d = str.charCodeAt(i++) & 1023;
      crc = (crc >>> 8) ^ table[(crc ^ (240 | ((c >> 8) & 7))) & 0xFF];
      crc = (crc >>> 8) ^ table[(crc ^ (128 | ((c >> 2) & 63))) & 0xFF];
      crc = (crc >>> 8) ^ table[(crc ^ (128 | ((d >> 6) & 15) | (c & 3))) & 0xFF];
      crc = (crc >>> 8) ^ table[(crc ^ (128 | (d & 63))) & 0xFF];
    } else {
      crc = (crc >>> 8) ^ table[(crc ^ (224 | ((c >> 12) & 15))) & 0xFF];
      crc = (crc >>> 8) ^ table[(crc ^ (128 | ((c >> 6) & 63))) & 0xFF];
      crc = (crc >>> 8) ^ table[(crc ^ (128 | (c & 63))) & 0xFF];
    }
  }
  return crc ^ -1;
}

module.exports = crc32_str;