| 'use strict'; |
| |
| // Note: we can't get significant speed boost here. |
| // So write code to minimize size - no pregenerated tables |
| // and array tools dependencies. |
| |
| // (C) 1995-2013 Jean-loup Gailly and Mark Adler |
| // (C) 2014-2017 Vitaly Puzrin and Andrey Tupitsin |
| // |
| // This software is provided 'as-is', without any express or implied |
| // warranty. In no event will the authors be held liable for any damages |
| // arising from the use of this software. |
| // |
| // Permission is granted to anyone to use this software for any purpose, |
| // including commercial applications, and to alter it and redistribute it |
| // freely, subject to the following restrictions: |
| // |
| // 1. The origin of this software must not be misrepresented; you must not |
| // claim that you wrote the original software. If you use this software |
| // in a product, an acknowledgment in the product documentation would be |
| // appreciated but is not required. |
| // 2. Altered source versions must be plainly marked as such, and must not be |
| // misrepresented as being the original software. |
| // 3. This notice may not be removed or altered from any source distribution. |
| |
| // Use ordinary array, since untyped makes no boost here |
| function makeTable() { |
| var c, table = []; |
| |
| for (var n = 0; n < 256; n++) { |
| c = n; |
| for (var k = 0; k < 8; k++) { |
| c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1)); |
| } |
| table[n] = c; |
| } |
| |
| return table; |
| } |
| |
| // Create table on load. Just 255 signed longs. Not a problem. |
| var crcTable = makeTable(); |
| |
| |
| function crc32(crc, buf, len, pos) { |
| var t = crcTable, |
| end = pos + len; |
| |
| crc ^= -1; |
| |
| for (var i = pos; i < end; i++) { |
| crc = (crc >>> 8) ^ t[(crc ^ buf[i]) & 0xFF]; |
| } |
| |
| return (crc ^ (-1)); // >>> 0; |
| } |
| |
| |
| module.exports = crc32; |