# All files / node_modules/upng-js/node_modules/pako/lib/zlib crc32.js

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     '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;