# All files / node_modules/upng-js/node_modules/pako/lib/zlib adler32.js

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    18x
     'use strict';

    // Note: adler32 takes 12% for level 0 and 2% for level 6.
    // It isn't worth it to make additional optimizations as in original.
    // Small size is preferable.

    // (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.

    function adler32(adler, buf, len, pos) {
      var s1 = (adler & 0xffff) |0,
          s2 = ((adler >>> 16) & 0xffff) |0,
          n = 0;

      while (len !== 0) {
        // Set limit ~ twice less than 5552, to keep
        // s2 in 31-bits, because we force signed ints.
        // in other case %= will fail.
        n = len > 2000 ? 2000 : len;
        len -= n;

        do {
          s1 = (s1 + buf[pos++]) |0;
          s2 = (s2 + s1) |0;
        } while (--n);

        s1 %= 65521;
        s2 %= 65521;
      }

      return (s1 | (s2 << 16)) |0;
    }

    module.exports = adler32;