'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.

export class zlib_adler32
{
    public static adler32(adler: number, buf: Uint8Array, len: number, pos: number)
    {
        let s1: number = (adler & 0xffff) | 0,
            s2: number = ((adler >>> 16) & 0xffff) | 0,
            n: number = 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;
    }
}

