/*

 * Compute the Adler-32 checksum of a data stream.

 * This is a modified version based on adler32.c from the zlib library.

 *

 * Copyright (C) 1995 Mark Adler

 *

 * 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.

 */

/**

 * @file

 * Computes the Adler-32 checksum of a data stream

 *

 * This is a modified version based on adler32.c from the zlib library.

 * @author Mark Adler

 * @ingroup lavu_adler32

 */

#include "config.h"

#include "adler32.h"

#include "intreadwrite.h"

#include "macros.h"

#define BASE 65521L /* largest prime smaller than 65536 */

#define DO1(buf)  { s1 += *buf++; s2 += s1; }

#define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);

#define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);

AVAdler av_adler32_update(AVAdler adler, const uint8_t *buf, size_t len)

{

    unsigned long s1 = adler & 0xffff;

    unsigned long s2 = adler >> 16;

    while (len > 0) {

#if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL

        unsigned len2 = FFMIN((len-1) & ~7, 23*8);

        if (len2) {

            uint64_t a1= 0;

            uint64_t a2= 0;

            uint64_t b1= 0;

            uint64_t b2= 0;

            len -= len2;

            s2 += s1*len2;

            while (len2 >= 8) {

                uint64_t v = AV_RN64(buf);

                a2 += a1;

                b2 += b1;

                a1 +=  v    &0x00FF00FF00FF00FF;

                b1 += (v>>8)&0x00FF00FF00FF00FF;

                len2 -= 8;

                buf+=8;

            }

            //We combine the 8 interleaved adler32 checksums without overflows

            //Decreasing the number of iterations would allow below code to be

            //simplified but would likely be slower due to the fewer iterations

            //of the inner loop

            s1 += ((a1+b1)*0x1000100010001)>>48;

            s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32)

#if HAVE_BIGENDIAN

                 + 2*((b1*0x1000200030004)>>48)

                 +   ((a1*0x1000100010001)>>48)

                 + 2*((a1*0x0000100020003)>>48);

#else

                 + 2*((a1*0x4000300020001)>>48)

                 +   ((b1*0x1000100010001)>>48)

                 + 2*((b1*0x3000200010000)>>48);

#endif

        }

#else

        while (len > 4  && s2 < (1U << 31)) {

            DO4(buf);

            len -= 4;

        }

#endif

        DO1(buf); len--;

        s1 %= BASE;

        s2 %= BASE;

    }

    return (s2 << 16) | s1;

}