/*
  * 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 "common.h"

 #include "intreadwrite.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);

 unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf,
                                 unsigned int 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;
 }