/*
  * 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.

  */
 

 #include "config.h"

 #include "adler32.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 CONFIG_SMALL

         while(len>4 && s2 < (1U<<31)){
             DO4(buf); len-=4;
 #else
         while(len>16 && s2 < (1U<<31)){
             DO16(buf); len-=16;

 #endif
         }

         DO1(buf); len--;

         s1 %= BASE;
         s2 %= BASE;
     }
     return (s2 << 16) | s1;
 }

 
 #ifdef TEST
 #include "log.h"

 #include "timer.h"

 #define LEN 7001
 volatile int checksum;

 int main(void){

     int i;
     char data[LEN];

     av_log_set_level(AV_LOG_DEBUG);

     for(i=0; i<LEN; i++)
         data[i]= ((i*i)>>3) + 123*i;
     for(i=0; i<1000; i++){
         START_TIMER
         checksum= av_adler32_update(1, data, LEN);
         STOP_TIMER("adler")
     }
     av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);

     return 0;

 }
 #endif