libavutil/adler32.c

   1 /*
   2  * Compute the Adler-32 checksum of a data stream.
   3  * This is a modified version based on adler32.c from the zlib library.
   4  *
   5  * Copyright (C) 1995 Mark Adler
   6  *
   7  * This software is provided 'as-is', without any express or implied
   8  * warranty.  In no event will the authors be held liable for any damages
   9  * arising from the use of this software.
  10  *
  11  * Permission is granted to anyone to use this software for any purpose,
  12  * including commercial applications, and to alter it and redistribute it
  13  * freely, subject to the following restrictions:
  14  *
  15  * 1. The origin of this software must not be misrepresented; you must not
  16  *    claim that you wrote the original software. If you use this software
  17  *    in a product, an acknowledgment in the product documentation would be
  18  *    appreciated but is not required.
  19  * 2. Altered source versions must be plainly marked as such, and must not be
  20  *    misrepresented as being the original software.
  21  * 3. This notice may not be removed or altered from any source distribution.
  22  */
  23
  24 #include "common.h"
  25 #include "adler32.h"
  26
  27 #define BASE 65521L /* largest prime smaller than 65536 */
  28
  29 #define DO1(buf)  {s1 += *buf++; s2 += s1;}
  30 #define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
  31 #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
  32
  33 unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)
  34 {
  35     unsigned long s1 = adler & 0xffff;
  36     unsigned long s2 = adler >> 16;
  37
  38     while (len>0) {
  39 #if CONFIG_SMALL
  40         while(len>4 && s2 < (1U<<31)){
  41             DO4(buf); len-=4;
  42 #else
  43         while(len>16 && s2 < (1U<<31)){
  44             DO16(buf); len-=16;
  45 #endif
  46         }
  47         DO1(buf); len--;
  48         s1 %= BASE;
  49         s2 %= BASE;
  50     }
  51     return (s2 << 16) | s1;
  52 }
  53
  54 #ifdef TEST
  55 #include "log.h"
  56 #define LEN 7001
  57 volatile int checksum;
  58 int main(void){
  59     int i;
  60     char data[LEN];
  61     av_log_set_level(AV_LOG_DEBUG);
  62     for(i=0; i<LEN; i++)
  63         data[i]= ((i*i)>>3) + 123*i;
  64     for(i=0; i<1000; i++){
  65         START_TIMER
  66         checksum= av_adler32_update(1, data, LEN);
  67         STOP_TIMER("adler")
  68     }
  69     av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
  70     return 0;
  71 }
  72 #endif