libavutil/adler32.c

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