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* 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 "common.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) {
while(len>4 && s2 < (1U<<31)){
DO4(buf); len-=4;
while(len>16 && s2 < (1U<<31)){
DO16(buf); len-=16;
DO1(buf); len--;
s1 %= BASE;
s2 %= BASE;
return (s2 << 16) | s1;
#ifdef TEST
#include "log.h"
#define LEN 7001
volatile int checksum;
int main(void){
int i;
char data[LEN];
av_log_level = AV_LOG_DEBUG;
for(i=0; i<LEN; i++)
data[i]= ((i*i)>>3) + 123*i;
for(i=0; i<1000; i++){
checksum= av_adler32_update(1, data, LEN);
av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
return 0;