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 "config.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 33unsigned 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#include "timer.h" 57#define LEN 7001 58volatile int checksum; 59int main(void){ 60 int i; 61 char data[LEN]; 62 av_log_set_level(AV_LOG_DEBUG); 63 for(i=0; i<LEN; i++) 64 data[i]= ((i*i)>>3) + 123*i; 65 for(i=0; i<1000; i++){ 66 START_TIMER 67 checksum= av_adler32_update(1, data, LEN); 68 STOP_TIMER("adler") 69 } 70 av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum); 71 return 0; 72} 73#endif 74