Libav
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00001 /* 00002 * Compute the Adler-32 checksum of a data stream. 00003 * This is a modified version based on adler32.c from the zlib library. 00004 * 00005 * Copyright (C) 1995 Mark Adler 00006 * 00007 * This software is provided 'as-is', without any express or implied 00008 * warranty. In no event will the authors be held liable for any damages 00009 * arising from the use of this software. 00010 * 00011 * Permission is granted to anyone to use this software for any purpose, 00012 * including commercial applications, and to alter it and redistribute it 00013 * freely, subject to the following restrictions: 00014 * 00015 * 1. The origin of this software must not be misrepresented; you must not 00016 * claim that you wrote the original software. If you use this software 00017 * in a product, an acknowledgment in the product documentation would be 00018 * appreciated but is not required. 00019 * 2. Altered source versions must be plainly marked as such, and must not be 00020 * misrepresented as being the original software. 00021 * 3. This notice may not be removed or altered from any source distribution. 00022 */ 00023 00024 #include "config.h" 00025 #include "adler32.h" 00026 00027 #define BASE 65521L /* largest prime smaller than 65536 */ 00028 00029 #define DO1(buf) {s1 += *buf++; s2 += s1;} 00030 #define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf); 00031 #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf); 00032 00033 unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len) 00034 { 00035 unsigned long s1 = adler & 0xffff; 00036 unsigned long s2 = adler >> 16; 00037 00038 while (len>0) { 00039 #if CONFIG_SMALL 00040 while(len>4 && s2 < (1U<<31)){ 00041 DO4(buf); len-=4; 00042 #else 00043 while(len>16 && s2 < (1U<<31)){ 00044 DO16(buf); len-=16; 00045 #endif 00046 } 00047 DO1(buf); len--; 00048 s1 %= BASE; 00049 s2 %= BASE; 00050 } 00051 return (s2 << 16) | s1; 00052 } 00053 00054 #ifdef TEST 00055 #include "log.h" 00056 #include "timer.h" 00057 #define LEN 7001 00058 volatile int checksum; 00059 int main(void){ 00060 int i; 00061 char data[LEN]; 00062 av_log_set_level(AV_LOG_DEBUG); 00063 for(i=0; i<LEN; i++) 00064 data[i]= ((i*i)>>3) + 123*i; 00065 for(i=0; i<1000; i++){ 00066 START_TIMER 00067 checksum= av_adler32_update(1, data, LEN); 00068 STOP_TIMER("adler") 00069 } 00070 av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum); 00071 return 0; 00072 } 00073 #endif