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54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/* adler32.c -- compute the Adler-32 checksum of a data stream
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* Copyright (C) 1995 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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#include "common.h"
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#include "adler32.h"
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#define BASE 65521L /* largest prime smaller than 65536 */
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#define DO1(buf) {s1 += *buf++; s2 += s1;}
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#define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf);
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#define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
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unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)
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{
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unsigned long s1 = adler & 0xffff;
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unsigned long s2 = adler >> 16;
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while (len>0) {
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#ifdef CONFIG_SMALL
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while(len>4 && s2 < (1U<<31)){
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DO4(buf); len-=4;
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#else
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while(len>16 && s2 < (1U<<31)){
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DO16(buf); len-=16;
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#endif
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}
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DO1(buf); len--;
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s1 %= BASE;
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s2 %= BASE;
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}
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return (s2 << 16) | s1;
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}
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#ifdef TEST
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#include "log.h"
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#define LEN 7001
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volatile int checksum;
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int main(){
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int i;
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char data[LEN];
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av_log_level = AV_LOG_DEBUG;
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for(i=0; i<LEN; i++)
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data[i]= ((i*i)>>3) + 123*i;
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for(i=0; i<1000; i++){
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START_TIMER
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checksum= av_adler32_update(1, data, LEN);
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STOP_TIMER("adler")
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}
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av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
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}
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#endif
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