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ffmpeg / libavutil / adler32.c @ 4869f47e

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/* adler32.c -- compute the Adler-32 checksum of a data stream
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 * This is a modified version based on adler32.c from the zlib library.
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 *
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 * Copyright (C) 1995 Mark Adler
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 *
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 * This software is provided 'as-is', without any express or implied
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 * warranty.  In no event will the authors be held liable for any damages
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 * arising from the use of this software.
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 *
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 * Permission is granted to anyone to use this software for any purpose,
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 * including commercial applications, and to alter it and redistribute it
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 * freely, subject to the following restrictions:
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 *
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 * 1. The origin of this software must not be misrepresented; you must not
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 *    claim that you wrote the original software. If you use this software
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 *    in a product, an acknowledgment in the product documentation would be
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 *    appreciated but is not required.
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 * 2. Altered source versions must be plainly marked as such, and must not be
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 *    misrepresented as being the original software.
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 * 3. This notice may not be removed or altered from any source distribution.
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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(void){
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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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    return 0;
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}
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#endif