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simpler, smaller and faster

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Originally committed as revision 5800 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2006-07-20 08:34:01 +00:00
parent d9cf32d920
commit f296446564
1 changed files with 28 additions and 13 deletions
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41
libavutil/adler32.c
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@ -7,8 +7,6 @@
#include "adler32.h"
#define BASE 65521L /* largest prime smaller than 65536 */
#define NMAX 5552
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
#define DO1(buf) {s1 += *buf++; s2 += s1;}
#define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf);
@ -17,22 +15,39 @@
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) & 0xffff;
unsigned long s2 = adler >> 16;
while (len > 0) {
int k = FFMIN(len, NMAX);
len -= k;
#ifndef CONFIG_SMALL
while (k >= 16) {
DO16(buf);
k -= 16;
}
while (len>0) {
#ifdef CONFIG_SMALL
while(len>4 && s2 < (1U<<31)){
DO4(buf); len-=4;
#else
while(len>16 && s2 < (1U<<31)){
DO16(buf); len-=16;
#endif
while(k--) {
DO1(buf);
}
DO1(buf); len--;
s1 %= BASE;
s2 %= BASE;
}
return (s2 << 16) | s1;
}
#ifdef TEST
#include "log.h"
#define LEN 7001
volatile int checksum;
int main(){
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++){
START_TIMER
checksum= av_adler32_update(1, data, LEN);
STOP_TIMER("adler")
}
av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
}
#endif