mirror of
https://git.videolan.org/git/ffmpeg.git
synced 2024-08-03 09:49:58 +02:00
39 lines
1023 B
C
39 lines
1023 B
C
/* adler32.c -- compute the Adler-32 checksum of a data stream
|
|
* Copyright (C) 1995 Mark Adler
|
|
* For conditions of distribution and use, see copyright notice in zlib.h
|
|
*/
|
|
|
|
#include "common.h"
|
|
#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);
|
|
#define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
|
|
|
|
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;
|
|
|
|
while (len > 0) {
|
|
int k = FFMIN(len, NMAX);
|
|
len -= k;
|
|
#ifndef CONFIG_SMALL
|
|
while (k >= 16) {
|
|
DO16(buf);
|
|
k -= 16;
|
|
}
|
|
#endif
|
|
while(k--) {
|
|
DO1(buf);
|
|
}
|
|
s1 %= BASE;
|
|
s2 %= BASE;
|
|
}
|
|
return (s2 << 16) | s1;
|
|
}
|