mirror of
https://github.com/opencv/opencv.git
synced 2024-12-16 02:19:12 +08:00
55 lines
1.6 KiB
C
55 lines
1.6 KiB
C
|
/* adler32.c -- compute the Adler-32 checksum of a data stream
|
||
|
|
* Copyright (C) 1995-2011, 2016 Mark Adler
|
||
|
|
* For conditions of distribution and use, see copyright notice in zlib.h
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "zbuild.h"
|
||
|
|
#include "functable.h"
|
||
|
|
#include "adler32_p.h"
|
||
|
|
|
||
|
|
/* ========================================================================= */
|
||
|
|
Z_INTERNAL uint32_t adler32_c(uint32_t adler, const uint8_t *buf, size_t len) {
|
||
|
|
uint32_t sum2;
|
||
|
|
unsigned n;
|
||
|
|
|
||
|
|
/* split Adler-32 into component sums */
|
||
|
|
sum2 = (adler >> 16) & 0xffff;
|
||
|
|
adler &= 0xffff;
|
||
|
|
|
||
|
|
/* in case user likes doing a byte at a time, keep it fast */
|
||
|
|
if (UNLIKELY(len == 1))
|
||
|
|
return adler32_len_1(adler, buf, sum2);
|
||
|
|
|
||
|
|
/* initial Adler-32 value (deferred check for len == 1 speed) */
|
||
|
|
if (UNLIKELY(buf == NULL))
|
||
|
|
return 1L;
|
||
|
|
|
||
|
|
/* in case short lengths are provided, keep it somewhat fast */
|
||
|
|
if (UNLIKELY(len < 16))
|
||
|
|
return adler32_len_16(adler, buf, len, sum2);
|
||
|
|
|
||
|
|
/* do length NMAX blocks -- requires just one modulo operation */
|
||
|
|
while (len >= NMAX) {
|
||
|
|
len -= NMAX;
|
||
|
|
#ifdef UNROLL_MORE
|
||
|
|
n = NMAX / 16; /* NMAX is divisible by 16 */
|
||
|
|
#else
|
||
|
|
n = NMAX / 8; /* NMAX is divisible by 8 */
|
||
|
|
#endif
|
||
|
|
do {
|
||
|
|
#ifdef UNROLL_MORE
|
||
|
|
DO16(adler, sum2, buf); /* 16 sums unrolled */
|
||
|
|
buf += 16;
|
||
|
|
#else
|
||
|
|
DO8(adler, sum2, buf, 0); /* 8 sums unrolled */
|
||
|
|
buf += 8;
|
||
|
|
#endif
|
||
|
|
} while (--n);
|
||
|
|
adler %= BASE;
|
||
|
|
sum2 %= BASE;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* do remaining bytes (less than NMAX, still just one modulo) */
|
||
|
|
return adler32_len_64(adler, buf, len, sum2);
|
||
|
|
}
|