mirror of
https://github.com/opencv/opencv.git
synced 2024-12-05 17:59:13 +08:00
187 lines
5.1 KiB
C
187 lines
5.1 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
|
|
*/
|
|
|
|
/* @(#) $Id$ */
|
|
|
|
#include "zutil.h"
|
|
|
|
local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2));
|
|
|
|
#define BASE 65521U /* 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,i) {adler += (buf)[i]; sum2 += adler;}
|
|
#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
|
|
#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
|
|
#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
|
|
#define DO16(buf) DO8(buf,0); DO8(buf,8);
|
|
|
|
/* use NO_DIVIDE if your processor does not do division in hardware --
|
|
try it both ways to see which is faster */
|
|
#ifdef NO_DIVIDE
|
|
/* note that this assumes BASE is 65521, where 65536 % 65521 == 15
|
|
(thank you to John Reiser for pointing this out) */
|
|
# define CHOP(a) \
|
|
do { \
|
|
unsigned long tmp = a >> 16; \
|
|
a &= 0xffffUL; \
|
|
a += (tmp << 4) - tmp; \
|
|
} while (0)
|
|
# define MOD28(a) \
|
|
do { \
|
|
CHOP(a); \
|
|
if (a >= BASE) a -= BASE; \
|
|
} while (0)
|
|
# define MOD(a) \
|
|
do { \
|
|
CHOP(a); \
|
|
MOD28(a); \
|
|
} while (0)
|
|
# define MOD63(a) \
|
|
do { /* this assumes a is not negative */ \
|
|
z_off64_t tmp = a >> 32; \
|
|
a &= 0xffffffffL; \
|
|
a += (tmp << 8) - (tmp << 5) + tmp; \
|
|
tmp = a >> 16; \
|
|
a &= 0xffffL; \
|
|
a += (tmp << 4) - tmp; \
|
|
tmp = a >> 16; \
|
|
a &= 0xffffL; \
|
|
a += (tmp << 4) - tmp; \
|
|
if (a >= BASE) a -= BASE; \
|
|
} while (0)
|
|
#else
|
|
# define MOD(a) a %= BASE
|
|
# define MOD28(a) a %= BASE
|
|
# define MOD63(a) a %= BASE
|
|
#endif
|
|
|
|
/* ========================================================================= */
|
|
uLong ZEXPORT adler32_z(adler, buf, len)
|
|
uLong adler;
|
|
const Bytef *buf;
|
|
z_size_t len;
|
|
{
|
|
unsigned long 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 (len == 1) {
|
|
adler += buf[0];
|
|
if (adler >= BASE)
|
|
adler -= BASE;
|
|
sum2 += adler;
|
|
if (sum2 >= BASE)
|
|
sum2 -= BASE;
|
|
return adler | (sum2 << 16);
|
|
}
|
|
|
|
/* initial Adler-32 value (deferred check for len == 1 speed) */
|
|
if (buf == Z_NULL)
|
|
return 1L;
|
|
|
|
/* in case short lengths are provided, keep it somewhat fast */
|
|
if (len < 16) {
|
|
while (len--) {
|
|
adler += *buf++;
|
|
sum2 += adler;
|
|
}
|
|
if (adler >= BASE)
|
|
adler -= BASE;
|
|
MOD28(sum2); /* only added so many BASE's */
|
|
return adler | (sum2 << 16);
|
|
}
|
|
|
|
/* do length NMAX blocks -- requires just one modulo operation */
|
|
while (len >= NMAX) {
|
|
len -= NMAX;
|
|
n = NMAX / 16; /* NMAX is divisible by 16 */
|
|
do {
|
|
DO16(buf); /* 16 sums unrolled */
|
|
buf += 16;
|
|
} while (--n);
|
|
MOD(adler);
|
|
MOD(sum2);
|
|
}
|
|
|
|
/* do remaining bytes (less than NMAX, still just one modulo) */
|
|
if (len) { /* avoid modulos if none remaining */
|
|
while (len >= 16) {
|
|
len -= 16;
|
|
DO16(buf);
|
|
buf += 16;
|
|
}
|
|
while (len--) {
|
|
adler += *buf++;
|
|
sum2 += adler;
|
|
}
|
|
MOD(adler);
|
|
MOD(sum2);
|
|
}
|
|
|
|
/* return recombined sums */
|
|
return adler | (sum2 << 16);
|
|
}
|
|
|
|
/* ========================================================================= */
|
|
uLong ZEXPORT adler32(adler, buf, len)
|
|
uLong adler;
|
|
const Bytef *buf;
|
|
uInt len;
|
|
{
|
|
return adler32_z(adler, buf, len);
|
|
}
|
|
|
|
/* ========================================================================= */
|
|
local uLong adler32_combine_(adler1, adler2, len2)
|
|
uLong adler1;
|
|
uLong adler2;
|
|
z_off64_t len2;
|
|
{
|
|
unsigned long sum1;
|
|
unsigned long sum2;
|
|
unsigned rem;
|
|
|
|
/* for negative len, return invalid adler32 as a clue for debugging */
|
|
if (len2 < 0)
|
|
return 0xffffffffUL;
|
|
|
|
/* the derivation of this formula is left as an exercise for the reader */
|
|
MOD63(len2); /* assumes len2 >= 0 */
|
|
rem = (unsigned)len2;
|
|
sum1 = adler1 & 0xffff;
|
|
sum2 = rem * sum1;
|
|
MOD(sum2);
|
|
sum1 += (adler2 & 0xffff) + BASE - 1;
|
|
sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
|
|
if (sum1 >= BASE) sum1 -= BASE;
|
|
if (sum1 >= BASE) sum1 -= BASE;
|
|
if (sum2 >= ((unsigned long)BASE << 1)) sum2 -= ((unsigned long)BASE << 1);
|
|
if (sum2 >= BASE) sum2 -= BASE;
|
|
return sum1 | (sum2 << 16);
|
|
}
|
|
|
|
/* ========================================================================= */
|
|
uLong ZEXPORT adler32_combine(adler1, adler2, len2)
|
|
uLong adler1;
|
|
uLong adler2;
|
|
z_off_t len2;
|
|
{
|
|
return adler32_combine_(adler1, adler2, len2);
|
|
}
|
|
|
|
uLong ZEXPORT adler32_combine64(adler1, adler2, len2)
|
|
uLong adler1;
|
|
uLong adler2;
|
|
z_off64_t len2;
|
|
{
|
|
return adler32_combine_(adler1, adler2, len2);
|
|
}
|