ClickHouse/contrib/libzlib-ng/adler32.c

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/* adler32.c -- compute the Adler-32 checksum of a data stream
* Copyright (C) 1995-2011 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*/
/* @(#) $Id$ */
#include "zutil.h"
static uint32_t adler32_combine_(uint32_t adler1, uint32_t 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 { \
uint32_t tmp = a >> 16; \
a &= 0xffff; \
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
/* ========================================================================= */
uint32_t ZEXPORT adler32(uint32_t adler, const unsigned char *buf, uint32_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 (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;
#ifndef UNROLL_LESS
n = NMAX / 16; /* NMAX is divisible by 16 */
#else
n = NMAX / 8; /* NMAX is divisible by 8 */
#endif
do {
#ifndef UNROLL_LESS
DO16(buf); /* 16 sums unrolled */
buf += 16;
#else
DO8(buf, 0); /* 8 sums unrolled */
buf += 8;
#endif
} while (--n);
MOD(adler);
MOD(sum2);
}
/* do remaining bytes (less than NMAX, still just one modulo) */
if (len) { /* avoid modulos if none remaining */
#ifndef UNROLL_LESS
while (len >= 16) {
len -= 16;
DO16(buf);
buf += 16;
#else
while (len >= 8) {
len -= 8;
DO8(buf, 0);
buf += 8;
#endif
}
while (len--) {
adler += *buf++;
sum2 += adler;
}
MOD(adler);
MOD(sum2);
}
/* return recombined sums */
return adler | (sum2 << 16);
}
/* ========================================================================= */
static uint32_t adler32_combine_(uint32_t adler1, uint32_t adler2, z_off64_t len2) {
uint32_t sum1;
uint32_t sum2;
unsigned rem;
/* for negative len, return invalid adler32 as a clue for debugging */
if (len2 < 0)
return 0xffffffff;
/* 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);
}
/* ========================================================================= */
uint32_t ZEXPORT adler32_combine(uint32_t adler1, uint32_t adler2, z_off_t len2) {
return adler32_combine_(adler1, adler2, len2);
}
uint32_t ZEXPORT adler32_combine64(uint32_t adler1, uint32_t adler2, z_off64_t len2) {
return adler32_combine_(adler1, adler2, len2);
}