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/* xdelta 3 - delta compression tools and library
* Copyright (C) 2001, 2003, 2004, 2005, 2006, 2007, 2011, 2012, 2014.
* Joshua P. MacDonald
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef _XDELTA3_HASH_H_
#define _XDELTA3_HASH_H_
#include "xdelta3-internal.h"
#if XD3_DEBUG
#define SMALL_HASH_DEBUG1(s,inp) \
uint32_t debug_state; \
uint32_t debug_hval = xd3_checksum_hash (& (s)->small_hash, \
xd3_scksum (&debug_state, (inp), (s)->smatcher.small_look))
#define SMALL_HASH_DEBUG2(s,inp) \
XD3_ASSERT (debug_hval == xd3_checksum_hash (& (s)->small_hash, \
xd3_scksum (&debug_state, (inp), (s)->smatcher.small_look)))
#else
#define SMALL_HASH_DEBUG1(s,inp)
#define SMALL_HASH_DEBUG2(s,inp)
#endif /* XD3_DEBUG */
#if UNALIGNED_OK
#define UNALIGNED_READ32(dest,src) (*(dest)) = (*(uint32_t*)(src))
#else
#define UNALIGNED_READ32(dest,src) memcpy((dest), (src), 4);
#endif
/* These are good hash multipliers for 32-bit and 64-bit LCGs: see
* "linear congruential generators of different sizes and good lattice
* structure" */
#define xd3_hash_multiplier32 1597334677U
#define xd3_hash_multiplier64 1181783497276652981ULL
/* TODO: small cksum is hard-coded for 4 bytes (i.e., "look" is unused) */
static inline uint32_t
xd3_scksum (uint32_t *state,
const uint8_t *base,
const usize_t look)
{
UNALIGNED_READ32(state, base);
return (*state) * xd3_hash_multiplier32;
}
static inline uint32_t
xd3_small_cksum_update (uint32_t *state,
const uint8_t *base,
usize_t look)
{
UNALIGNED_READ32(state, base+1);
return (*state) * xd3_hash_multiplier32;
}
#if XD3_ENCODER
inline usize_t
xd3_checksum_hash (const xd3_hash_cfg *cfg, const usize_t cksum)
{
return (cksum >> cfg->shift) ^ (cksum & cfg->mask);
}
#if SIZEOF_USIZE_T == 4
inline uint32_t
xd3_large32_cksum (xd3_hash_cfg *cfg, const uint8_t *base, const usize_t look)
{
uint32_t h = 0;
for (usize_t i = 0; i < look; i++) {
h += base[i] * cfg->powers[i];
}
return h;
}
inline uint32_t
xd3_large32_cksum_update (xd3_hash_cfg *cfg, const uint32_t cksum,
const uint8_t *base, const usize_t look)
{
return xd3_hash_multiplier32 * cksum - cfg->multiplier * base[0] + base[look];
}
#endif
#if SIZEOF_USIZE_T == 8
inline uint64_t
xd3_large64_cksum (xd3_hash_cfg *cfg, const uint8_t *base, const usize_t look)
{
uint64_t h = 0;
for (usize_t i = 0; i < look; i++) {
h += base[i] * cfg->powers[i];
}
return h;
}
inline uint64_t
xd3_large64_cksum_update (xd3_hash_cfg *cfg, const uint64_t cksum,
const uint8_t *base, const usize_t look)
{
return xd3_hash_multiplier64 * cksum - cfg->multiplier * base[0] + base[look];
}
#endif
static usize_t
xd3_size_hashtable_bits (usize_t slots)
{
usize_t bits = (SIZEOF_USIZE_T * 8) - 1;
usize_t i;
for (i = 3; i <= bits; i += 1)
{
if (slots < (1U << i))
{
/* Note: this is the compaction=1 setting measured in
* checksum_test */
bits = i - 1;
break;
}
}
return bits;
}
int
xd3_size_hashtable (xd3_stream *stream,
usize_t slots,
usize_t look,
xd3_hash_cfg *cfg)
{
usize_t bits = xd3_size_hashtable_bits (slots);
cfg->size = (1U << bits);
cfg->mask = (cfg->size - 1);
cfg->shift = (SIZEOF_USIZE_T * 8) - bits;
cfg->look = look;
if ((cfg->powers =
(usize_t*) xd3_alloc0 (stream, look, sizeof (usize_t))) == NULL)
{
return ENOMEM;
}
cfg->powers[look-1] = 1;
for (int i = look-2; i >= 0; i--)
{
cfg->powers[i] = cfg->powers[i+1] * xd3_hash_multiplier;
}
cfg->multiplier = cfg->powers[0] * xd3_hash_multiplier;
return 0;
}
#endif /* XD3_ENCODER */
#endif /* _XDELTA3_HASH_H_ */
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