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/* xdelta 3 - delta compression tools and library
* Copyright (C) 2001, 2003, 2004, 2005, 2006, 2007. 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
*/
/* To know more about Xdelta, start by reading xdelta3.c. If you are
* ready to use the API, continue reading here. There are two
* interfaces -- xd3_encode_input and xd3_decode_input -- plus a dozen
* or so related calls. This interface is styled after Zlib. */
#ifndef _XDELTA3_HASH_H_
#define _XDELTA3_HASH_H_
#if XD3_DEBUG
#define SMALL_HASH_DEBUG1(s,inp) \
usize_t debug_hval = xd3_checksum_hash (& (s)->small_hash, \
xd3_scksum ((inp), (s)->smatcher.small_look))
#define SMALL_HASH_DEBUG2(s,inp) \
XD3_ASSERT (debug_hval == xd3_checksum_hash (& (s)->small_hash, \
xd3_scksum ((inp), (s)->smatcher.small_look)))
#else
#define SMALL_HASH_DEBUG1(s,inp)
#define SMALL_HASH_DEBUG2(s,inp)
#endif /* XD3_DEBUG */
/* Update the run-length state */
#define NEXTRUN(c) do { if ((c) == run_c) { run_l += 1; } \
else { run_c = (c); run_l = 1; } } while (0)
/* Update the checksum state. */
#define OLD_LARGE_CKSUM 1
#if OLD_LARGE_CKSUM
#define LARGE_CKSUM_UPDATE(cksum,base,look) \
do { \
uint32_t old_c = PERMUTE((base)[0]); \
uint32_t new_c = PERMUTE((base)[(look)]); \
uint32_t low = (((cksum) & 0xffff) - old_c + new_c) & 0xffff; \
uint32_t high = (((cksum) >> 16) - (old_c * (look)) + low) & 0xffff; \
(cksum) = (high << 16) | low; \
} while (0)
#else
#define LARGE_CKSUM_UPDATE(cksum,base,look) \
do { \
// linear congruential generators of different
// sizes and good lattice structure
} while (1)
#endif
/* Multiply and add hash function */
#if ARITH_SMALL_CKSUM
#define SMALL_CKSUM_UPDATE(cksum,base,look) (cksum) = ((*(unsigned long*)(base+1)) * 71143)
#else
#define SMALL_CKSUM_UPDATE LARGE_CKSUM_UPDATE
#endif
/***********************************************************************
Permute stuff
***********************************************************************/
#if HASH_PERMUTE == 0
#define PERMUTE(x) (x)
#else
#define PERMUTE(x) (__single_hash[(uint)x])
static const uint16_t __single_hash[256] =
{
/* Random numbers generated using SLIB's pseudo-random number generator. This hashes
* the input alphabet. */
0xbcd1, 0xbb65, 0x42c2, 0xdffe, 0x9666, 0x431b, 0x8504, 0xeb46,
0x6379, 0xd460, 0xcf14, 0x53cf, 0xdb51, 0xdb08, 0x12c8, 0xf602,
0xe766, 0x2394, 0x250d, 0xdcbb, 0xa678, 0x02af, 0xa5c6, 0x7ea6,
0xb645, 0xcb4d, 0xc44b, 0xe5dc, 0x9fe6, 0x5b5c, 0x35f5, 0x701a,
0x220f, 0x6c38, 0x1a56, 0x4ca3, 0xffc6, 0xb152, 0x8d61, 0x7a58,
0x9025, 0x8b3d, 0xbf0f, 0x95a3, 0xe5f4, 0xc127, 0x3bed, 0x320b,
0xb7f3, 0x6054, 0x333c, 0xd383, 0x8154, 0x5242, 0x4e0d, 0x0a94,
0x7028, 0x8689, 0x3a22, 0x0980, 0x1847, 0xb0f1, 0x9b5c, 0x4176,
0xb858, 0xd542, 0x1f6c, 0x2497, 0x6a5a, 0x9fa9, 0x8c5a, 0x7743,
0xa8a9, 0x9a02, 0x4918, 0x438c, 0xc388, 0x9e2b, 0x4cad, 0x01b6,
0xab19, 0xf777, 0x365f, 0x1eb2, 0x091e, 0x7bf8, 0x7a8e, 0x5227,
0xeab1, 0x2074, 0x4523, 0xe781, 0x01a3, 0x163d, 0x3b2e, 0x287d,
0x5e7f, 0xa063, 0xb134, 0x8fae, 0x5e8e, 0xb7b7, 0x4548, 0x1f5a,
0xfa56, 0x7a24, 0x900f, 0x42dc, 0xcc69, 0x02a0, 0x0b22, 0xdb31,
0x71fe, 0x0c7d, 0x1732, 0x1159, 0xcb09, 0xe1d2, 0x1351, 0x52e9,
0xf536, 0x5a4f, 0xc316, 0x6bf9, 0x8994, 0xb774, 0x5f3e, 0xf6d6,
0x3a61, 0xf82c, 0xcc22, 0x9d06, 0x299c, 0x09e5, 0x1eec, 0x514f,
0x8d53, 0xa650, 0x5c6e, 0xc577, 0x7958, 0x71ac, 0x8916, 0x9b4f,
0x2c09, 0x5211, 0xf6d8, 0xcaaa, 0xf7ef, 0x287f, 0x7a94, 0xab49,
0xfa2c, 0x7222, 0xe457, 0xd71a, 0x00c3, 0x1a76, 0xe98c, 0xc037,
0x8208, 0x5c2d, 0xdfda, 0xe5f5, 0x0b45, 0x15ce, 0x8a7e, 0xfcad,
0xaa2d, 0x4b5c, 0xd42e, 0xb251, 0x907e, 0x9a47, 0xc9a6, 0xd93f,
0x085e, 0x35ce, 0xa153, 0x7e7b, 0x9f0b, 0x25aa, 0x5d9f, 0xc04d,
0x8a0e, 0x2875, 0x4a1c, 0x295f, 0x1393, 0xf760, 0x9178, 0x0f5b,
0xfa7d, 0x83b4, 0x2082, 0x721d, 0x6462, 0x0368, 0x67e2, 0x8624,
0x194d, 0x22f6, 0x78fb, 0x6791, 0xb238, 0xb332, 0x7276, 0xf272,
0x47ec, 0x4504, 0xa961, 0x9fc8, 0x3fdc, 0xb413, 0x007a, 0x0806,
0x7458, 0x95c6, 0xccaa, 0x18d6, 0xe2ae, 0x1b06, 0xf3f6, 0x5050,
0xc8e8, 0xf4ac, 0xc04c, 0xf41c, 0x992f, 0xae44, 0x5f1b, 0x1113,
0x1738, 0xd9a8, 0x19ea, 0x2d33, 0x9698, 0x2fe9, 0x323f, 0xcde2,
0x6d71, 0xe37d, 0xb697, 0x2c4f, 0x4373, 0x9102, 0x075d, 0x8e25,
0x1672, 0xec28, 0x6acb, 0x86cc, 0x186e, 0x9414, 0xd674, 0xd1a5
};
#endif
/***********************************************************************
Ctable stuff
***********************************************************************/
#if HASH_PRIME
static const usize_t __primes[] =
{
11, 19, 37, 73, 109,
163, 251, 367, 557, 823,
1237, 1861, 2777, 4177, 6247,
9371, 14057, 21089, 31627, 47431,
71143, 106721, 160073, 240101, 360163,
540217, 810343, 1215497, 1823231, 2734867,
4102283, 6153409, 9230113, 13845163, 20767711,
31151543, 46727321, 70090921, 105136301, 157704401,
236556601, 354834919, 532252367, 798378509, 1197567719,
1796351503
};
static const usize_t __nprimes = SIZEOF_ARRAY (__primes);
#endif
static inline usize_t
xd3_checksum_hash (const xd3_hash_cfg *cfg, const usize_t cksum)
{
#if HASH_PRIME
/* If the table is prime compute the modulus. */
return (cksum % cfg->size);
#else
/* If the table is power-of-two compute the mask.*/
return (cksum ^ (cksum >> cfg->shift)) & cfg->mask;
#endif
}
/***********************************************************************
Cksum function
***********************************************************************/
static inline uint32_t
xd3_lcksum (const uint8_t *seg, const int ln)
{
int i = 0;
uint32_t low = 0;
uint32_t high = 0;
for (; i < ln; i += 1)
{
low += PERMUTE(*seg++);
high += low;
}
return ((high & 0xffff) << 16) | (low & 0xffff);
}
#if ARITH_SMALL_CKSUM
static inline usize_t
xd3_scksum (const uint8_t *seg, const int ln)
{
usize_t c;
/* The -1 is because UPDATE operates on seg[1..ln] */
SMALL_CKSUM_UPDATE (c,(seg-1),ln);
return c;
}
#else
#define xd3_scksum(seg,ln) xd3_lcksum(seg,ln)
#endif
#if XD3_ENCODER
#if !HASH_PRIME
static usize_t
xd3_size_log2 (usize_t slots)
{
int bits = 28; /* This should not be an unreasonable limit. */
int i;
for (i = 3; i <= bits; i += 1)
{
if (slots < (1U << i))
{
bits = i-1;
break;
}
}
return bits;
}
#endif
#endif
static void
xd3_size_hashtable (xd3_stream *stream,
usize_t slots,
xd3_hash_cfg *cfg)
{
/* initialize ctable: the number of hash buckets is computed from the table of primes or
* the nearest power-of-two, in both cases rounding down in favor of using less
* memory. */
#if HASH_PRIME
usize_t i;
cfg->size = __primes[__nprimes-1];
for (i = 1; i < __nprimes; i += 1)
{
if (slots < __primes[i])
{
cfg->size = __primes[i-1];
break;
}
}
#else
int bits = xd3_size_log2 (slots);
cfg->size = (1 << bits);
cfg->mask = (cfg->size - 1);
cfg->shift = min (32 - bits, 16);
#endif
}
#endif
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