1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
/* 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
*/
#ifndef _XDELTA3_HASH_H_
#define _XDELTA3_HASH_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 */
/* This is a good hash multiplier for 32-bit LCGs: see "linear
* congruential generators of different sizes and good lattice
* structure" */
static const uint32_t hash_multiplier = 1597334677U;
/***********************************************************************
Permute stuff
***********************************************************************/
#if HASH_PERMUTE == 0
#define PERMUTE(x) (x)
#else
#define PERMUTE(x) (__single_hash[(uint32_t)x])
extern const uint16_t __single_hash[256];
#endif
/* Update the checksum state. */
#if ADLER_LARGE_CKSUM
inline uint32_t
xd3_large_cksum_update (uint32_t cksum,
const uint8_t *base,
usize_t look) {
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;
return (high << 16) | low;
}
#else
/* TODO: revisit this topic */
#endif
#if UNALIGNED_OK
#define UNALIGNED_READ32(dest,src) (*(dest)) = (*(uint32_t*)(src))
#else
#define UNALIGNED_READ32(dest,src) memcpy((dest), (src), 4);
#endif
/* 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) * hash_multiplier;
}
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) * hash_multiplier;
}
/***********************************************************************
Ctable stuff
***********************************************************************/
static inline usize_t
xd3_checksum_hash (const xd3_hash_cfg *cfg, const usize_t cksum)
{
return (cksum >> cfg->shift) ^ (cksum & cfg->mask);
}
/***********************************************************************
Cksum function
***********************************************************************/
#if ADLER_LARGE_CKSUM
static inline uint32_t
xd3_lcksum (const uint8_t *seg, const usize_t ln)
{
usize_t 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);
}
#else
static inline uint32_t
xd3_lcksum (const uint8_t *seg, const usize_t ln)
{
usize_t i, j;
uint32_t h = 0;
for (i = 0, j = ln - 1; i < ln; ++i, --j) {
h += PERMUTE(seg[i]) * hash_multiplier_powers[j];
}
return h;
}
#endif
#if XD3_ENCODER
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))
{
/* TODO: this is compaction=1 in checksum_test.cc and maybe should
* not be fixed at -1. */
bits = i - 1;
break;
}
}
return bits;
}
static void
xd3_size_hashtable (xd3_stream *stream,
usize_t slots,
xd3_hash_cfg *cfg)
{
int bits = xd3_size_log2 (slots);
/* TODO: there's a 32-bit assumption here */
cfg->size = (1 << bits);
cfg->mask = (cfg->size - 1);
cfg->shift = 32 - bits;
}
#endif
#endif
|
