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
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
/* $OpenBSD: hash_func.c,v 1.10 2005/08/05 13:03:00 espie Exp $ */
/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Margo Seltzer.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/types.h>
#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"
#ifdef notdef
static u_int32_t hash1(const void *, size_t);
static u_int32_t hash2(const void *, size_t);
static u_int32_t hash3(const void *, size_t);
#endif
static u_int32_t hash4(const void *, size_t);
/* Default hash function. */
u_int32_t (*__default_hash)(const void *, size_t) = hash4;
#ifdef notdef
/*
* Assume that we've already split the bucket to which this key hashes,
* calculate that bucket, and check that in fact we did already split it.
*
* EJB's original hsearch hash.
*/
#define PRIME1 37
#define PRIME2 1048583
u_int32_t
hash1(const void *key, size_t len)
{
u_int32_t h;
u_int8_t *k;
h = 0;
k = (u_int8_t *)key;
/* Convert string to integer */
while (len--)
h = h * PRIME1 ^ (*k++ - ' ');
h %= PRIME2;
return (h);
}
/*
* Phong Vo's linear congruential hash
*/
#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
u_int32_t
hash2(const void *key, size_t len)
{
u_int32_t h;
u_int8_t *e, c, *k;
k = (u_int8_t *)key;
e = k + len;
for (h = 0; k != e;) {
c = *k++;
if (!c && k > e)
break;
dcharhash(h, c);
}
return (h);
}
/*
* This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
* units. On the first time through the loop we get the "leftover bytes"
* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
* this routine is heavily used enough, it's worth the ugly coding.
*
* Ozan Yigit's original sdbm hash.
*/
u_int32_t
hash3(const void *key, size_t len)
{
u_int32_t n, loop;
u_int8_t *k;
#define HASHC n = *k++ + 65599 * n
n = 0;
k = (u_int8_t *)key;
if (len > 0) {
loop = (len + 8 - 1) >> 3;
switch (len & (8 - 1)) {
case 0:
do { /* All fall throughs */
HASHC;
case 7:
HASHC;
case 6:
HASHC;
case 5:
HASHC;
case 4:
HASHC;
case 3:
HASHC;
case 2:
HASHC;
case 1:
HASHC;
} while (--loop);
}
}
return (n);
}
#endif /* notdef */
/* Chris Torek's hash function. */
u_int32_t
hash4(const void *key, size_t len)
{
u_int32_t h, loop;
u_int8_t *k;
#define HASH4a h = (h << 5) - h + *k++;
#define HASH4b h = (h << 5) + h + *k++;
#define HASH4 HASH4b
h = 0;
k = (u_int8_t *)key;
if (len > 0) {
loop = (len + 8 - 1) >> 3;
switch (len & (8 - 1)) {
case 0:
do { /* All fall throughs */
HASH4;
case 7:
HASH4;
case 6:
HASH4;
case 5:
HASH4;
case 4:
HASH4;
case 3:
HASH4;
case 2:
HASH4;
case 1:
HASH4;
} while (--loop);
}
}
return (h);
}
|
