1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Margo Seltzer.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #define _DEFAULT_SOURCE
34 #if defined(LIBC_SCCS) && !defined(lint)
35 static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
36 #endif /* LIBC_SCCS and not lint */
37 #include <sys/cdefs.h>
38 #include <sys/types.h>
39
40 #include "db_local.h"
41 #include "hash.h"
42 #include "page.h"
43 #include "extern.h"
44
45 #if 0
46 static __uint32_t hash1(const void *, size_t);
47 static __uint32_t hash2(const void *, size_t);
48 static __uint32_t hash3(const void *, size_t);
49 #endif
50
51 /*
52 * HASH FUNCTIONS
53 *
54 * Assume that we've already split the bucket to which this key hashes,
55 * calculate that bucket, and check that in fact we did already split it.
56 *
57 * This came from ejb's hsearch.
58 */
59
60 #define PRIME1 37
61 #define PRIME2 1048583
62
63 #if 0
64 static __uint32_t
65 hash1(keyarg, len)
66 const void *keyarg;
67 size_t len;
68 {
69 const u_char *key;
70 __uint32_t h;
71
72 /* Convert string to integer */
73 for (key = keyarg, h = 0; len--;)
74 h = h * PRIME1 ^ (*key++ - ' ');
75 h %= PRIME2;
76 return (h);
77 }
78 #endif
79
80 /*
81 * Phong's linear congruential hash
82 */
83 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
84
85 #if 0
86 static __uint32_t
87 hash2(keyarg, len)
88 const void *keyarg;
89 size_t len;
90 {
91 const u_char *e, *key;
92 __uint32_t h;
93 u_char c;
94
95 key = keyarg;
96 e = key + len;
97 for (h = 0; key != e;) {
98 c = *key++;
99 if (!c && key > e)
100 break;
101 dcharhash(h, c);
102 }
103 return (h);
104 }
105 #endif
106
107 /*
108 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
109 * units. On the first time through the loop we get the "leftover bytes"
110 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
111 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
112 * this routine is heavily used enough, it's worth the ugly coding.
113 *
114 * OZ's original sdbm hash
115 */
116 #if 0
117 static __uint32_t
118 hash3(keyarg, len)
119 const void *keyarg;
120 size_t len;
121 {
122 const u_char *key;
123 size_t loop;
124 __uint32_t h;
125
126 #define HASHC h = *key++ + 65599 * h
127
128 h = 0;
129 key = keyarg;
130 if (len > 0) {
131 loop = (len + 8 - 1) >> 3;
132
133 switch (len & (8 - 1)) {
134 case 0:
135 do {
136 HASHC;
137 __PICOLIBC_FALLTHROUGH;
138 case 7:
139 HASHC;
140 __PICOLIBC_FALLTHROUGH;
141 case 6:
142 HASHC;
143 __PICOLIBC_FALLTHROUGH;
144 case 5:
145 HASHC;
146 __PICOLIBC_FALLTHROUGH;
147 case 4:
148 HASHC;
149 __PICOLIBC_FALLTHROUGH;
150 case 3:
151 HASHC;
152 __PICOLIBC_FALLTHROUGH;
153 case 2:
154 HASHC;
155 __PICOLIBC_FALLTHROUGH;
156 case 1:
157 HASHC;
158 } while (--loop);
159 }
160 }
161 return (h);
162 }
163 #endif
164
165 /* Hash function from Chris Torek. */
166 __uint32_t
__default_hash(const void * keyarg,size_t len)167 __default_hash(const void *keyarg, size_t len)
168 {
169 const u_char *key;
170 __uint32_t h;
171
172 #define HASH4a h = (h << 5) - h + *key++;
173 #define HASH4b h = (h << 5) + h + *key++;
174 #define HASH4 HASH4b
175
176 h = 0;
177 key = keyarg;
178 while (len--) {
179 HASH4;
180 }
181 return (h);
182 }
183
