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/types.h>
38
39 #include "db_local.h"
40 #include "hash.h"
41 #include "page.h"
42 #include "extern.h"
43
44 #if 0
45 static __uint32_t hash1(const void *, size_t);
46 static __uint32_t hash2(const void *, size_t);
47 static __uint32_t hash3(const void *, size_t);
48 #endif
49
50 /*
51 * HASH FUNCTIONS
52 *
53 * Assume that we've already split the bucket to which this key hashes,
54 * calculate that bucket, and check that in fact we did already split it.
55 *
56 * This came from ejb's hsearch.
57 */
58
59 #define PRIME1 37
60 #define PRIME2 1048583
61
62 #if 0
63 static __uint32_t
64 hash1(keyarg, len)
65 const void *keyarg;
66 size_t len;
67 {
68 const u_char *key;
69 __uint32_t h;
70
71 /* Convert string to integer */
72 for (key = keyarg, h = 0; len--;)
73 h = h * PRIME1 ^ (*key++ - ' ');
74 h %= PRIME2;
75 return (h);
76 }
77 #endif
78
79 /*
80 * Phong's linear congruential hash
81 */
82 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
83
84 #if 0
85 static __uint32_t
86 hash2(keyarg, len)
87 const void *keyarg;
88 size_t len;
89 {
90 const u_char *e, *key;
91 __uint32_t h;
92 u_char c;
93
94 key = keyarg;
95 e = key + len;
96 for (h = 0; key != e;) {
97 c = *key++;
98 if (!c && key > e)
99 break;
100 dcharhash(h, c);
101 }
102 return (h);
103 }
104 #endif
105
106 /*
107 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
108 * units. On the first time through the loop we get the "leftover bytes"
109 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
110 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
111 * this routine is heavily used enough, it's worth the ugly coding.
112 *
113 * OZ's original sdbm hash
114 */
115 #if 0
116 static __uint32_t
117 hash3(keyarg, len)
118 const void *keyarg;
119 size_t len;
120 {
121 const u_char *key;
122 size_t loop;
123 __uint32_t h;
124
125 #define HASHC h = *key++ + 65599 * h
126
127 h = 0;
128 key = keyarg;
129 if (len > 0) {
130 loop = (len + 8 - 1) >> 3;
131
132 switch (len & (8 - 1)) {
133 case 0:
134 do {
135 HASHC;
136 __PICOLIBC_FALLTHROUGH;
137 case 7:
138 HASHC;
139 __PICOLIBC_FALLTHROUGH;
140 case 6:
141 HASHC;
142 __PICOLIBC_FALLTHROUGH;
143 case 5:
144 HASHC;
145 __PICOLIBC_FALLTHROUGH;
146 case 4:
147 HASHC;
148 __PICOLIBC_FALLTHROUGH;
149 case 3:
150 HASHC;
151 __PICOLIBC_FALLTHROUGH;
152 case 2:
153 HASHC;
154 __PICOLIBC_FALLTHROUGH;
155 case 1:
156 HASHC;
157 } while (--loop);
158 }
159 }
160 return (h);
161 }
162 #endif
163
164 /* Hash function from Chris Torek. */
165 __uint32_t
__default_hash(const void * keyarg,size_t len)166 __default_hash(const void *keyarg, size_t len)
167 {
168 const u_char *key;
169 __uint32_t h;
170
171 #define HASH4a h = (h << 5) - h + *key++;
172 #define HASH4b h = (h << 5) + h + *key++;
173 #define HASH4 HASH4b
174
175 h = 0;
176 key = keyarg;
177 while (len--) {
178 HASH4;
179 }
180 return (h);
181 }
182
