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comparison nss/lib/dbm/src/h_func.c @ 3:150b72113545

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Add DBM and legacydb support
author Andre Heinecke <andre.heinecke@intevation.de>
date Tue, 05 Aug 2014 18:32:02 +0200
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2:a945361df361 3:150b72113545
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. ***REMOVED*** - see
17 * ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
37 #endif /* LIBC_SCCS and not lint */
38
39 #ifndef macintosh
40 #include <sys/types.h>
41 #endif
42 #include "mcom_db.h"
43 #include "hash.h"
44 #include "page.h"
45 /* #include "extern.h" */
46
47 #if 0
48 static uint32 hash1 __P((const void *, size_t));
49 static uint32 hash2 __P((const void *, size_t));
50 static uint32 hash3 __P((const void *, size_t));
51 #endif
52 static uint32 hash4 __P((const void *, size_t));
53
54 /* Global default hash function */
55 uint32 (*__default_hash) __P((const void *, size_t)) = hash4;
56
57 /*
58 * HASH FUNCTIONS
59 *
60 * Assume that we've already split the bucket to which this key hashes,
61 * calculate that bucket, and check that in fact we did already split it.
62 *
63 * This came from ejb's hsearch.
64 */
65
66 #define PRIME1 37
67 #define PRIME2 1048583
68
69 #if 0
70 static uint32
71 hash1(const void *keyarg, register size_t len)
72 {
73 register const uint8 *key;
74 register uint32 h;
75
76 /* Convert string to integer */
77 for (key = (const uint8 *)keyarg, h = 0; len--;)
78 h = h * PRIME1 ^ (*key++ - ' ');
79 h %= PRIME2;
80 return (h);
81 }
82
83 /*
84 * Phong's linear congruential hash
85 */
86 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
87
88 static uint32
89 hash2(const void *keyarg, size_t len)
90 {
91 register const uint8 *e, *key;
92 register uint32 h;
93 register uint8 c;
94
95 key = (const uint8 *)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
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 static uint32
116 hash3(const void *keyarg, register size_t len)
117 {
118 register const uint8 *key;
119 register size_t loop;
120 register uint32 h;
121
122 #define HASHC h = *key++ + 65599 * h
123
124 h = 0;
125 key = (const uint8 *)keyarg;
126 if (len > 0) {
127 loop = (len + 8 - 1) >> 3;
128
129 switch (len & (8 - 1)) {
130 case 0:
131 do {
132 HASHC;
133 /* FALLTHROUGH */
134 case 7:
135 HASHC;
136 /* FALLTHROUGH */
137 case 6:
138 HASHC;
139 /* FALLTHROUGH */
140 case 5:
141 HASHC;
142 /* FALLTHROUGH */
143 case 4:
144 HASHC;
145 /* FALLTHROUGH */
146 case 3:
147 HASHC;
148 /* FALLTHROUGH */
149 case 2:
150 HASHC;
151 /* FALLTHROUGH */
152 case 1:
153 HASHC;
154 } while (--loop);
155 }
156 }
157 return (h);
158 }
159 #endif /* 0 */
160
161 /* Hash function from Chris Torek. */
162 static uint32
163 hash4(const void *keyarg, register size_t len)
164 {
165 register const uint8 *key;
166 register size_t loop;
167 register uint32 h;
168
169 #define HASH4a h = (h << 5) - h + *key++;
170 #define HASH4b h = (h << 5) + h + *key++;
171 #define HASH4 HASH4b
172
173 h = 0;
174 key = (const uint8 *)keyarg;
175 if (len > 0) {
176 loop = (len + 8 - 1) >> 3;
177
178 switch (len & (8 - 1)) {
179 case 0:
180 do {
181 HASH4;
182 /* FALLTHROUGH */
183 case 7:
184 HASH4;
185 /* FALLTHROUGH */
186 case 6:
187 HASH4;
188 /* FALLTHROUGH */
189 case 5:
190 HASH4;
191 /* FALLTHROUGH */
192 case 4:
193 HASH4;
194 /* FALLTHROUGH */
195 case 3:
196 HASH4;
197 /* FALLTHROUGH */
198 case 2:
199 HASH4;
200 /* FALLTHROUGH */
201 case 1:
202 HASH4;
203 } while (--loop);
204 }
205 }
206 return (h);
207 }
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