FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_hash.c
1 /*-
2 * Copyright (c) 1982, 1986, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
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 * @(#)kern_subr.c 8.3 (Berkeley) 1/21/94
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD: releng/9.0/sys/kern/subr_hash.c 204176 2010-02-21 19:53:33Z ed $");
39
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/malloc.h>
43
44 /*
45 * General routine to allocate a hash table with control of memory flags.
46 */
47 void *
48 hashinit_flags(int elements, struct malloc_type *type, u_long *hashmask,
49 int flags)
50 {
51 long hashsize;
52 LIST_HEAD(generic, generic) *hashtbl;
53 int i;
54
55 if (elements <= 0)
56 panic("hashinit: bad elements");
57
58 /* Exactly one of HASH_WAITOK and HASH_NOWAIT must be set. */
59 KASSERT((flags & HASH_WAITOK) ^ (flags & HASH_NOWAIT),
60 ("Bad flags (0x%x) passed to hashinit_flags", flags));
61
62 for (hashsize = 1; hashsize <= elements; hashsize <<= 1)
63 continue;
64 hashsize >>= 1;
65
66 if (flags & HASH_NOWAIT)
67 hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl),
68 type, M_NOWAIT);
69 else
70 hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl),
71 type, M_WAITOK);
72
73 if (hashtbl != NULL) {
74 for (i = 0; i < hashsize; i++)
75 LIST_INIT(&hashtbl[i]);
76 *hashmask = hashsize - 1;
77 }
78 return (hashtbl);
79 }
80
81 /*
82 * Allocate and initialize a hash table with default flag: may sleep.
83 */
84 void *
85 hashinit(int elements, struct malloc_type *type, u_long *hashmask)
86 {
87
88 return (hashinit_flags(elements, type, hashmask, HASH_WAITOK));
89 }
90
91 void
92 hashdestroy(void *vhashtbl, struct malloc_type *type, u_long hashmask)
93 {
94 LIST_HEAD(generic, generic) *hashtbl, *hp;
95
96 hashtbl = vhashtbl;
97 for (hp = hashtbl; hp <= &hashtbl[hashmask]; hp++)
98 if (!LIST_EMPTY(hp))
99 panic("hashdestroy: hash not empty");
100 free(hashtbl, type);
101 }
102
103 static const int primes[] = { 1, 13, 31, 61, 127, 251, 509, 761, 1021, 1531,
104 2039, 2557, 3067, 3583, 4093, 4603, 5119, 5623, 6143,
105 6653, 7159, 7673, 8191, 12281, 16381, 24571, 32749 };
106 #define NPRIMES (sizeof(primes) / sizeof(primes[0]))
107
108 /*
109 * General routine to allocate a prime number sized hash table.
110 */
111 void *
112 phashinit(int elements, struct malloc_type *type, u_long *nentries)
113 {
114 long hashsize;
115 LIST_HEAD(generic, generic) *hashtbl;
116 int i;
117
118 if (elements <= 0)
119 panic("phashinit: bad elements");
120 for (i = 1, hashsize = primes[1]; hashsize <= elements;) {
121 i++;
122 if (i == NPRIMES)
123 break;
124 hashsize = primes[i];
125 }
126 hashsize = primes[i - 1];
127 hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), type, M_WAITOK);
128 for (i = 0; i < hashsize; i++)
129 LIST_INIT(&hashtbl[i]);
130 *nentries = hashsize;
131 return (hashtbl);
132 }
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