1 /* $OpenBSD: hash.h,v 1.4 2004/05/25 18:37:23 jmc Exp $ */
2
3 /*
4 * Copyright (c) 2001 Tobias Weingartner
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #ifndef _SYS_HASH_H_
29 #define _SYS_HASH_H_
30 #include <sys/types.h>
31
32 /*
33 * Note: SMALL_KERNEL might be used to shrink these, right now I
34 * do not see the point, as my kernel did not grow appreciably when
35 * I switched to these from other inline code. This may have to be
36 * revisited when/if these functions become more prevalent in the
37 * kernel.
38 */
39
40 /* Convenience */
41 #ifndef HASHINIT
42 #define HASHINIT 5381
43 #define HASHSTEP(x,c) (((x << 5) + x) + (c))
44 #endif
45
46 /*
47 * Return a 32-bit hash of the given buffer. The init
48 * value should be 0, or the previous hash value to extend
49 * the previous hash.
50 */
51 static __inline uint32_t
52 hash32_buf(const void *buf, size_t len, uint32_t hash)
53 {
54 const unsigned char *p = buf;
55
56 while (len--)
57 hash = HASHSTEP(hash, *p++);
58
59 return hash;
60 }
61
62 /*
63 * Return a 32-bit hash of the given string.
64 */
65 static __inline uint32_t
66 hash32_str(const void *buf, uint32_t hash)
67 {
68 const unsigned char *p = buf;
69
70 while (*p)
71 hash = HASHSTEP(hash, *p++);
72
73 return hash;
74 }
75
76 /*
77 * Return a 32-bit hash of the given string, limited by N.
78 */
79 static __inline uint32_t
80 hash32_strn(const void *buf, size_t len, uint32_t hash)
81 {
82 const unsigned char *p = buf;
83
84 while (*p && len--)
85 hash = HASHSTEP(hash, *p++);
86
87 return hash;
88 }
89
90 /*
91 * Return a 32-bit hash of the given string terminated by C,
92 * (as well as 0). This is mainly here as a helper for the
93 * namei() hashing of path name parts.
94 */
95 static __inline uint32_t
96 hash32_stre(const void *buf, int end, char **ep, uint32_t hash)
97 {
98 const unsigned char *p = buf;
99
100 while (*p && (*p != end))
101 hash = HASHSTEP(hash, *p++);
102
103 if (ep)
104 *ep = (char *)p;
105
106 return hash;
107 }
108
109 /*
110 * Return a 32-bit hash of the given string, limited by N,
111 * and terminated by C (as well as 0). This is mainly here
112 * as a helper for the namei() hashing of path name parts.
113 */
114 static __inline uint32_t
115 hash32_strne(const void *buf, size_t len, int end, char **ep, uint32_t hash)
116 {
117 const unsigned char *p = buf;
118
119 while (*p && (*p != end) && len--)
120 hash = HASHSTEP(hash, *p++);
121
122 if (ep)
123 *ep = (char *)p;
124
125 return hash;
126 }
127 #endif /* !_SYS_HASH_H_ */