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15637ed4 RG |
1 | /*- |
2 | * Copyright (c) 1990 The Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
5 | * This code is derived from software contributed to Berkeley by | |
6 | * Mike Olson. | |
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. All advertising materials mentioning features or use of this software | |
17 | * must display the following acknowledgement: | |
18 | * This product includes software developed by the University of | |
19 | * California, Berkeley and its contributors. | |
20 | * 4. Neither the name of the University nor the names of its contributors | |
21 | * may be used to endorse or promote products derived from this software | |
22 | * without specific prior written permission. | |
23 | * | |
24 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
25 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
26 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
27 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
28 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
29 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
30 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
31 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
32 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
33 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
34 | * SUCH DAMAGE. | |
35 | */ | |
36 | ||
37 | #if defined(LIBC_SCCS) && !defined(lint) | |
38 | static char sccsid[] = "@(#)lruhash.c 5.2 (Berkeley) 2/22/91"; | |
39 | #endif /* LIBC_SCCS and not lint */ | |
40 | ||
41 | #include <stdlib.h> | |
42 | #include "lrucache.h" | |
43 | ||
44 | #define HASH(l, pgno) (pgno % l->lru_csize) | |
45 | ||
46 | /* | |
47 | * LRUHASHGET -- Look up a block in the LRU cache by page number. | |
48 | * | |
49 | * Parameters: | |
50 | * l -- LRU cache | |
51 | * pgno -- number of the logical page to get | |
52 | * | |
53 | * Returns: | |
54 | * (CACHE_ENT *) pointer to the associated hash table entry | |
55 | * (if any), or NULL (if none). | |
56 | */ | |
57 | ||
58 | CACHE_ENT * | |
59 | lruhashget(l, pgno) | |
60 | LRUCACHE *l; | |
61 | int pgno; | |
62 | { | |
63 | int hashind; | |
64 | CACHE_ENT *ce; | |
65 | ||
66 | hashind = HASH(l, pgno); | |
67 | ||
68 | /* walk the chain */ | |
69 | for (ce = l->lru_cache[hashind]; | |
70 | ce != (CACHE_ENT *) NULL; | |
71 | ce = ce->c_chain) { | |
72 | if (ce->c_pgno == pgno) | |
73 | return (ce); | |
74 | } | |
75 | ||
76 | return ((CACHE_ENT *) NULL); | |
77 | } | |
78 | ||
79 | /* | |
80 | * LRUHASHPUT -- Add an entry for a given page to the cache hash table. | |
81 | * | |
82 | * This routine assumes that the given page does not yet have an entry | |
83 | * in the table. | |
84 | * | |
85 | * Parameters: | |
86 | * l -- LRU cache | |
87 | * pgno -- logical page number for this entry | |
88 | * lruent -- LRU list entry at which hash table entry should | |
89 | * point | |
90 | * | |
91 | * Returns: | |
92 | * (CACHE_ENT *) pointer to the new hash table entry on success, | |
93 | * or NULL on failure. | |
94 | * | |
95 | * Side Effects: | |
96 | * Allocates memory which should be freed when the hash table | |
97 | * entry is removed. | |
98 | */ | |
99 | ||
100 | CACHE_ENT * | |
101 | lruhashput(l, pgno, lruent) | |
102 | LRUCACHE *l; | |
103 | int pgno; | |
104 | LRU_ENT *lruent; | |
105 | { | |
106 | int hashind; | |
107 | CACHE_ENT *ce; | |
108 | ||
109 | if ((ce = (CACHE_ENT *) malloc((unsigned) sizeof(CACHE_ENT))) | |
110 | == (CACHE_ENT *) NULL) | |
111 | return ((CACHE_ENT *) NULL); | |
112 | ||
113 | hashind = HASH(l, pgno); | |
114 | ||
115 | ce->c_pgno = pgno; | |
116 | ce->c_lruent = lruent; | |
117 | ce->c_chain = l->lru_cache[hashind]; | |
118 | l->lru_cache[hashind] = ce; | |
119 | ||
120 | return (ce); | |
121 | } | |
122 | ||
123 | /* | |
124 | * LRUHASHDEL -- Delete the entry for a given page from the LRU cache | |
125 | * hash table. | |
126 | * | |
127 | * Parameters: | |
128 | * l -- LRU cache | |
129 | * pgno -- page number for which we should delete htable entry | |
130 | * | |
131 | * Returns: | |
132 | * Zero on success, -1 on failure. | |
133 | * | |
134 | * Side Effects: | |
135 | * Releases the memory occupied by the hash table entry. | |
136 | */ | |
137 | ||
138 | int | |
139 | lruhashdel(l, pgno) | |
140 | LRUCACHE *l; | |
141 | int pgno; | |
142 | { | |
143 | CACHE_ENT *ce; | |
144 | CACHE_ENT *sce; | |
145 | int hashind; | |
146 | ||
147 | sce = (CACHE_ENT *) NULL; | |
148 | hashind = HASH(l, pgno); | |
149 | ||
150 | /* find the entry we want to delete */ | |
151 | for (ce = l->lru_cache[hashind]; | |
152 | ce != (CACHE_ENT *) NULL; | |
153 | ce = ce->c_chain) { | |
154 | if (ce->c_pgno == pgno) | |
155 | break; | |
156 | sce = ce; | |
157 | } | |
158 | ||
159 | if (ce == (CACHE_ENT *) NULL) | |
160 | return (-1); | |
161 | ||
162 | /* remove it from the chain */ | |
163 | if (sce == (CACHE_ENT *) NULL) | |
164 | l->lru_cache[hashind] = ce->c_chain; | |
165 | else | |
166 | sce->c_chain = ce->c_chain; | |
167 | ||
168 | /* release it */ | |
169 | free ((char *) ce); | |
170 | ||
171 | /* success */ | |
172 | return (0); | |
173 | } |