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1 | /* $Header$ | |
2 | * | |
3 | * Generic hash table routines. Uses integer keys to store char * values. | |
4 | * | |
5 | * (c) Copyright 1988 by the Massachusetts Institute of Technology. | |
6 | * For copying and distribution information, please see the file | |
7 | * <mit-copyright.h>. | |
8 | */ | |
9 | ||
10 | #include <mit-copyright.h> | |
11 | #include <ctype.h> | |
12 | #include <sms.h> | |
13 | ||
14 | #define NULL 0 | |
15 | ||
16 | ||
17 | /* Create a hash table. The size is just a hint, not a maximum. */ | |
18 | ||
19 | struct hash *create_hash(size) | |
20 | int size; | |
21 | { | |
22 | struct hash *h; | |
23 | ||
24 | h = (struct hash *) malloc(sizeof(struct hash)); | |
25 | h->size = size; | |
26 | h->data = (struct bucket **) malloc(size * sizeof(char *)); | |
27 | bzero(h->data, size * sizeof(char *)); | |
28 | return(h); | |
29 | } | |
30 | ||
31 | /* Lookup an object in the hash table. Returns the value associated with | |
32 | * the key, or NULL (thus NULL is not a very good value to store...) | |
33 | */ | |
34 | ||
35 | char *hash_lookup(h, key) | |
36 | struct hash *h; | |
37 | register int key; | |
38 | { | |
39 | register struct bucket *b; | |
40 | ||
41 | b = h->data[key % h->size]; | |
42 | while (b && b->key != key) | |
43 | b = b->next; | |
44 | if (b && b->key == key) | |
45 | return(b->data); | |
46 | else | |
47 | return(NULL); | |
48 | } | |
49 | ||
50 | ||
51 | /* Update an existing object in the hash table. Returns 1 if the object | |
52 | * existed, or 0 if not. | |
53 | */ | |
54 | ||
55 | int hash_update(h, key, value) | |
56 | struct hash *h; | |
57 | register int key; | |
58 | char *value; | |
59 | { | |
60 | register struct bucket *b; | |
61 | ||
62 | b = h->data[key % h->size]; | |
63 | while (b && b->key != key) | |
64 | b = b->next; | |
65 | if (b && b->key == key) { | |
66 | b->data = value; | |
67 | return(1); | |
68 | } else | |
69 | return(0); | |
70 | } | |
71 | ||
72 | ||
73 | /* Store an item in the hash table. Returns 0 if the key was not previously | |
74 | * there, or 1 if it was. | |
75 | */ | |
76 | ||
77 | int hash_store(h, key, value) | |
78 | struct hash *h; | |
79 | register int key; | |
80 | char *value; | |
81 | { | |
82 | register struct bucket *b, **p; | |
83 | ||
84 | p = &(h->data[key % h->size]); | |
85 | if (*p == NULL) { | |
86 | b = *p = (struct bucket *) malloc(sizeof(struct bucket)); | |
87 | b->next = NULL; | |
88 | b->key = key; | |
89 | b->data = value; | |
90 | return(0); | |
91 | } | |
92 | ||
93 | for (b = *p; b && b->key != key; b = *p) | |
94 | p = (struct bucket **) *p; | |
95 | if (b && b->key == key) { | |
96 | b->data = value; | |
97 | return(1); | |
98 | } | |
99 | b = *p = (struct bucket *) malloc(sizeof(struct bucket)); | |
100 | b->next = NULL; | |
101 | b->key = key; | |
102 | b->data = value; | |
103 | return(0); | |
104 | } | |
105 | ||
106 | ||
107 | /* Search through the hash table for a given value. For each piece of | |
108 | * data with that value, call the callback proc with the corresponding key. | |
109 | */ | |
110 | ||
111 | hash_search(h, value, callback) | |
112 | struct hash *h; | |
113 | register char *value; | |
114 | void (*callback)(); | |
115 | { | |
116 | register struct bucket *b, **p; | |
117 | ||
118 | for (p = &(h->data[h->size - 1]); p >= h->data; p--) { | |
119 | for (b = *p; b; b = b->next) { | |
120 | if (b->data == value) | |
121 | (*callback)(b->key); | |
122 | } | |
123 | } | |
124 | } | |
125 | ||
126 | ||
127 | /* Step through the hash table, calling the callback proc with each key. | |
128 | */ | |
129 | ||
130 | hash_step(h, callback, hint) | |
131 | struct hash *h; | |
132 | void (*callback)(); | |
133 | char *hint; | |
134 | { | |
135 | register struct bucket *b, **p; | |
136 | ||
137 | for (p = &(h->data[h->size - 1]); p >= h->data; p--) { | |
138 | for (b = *p; b; b = b->next) { | |
139 | (*callback)(b->key, b->data, hint); | |
140 | } | |
141 | } | |
142 | } | |
143 | ||
144 | ||
145 | /* Deallocate all of the memory associated with a table */ | |
146 | ||
147 | hash_destroy(h) | |
148 | struct hash *h; | |
149 | { | |
150 | register struct bucket *b, **p, *b1; | |
151 | ||
152 | for (p = &(h->data[h->size - 1]); p >= h->data; p--) { | |
153 | for (b = *p; b; b = b1) { | |
154 | b1 = b->next; | |
155 | free(b); | |
156 | } | |
157 | } | |
158 | } |