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1 | /* An expandable hash tables datatype. |
2 | Copyright (C) 1999, 2000 Free Software Foundation, Inc. | |
3 | Contributed by Vladimir Makarov (vmakarov@cygnus.com). | |
4 | ||
5 | This program is free software; you can redistribute it and/or modify | |
6 | it under the terms of the GNU General Public License as published by | |
7 | the Free Software Foundation; either version 2 of the License, or | |
8 | (at your option) any later version. | |
9 | ||
10 | This program is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | GNU General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU General Public License | |
16 | along with this program; if not, write to the Free Software | |
17 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ | |
18 | ||
19 | /* This package implements basic hash table functionality. It is possible | |
20 | to search for an entry, create an entry and destroy an entry. | |
21 | ||
22 | Elements in the table are generic pointers. | |
23 | ||
24 | The size of the table is not fixed; if the occupancy of the table | |
25 | grows too high the hash table will be expanded. | |
26 | ||
27 | The abstract data implementation is based on generalized Algorithm D | |
28 | from Knuth's book "The art of computer programming". Hash table is | |
29 | expanded by creation of new hash table and transferring elements from | |
30 | the old table to the new table. */ | |
31 | ||
32 | #ifndef __HASHTAB_H__ | |
33 | #define __HASHTAB_H__ | |
34 | ||
35 | #ifdef __cplusplus | |
36 | extern "C" { | |
37 | #endif /* __cplusplus */ | |
38 | ||
39 | /* The type for a hash code. */ | |
40 | typedef unsigned int hashval_t; | |
41 | ||
42 | /* Callback function pointer types. */ | |
43 | ||
44 | /* Calculate hash of a table entry. */ | |
45 | typedef hashval_t (*htab_hash) (const void *); | |
46 | ||
47 | /* Compare a table entry with a possible entry. The entry already in | |
48 | the table always comes first, so the second element can be of a | |
49 | different type (but in this case htab_find and htab_find_slot | |
50 | cannot be used; instead the variants that accept a hash value | |
51 | must be used). */ | |
52 | typedef int (*htab_eq) (const void *, const void *); | |
53 | ||
54 | /* Cleanup function called whenever a live element is removed from | |
55 | the hash table. */ | |
56 | typedef void (*htab_del) (void *); | |
57 | ||
58 | /* Function called by htab_traverse for each live element. The first | |
59 | arg is the slot of the element (which can be passed to htab_clear_slot | |
60 | if desired), the second arg is the auxiliary pointer handed to | |
61 | htab_traverse. Return 1 to continue scan, 0 to stop. */ | |
62 | typedef int (*htab_trav) (void **, void *); | |
63 | ||
64 | /* Hash tables are of the following type. The structure | |
65 | (implementation) of this type is not needed for using the hash | |
66 | tables. All work with hash table should be executed only through | |
67 | functions mentioned below. */ | |
68 | ||
69 | struct htab | |
70 | { | |
71 | /* Pointer to hash function. */ | |
72 | htab_hash hash_f; | |
73 | ||
74 | /* Pointer to comparison function. */ | |
75 | htab_eq eq_f; | |
76 | ||
77 | /* Pointer to cleanup function. */ | |
78 | htab_del del_f; | |
79 | ||
80 | /* Table itself. */ | |
81 | void **entries; | |
82 | ||
83 | /* Current size (in entries) of the hash table */ | |
84 | size_t size; | |
85 | ||
86 | /* Current number of elements including also deleted elements */ | |
87 | size_t n_elements; | |
88 | ||
89 | /* Current number of deleted elements in the table */ | |
90 | size_t n_deleted; | |
91 | ||
92 | /* The following member is used for debugging. Its value is number | |
93 | of all calls of `htab_find_slot' for the hash table. */ | |
94 | unsigned int searches; | |
95 | ||
96 | /* The following member is used for debugging. Its value is number | |
97 | of collisions fixed for time of work with the hash table. */ | |
98 | unsigned int collisions; | |
99 | ||
100 | /* This is non-zero if we are allowed to return NULL for function calls | |
101 | that allocate memory. */ | |
102 | int return_allocation_failure; | |
103 | }; | |
104 | ||
105 | typedef struct htab *htab_t; | |
106 | ||
107 | /* An enum saying whether we insert into the hash table or not. */ | |
108 | enum insert_option {NO_INSERT, INSERT}; | |
109 | ||
110 | /* The prototypes of the package functions. */ | |
111 | ||
112 | /* This function is like htab_create, but may return NULL if memory | |
113 | allocation fails, and also signals that htab_find_slot_with_hash and | |
114 | htab_find_slot are allowed to return NULL when inserting. */ | |
115 | extern htab_t htab_try_create (size_t, htab_hash, htab_eq, htab_del); | |
116 | extern void htab_delete (htab_t); | |
117 | extern void htab_empty (htab_t); | |
118 | ||
119 | extern void *htab_find (htab_t, const void *); | |
120 | extern void **htab_find_slot (htab_t, const void *, enum insert_option); | |
121 | extern void *htab_find_with_hash (htab_t, const void *, hashval_t); | |
122 | extern void **htab_find_slot_with_hash (htab_t, const void *, hashval_t, | |
123 | enum insert_option); | |
124 | extern void htab_clear_slot (htab_t, void **); | |
125 | extern void htab_remove_elt (htab_t, void *); | |
126 | ||
127 | extern void htab_traverse (htab_t, htab_trav, void *); | |
128 | ||
129 | extern size_t htab_size (htab_t); | |
130 | extern size_t htab_elements (htab_t); | |
131 | extern double htab_collisions (htab_t); | |
132 | ||
133 | /* A hash function for pointers. */ | |
134 | extern htab_hash htab_hash_pointer; | |
135 | ||
136 | /* An equality function for pointers. */ | |
137 | extern htab_eq htab_eq_pointer; | |
138 | ||
139 | #ifdef __cplusplus | |
140 | } | |
141 | #endif /* __cplusplus */ | |
142 | ||
143 | #endif /* __HASHTAB_H */ |