1 /* An expandable hash tables datatype.
2 Copyright (C) 1999-2023 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., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, 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 #include "ansidecl.h"
40
41 /* The type for a hash code. */
42 typedef unsigned int hashval_t;
43
44 /* Callback function pointer types. */
45
46 /* Calculate hash of a table entry. */
47 typedef hashval_t (*htab_hash) (const void *);
48
49 /* Compare a table entry with a possible entry. The entry already in
50 the table always comes first, so the second element can be of a
51 different type (but in this case htab_find and htab_find_slot
52 cannot be used; instead the variants that accept a hash value
53 must be used). */
54 typedef int (*htab_eq) (const void *, const void *);
55
56 /* Cleanup function called whenever a live element is removed from
57 the hash table. */
58 typedef void (*htab_del) (void *);
59
60 /* Function called by htab_traverse for each live element. The first
61 arg is the slot of the element (which can be passed to htab_clear_slot
62 if desired), the second arg is the auxiliary pointer handed to
63 htab_traverse. Return 1 to continue scan, 0 to stop. */
64 typedef int (*htab_trav) (void **, void *);
65
66 /* Memory-allocation function, with the same functionality as calloc().
67 Iff it returns NULL, the hash table implementation will pass an error
68 code back to the user, so if your code doesn't handle errors,
69 best if you use xcalloc instead. */
70 typedef void *(*htab_alloc) (size_t, size_t);
71
72 /* We also need a free() routine. */
73 typedef void (*htab_free) (void *);
74
75 /* Memory allocation and deallocation; variants which take an extra
76 argument. */
77 typedef void *(*htab_alloc_with_arg) (void *, size_t, size_t);
78 typedef void (*htab_free_with_arg) (void *, void *);
79
80 /* This macro defines reserved value for empty table entry. */
81
82 #define HTAB_EMPTY_ENTRY ((void *) 0)
83
84 /* This macro defines reserved value for table entry which contained
85 a deleted element. */
86
87 #define HTAB_DELETED_ENTRY ((void *) 1)
88
89 /* Hash tables are of the following type. The structure
90 (implementation) of this type is not needed for using the hash
91 tables. All work with hash table should be executed only through
92 functions mentioned below. The size of this structure is subject to
93 change. */
94
95 struct htab {
96 /* Pointer to hash function. */
97 htab_hash hash_f;
98
99 /* Pointer to comparison function. */
100 htab_eq eq_f;
101
102 /* Pointer to cleanup function. */
103 htab_del del_f;
104
105 /* Table itself. */
106 void **entries;
107
108 /* Current size (in entries) of the hash table. */
109 size_t size;
110
111 /* Current number of elements including also deleted elements. */
112 size_t n_elements;
113
114 /* Current number of deleted elements in the table. */
115 size_t n_deleted;
116
117 /* The following member is used for debugging. Its value is number
118 of all calls of `htab_find_slot' for the hash table. */
119 unsigned int searches;
120
121 /* The following member is used for debugging. Its value is number
122 of collisions fixed for time of work with the hash table. */
123 unsigned int collisions;
124
125 /* Pointers to allocate/free functions. */
126 htab_alloc alloc_f;
127 htab_free free_f;
128
129 /* Alternate allocate/free functions, which take an extra argument. */
130 void *alloc_arg;
131 htab_alloc_with_arg alloc_with_arg_f;
132 htab_free_with_arg free_with_arg_f;
133
134 /* Current size (in entries) of the hash table, as an index into the
135 table of primes. */
136 unsigned int size_prime_index;
137 };
138
139 typedef struct htab *htab_t;
140
141 /* An enum saying whether we insert into the hash table or not. */
142 enum insert_option {NO_INSERT, INSERT};
143
144 /* The prototypes of the package functions. */
145
146 extern htab_t htab_create_alloc (size_t, htab_hash,
147 htab_eq, htab_del,
148 htab_alloc, htab_free);
149
150 extern htab_t htab_create_alloc_ex (size_t, htab_hash,
151 htab_eq, htab_del,
152 void *, htab_alloc_with_arg,
153 htab_free_with_arg);
154
155 extern htab_t htab_create_typed_alloc (size_t, htab_hash, htab_eq, htab_del,
156 htab_alloc, htab_alloc, htab_free);
157
158 /* Backward-compatibility functions. */
159 extern htab_t htab_create (size_t, htab_hash, htab_eq, htab_del);
160 extern htab_t htab_try_create (size_t, htab_hash, htab_eq, htab_del);
161
162 extern void htab_set_functions_ex (htab_t, htab_hash,
163 htab_eq, htab_del,
164 void *, htab_alloc_with_arg,
165 htab_free_with_arg);
166
167 extern void htab_delete (htab_t);
168 extern void htab_empty (htab_t);
169
170 extern void * htab_find (htab_t, const void *);
171 extern void ** htab_find_slot (htab_t, const void *, enum insert_option);
172 extern void * htab_find_with_hash (htab_t, const void *, hashval_t);
173 extern void ** htab_find_slot_with_hash (htab_t, const void *,
174 hashval_t, enum insert_option);
175 extern void htab_clear_slot (htab_t, void **);
176 extern void htab_remove_elt (htab_t, const void *);
177 extern void htab_remove_elt_with_hash (htab_t, const void *, hashval_t);
178
179 extern void htab_traverse (htab_t, htab_trav, void *);
180 extern void htab_traverse_noresize (htab_t, htab_trav, void *);
181
182 extern size_t htab_size (htab_t);
183 extern size_t htab_elements (htab_t);
184 extern double htab_collisions (htab_t);
185
186 /* A hash function for pointers. */
187 extern htab_hash htab_hash_pointer;
188
189 /* An equality function for pointers. */
190 extern htab_eq htab_eq_pointer;
191
192 /* A hash function for null-terminated strings. */
193 extern hashval_t htab_hash_string (const void *);
194
195 /* An equality function for null-terminated strings. */
196 extern int htab_eq_string (const void *, const void *);
197
198 /* An iterative hash function for arbitrary data. */
199 extern hashval_t iterative_hash (const void *, size_t, hashval_t);
200 /* Shorthand for hashing something with an intrinsic size. */
201 #define iterative_hash_object(OB,INIT) iterative_hash (&OB, sizeof (OB), INIT)
202
203 #ifdef __cplusplus
204 }
205 #endif /* __cplusplus */
206
207 #endif /* __HASHTAB_H */