1 /* Fully-inline hash table, used mainly for managing TLS descriptors.
2 Copyright (C) 1999-2013 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Alexandre Oliva <aoliva@redhat.com>
6 This file is derived from a 2003's version of libiberty's
7 hashtab.c, contributed by Vladimir Makarov (vmakarov@cygnus.com),
8 but with most adaptation points and support for deleting elements
11 The GNU C Library is free software; you can redistribute it and/or
12 modify it under the terms of the GNU Lesser General Public
13 License as published by the Free Software Foundation; either
14 version 2.1 of the License, or (at your option) any later version.
16 The GNU C Library is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 Lesser General Public License for more details.
21 You should have received a copy of the GNU Lesser General Public
22 License along with the GNU C Library; if not, see
23 <http://www.gnu.org/licenses/>. */
25 #ifndef INLINE_HASHTAB_H
26 # define INLINE_HASHTAB_H 1
28 extern void weak_function free (void *ptr);
35 /* Current size (in entries) of the hash table */
38 /* Current number of elements. */
41 /* Free function for the entries array. This may vary depending on
42 how early the array was allocated. If it is NULL, then the array
44 void (*free) (void *ptr);
47 inline static struct hashtab *
50 struct hashtab *ht = malloc (sizeof (struct hashtab));
55 ht->entries = malloc (sizeof (void *) * ht->size);
66 memset (ht->entries, 0, sizeof (void *) * ht->size);
71 /* This is only called from _dl_unmap, so it's safe to call
74 htab_delete (struct hashtab *htab)
78 for (i = htab->size - 1; i >= 0; i--)
79 free (htab->entries[i]);
82 htab->free (htab->entries);
86 /* Similar to htab_find_slot, but without several unwanted side effects:
87 - Does not call htab->eq_f when it finds an existing entry.
88 - Does not change the count of elements/searches/collisions in the
90 This function also assumes there are no deleted entries in the table.
91 HASH is the hash value for the element to be inserted. */
94 find_empty_slot_for_expand (struct hashtab *htab, int hash)
96 size_t size = htab->size;
97 unsigned int index = hash % size;
98 void **slot = htab->entries + index;
104 hash2 = 1 + hash % (size - 2);
111 slot = htab->entries + index;
117 /* The following function changes size of memory allocated for the
118 entries and repeatedly inserts the table elements. The occupancy
119 of the table after the call will be about 50%. Naturally the hash
120 table must already exist. Remember also that the place of the
121 table entries is changed. If memory allocation failures are allowed,
122 this function will return zero, indicating that the table could not be
123 expanded. If all goes well, it will return a non-zero value. */
126 htab_expand (struct hashtab *htab, int (*hash_fn) (void *))
134 oentries = htab->entries;
135 olimit = oentries + htab->size;
137 /* Resize only when table after removal of unused elements is either
138 too full or too empty. */
139 if (htab->n_elements * 2 > htab->size)
140 nsize = _dl_higher_prime_number (htab->n_elements * 2);
144 nentries = calloc (sizeof (void *), nsize);
145 if (nentries == NULL)
147 htab->entries = nentries;
154 *find_empty_slot_for_expand (htab, hash_fn (*p))
161 /* Without recording the free corresponding to the malloc used to
162 allocate the table, we couldn't tell whether this was allocated
163 by the malloc() built into ld.so or the one in the main
164 executable or libc. Calling free() for something that was
165 allocated by the early malloc(), rather than the final run-time
166 malloc() could do Very Bad Things (TM). We will waste memory
167 allocated early as long as there's no corresponding free(), but
168 this isn't so much memory as to be significant. */
171 htab->free (oentries);
173 /* Use the free() corresponding to the malloc() above to free this
180 /* This function searches for a hash table slot containing an entry
181 equal to the given element. To delete an entry, call this with
182 INSERT = 0, then call htab_clear_slot on the slot returned (possibly
183 after doing some checks). To insert an entry, call this with
184 INSERT = 1, then write the value you want into the returned slot.
185 When inserting an entry, NULL may be returned if memory allocation
188 inline static void **
189 htab_find_slot (struct hashtab *htab, void *ptr, int insert,
190 int (*hash_fn)(void *), int (*eq_fn)(void *, void *))
197 if (htab->size * 3 <= htab->n_elements * 4
198 && htab_expand (htab, hash_fn) == 0)
201 hash = hash_fn (ptr);
206 entry = &htab->entries[index];
209 else if (eq_fn (*entry, ptr))
212 hash2 = 1 + hash % (size - 2);
219 entry = &htab->entries[index];
222 else if (eq_fn (*entry, ptr))
234 #endif /* INLINE_HASHTAB_H */