1 /* Fully-inline hash table, used mainly for managing TLS descriptors.
2 Copyright (C) 1999-2020 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 <https://www.gnu.org/licenses/>. */
25 #ifndef INLINE_HASHTAB_H
26 # define INLINE_HASHTAB_H 1
33 /* Current size (in entries) of the hash table */
36 /* Current number of elements. */
39 /* Free function for the entries array. This may vary depending on
40 how early the array was allocated. If it is NULL, then the array
42 void (*free
) (void *ptr
);
45 inline static struct hashtab
*
48 struct hashtab
*ht
= malloc (sizeof (struct hashtab
));
53 ht
->entries
= malloc (sizeof (void *) * ht
->size
);
54 ht
->free
= __rtld_free
;
63 memset (ht
->entries
, 0, sizeof (void *) * ht
->size
);
68 /* This is only called from _dl_unmap, so it's safe to call
71 htab_delete (struct hashtab
*htab
)
75 for (i
= htab
->size
- 1; i
>= 0; i
--)
76 free (htab
->entries
[i
]);
78 htab
->free (htab
->entries
);
82 /* Similar to htab_find_slot, but without several unwanted side effects:
83 - Does not call htab->eq_f when it finds an existing entry.
84 - Does not change the count of elements/searches/collisions in the
86 This function also assumes there are no deleted entries in the table.
87 HASH is the hash value for the element to be inserted. */
90 find_empty_slot_for_expand (struct hashtab
*htab
, int hash
)
92 size_t size
= htab
->size
;
93 unsigned int index
= hash
% size
;
94 void **slot
= htab
->entries
+ index
;
100 hash2
= 1 + hash
% (size
- 2);
107 slot
= htab
->entries
+ index
;
113 /* The following function changes size of memory allocated for the
114 entries and repeatedly inserts the table elements. The occupancy
115 of the table after the call will be about 50%. Naturally the hash
116 table must already exist. Remember also that the place of the
117 table entries is changed. If memory allocation failures are allowed,
118 this function will return zero, indicating that the table could not be
119 expanded. If all goes well, it will return a non-zero value. */
122 htab_expand (struct hashtab
*htab
, int (*hash_fn
) (void *))
130 oentries
= htab
->entries
;
131 olimit
= oentries
+ htab
->size
;
133 /* Resize only when table after removal of unused elements is either
134 too full or too empty. */
135 if (htab
->n_elements
* 2 > htab
->size
)
136 nsize
= _dl_higher_prime_number (htab
->n_elements
* 2);
140 nentries
= calloc (sizeof (void *), nsize
);
141 if (nentries
== NULL
)
143 htab
->entries
= nentries
;
150 *find_empty_slot_for_expand (htab
, hash_fn (*p
))
157 /* Without recording the free corresponding to the malloc used to
158 allocate the table, we couldn't tell whether this was allocated
159 by the malloc() built into ld.so or the one in the main
160 executable or libc. Calling free() for something that was
161 allocated by the early malloc(), rather than the final run-time
162 malloc() could do Very Bad Things (TM). We will waste memory
163 allocated early as long as there's no corresponding free(), but
164 this isn't so much memory as to be significant. */
166 htab
->free (oentries
);
168 /* Use the free() corresponding to the malloc() above to free this
170 htab
->free
= __rtld_free
;
175 /* This function searches for a hash table slot containing an entry
176 equal to the given element. To delete an entry, call this with
177 INSERT = 0, then call htab_clear_slot on the slot returned (possibly
178 after doing some checks). To insert an entry, call this with
179 INSERT = 1, then write the value you want into the returned slot.
180 When inserting an entry, NULL may be returned if memory allocation
183 inline static void **
184 htab_find_slot (struct hashtab
*htab
, void *ptr
, int insert
,
185 int (*hash_fn
)(void *), int (*eq_fn
)(void *, void *))
192 if (htab
->size
* 3 <= htab
->n_elements
* 4
193 && htab_expand (htab
, hash_fn
) == 0)
196 hash
= hash_fn (ptr
);
201 entry
= &htab
->entries
[index
];
204 else if (eq_fn (*entry
, ptr
))
207 hash2
= 1 + hash
% (size
- 2);
214 entry
= &htab
->entries
[index
];
217 else if (eq_fn (*entry
, ptr
))
229 #endif /* INLINE_HASHTAB_H */