hcreate_r.c revision 292767 
1/*-
2 * Copyright (c) 2015 Nuxi, https://nuxi.nl/
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26#include <sys/cdefs.h>
27__FBSDID("$FreeBSD: head/lib/libc/stdlib/hcreate_r.c 292767 2015-12-27 07:50:11Z ed $");
28
29#include <search.h>
30#include <stdlib.h>
31
32#include "hsearch.h"
33
34int
35hcreate_r(size_t nel, struct hsearch_data *htab)
36{
37	struct __hsearch *hsearch;
38
39	/*
40	 * Allocate a hash table object. Ignore the provided hint and start
41	 * off with a table of sixteen entries. In most cases this hint is
42	 * just a wild guess. Resizing the table dynamically if the use
43	 * increases a threshold does not affect the worst-case running time.
44	 */
45	hsearch = malloc(sizeof(*hsearch));
46	if (hsearch == NULL)
47		return 0;
48	hsearch->entries = calloc(16, sizeof(ENTRY));
49	if (hsearch->entries == NULL) {
50		free(hsearch);
51		return 0;
52	}
53
54	/*
55	 * Pick a random initialization for the FNV-1a hashing. This makes it
56	 * hard to come up with a fixed set of keys to force hash collisions.
57	 */
58	arc4random_buf(&hsearch->offset_basis, sizeof(hsearch->offset_basis));
59	hsearch->index_mask = 0xf;
60	hsearch->entries_used = 0;
61	htab->__hsearch = hsearch;
62	return 1;
63}
64