freebsd-skq/lib/libc/stdlib/hcreate.c
2002-06-27 13:18:27 +00:00

186 lines
4.9 KiB
C

/* $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $ */
/*
* Copyright (c) 2001 Christopher G. Demetriou
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed for the
* NetBSD Project. See http://www.netbsd.org/ for
* information about NetBSD.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
*/
/*
* hcreate() / hsearch() / hdestroy()
*
* SysV/XPG4 hash table functions.
*
* Implementation done based on NetBSD manual page and Solaris manual page,
* plus my own personal experience about how they're supposed to work.
*
* I tried to look at Knuth (as cited by the Solaris manual page), but
* nobody had a copy in the office, so...
*/
#include <sys/cdefs.h>
#if 0
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $");
#endif /* LIBC_SCCS and not lint */
#endif
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/queue.h>
#include <errno.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
/*
* DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
* ptr machine) without adjusting MAX_BUCKETS_LG2 below.
*/
struct internal_entry {
SLIST_ENTRY(internal_entry) link;
ENTRY ent;
};
SLIST_HEAD(internal_head, internal_entry);
#define MIN_BUCKETS_LG2 4
#define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
/*
* max * sizeof internal_entry must fit into size_t.
* assumes internal_entry is <= 32 (2^5) bytes.
*/
#define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
#define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
/* Default hash function, from db/hash/hash_func.c */
extern u_int32_t (*__default_hash)(const void *, size_t);
static struct internal_head *htable;
static size_t htablesize;
int
hcreate(size_t nel)
{
size_t idx;
unsigned int p2;
/* Make sure this this isn't called when a table already exists. */
if (htable != NULL) {
errno = EINVAL;
return 0;
}
/* If nel is too small, make it min sized. */
if (nel < MIN_BUCKETS)
nel = MIN_BUCKETS;
/* If it's too large, cap it. */
if (nel > MAX_BUCKETS)
nel = MAX_BUCKETS;
/* If it's is not a power of two in size, round up. */
if ((nel & (nel - 1)) != 0) {
for (p2 = 0; nel != 0; p2++)
nel >>= 1;
nel = 1 << p2;
}
/* Allocate the table. */
htablesize = nel;
htable = malloc(htablesize * sizeof htable[0]);
if (htable == NULL) {
errno = ENOMEM;
return 0;
}
/* Initialize it. */
for (idx = 0; idx < htablesize; idx++)
SLIST_INIT(&htable[idx]);
return 1;
}
void
hdestroy(void)
{
struct internal_entry *ie;
size_t idx;
if (htable == NULL)
return;
for (idx = 0; idx < htablesize; idx++) {
while (!SLIST_EMPTY(&htable[idx])) {
ie = SLIST_FIRST(&htable[idx]);
SLIST_REMOVE_HEAD(&htable[idx], link);
free(ie->ent.key);
free(ie);
}
}
free(htable);
htable = NULL;
}
ENTRY *
hsearch(ENTRY item, ACTION action)
{
struct internal_head *head;
struct internal_entry *ie;
uint32_t hashval;
size_t len;
len = strlen(item.key);
hashval = (*__default_hash)(item.key, len);
head = &htable[hashval & (htablesize - 1)];
ie = SLIST_FIRST(head);
while (ie != NULL) {
if (strcmp(ie->ent.key, item.key) == 0)
break;
ie = SLIST_NEXT(ie, link);
}
if (ie != NULL)
return &ie->ent;
else if (action == FIND)
return NULL;
ie = malloc(sizeof *ie);
if (ie == NULL)
return NULL;
ie->ent.key = item.key;
ie->ent.data = item.data;
SLIST_INSERT_HEAD(head, ie, link);
return &ie->ent;
}