diff options
Diffstat (limited to 'lib/libc/stdlib/hcreate.c')
| -rw-r--r-- | lib/libc/stdlib/hcreate.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/lib/libc/stdlib/hcreate.c b/lib/libc/stdlib/hcreate.c new file mode 100644 index 0000000..ecc2431 --- /dev/null +++ b/lib/libc/stdlib/hcreate.c @@ -0,0 +1,184 @@ +/* $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $ */ +/* $FreeBSD$ */ + +/* + * 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 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 */ + +#include <sys/types.h> +#include <sys/queue.h> +#include <errno.h> +#include <search.h> +#include <stdlib.h> +#include <string.h> +#include "namespace.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; +} |
