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ec7d12549c
Obtained from: NetBSD MFC after: 1 month
185 lines
4.9 KiB
C
185 lines
4.9 KiB
C
/* $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $ */
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/* $FreeBSD$ */
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/*
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* Copyright (c) 2001 Christopher G. Demetriou
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed for the
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* NetBSD Project. See http://www.netbsd.org/ for
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* information about NetBSD.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
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*/
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/*
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* hcreate() / hsearch() / hdestroy()
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*
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* SysV/XPG4 hash table functions.
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*
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* Implementation done based on NetBSD manual page and Solaris manual page,
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* plus my own personal experience about how they're supposed to work.
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*
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* I tried to look at Knuth (as cited by the Solaris manual page), but
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* nobody had a copy in the office, so...
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*/
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#include <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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__RCSID("$NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $");
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#endif /* LIBC_SCCS and not lint */
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#include <sys/types.h>
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#include <sys/queue.h>
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#include <errno.h>
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#include <search.h>
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#include <stdlib.h>
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#include <string.h>
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#include "namespace.h"
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/*
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* DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
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* ptr machine) without adjusting MAX_BUCKETS_LG2 below.
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*/
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struct internal_entry {
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SLIST_ENTRY(internal_entry) link;
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ENTRY ent;
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};
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SLIST_HEAD(internal_head, internal_entry);
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#define MIN_BUCKETS_LG2 4
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#define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
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/*
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* max * sizeof internal_entry must fit into size_t.
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* assumes internal_entry is <= 32 (2^5) bytes.
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*/
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#define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
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#define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
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/* Default hash function, from db/hash/hash_func.c */
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extern u_int32_t (*__default_hash)(const void *, size_t);
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static struct internal_head *htable;
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static size_t htablesize;
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int
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hcreate(size_t nel)
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{
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size_t idx;
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unsigned int p2;
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/* Make sure this this isn't called when a table already exists. */
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if (htable != NULL) {
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errno = EINVAL;
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return 0;
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}
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/* If nel is too small, make it min sized. */
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if (nel < MIN_BUCKETS)
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nel = MIN_BUCKETS;
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/* If it's too large, cap it. */
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if (nel > MAX_BUCKETS)
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nel = MAX_BUCKETS;
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/* If it's is not a power of two in size, round up. */
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if ((nel & (nel - 1)) != 0) {
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for (p2 = 0; nel != 0; p2++)
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nel >>= 1;
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nel = 1 << p2;
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}
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/* Allocate the table. */
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htablesize = nel;
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htable = malloc(htablesize * sizeof htable[0]);
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if (htable == NULL) {
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errno = ENOMEM;
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return 0;
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}
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/* Initialize it. */
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for (idx = 0; idx < htablesize; idx++)
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SLIST_INIT(&htable[idx]);
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return 1;
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}
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void
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hdestroy(void)
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{
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struct internal_entry *ie;
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size_t idx;
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if (htable == NULL)
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return;
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for (idx = 0; idx < htablesize; idx++) {
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while (!SLIST_EMPTY(&htable[idx])) {
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ie = SLIST_FIRST(&htable[idx]);
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SLIST_REMOVE_HEAD(&htable[idx], link);
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free(ie->ent.key);
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free(ie);
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}
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}
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free(htable);
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htable = NULL;
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}
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ENTRY *
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hsearch(ENTRY item, ACTION action)
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{
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struct internal_head *head;
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struct internal_entry *ie;
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uint32_t hashval;
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size_t len;
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len = strlen(item.key);
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hashval = (*__default_hash)(item.key, len);
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head = &htable[hashval & (htablesize - 1)];
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ie = SLIST_FIRST(head);
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while (ie != NULL) {
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if (strcmp(ie->ent.key, item.key) == 0)
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break;
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ie = SLIST_NEXT(ie, link);
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}
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if (ie != NULL)
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return &ie->ent;
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else if (action == FIND)
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return NULL;
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ie = malloc(sizeof *ie);
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if (ie == NULL)
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return NULL;
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ie->ent.key = item.key;
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ie->ent.data = item.data;
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SLIST_INSERT_HEAD(head, ie, link);
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return &ie->ent;
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}
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