IABSD.fr/src/lib/libc/stdlib/hcreate.c

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• Author : guenther
  Date : 2016-05-29 20:47:49
  Hash : b5745d08
  Message : Remove dead support for changing BDB hash algorithm and cache of alternatives ok natano@ millert@ deraadt@

• lib/libc/stdlib/hcreate.c

• /*	$OpenBSD: hcreate.c,v 1.7 2016/05/29 20:47:49 guenther Exp $	*/
  /*	$NetBSD: hcreate.c,v 1.5 2004/04/23 02:48:12 simonb 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 <assert.h>
  #include <errno.h>
  #include <stdint.h>
  #include <search.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/queue.h>
  
  #include <db.h>		/* for __default_hash */
  
  #ifndef _DIAGASSERT
  #define _DIAGASSERT(x)
  #endif
  
  /*
   * 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)
  
  static struct internal_head *htable;
  static size_t htablesize;
  
  int
  hcreate(size_t nel)
  {
  	size_t idx;
  	unsigned int p2;
  
  	/* Make sure this isn't called when a table already exists. */
  	_DIAGASSERT(htable == NULL);
  	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;
  		_DIAGASSERT(p2 <= MAX_BUCKETS_LG2);
  		nel = 1 << p2;
  	}
  	
  	/* Allocate the table. */
  	htablesize = nel;
  	htable = calloc(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;
  
  	_DIAGASSERT(htable != NULL);
  	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;
  
  	_DIAGASSERT(htable != NULL);
  	_DIAGASSERT(item.key != NULL);
  	_DIAGASSERT(action == ENTER || action == FIND);
  
  	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;
  }