hash_newtab.c

来自「OTP是开放电信平台的简称」· C语言 代码 · 共 50 行

/* ``The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved via the world wide web at http://www.erlang.org/.
 * 
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 * 
 * The Initial Developer of the Original Code is Ericsson Utvecklings AB.
 * Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
 * AB. All Rights Reserved.''
 * 
 *     $Id$
 */
#include <stdlib.h>
#include <string.h>
#include "hash.h"

ei_hash *ei_hash_newtab(int tabsize)
{
  ei_hash *tab=NULL;
  int bucketpos=sizeof(*tab);
  
  /* make sure size is odd, then increase until prime */
  tabsize |= 0x1; 
  while (!ei_isprime(tabsize)) tabsize +=2;

  /* we will only do one malloc, so "sizeof(*tab)" 
   * must be adjusted to align tab->tab properly
   */
  ei_align(bucketpos);

  /* single malloc, then fill in all fields */
  if ((tab = malloc(bucketpos + (tabsize * (sizeof(*(tab->tab))))))) {
    tab->tab = (ei_bucket **)((char *)tab + bucketpos);
    memset(tab->tab,0,tabsize*sizeof(*(tab->tab)));
    tab->hash = ei_dohash;
    tab->size = tabsize;
    tab->npos = 0;
    tab->nelem = 0;
    tab->freelist = NULL;
  }

  return tab;
}