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hashsize.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*                  Copyright (c) 1985-2005 AT&T Corp.                  *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                            by AT&T Corp.                             *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#pragma prototyped
/*
 * Glenn Fowler
 * AT&T Research
 *
 * hash table library
 */

#include "hashlib.h"

/*
 * change table size and rehash
 * size must be a power of 2
 */

void
hashsize(register Hash_table_t* tab, int size)
{
      register Hash_bucket_t**      old_s;
      register Hash_bucket_t**      new_s;
      register Hash_bucket_t*       old_b;
      register Hash_bucket_t*       new_b;
      Hash_bucket_t**               old_sx;
      unsigned int                  index;
      Hash_region_f                 region;
      void*                   handle;

      if (size > 0 && size != tab->size && !(size & (size - 1)))
      {
            if (region = tab->root->local->region)
            {
                  handle = tab->root->local->handle;
                  new_s = (Hash_bucket_t**)(*region)(handle, NiL, sizeof(Hash_bucket_t*) * size, 0);
            }
            else new_s = newof(0, Hash_bucket_t*, size, 0);
            if (!new_s) tab->flags |= HASH_FIXED;
            else
            {
                  old_sx = (old_s = tab->table) + tab->size;
                  tab->size = size;
                  while (old_s < old_sx)
                  {
                        old_b = *old_s++;
                        while (old_b)
                        {
                              new_b = old_b;
                              old_b = old_b->next;
                              index = new_b->hash;
                              HASHMOD(tab, index);
                              new_b->next = new_s[index];
                              new_s[index] = new_b;
                        }
                  }
                  if ((tab->flags & (HASH_RESIZE|HASH_STATIC)) != HASH_STATIC)
                  {
                        if (region) (*region)(handle, tab->table, 0, 0);
                        else free(tab->table);
                  }
                  tab->table = new_s;
                  tab->flags |= HASH_RESIZE;
            }
      }
}

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