File: hash.c

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/*
 * Copyright (C) 1996-8 Michael R. Elkins <me@cs.hmc.edu>
 *
 *     This program is free software; you can redistribute it and/or modify
 *     it under the terms of the GNU General Public License as published by
 *     the Free Software Foundation; either version 2 of the License, or
 *     (at your option) any later version.
 * 
 *     This program is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 * 
 *     You should have received a copy of the GNU General Public License
 *     along with this program; if not, write to the Free Software
 *     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */ 

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "hash.h"

int hash_string (unsigned char *s, int n)
{
  int h = 0;
  while (*s)
    h += *s++;
  return (h % n);
}

HASH *hash_create (int nelem)
{
  HASH *table = malloc (sizeof (HASH));
  table->nelem = nelem;
  table->table = calloc (nelem, sizeof (struct hash_elem *));
  return table;
}

/* table	hash table to update
   key		key to hash on
   data		data to associate with `key'
   allow_dup	if nonzero, duplicate keys are allowed in the table */
int hash_insert (HASH *table, char *key, void *data, int allow_dup)
{
  struct hash_elem *ptr = malloc (sizeof (struct hash_elem));
  int h = hash_string ((unsigned char *) key, table->nelem);

  ptr->key = key;
  ptr->data = data;

  if (allow_dup)
  {
    ptr->next = table->table[h];
    table->table[h] = ptr;
  }
  else
  {
    struct hash_elem *tmp, *last;
    int r;

    for (tmp = table->table[h], last = NULL; tmp; last = tmp, tmp = tmp->next)
    {
      r = strcmp (tmp->key, key);
      if (r == 0)
      {
	free (ptr);
	return (-1);
      }
      if (r > 0)
	break;
    }
    if (last)
      last->next = ptr;
    else
      table->table[h] = ptr;
    ptr->next = tmp;
  }
  return h;
}

void *hash_find_hash (HASH *table, int hash, char *key)
{
  struct hash_elem *ptr = table->table[hash];
  for (; ptr; ptr = ptr->next)
  {
    if (strcmp (key, ptr->key) == 0)
      return (ptr->data);
  }
  return NULL;
}

void hash_delete_hash (HASH *table, int hash, char *key, void *data,
		       void (*destroy) (void *))
{
  struct hash_elem *ptr = table->table[hash];
  struct hash_elem *last = NULL;
  for (; ptr; last = ptr, ptr = ptr->next)
  {
    /* if `data' is given, look for a matching ->data member.  this is
       required for the case where we have multiple entries with the same
       key */
    if (data == ptr->data || (!data && strcmp (ptr->key, key) == 0))
    {
      if (last)
	last->next = ptr->next;
      else
	table->table[hash] = ptr->next;
      if (destroy)
	destroy (ptr->data);
      memset (ptr, 0, sizeof (struct hash_elem));
      free (ptr);
      ptr = 0;
      return;
    }
  }
}

/* ptr		pointer to the hash table to be freed
   destroy()	function to call to free the ->data member (optional) */
void hash_destroy (HASH **ptr, void (*destroy) (void *))
{
  int i;
  HASH *pptr = *ptr;
  struct hash_elem *elem, *tmp;

  for (i = 0 ; i < pptr->nelem; i++)
  {
    for (elem = pptr->table[i]; elem; )
    {
      tmp = elem;
      elem = elem->next;
      if (destroy)
	destroy (tmp->data);
      memset (tmp, 0, sizeof (struct hash_elem));
      free (tmp);
    }
  }
  free (pptr);
  *ptr = NULL;
}