/*
	hash.h

	hash tables

	Copyright (C) 2000  Bill Currie <bill@taniwha.org>

	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:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

	$Id$
*/

#ifndef __hash_h
#define __hash_h

typedef struct hashtab_s hashtab_t;

/** create a new hash table:
		tsize:	table size. larger values will give better distribution, but
				use more memory.
		gk:		a function that returns a string to be used as the key for
				inserting or finding the element. First parameter is a pointer
				to the element from which to extract the key, the second is
				the user data pointer.
		f:		a function to free the element. Only ever called from
				Hash_FlushTable and Hash_DelTable. The first parameter is the
				element to be freed and the second is the user data pointer.
		ud:		user data pointer. set to whatever you want, it will be passed
				to the get key and free functions as the second parameter.
	returns a pointer to the hash table (to be passed to the other functions)
	or 0 on error.

	Hash_Add, Hash_Find, Hash_FindList and Hash_Del use gk and strcmp.

	multiple inserions of the same key are fine; later insertions override
	previous ones until the later one is removed (Hash_Del).
*/
hashtab_t *Hash_NewTable (int tsize, const char *(*gk)(void*,void*),
						  void (*f)(void*,void*), void *ud);

/** change the hash and compare functions used by the Hash_*Element functions.
	the default hash function just returns the address of the element, and the
	default compare just compares the addresses. compare is to return 0 for not
	equal and non-0 otherwise.

	With suitably crafted gh and cmp functions, Hash_*Element functions can
	be mixed with the non-element functions, but by default the results will
	be undefined.

	gh takes the same parameters as gk above
	cmp is element 1, element 2, userdata
*/
void Hash_SetHashCompare (hashtab_t *tab, unsigned long (*gh)(void*,void*),
						  int (*cmp)(void*,void*,void*));


/** delete a hash table:
		tab:	the table to be deleted
*/
void Hash_DelTable (hashtab_t *tab);

/** clean out all the entries from a hash table, starting over again:
		tab:	the table to be cleared
*/
void Hash_FlushTable (hashtab_t *tab);

//@{
/** add an entry to a hash table:
		tab:	the table to be added to
		ele:	the element to add to the table
	returns 0 for success, -1 for error.
*/
int Hash_Add (hashtab_t *tab, void *ele);
int Hash_AddElement (hashtab_t *tab, void *ele);
//@}

//@{
/** find an element within a hash table:
		tab:	the table to search
		key:	the key string identifying the element being searched for
	returns a pointer to the element if found, otherwise 0.
*/
void *Hash_Find (hashtab_t *tab, const char *key);
void *Hash_FindElement (hashtab_t *tab, void *ele);
//@}

//@{
/** find a list of elements within a hash table:
		tab:	the table to search
		key:	the key string identifying the elements being searched for
	returns a null terminated list of element pointers if at least one found,
	otherwise 0.
*/
void **Hash_FindList (hashtab_t *tab, const char *key);
void **Hash_FindElementList (hashtab_t *tab, void *ele);
//@}

//@{
/** delete an element from a hash table:
		tab:	the table to remove the element from
		key:	the key string identifying the element to be deleted
	returns a pointer to the element on success, 0 if the element could not
	be found.
	Does /NOT/ call the free element function. That is the caller's
	responsibility.
*/
void *Hash_Del (hashtab_t *tab, const char *key);
void *Hash_DelElement (hashtab_t *tab, void *ele);
//@}

/** calls the free element function for the supplied ele
	eg:
	Hash_Free (tab, Hash_Del (tab, key));
*/
void Hash_Free (hashtab_t *tab, void *ele);

/** returh the hash value of a string. this is the same function as used
	internally.
*/
unsigned long Hash_String (const char *str);

/** returh the hash value of a buffer.
*/
unsigned long Hash_Buffer (const void *buf, int len);

/** return a list of all elements in the table. it is the caller's
	responsibilty to free() the array. Null terminated.
*/
void **Hash_GetList (hashtab_t *tab);

/** dump statistics about the hash table
*/
void Hash_Stats (hashtab_t *tab);

#endif // __hash_h