/*
	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. returned list is guaranteed to be in reverse order of
	insertion. ie, deleting items from the list in list order will delete the
	correct items.
*/
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 the number of elements in the table.
*/
size_t Hash_NumElements (hashtab_t *tab);

/** 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