/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef CAIRO_CACHE_PRIVATE_H
#define CAIRO_CACHE_PRIVATE_H

#include "cairo-compiler-private.h"
#include "cairo-types-private.h"

/**
 * cairo_cache_entry_t:
 *
 * A #cairo_cache_entry_t contains both a key and a value for
 * #cairo_cache_t. User-derived types for #cairo_cache_entry_t must
 * have a #cairo_cache_entry_t as their first field. For example:
 *
 * 	typedef _my_entry {
 *	    cairo_cache_entry_t base;
 *	    ... Remainder of key and value fields here ..
 *	} my_entry_t;
 *
 * which then allows a pointer to my_entry_t to be passed to any of
 * the #cairo_cache_t functions as follows without requiring a cast:
 *
 *	_cairo_cache_insert (cache, &my_entry->base, size);
 *
 * IMPORTANT: The caller is responsible for initializing
 * my_entry->base.hash with a hash code derived from the key.  The
 * essential property of the hash code is that keys_equal must never
 * return %TRUE for two keys that have different hashes. The best hash
 * code will reduce the frequency of two keys with the same code for
 * which keys_equal returns %FALSE.
 *
 * The user must also initialize my_entry->base.size to indicate
 * the size of the current entry. What units to use for size is
 * entirely up to the caller, (though the same units must be used for
 * the max_size parameter passed to _cairo_cache_create()). If all
 * entries are close to the same size, the simplest thing to do is to
 * just use units of "entries", (eg. set size==1 in all entries and
 * set max_size to the number of entries which you want to be saved
 * in the cache).
 *
 * Which parts of the entry make up the "key" and which part make up
 * the value are entirely up to the caller, (as determined by the
 * computation going into base.hash as well as the keys_equal
 * function). A few of the #cairo_cache_t functions accept an entry which
 * will be used exclusively as a "key", (indicated by a parameter name
 * of key). In these cases, the value-related fields of the entry need
 * not be initialized if so desired.
 **/
typedef struct _cairo_cache_entry {
    uintptr_t hash;
    unsigned long size;
} cairo_cache_entry_t;

typedef cairo_bool_t (*cairo_cache_predicate_func_t) (const void *entry);

struct _cairo_cache {
    cairo_hash_table_t *hash_table;

    cairo_cache_predicate_func_t predicate;
    cairo_destroy_func_t entry_destroy;

    unsigned long max_size;
    unsigned long size;

    int freeze_count;
};

typedef cairo_bool_t
(*cairo_cache_keys_equal_func_t) (const void *key_a, const void *key_b);

typedef void
(*cairo_cache_callback_func_t) (void *entry,
				void *closure);

cairo_private cairo_status_t
_cairo_cache_init (cairo_cache_t *cache,
	           cairo_cache_keys_equal_func_t keys_equal,
		   cairo_cache_predicate_func_t  predicate,
		   cairo_destroy_func_t	   entry_destroy,
		   unsigned long		   max_size);

cairo_private void
_cairo_cache_fini (cairo_cache_t *cache);

cairo_private void
_cairo_cache_freeze (cairo_cache_t *cache);

cairo_private void
_cairo_cache_thaw (cairo_cache_t *cache);

cairo_private void *
_cairo_cache_lookup (cairo_cache_t	  *cache,
		     cairo_cache_entry_t  *key);

cairo_private cairo_status_t
_cairo_cache_insert (cairo_cache_t	 *cache,
		     cairo_cache_entry_t *entry);

cairo_private void
_cairo_cache_remove (cairo_cache_t	 *cache,
		     cairo_cache_entry_t *entry);

cairo_private void
_cairo_cache_foreach (cairo_cache_t		 *cache,
		      cairo_cache_callback_func_t cache_callback,
		      void			 *closure);

#endif