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#include <glib.h>
#include "gimprc.h"
#include "tile_cache.h"
#include "tile_swap.h"
/* This is the percentage of the maximum cache size that should be cleared
* from the cache when an eviction is necessary
*/
#define FREE_QUANTUM 0.1
static void tile_cache_init (void);
static void tile_cache_zorch_next (void);
static guint tile_cache_hash (Tile *tile);
static int initialize = TRUE;
static GHashTable *tile_hash_table = NULL;
static GList *tile_list_head = NULL;
static GList *tile_list_tail = NULL;
static unsigned long max_tile_size = TILE_WIDTH * TILE_HEIGHT * 4;
static unsigned long cur_cache_size = 0;
static unsigned long max_cache_size = 0;
void
tile_cache_insert (Tile *tile)
{
GList *tmp;
if (initialize)
tile_cache_init ();
/* First check and see if the tile is already
* in the cache. In that case we will simply place
* it at the end of the tile list to indicate that
* it was the most recently accessed tile.
*/
tmp = g_hash_table_lookup (tile_hash_table, tile);
if (tmp)
{
/* The tile was already in the cache. Place it at
* the end of the tile list.
*/
if (tmp == tile_list_tail)
tile_list_tail = tile_list_tail->prev;
tile_list_head = g_list_remove_link (tile_list_head, tmp);
if (!tile_list_head)
tile_list_tail = NULL;
g_list_free (tmp);
/* Remove the old reference to the tiles list node
* in the tile hash table.
*/
g_hash_table_remove (tile_hash_table, tile);
tile_list_tail = g_list_append (tile_list_tail, tile);
if (!tile_list_head)
tile_list_head = tile_list_tail;
tile_list_tail = g_list_last (tile_list_tail);
/* Add the tiles list node to the tile hash table. The
* list node is indexed by the tile itself. This makes
* for a quick lookup of which list node the tile is in.
*/
g_hash_table_insert (tile_hash_table, tile, tile_list_tail);
}
else
{
/* The tile was not in the cache. First check and see
* if there is room in the cache. If not then we'll have
* to make room first. Note: it might be the case that the
* cache is smaller than the size of a tile in which case
* it won't be possible to put it in the cache.
*/
if ((cur_cache_size + max_tile_size) > max_cache_size)
{
while (tile_list_head && (cur_cache_size + max_cache_size * FREE_QUANTUM) > max_cache_size)
tile_cache_zorch_next ();
if ((cur_cache_size + max_tile_size) > max_cache_size)
return;
}
/* Place the tile at the end of the tile list.
*/
tile_list_tail = g_list_append (tile_list_tail, tile);
if (!tile_list_head)
tile_list_head = tile_list_tail;
tile_list_tail = g_list_last (tile_list_tail);
/* Add the tiles list node to the tile hash table.
*/
g_hash_table_insert (tile_hash_table, tile, tile_list_tail);
/* Note the increase in the number of bytes the cache
* is referencing.
*/
cur_cache_size += tile_size (tile);
/* Reference the tile so that it won't be swapped out
* to disk. Swap the tile in if necessary.
* "tile_ref" cannot be used here since it calls this
* function.
*/
tile->ref_count += 1;
{
extern int tile_ref_count;
tile_ref_count += 1;
}
if (tile->ref_count == 1)
{
tile_swap_in (tile);
/* the tile must be clean */
tile->dirty = FALSE;
}
}
}
void
tile_cache_flush (Tile *tile)
{
GList *tmp;
if (initialize)
tile_cache_init ();
/* Find where the tile is in the cache.
*/
tmp = g_hash_table_lookup (tile_hash_table, tile);
if (tmp)
{
/* If the tile is in the cache, then remove it from the
* tile list.
*/
if (tmp == tile_list_tail)
tile_list_tail = tile_list_tail->prev;
tile_list_head = g_list_remove_link (tile_list_head, tmp);
if (!tile_list_head)
tile_list_tail = NULL;
g_list_free (tmp);
/* Remove the tile from the tile hash table.
*/
g_hash_table_remove (tile_hash_table, tile);
/* Note the decrease in the number of bytes the cache
* is referencing.
*/
cur_cache_size -= tile_size (tile);
/* Unreference the tile.
* "tile_unref" may be used here since it does not call
* this function (or any of the cache functions).
*/
tile_unref (tile, FALSE);
}
}
void
tile_cache_set_size (unsigned long cache_size)
{
if (initialize)
tile_cache_init ();
max_cache_size = cache_size;
if (max_cache_size >= max_tile_size)
{
while (cur_cache_size > max_cache_size)
tile_cache_zorch_next ();
}
}
static void
tile_cache_init ()
{
if (initialize)
{
initialize = FALSE;
tile_hash_table = g_hash_table_new ((GHashFunc) tile_cache_hash, NULL);
max_cache_size = tile_cache_size;
}
}
static void
tile_cache_zorch_next ()
{
if (tile_list_head)
tile_cache_flush ((Tile*) tile_list_head->data);
}
static guint
tile_cache_hash (Tile *tile)
{
return (gulong) tile;
}
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