cache: switch to gradual cache clearing

Advantages over the old algorithm consist of the following.
 * There are no glitches due to full cache clearing.
   Items are arranged into linked list ordered by time of last use.
   Only the oldest items get deleted at the clearing event.
 * Each item now keeps track of number of references.
   Referenced cache values are immune to clearing.
 * Reduced amount of total cache memory for the same performance.
 * Reduced number of memory allocations per cache item.

1 files changed, 8 insertions, 3 deletions

diff --git a/libass/ass_cache.h b/libass/ass_cache.h
index af814ac..63e9e59 100644
--- a/libass/ass_cache.h
+++ b/libass/ass_cache.h
@@ -106,11 +106,16 @@ typedef struct {
 Cache *ass_cache_create(HashFunction hash_func, HashCompare compare_func,
                         CacheItemDestructor destruct_func, ItemSize size_func,
                         size_t key_size, size_t value_size);
-void *ass_cache_put(Cache *cache, void *key, void *value);
-void *ass_cache_get(Cache *cache, void *key);
-int ass_cache_empty(Cache *cache, size_t max_size);
+bool ass_cache_get(Cache *cache, void *key, void *value_ptr);
+void *ass_cache_get_key(void *value);
+void ass_cache_commit(void *value);
+void ass_cache_cancel(void *value);
+void ass_cache_inc_ref(void *value);
+void ass_cache_dec_ref(void *value);
+void ass_cache_cut(Cache *cache, size_t max_size);
 void ass_cache_stats(Cache *cache, size_t *size, unsigned *hits,
                      unsigned *misses, unsigned *count);
+void ass_cache_empty(Cache *cache);
 void ass_cache_done(Cache *cache);
 Cache *ass_font_cache_create(void);
 Cache *ass_outline_cache_create(void);