Introduce simple cache memory management

libass' cache was basically unmanaged; it would grow without any limits,
depending on how complex the subtitles are.  Introduce a simple limiting
that resets the cache if certain limits are exceeded.  The bitmap cache
is limited to approx. 50 MB size by default, while the glyph cache
allows storing up to 1000 glyphs by default.  A few tests with rather
heavily softsubbed fansubs show that these limits are fine.
The API was extended with the function ass_set_cache_limits which allows
modification of these limits.

1 files changed, 39 insertions, 5 deletions

diff --git a/libass/ass_render.c b/libass/ass_render.c
index 5caf8eb..aeeb0ac 100644
--- a/libass/ass_render.c
+++ b/libass/ass_render.c
@@ -44,6 +44,8 @@
 #define MAX_BE 127
 #define SUBPIXEL_MASK 63
 #define SUBPIXEL_ACCURACY 7    // d6 mask for subpixel accuracy adjustment
+#define GLYPH_CACHE_MAX 1000
+#define BITMAP_CACHE_MAX_SIZE 50 * 1048576;
 
 static int last_render_id = 0;
 
@@ -206,6 +208,8 @@ typedef struct cache_store_s {
     hashmap_t *glyph_cache;
     hashmap_t *bitmap_cache;
     hashmap_t *composite_cache;
+    size_t glyph_max;
+    size_t bitmap_max_size;
 } cache_store_t;
 
 struct ass_renderer_s {
@@ -319,6 +323,8 @@ ass_renderer_t *ass_renderer_init(ass_library_t *library)
     priv->cache.bitmap_cache = ass_bitmap_cache_init(library);
     priv->cache.composite_cache = ass_composite_cache_init(library);
     priv->cache.glyph_cache = ass_glyph_cache_init(library);
+    priv->cache.glyph_max = GLYPH_CACHE_MAX;
+    priv->cache.bitmap_max_size = BITMAP_CACHE_MAX_SIZE;
 
     priv->text_info.max_glyphs = MAX_GLYPHS_INITIAL;
     priv->text_info.max_lines = MAX_LINES_INITIAL;
@@ -335,6 +341,14 @@ ass_renderer_t *ass_renderer_init(ass_library_t *library)
     return priv;
 }
 
+void ass_set_cache_limits(ass_renderer_t *render_priv, int glyph_max,
+                          int bitmap_max)
+{
+    render_priv->cache.glyph_max = glyph_max ? glyph_max : GLYPH_CACHE_MAX;
+    render_priv->cache.bitmap_max_size = bitmap_max ? 1048576 * bitmap_max :
+                                         BITMAP_CACHE_MAX_SIZE;
+}
+
 static void free_list_clear(ass_renderer_t *render_priv)
 {
     if (render_priv->free_head) {
@@ -2873,6 +2887,7 @@ ass_render_event(ass_renderer_t *render_priv, ass_event_t *event,
         }
     }
 
+
     if (text_info->length == 0) {
         // no valid symbols in the event; this can be smth like {comment}
         free_render_context(render_priv);
@@ -3223,17 +3238,18 @@ static int
 ass_start_frame(ass_renderer_t *render_priv, ass_track_t *track,
                 long long now)
 {
-    if (render_priv->library != track->library)
-        return 1;
-
-    free_list_clear(render_priv);
-
     ass_settings_t *settings_priv = &render_priv->settings;
+    cache_store_t *cache = &render_priv->cache;
 
     if (!render_priv->settings.frame_width
         && !render_priv->settings.frame_height)
         return 1;               // library not initialized
 
+    if (render_priv->library != track->library)
+        return 1;
+
+    free_list_clear(render_priv);
+
     if (track->n_events == 0)
         return 1;               // nothing to do
 
@@ -3274,6 +3290,24 @@ ass_start_frame(ass_renderer_t *render_priv, ass_track_t *track,
     render_priv->prev_images_root = render_priv->images_root;
     render_priv->images_root = 0;
 
+    if (cache->bitmap_cache->cache_size > cache->bitmap_max_size) {
+        ass_msg(render_priv->library, MSGL_V,
+                "Hitting hard bitmap cache limit (was: %ld bytes), "
+                "resetting.", (long) cache->bitmap_cache->cache_size);
+        cache->bitmap_cache = ass_bitmap_cache_reset(cache->bitmap_cache);
+        cache->composite_cache = ass_composite_cache_reset(
+            cache->composite_cache);
+        ass_free_images(render_priv->prev_images_root);
+        render_priv->prev_images_root = 0;
+    }
+
+    if (cache->glyph_cache->count > cache->glyph_max) {
+        ass_msg(render_priv->library, MSGL_V,
+            "Hitting hard glyph cache limit (was: %ld glyphs), resetting.",
+            (long) cache->glyph_cache->count);
+        cache->glyph_cache = ass_glyph_cache_reset(cache->glyph_cache);
+    }
+
     return 0;
 }