add "minimise" signal

on end of an image loop, send a "minimise" signal down the pipeline

tilecache listens for this signal on its output and drops the cache

helps reduce ruby memuse

ChangeLog

@@ -7,6 +7,7 @@
 - remove im_rightshift_size(), just a convenience function now
 - vipsthumbnail no longer removes profiles by default
 - much more gentle sharpening in thumbnails
+- added "minimise" signal, used by tilecache to drop
 
 18/6/12 started 7.28.9
 - slightly more memory debugging output

TODO

@@ -1,3 +1,11 @@
+- tile cache doesn't need to copy if request fits within a tile
+
+  though doing a copy means that we can safely drop the cache without leaving
+  dangling pointers
+
+- could jpeg load via memory buffer support minimise too?
+
+
 blocking bugs
 =============
 

libvips/conversion/tilecache.c

@@ -116,16 +116,21 @@ tile_destroy( Tile *tile )
 }
 
 static void
-vips_tile_cache_dispose( GObject *gobject )
+vips_tile_cache_drop_all( VipsTileCache *cache )
 {
-	VipsTileCache *cache = (VipsTileCache *) gobject;
-
 	while( cache->tiles ) {
 		Tile *tile = (Tile *) cache->tiles->data;
 
 		tile_destroy( tile );
 	}
+}
 
+static void
+vips_tile_cache_dispose( GObject *gobject )
+{
+	VipsTileCache *cache = (VipsTileCache *) gobject;
+
+	vips_tile_cache_drop_all( cache );
 	VIPS_FREEF( g_mutex_free, cache->lock );
 
 	G_OBJECT_CLASS( vips_tile_cache_parent_class )->dispose( gobject );
@@ -375,6 +380,14 @@ vips_tile_cache_gen( VipsRegion *or,
 	return( 0 );
 }
 
+static void
+vips_tile_cache_minimise( VipsImage *image, VipsTileCache *cache )
+{
+	printf( "vips_tile_cache_minimise:\n" );
+
+	vips_tile_cache_drop_all( cache );
+}
+
 static int
 vips_tile_cache_build( VipsObject *object )
 {
@@ -394,6 +407,9 @@ vips_tile_cache_build( VipsObject *object )
         vips_demand_hint( conversion->out, 
 		VIPS_DEMAND_STYLE_SMALLTILE, cache->in, NULL );
 
+	g_signal_connect( conversion->out, "minimise", 
+		G_CALLBACK( vips_tile_cache_minimise ), cache );
+
 	if( vips_image_generate( conversion->out,
 		vips_start_one, vips_tile_cache_gen, vips_stop_one, 
 		cache->in, cache ) )

libvips/include/vips/image.h

@@ -419,6 +419,16 @@ typedef struct _VipsImageClass {
 	 */
 	void (*invalidate)( VipsImage *image );
 
+	/* Minimise this pipeline. 
+	 *
+	 * This is triggered (sometimes) at the end of eval to signal that
+	 * we're probably done and that operations involved should try to
+	 * minimise memory use by, for example, dropping caches. 
+	 *
+	 * See vips_tilecache().
+	 */
+	void (*minimise)( VipsImage *image );
+
 } VipsImageClass;
 
 GType vips_image_get_type( void );
@@ -475,6 +485,8 @@ int vips_image_written( VipsImage *image );
 
 void vips_image_invalidate_all( VipsImage *image );
 
+void vips_image_minimise_all( VipsImage *image );
+
 void vips_image_preeval( VipsImage *image );
 void vips_image_eval( VipsImage *image, guint64 processed );
 void vips_image_posteval( VipsImage *image );

libvips/include/vips/internal.h

@@ -93,7 +93,8 @@ int vips_image_open_input( VipsImage *image );
 int vips_image_open_output( VipsImage *image );
 
 void vips__link_break_all( VipsImage *im );
-void *vips__link_map( VipsImage *im, VipsSListMap2Fn fn, void *a, void *b );
+void *vips__link_map( VipsImage *image, gboolean upstream, 
+	VipsSListMap2Fn fn, void *a, void *b );
 
 char *vips__b64_encode( const unsigned char *data, size_t data_length );
 unsigned char *vips__b64_decode( const char *buffer, size_t *data_length );

libvips/iofuncs/generate.c

@@ -181,23 +181,31 @@ vips__link_break_all( VipsImage *image )
 	g_assert( !image->downstream );
 }
 
+typedef struct _LinkMap {
+	gboolean upstream;
+	int *serial;
+	VipsSListMap2Fn fn;
+	void *a;
+	void *b;
+} LinkMap;
+
 static void *
-vips__link_mapp( VipsImage *image, 
+vips__link_mapp( VipsImage *image, LinkMap *map ) 
-	VipsSListMap2Fn fn, int *serial, void *a, void *b )
 {
 	void *res;
 
 	/* Loop?
 	 */
-	if( image->serial == *serial )
+	if( image->serial == *map->serial )
 		return( NULL );
-	image->serial = *serial;
+	image->serial = *map->serial;
 
-	if( (res = fn( image, a, b )) )
+	if( (res = map->fn( image, map->a, map->b )) )
 		return( res );
 
-	return( vips_slist_map4( image->downstream,
+	return( vips_slist_map2( map->upstream ? 
-		(VipsSListMap4Fn) vips__link_mapp, fn, serial, a, b ) );
+		image->upstream : image->downstream,
+		(VipsSListMap2Fn) vips__link_mapp, map, NULL ) );
 }
 
 static void *
@@ -208,27 +216,37 @@ vips__link_map_cb( VipsImage *image, GSList **images )
 	return( NULL );
 }
 
-/* Apply a function to an image and all downstream images, direct and indirect. 
+/* Apply a function to an image and all upstream or downstream images, 
+ * direct and indirect. 
  */
 void *
-vips__link_map( VipsImage *image, VipsSListMap2Fn fn, void *a, void *b )
+vips__link_map( VipsImage *image, gboolean upstream, 
+	VipsSListMap2Fn fn, void *a, void *b )
 {
 	static int serial = 0;
 
+	LinkMap map;
 	GSList *images;
 	GSList *p;
 	void *result;
 
+	serial += 1;
+
+	images = NULL;
+
 	/* The function might do anything, including removing images
 	 * or invalidating other images, so we can't trigger them from within 
 	 * the image loop. Instead we collect a list of images, ref them,
 	 * run the functions, and unref.
 	 */
 
-	serial += 1;
+	map.upstream = upstream;
-	images = NULL;
+	map.serial = &serial;
-	vips__link_mapp( image, 
+	map.fn = (VipsSListMap2Fn) vips__link_map_cb;
-		(VipsSListMap2Fn) vips__link_map_cb, &serial, &images, NULL );
+	map.a = (void *) &images;
+	map.b = NULL;
+
+	vips__link_mapp( image, &map ); 
 
 	for( p = images; p; p = p->next ) 
 		g_object_ref( p->data );

libvips/iofuncs/image.c

@@ -158,6 +158,7 @@ enum {
 	SIG_POSTEVAL,		
 	SIG_WRITTEN,		
 	SIG_INVALIDATE,		
+	SIG_MINIMISE,		
 	SIG_LAST
 };
 
@@ -793,6 +794,12 @@ vips_image_real_invalidate( VipsImage *image )
 	g_mutex_unlock( image->sslock );
 }
 
+static void 
+vips_image_real_minimise( VipsImage *image )
+{
+	VIPS_DEBUG_MSG( "vips_image_real_minimise: %p\n", image );
+}
+
 static void
 vips_image_class_init( VipsImageClass *class )
 {
@@ -829,6 +836,8 @@ vips_image_class_init( VipsImageClass *class )
 
 	class->invalidate = vips_image_real_invalidate;
 
+	class->minimise = vips_image_real_minimise;
+
 	/* Create properties.
 	 */
 
@@ -998,6 +1007,15 @@ vips_image_class_init( VipsImageClass *class )
 		NULL, NULL,
 		g_cclosure_marshal_VOID__VOID,
 		G_TYPE_NONE, 0 );
+
+	vips_image_signals[SIG_MINIMISE] = g_signal_new( "minimise",
+		G_TYPE_FROM_CLASS( class ),
+		G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+		G_STRUCT_OFFSET( VipsImageClass, minimise ), 
+		NULL, NULL,
+		g_cclosure_marshal_VOID__VOID,
+		G_TYPE_NONE, 0 );
+
 }
 
 static void
@@ -1053,16 +1071,52 @@ vips_image_invalidate_all_cb( VipsImage *image )
  * vips_image_invalidate_all:
  * @image: #VipsImage to invalidate
  *
- * Invalidate all pixel caches on an @image and any derived images. The 
+ * Invalidate all pixel caches on an @image and any downstream images, that
- * "invalidate" callback is triggered for all invalidated images.
+ * is, images which depend on this image. 
+ *
+ * The "invalidate" callback is triggered for all invalidated images.
  */
 void
 vips_image_invalidate_all( VipsImage *image )
 {
-	(void) vips__link_map( image, 
+	(void) vips__link_map( image, FALSE,
 		(VipsSListMap2Fn) vips_image_invalidate_all_cb, NULL, NULL );
 }
 
+void
+vips_image_minimise( VipsImage *image )
+{
+	VIPS_DEBUG_MSG( "vips_image_minimise: %p\n", image );
+
+	g_signal_emit( image, vips_image_signals[SIG_MINIMISE], 0 );
+}
+
+static void *
+vips_image_minimise_all_cb( VipsImage *image )
+{
+	vips_image_minimise( image );
+
+	return( NULL );
+}
+
+/**
+ * vips_image_minimise_all:
+ * @image: #VipsImage to minimise
+ *
+ * Minimise memory use on this image and any upstream images, that is, images
+ * which this image depends upon. 
+ *
+ * The "minimise" callback is triggered for all minimised images.
+ */
+void 
+vips_image_minimise_all( VipsImage *image )
+{
+	printf( "vips_image_minimise_all:\n" ); 
+
+	(void) vips__link_map( image, TRUE,
+		(VipsSListMap2Fn) vips_image_minimise_all_cb, NULL, NULL );
+}
+
 /* Attach a new time struct, if necessary, and reset it.
  */
 static int

libvips/iofuncs/threadpool.c

@@ -913,6 +913,10 @@ vips_threadpool_run( VipsImage *im,
 
 	vips_threadpool_free( pool );
 
+	/* Ask the pipeline to drop into low-mem-use mode now we're done.
+	 */
+	vips_image_minimise_all( im );
+
 	return( result );
 }