[mime-data] Copy a reference to the mime-data on snapshotting.

Instead of doing a full-copy of the mime data (which can be 10K-100K,
or even larger) just copy a reference to the original mime to the
snapshot surface (as suggested by Behdad).

src/cairo-surface-fallback.c

@@ -1035,8 +1035,6 @@ _cairo_surface_fallback_snapshot (cairo_surface_t *surface)
     cairo_status_t status;
     cairo_surface_pattern_t pattern;
     cairo_image_surface_t *image;
-    const unsigned char *mime_data;
-    unsigned int mime_data_length;
     void *image_extra;
 
     status = _cairo_surface_acquire_source_image (surface,
@@ -1081,28 +1079,11 @@ _cairo_surface_fallback_snapshot (cairo_surface_t *surface)
      * For now, just copy "image/jpeg", but in future we should construct
      * an array of known types and iterate.
      */
-    cairo_surface_get_mime_data (surface, CAIRO_MIME_TYPE_JPEG,
-				 &mime_data, &mime_data_length);
-    if (mime_data != NULL) {
-	unsigned char *mime_data_copy;
-
-	mime_data_copy = malloc (mime_data_length);
-	if (mime_data == NULL) {
-	    cairo_surface_destroy (snapshot);
-	    return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
-	}
-	memcpy (mime_data_copy, mime_data, mime_data_length);
-
-	status = cairo_surface_set_mime_data (snapshot,
-					      CAIRO_MIME_TYPE_JPEG,
-					      mime_data_copy,
-					      mime_data_length,
-					      free);
-	if (status) {
-	    free (mime_data_copy);
-	    cairo_surface_destroy (snapshot);
-	    return _cairo_surface_create_in_error (status);
-	}
+    status = _cairo_surface_copy_mime_data (snapshot, surface,
+	                                    CAIRO_MIME_TYPE_JPEG);
+    if (status) {
+	cairo_surface_destroy (snapshot);
+	return _cairo_surface_create_in_error (status);
     }
 
     snapshot->is_snapshot = TRUE;

src/cairo-surface.c

@@ -637,6 +637,9 @@ _cairo_mime_data_destroy (void *ptr)
 {
     cairo_mime_data_t *mime_data = ptr;
 
+    if (! _cairo_reference_count_dec_and_test (&mime_data->ref_count))
+	return;
+
     if (mime_data->destroy && mime_data->data)
 	mime_data->destroy (mime_data->data);
 
@@ -679,36 +682,64 @@ cairo_surface_set_mime_data (cairo_surface_t		*surface,
     if (status)
 	return _cairo_surface_set_error (surface, status);
 
-    mime_data = _cairo_user_data_array_get_data (&surface->user_data,
-						 (cairo_user_data_key_t *) mime_type);
-    if (mime_data != NULL) {
-	if (mime_data->destroy && mime_data->data)
-	    mime_data->destroy (mime_data->data);
+    mime_data = malloc (sizeof (cairo_mime_data_t));
+    if (mime_data == NULL)
+	return _cairo_surface_set_error (surface, _cairo_error (CAIRO_STATUS_NO_MEMORY));
 
-	mime_data->data = (unsigned char *) data;
-	mime_data->length = length;
-	mime_data->destroy = destroy;
-    } else {
-	mime_data = malloc (sizeof (cairo_mime_data_t));
-	if (mime_data == NULL)
-	    return _cairo_surface_set_error (surface, _cairo_error (CAIRO_STATUS_NO_MEMORY));
+    CAIRO_REFERENCE_COUNT_INIT (&mime_data->ref_count, 1);
 
-	mime_data->data = (unsigned char *) data;
-	mime_data->length = length;
-	mime_data->destroy = destroy;
+    mime_data->data = (unsigned char *) data;
+    mime_data->length = length;
+    mime_data->destroy = destroy;
 
-	status = _cairo_user_data_array_set_data (&surface->user_data,
-						  (cairo_user_data_key_t *) mime_type,
-						  mime_data,
-						  _cairo_mime_data_destroy);
-	if (status)
-	    return _cairo_surface_set_error (surface, status);
-    }
+    status = _cairo_user_data_array_set_data (&surface->user_data,
+					      (cairo_user_data_key_t *) mime_type,
+					      mime_data,
+					      _cairo_mime_data_destroy);
+    if (status)
+	return _cairo_surface_set_error (surface, status);
 
     return CAIRO_STATUS_SUCCESS;
 }
 slim_hidden_def (cairo_surface_set_mime_data);
 
+cairo_status_t
+_cairo_surface_copy_mime_data (cairo_surface_t *dst,
+			       cairo_surface_t *src,
+			       const char *mime_type)
+{
+    cairo_status_t status;
+    cairo_mime_data_t *mime_data;
+
+    if (dst->status)
+	return dst->status;
+
+    if (src->status)
+	return _cairo_surface_set_error (dst, src->status);
+
+    status = _cairo_intern_string (&mime_type, -1);
+    if (status)
+	return _cairo_surface_set_error (dst, status);
+
+    mime_data = _cairo_user_data_array_get_data (&src->user_data,
+						 (cairo_user_data_key_t *) mime_type);
+    if (mime_data == NULL)
+	return CAIRO_STATUS_SUCCESS;
+
+    _cairo_reference_count_inc (&mime_data->ref_count);
+
+    status = _cairo_user_data_array_set_data (&dst->user_data,
+					      (cairo_user_data_key_t *) mime_type,
+					      mime_data,
+					      _cairo_mime_data_destroy);
+    if (status) {
+	_cairo_mime_data_destroy (mime_data);
+	return _cairo_surface_set_error (dst, status);
+    }
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
 /**
  * _cairo_surface_set_font_options:
  * @surface: a #cairo_surface_t

src/cairo-types-private.h

@@ -41,6 +41,7 @@
 
 #include "cairo.h"
 #include "cairo-fixed-type-private.h"
+#include "cairo-reference-count-private.h"
 
 typedef struct _cairo_array cairo_array_t;
 typedef struct _cairo_cache cairo_cache_t;
@@ -344,6 +345,7 @@ typedef enum _cairo_image_transparency {
 } cairo_image_transparency_t;
 
 struct _cairo_mime_data {
+    cairo_reference_count_t ref_count;
     unsigned char *data;
     unsigned int length;
     cairo_destroy_func_t destroy;

src/cairoint.h

@@ -1665,6 +1665,11 @@ _cairo_stroke_style_max_distance_from_path (const cairo_stroke_style_t *style,
 cairo_private cairo_surface_t *
 _cairo_surface_create_in_error (cairo_status_t status);
 
+cairo_private cairo_status_t
+_cairo_surface_copy_mime_data (cairo_surface_t *dst,
+			       cairo_surface_t *src,
+			       const char *mime_type);
+
 cairo_private cairo_status_t
 _cairo_surface_set_error (cairo_surface_t	*surface,
 			  cairo_status_t	 status);