caps: improve _do_simplify

Make gst_caps_do_simplify() take ownership of the input caps and produce a
simplified output caps. This removes the requirement of having writable input
caps and the method can make the caps writable only when needed.

gst/gstcaps.c

@@ -1498,7 +1498,7 @@ gst_caps_subtract (GstCaps * minuend, GstCaps * subtrahend)
   }
 
   gst_caps_unref (src);
-  gst_caps_do_simplify (dest);
+  dest = gst_caps_do_simplify (dest);
   return dest;
 }
 
@@ -1575,7 +1575,7 @@ gst_caps_union (GstCaps * caps1, GstCaps * caps2)
   dest1 = _gst_caps_copy (caps1);
   gst_caps_append (dest1, gst_caps_ref (caps2));
 
-  gst_caps_do_simplify (dest1);
+  dest1 = gst_caps_do_simplify (dest1);
   return dest1;
 }
 
@@ -1765,36 +1765,36 @@ gst_caps_switch_structures (GstCaps * caps, GstStructure * old,
 
 /**
  * gst_caps_do_simplify:
- * @caps: a #GstCaps to simplify
+ * @caps: (transfer full): a #GstCaps to simplify
  *
  * Modifies the given @caps inplace into a representation that represents the
  * same set of formats, but in a simpler form.  Component structures that are
  * identical are merged.  Component structures that have values that can be
  * merged are also merged.
  *
- * Returns: TRUE, if the caps could be simplified
+ * Returns: The simplified caps.
  */
-gboolean
+GstCaps *
 gst_caps_do_simplify (GstCaps * caps)
 {
   GstStructure *simplify, *compare, *result = NULL;
   gint i, j, start;
-  gboolean changed = FALSE;
 
-  g_return_val_if_fail (caps != NULL, FALSE);
-  g_return_val_if_fail (IS_WRITABLE (caps), FALSE);
+  g_return_val_if_fail (GST_IS_CAPS (caps), NULL);
 
-  if (gst_caps_get_size (caps) < 2)
-    return FALSE;
+  if (gst_caps_is_fixed (caps))
+    return caps;
+
+  caps = gst_caps_make_writable (caps);
 
   g_ptr_array_sort (GST_CAPS_ARRAY (caps), gst_caps_compare_structures);
 
   start = GST_CAPS_LEN (caps) - 1;
-  for (i = GST_CAPS_LEN (caps) - 1; i >= 0; i--) {
+  for (i = start; i >= 0; i--) {
     simplify = gst_caps_get_structure_unchecked (caps, i);
+    compare = gst_caps_get_structure_unchecked (caps, start);
     if (gst_structure_get_name_id (simplify) !=
-        gst_structure_get_name_id (gst_caps_get_structure_unchecked (caps,
-                start)))
+        gst_structure_get_name_id (compare))
       start = i;
     for (j = start; j >= 0; j--) {
       if (j == i)
@@ -1813,16 +1813,10 @@ gst_caps_do_simplify (GstCaps * caps)
           start--;
           break;
         }
-        changed = TRUE;
       }
     }
   }
-
-  if (!changed)
-    return FALSE;
-
-  /* gst_caps_do_simplify (caps); */
-  return TRUE;
+  return caps;
 }
 
 /**

gst/gstcaps.h

@@ -438,7 +438,7 @@ GstCaps *         gst_caps_subtract		   (GstCaps *minuend,
 GstCaps *         gst_caps_union                   (GstCaps *caps1,
 						    GstCaps *caps2) G_GNUC_WARN_UNUSED_RESULT;
 GstCaps *         gst_caps_normalize               (GstCaps *caps) G_GNUC_WARN_UNUSED_RESULT;
-gboolean          gst_caps_do_simplify             (GstCaps *caps);
+GstCaps *         gst_caps_do_simplify             (GstCaps *caps) G_GNUC_WARN_UNUSED_RESULT;
 
 GstCaps *         gst_caps_fixate                  (GstCaps *caps) G_GNUC_WARN_UNUSED_RESULT;
 

gst/gstregistrychunks.c

@@ -321,16 +321,13 @@ gst_registry_chunks_save_feature (GList ** list, GstPluginFeature * feature)
     }
     /* save caps */
     if (factory->caps) {
-      /* we copy the caps here so we can simplify them before saving. This
-       * is a lot faster when loading them later on */
-      if (!gst_caps_is_fixed (factory->caps)) {
-        GstCaps *copy = gst_caps_copy (factory->caps);
-        gst_caps_do_simplify (copy);
-        str = gst_caps_to_string (copy);
-        gst_caps_unref (copy);
-      } else {
-        str = gst_caps_to_string (factory->caps);
-      }
+      GstCaps *fcaps = gst_caps_ref (factory->caps);
+      /* we simplify the caps before saving. This is a lot faster
+       * when loading them later on */
+      fcaps = gst_caps_do_simplify (fcaps);
+      str = gst_caps_to_string (fcaps);
+      gst_caps_unref (fcaps);
+
       gst_registry_chunks_save_string (list, str);
     } else {
       gst_registry_chunks_save_const_string (list, "");

plugins/elements/gstcapsfilter.c

@@ -298,8 +298,7 @@ gst_capsfilter_prepare_buf (GstBaseTransform * trans, GstBuffer * input,
       g_return_val_if_fail (out_caps != NULL, GST_FLOW_ERROR);
     }
 
-    out_caps = gst_caps_make_writable (out_caps);
-    gst_caps_do_simplify (out_caps);
+    out_caps = gst_caps_do_simplify (out_caps);
 
     if (gst_caps_is_fixed (out_caps) && !gst_caps_is_empty (out_caps)) {
       GST_DEBUG_OBJECT (trans, "Have fixed output caps %"

tests/check/gst/gstcaps.c

@@ -190,16 +190,14 @@ check_string_list (const GValue * format_value)
 GST_START_TEST (test_simplify)
 {
   GstStructure *s1;
-  gboolean did_simplify;
   GstCaps *caps;
 
   caps = gst_caps_from_string (non_simple_caps_string);
   fail_unless (caps != NULL,
       "gst_caps_from_string (non_simple_caps_string) failed");
 
-  did_simplify = gst_caps_do_simplify (caps);
-  fail_unless (did_simplify == TRUE,
-      "gst_caps_do_simplify() should have worked");
+  caps = gst_caps_do_simplify (caps);
+  fail_unless (caps != NULL, "gst_caps_do_simplify() should have worked");
 
   /* check simplified caps, should be:
    *