GstPad: Add new pad linking method with configurable checks.

To be used for cases where we don't need all checks to be validated.

API: gst_pad_link_full
API: GstPadLinkCheck

https://bugzilla.gnome.org/show_bug.cgi?id=622504

docs/gst/gstreamer-sections.txt

@@ -1343,6 +1343,8 @@ GstPadFlags
 GstPadLinkReturn
 GST_PAD_LINK_FAILED
 GST_PAD_LINK_SUCCESSFUL
+GstPadLinkCheck
+GST_PAD_LINK_CHECK_DEFAULT
 GstFlowReturn
 GstActivateMode
 
@@ -1354,6 +1356,7 @@ gst_pad_get_parent_element
 gst_pad_get_pad_template
 
 gst_pad_link
+gst_pad_link_full
 gst_pad_unlink
 gst_pad_is_linked
 gst_pad_can_link
@@ -1524,6 +1527,7 @@ GST_TYPE_PAD
 GST_TYPE_PAD_DIRECTION
 GST_TYPE_PAD_FLAGS
 GST_TYPE_PAD_LINK_RETURN
+GST_TYPE_PAD_LINK_CHECK
 GST_TYPE_PAD_PRESENCE
 GST_TYPE_FLOW_RETURN
 GST_TYPE_ACTIVATE_MODE
@@ -1533,6 +1537,7 @@ gst_pad_get_type
 gst_pad_direction_get_type
 gst_pad_flags_get_type
 gst_pad_link_return_get_type
+gst_pad_link_check_get_type
 gst_pad_presence_get_type
 gst_flow_return_get_type
 gst_activate_mode_get_type

gst/gst.c

@@ -713,6 +713,7 @@ init_post (GOptionContext * context, GOptionGroup * group, gpointer data,
   g_type_class_ref (gst_message_type_get_type ());
   g_type_class_ref (gst_mini_object_flags_get_type ());
   g_type_class_ref (gst_pad_link_return_get_type ());
+  g_type_class_ref (gst_pad_link_check_get_type ());
   g_type_class_ref (gst_flow_return_get_type ());
   g_type_class_ref (gst_activate_mode_get_type ());
   g_type_class_ref (gst_pad_direction_get_type ());
@@ -1079,6 +1080,7 @@ gst_deinit (void)
   g_type_class_unref (g_type_class_peek (gst_message_type_get_type ()));
   g_type_class_unref (g_type_class_peek (gst_mini_object_flags_get_type ()));
   g_type_class_unref (g_type_class_peek (gst_pad_link_return_get_type ()));
+  g_type_class_unref (g_type_class_peek (gst_pad_link_check_get_type ()));
   g_type_class_unref (g_type_class_peek (gst_flow_return_get_type ()));
   g_type_class_unref (g_type_class_peek (gst_activate_mode_get_type ()));
   g_type_class_unref (g_type_class_peek (gst_pad_direction_get_type ()));

gst/gstpad.c

@@ -1775,14 +1775,28 @@ gst_pad_is_linked (GstPad * pad)
  * pads
  */
 static gboolean
-gst_pad_link_check_compatible_unlocked (GstPad * src, GstPad * sink)
+gst_pad_link_check_compatible_unlocked (GstPad * src, GstPad * sink,
+    GstPadLinkCheck flags)
 {
-  GstCaps *srccaps;
+  GstCaps *srccaps = NULL;
-  GstCaps *sinkcaps;
+  GstCaps *sinkcaps = NULL;
   gboolean compatible = FALSE;
 
-  srccaps = gst_pad_get_caps_unlocked (src);
+  if (!(flags & (GST_PAD_LINK_CHECK_CAPS | GST_PAD_LINK_CHECK_TEMPLATE_CAPS)))
-  sinkcaps = gst_pad_get_caps_unlocked (sink);
+    return TRUE;
+
+  /* Doing the expensive caps checking takes priority over only checking the template caps */
+  if (flags & GST_PAD_LINK_CHECK_CAPS) {
+    srccaps = gst_pad_get_caps_unlocked (src);
+    sinkcaps = gst_pad_get_caps_unlocked (sink);
+  } else {
+    if (GST_PAD_PAD_TEMPLATE (src))
+      srccaps =
+          gst_caps_ref (GST_PAD_TEMPLATE_CAPS (GST_PAD_PAD_TEMPLATE (src)));
+    if (GST_PAD_PAD_TEMPLATE (sink))
+      sinkcaps =
+          gst_caps_ref (GST_PAD_TEMPLATE_CAPS (GST_PAD_PAD_TEMPLATE (sink)));
+  }
 
   GST_CAT_DEBUG (GST_CAT_CAPS, "src caps %" GST_PTR_FORMAT, srccaps);
   GST_CAT_DEBUG (GST_CAT_CAPS, "sink caps %" GST_PTR_FORMAT, sinkcaps);
@@ -1880,7 +1894,7 @@ wrong_grandparents:
 /* call with the two pads unlocked, when this function returns GST_PAD_LINK_OK,
  * the two pads will be locked in the srcpad, sinkpad order. */
 static GstPadLinkReturn
-gst_pad_link_prepare (GstPad * srcpad, GstPad * sinkpad)
+gst_pad_link_prepare (GstPad * srcpad, GstPad * sinkpad, GstPadLinkCheck flags)
 {
   GST_CAT_INFO (GST_CAT_PADS, "trying to link %s:%s and %s:%s",
       GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));
@@ -1897,11 +1911,12 @@ gst_pad_link_prepare (GstPad * srcpad, GstPad * sinkpad)
 
   /* check hierarchy, pads can only be linked if the grandparents
    * are the same. */
-  if (!gst_pad_link_check_hierarchy (srcpad, sinkpad))
+  if ((flags & GST_PAD_LINK_CHECK_HIERARCHY)
+      && !gst_pad_link_check_hierarchy (srcpad, sinkpad))
     goto wrong_hierarchy;
 
   /* check pad caps for non-empty intersection */
-  if (!gst_pad_link_check_compatible_unlocked (srcpad, sinkpad))
+  if (!gst_pad_link_check_compatible_unlocked (srcpad, sinkpad, flags))
     goto no_format;
 
   /* FIXME check pad scheduling for non-empty intersection */
@@ -1970,7 +1985,7 @@ gst_pad_can_link (GstPad * srcpad, GstPad * sinkpad)
   /* gst_pad_link_prepare does everything for us, we only release the locks
    * on the pads that it gets us. If this function returns !OK the locks are not
    * taken anymore. */
-  result = gst_pad_link_prepare (srcpad, sinkpad);
+  result = gst_pad_link_prepare (srcpad, sinkpad, GST_PAD_LINK_CHECK_DEFAULT);
   if (result != GST_PAD_LINK_OK)
     goto done;
 
@@ -1982,19 +1997,22 @@ done:
 }
 
 /**
- * gst_pad_link:
+ * gst_pad_link_full:
  * @srcpad: the source #GstPad to link.
  * @sinkpad: the sink #GstPad to link.
+ * @flags: the checks to validate when linking
  *
  * Links the source pad and the sink pad.
  *
  * Returns: A result code indicating if the connection worked or
  *          what went wrong.
  *
+ * Since: 0.10.30
+ *
  * MT Safe.
  */
 GstPadLinkReturn
-gst_pad_link (GstPad * srcpad, GstPad * sinkpad)
+gst_pad_link_full (GstPad * srcpad, GstPad * sinkpad, GstPadLinkCheck flags)
 {
   GstPadLinkReturn result;
   GstElement *parent;
@@ -2018,7 +2036,7 @@ gst_pad_link (GstPad * srcpad, GstPad * sinkpad)
   }
 
   /* prepare will also lock the two pads */
-  result = gst_pad_link_prepare (srcpad, sinkpad);
+  result = gst_pad_link_prepare (srcpad, sinkpad, flags);
 
   if (result != GST_PAD_LINK_OK)
     goto done;
@@ -2079,6 +2097,24 @@ done:
   return result;
 }
 
+/**
+ * gst_pad_link:
+ * @srcpad: the source #GstPad to link.
+ * @sinkpad: the sink #GstPad to link.
+ *
+ * Links the source pad and the sink pad.
+ *
+ * Returns: A result code indicating if the connection worked or
+ *          what went wrong.
+ *
+ * MT Safe.
+ */
+GstPadLinkReturn
+gst_pad_link (GstPad * srcpad, GstPad * sinkpad)
+{
+  return gst_pad_link_full (srcpad, sinkpad, GST_PAD_LINK_CHECK_DEFAULT);
+}
+
 static void
 gst_pad_set_pad_template (GstPad * pad, GstPadTemplate * templ)
 {

gst/gstpad.h

@@ -177,6 +177,35 @@ typedef enum {
 G_CONST_RETURN gchar*	gst_flow_get_name	(GstFlowReturn ret);
 GQuark			gst_flow_to_quark	(GstFlowReturn ret);
 
+/**
+ * GstPadLinkCheck:
+ * @GST_PAD_LINK_CHECK_NOTHING: Don't check hierarchy or compatibily
+ * @GST_PAD_LINK_CHECK_HIERARCHY: Check the pads have same parents/grandparents
+ * @GST_PAD_LINK_CHECK_TEMPLATE_CAPS: Check if the pads are compatible by using their
+ * template caps.
+ * @GST_PAD_LINK_CHECK_CAPS: Check if the pads are compatible by checking their full caps
+ *
+ * The amount of check to be done when linking pads.
+ *
+ * Since: 0.10.30
+ */
+
+typedef enum {
+  GST_PAD_LINK_CHECK_NOTHING       = 1 << 0,
+  GST_PAD_LINK_CHECK_HIERARCHY     = 1 << 1,
+  GST_PAD_LINK_CHECK_TEMPLATE_CAPS = 1 << 2,
+  GST_PAD_LINK_CHECK_CAPS          = 1 << 3,
+} GstPadLinkCheck;
+
+/**
+ * GST_PAD_LINK_CHECK_DEFAULT:
+ *
+ * The default checks done when linking pads (i.e. the ones used by #gst_pad_link.
+ *
+ * Since: 0.10.30
+ */
+#define GST_PAD_LINK_CHECK_DEFAULT (GST_PAD_LINK_CHECK_HIERARCHY | GST_PAD_LINK_CHECK_CAPS)
+
 /**
  * GstActivateMode:
  * @GST_ACTIVATE_NONE:	  	 Pad will not handle dataflow
@@ -892,6 +921,7 @@ void			gst_pad_set_unlink_function		(GstPad *pad, GstPadUnlinkFunction unlink);
 
 gboolean                gst_pad_can_link                        (GstPad *srcpad, GstPad *sinkpad);
 GstPadLinkReturn        gst_pad_link				(GstPad *srcpad, GstPad *sinkpad);
+GstPadLinkReturn        gst_pad_link_full			(GstPad *srcpad, GstPad *sinkpad, GstPadLinkCheck flags);
 gboolean		gst_pad_unlink				(GstPad *srcpad, GstPad *sinkpad);
 gboolean		gst_pad_is_linked			(GstPad *pad);
 

win32/common/libgstreamer.def

@@ -615,6 +615,8 @@ EXPORTS
 	gst_pad_iterate_internal_links
 	gst_pad_iterate_internal_links_default
 	gst_pad_link
+	gst_pad_link_check_get_type
+	gst_pad_link_full
 	gst_pad_link_return_get_type
 	gst_pad_load_and_link
 	gst_pad_new