taglist: add to_string and new_from_string functions

We want to make GstTagList opaque and not have people use
GstStructure API on it.

API: gst_tag_list_to_string()
API: gst_tag_list_new_from_string()

docs/gst/gstreamer-sections.txt

@@ -2366,6 +2366,8 @@ gst_tag_is_fixed
 gst_tag_list_new
 gst_tag_list_new_full
 gst_tag_list_new_full_valist
+gst_tag_list_new_from_string
+gst_tag_list_to_string
 gst_is_tag_list
 gst_tag_list_is_empty
 gst_tag_list_is_equal

gst/gsttaglist.c

@@ -697,6 +697,44 @@ gst_tag_list_new_full_valist (va_list var_args)
   return list;
 }
 
+/**
+ * gst_tag_list_to_string:
+ * @list: a #GstTagList
+ *
+ * Serializes a tag list to a string.
+ *
+ * Returns: a newly-allocated string, or NULL in case of an error. The
+ *    string must be freed with g_free() when no longer needed.
+ *
+ * Since: 0.10.36
+ */
+gchar *
+gst_tag_list_to_string (const GstTagList * list)
+{
+  g_return_val_if_fail (GST_IS_TAG_LIST (list), NULL);
+
+  return gst_structure_to_string (GST_STRUCTURE (list));
+}
+
+/**
+ * gst_tag_list_new_from_string:
+ * @str: a string created with gst_tag_list_to_string()
+ *
+ * Deserializes a tag list.
+ *
+ * Returns: a new #GstTagList, or NULL in case of an error.
+ *
+ * Since: 0.10.36
+ */
+GstTagList *
+gst_tag_list_new_from_string (const gchar * str)
+{
+  g_return_val_if_fail (str != NULL, NULL);
+  g_return_val_if_fail (g_str_has_prefix (str, "taglist"), NULL);
+
+  return GST_TAG_LIST (gst_structure_from_string (str, NULL));
+}
+
 /**
  * gst_tag_list_is_empty:
  * @list: A #GstTagList.

gst/gsttaglist.h

@@ -215,6 +215,9 @@ GstTagList * gst_tag_list_new               (void);
 GstTagList * gst_tag_list_new_full          (const gchar * tag, ...);
 GstTagList * gst_tag_list_new_full_valist   (va_list var_args);
 
+gchar      * gst_tag_list_to_string         (const GstTagList * list);
+GstTagList * gst_tag_list_new_from_string   (const gchar      * str);
+
 gboolean     gst_is_tag_list                (gconstpointer p);
 GstTagList * gst_tag_list_copy              (const GstTagList * list);
 gboolean     gst_tag_list_is_empty          (const GstTagList * list);

tests/check/gst/gsttag.c

@@ -274,11 +274,11 @@ GST_START_TEST (test_date_tags)
   tag_list = gst_tag_list_new ();
   gst_tag_list_add (tag_list, GST_TAG_MERGE_APPEND, GST_TAG_DATE, date, NULL);
 
-  str = gst_structure_to_string (tag_list);
+  str = gst_tag_list_to_string (tag_list);
   fail_if (str == NULL);
   fail_if (strstr (str, "2005-10-14") == NULL);
 
-  tag_list2 = gst_structure_from_string (str, NULL);
+  tag_list2 = gst_tag_list_new_from_string (str);
   fail_if (tag_list2 == NULL);
   fail_if (!gst_tag_list_get_date (tag_list2, GST_TAG_DATE, &date2));
   fail_unless (gst_tag_list_is_equal (tag_list2, tag_list));

win32/common/libgstreamer.def

@@ -1086,10 +1086,12 @@ EXPORTS
 	gst_tag_list_is_equal
 	gst_tag_list_merge
 	gst_tag_list_new
+	gst_tag_list_new_from_string
 	gst_tag_list_new_full
 	gst_tag_list_new_full_valist
 	gst_tag_list_peek_string_index
 	gst_tag_list_remove_tag
+	gst_tag_list_to_string
 	gst_tag_merge_mode_get_type
 	gst_tag_merge_strings_with_comma
 	gst_tag_merge_use_first