structure: Add GST_SERIALIZE_FLAG_STRICT

It makes serialization succeed only if all values have a type that can
be deserialized.

Sponsored-by: Netflix Inc.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5355>

subprojects/gstreamer/gst/gststructure.c

@@ -2033,6 +2033,7 @@ priv_gst_structure_append_to_gstring (const GstStructure * structure,
   guint i, len;
   gboolean nested_structs_brackets =
       !(flags & GST_SERIALIZE_FLAG_BACKWARD_COMPAT);
+  gboolean strict = (flags & GST_SERIALIZE_FLAG_STRICT) != 0;
 
   g_return_val_if_fail (s != NULL, FALSE);
 
@@ -2069,7 +2070,8 @@ priv_gst_structure_append_to_gstring (const GstStructure * structure,
 
       g_string_append_c (s, '[');
       g_string_append (s, g_quark_to_string (substruct->name));
-      priv_gst_structure_append_to_gstring (substruct, s, flags);
+      if (!priv_gst_structure_append_to_gstring (substruct, s, flags))
+        return FALSE;
       g_string_append_c (s, ']');
     } else if (nested_structs_brackets
         && G_VALUE_TYPE (&field->value) == GST_TYPE_CAPS) {
@@ -2081,9 +2083,13 @@ priv_gst_structure_append_to_gstring (const GstStructure * structure,
     } else if (t) {
       g_string_append (s, t);
       g_free (t);
+      if (strict && G_VALUE_HOLDS_OBJECT (&field->value))
+        return FALSE;
     } else if (G_TYPE_CHECK_VALUE_TYPE (&field->value, G_TYPE_POINTER)) {
       gpointer ptr = g_value_get_pointer (&field->value);
 
+      if (strict)
+        return FALSE;
       if (!ptr)
         g_string_append (s, "NULL");
       else
@@ -2093,6 +2099,8 @@ priv_gst_structure_append_to_gstring (const GstStructure * structure,
         GST_WARNING ("No value transform to serialize field '%s' of type '%s'",
             g_quark_to_string (field->name),
             _priv_gst_value_gtype_to_abbr (type));
+      if (strict)
+        return FALSE;
       /* TODO(ensonic): don't print NULL if field->value is not empty */
       g_string_append (s, "NULL");
     }
@@ -2168,7 +2176,10 @@ structure_serialize (const GstStructure * structure, GstSerializeFlags flags)
    * avoid unnecessary reallocs within GString */
   s = g_string_sized_new (STRUCTURE_ESTIMATED_STRING_LEN (structure));
   g_string_append (s, g_quark_to_string (structure->name));
-  priv_gst_structure_append_to_gstring (structure, s, flags);
+  if (!priv_gst_structure_append_to_gstring (structure, s, flags)) {
+    g_string_free (s, TRUE);
+    return NULL;
+  }
   return g_string_free (s, FALSE);
 
 }

subprojects/gstreamer/gst/gststructure.h

@@ -32,11 +32,23 @@ GST_API GType _gst_structure_type;
 
 typedef struct _GstStructure GstStructure;
 
+/**
+ * GST_SERIALIZE_FLAG_STRICT:
+ *
+ * Serialization fails if a value cannot be serialized instead of using
+ * placeholder "NULL" value (e.g. pointers, objects).
+ *
+ * Since: 1.24
+ */
+
 /**
  * GstSerializeFlags:
  * @GST_SERIALIZE_FLAG_NONE: No special flags specified.
  * @GST_SERIALIZE_FLAG_BACKWARD_COMPAT: Serialize using the old format for
  *                                      nested structures.
+ * @GST_SERIALIZE_FLAG_STRICT: Serialization fails if a value cannot be
+ *  serialized instead of using placeholder "NULL" value (e.g. pointers,
+ *  objects). (Since 1.24)
  *
  * Since: 1.20
  */
@@ -44,6 +56,7 @@ typedef enum
 {
   GST_SERIALIZE_FLAG_NONE = 0,
   GST_SERIALIZE_FLAG_BACKWARD_COMPAT = (1 << 0),
+  GST_SERIALIZE_FLAG_STRICT = (1 << 1),
 } GstSerializeFlags;
 
 #define GST_TYPE_STRUCTURE             (_gst_structure_type)

subprojects/gstreamer/tests/check/gst/gststructure.c

@@ -1034,6 +1034,25 @@ GST_START_TEST (test_flags)
 
 GST_END_TEST;
 
+GST_START_TEST (test_strict)
+{
+  GstStructure *s;
+
+  GstElement *bin = gst_bin_new ("mybin");
+  s = gst_structure_new ("test-struct", "obj", GST_TYPE_BIN, bin, NULL);
+  fail_unless (s);
+  fail_if (gst_structure_serialize (s, GST_SERIALIZE_FLAG_STRICT));
+  gst_structure_free (s);
+  gst_object_unref (bin);
+
+  s = gst_structure_new ("test-struct", "ptr", G_TYPE_POINTER, NULL, NULL);
+  fail_unless (s);
+  fail_if (gst_structure_serialize (s, GST_SERIALIZE_FLAG_STRICT));
+  gst_structure_free (s);
+}
+
+GST_END_TEST;
+
 static Suite *
 gst_structure_suite (void)
 {
@@ -1067,6 +1086,7 @@ gst_structure_suite (void)
   tcase_add_test (tc_chain, test_filter_and_map_in_place);
   tcase_add_test (tc_chain, test_flagset);
   tcase_add_test (tc_chain, test_flags);
+  tcase_add_test (tc_chain, test_strict);
   return s;
 }