structure: Add gst_structure_is_subset()

API: gst_structure_is_subset()

docs/gst/gstreamer-sections.txt

@@ -2209,6 +2209,7 @@ gst_structure_n_fields
 gst_structure_has_field
 gst_structure_has_field_typed
 gst_structure_is_equal
+gst_structure_is_subset
 gst_structure_can_intersect
 gst_structure_intersect
 gst_structure_id_has_field

gst/gstcaps.c

@@ -565,64 +565,6 @@ gst_caps_steal_structure (GstCaps * caps, guint index)
   return gst_caps_remove_and_get_structure (caps, index);
 }
 
-static gboolean
-gst_caps_structure_is_subset_field (GQuark field_id, const GValue * value,
-    gpointer user_data)
-{
-  GstStructure *superset = user_data;
-  GValue subtraction = { 0, };
-  const GValue *other;
-
-  if (!(other = gst_structure_id_get_value (superset, field_id)))
-    /* field is missing in the superset => is subset */
-    return TRUE;
-
-  /* equal values are subset */
-  if (gst_value_compare (other, value) == GST_VALUE_EQUAL)
-    return TRUE;
-
-  /*
-   * 1 - [1,2] = empty
-   * -> !subset
-   *
-   * [1,2] - 1 = 2
-   *  -> 1 - [1,2] = empty
-   *  -> subset
-   *
-   * [1,3] - [1,2] = 3
-   * -> [1,2] - [1,3] = empty
-   * -> subset
-   *
-   * {1,2} - {1,3} = 2
-   * -> {1,3} - {1,2} = 3
-   * -> !subset
-   *
-   *  First caps subtraction needs to return a non-empty set, second
-   *  subtractions needs to give en empty set.
-   */
-  if (gst_value_subtract (&subtraction, other, value)) {
-    g_value_unset (&subtraction);
-    /* !empty result, swapping must be empty */
-    if (!gst_value_subtract (&subtraction, value, other))
-      return TRUE;
-
-    g_value_unset (&subtraction);
-  }
-  return FALSE;
-}
-
-static gboolean
-gst_caps_structure_is_subset (const GstStructure * superset,
-    const GstStructure * subset)
-{
-  if ((superset->name != subset->name) ||
-      (gst_structure_n_fields (superset) > gst_structure_n_fields (subset)))
-    return FALSE;
-
-  return gst_structure_foreach ((GstStructure *) subset,
-      gst_caps_structure_is_subset_field, (gpointer) superset);
-}
-
 /**
  * gst_caps_append:
  * @caps1: the #GstCaps that will be appended to
@@ -792,7 +734,7 @@ gst_caps_merge_structure (GstCaps * caps, GstStructure * structure)
     for (i = caps->structs->len - 1; i >= 0; i--) {
       structure1 = gst_caps_get_structure_unchecked (caps, i);
       /* if structure is a subset of structure1, then skip it */
-      if (gst_caps_structure_is_subset (structure1, structure)) {
+      if (gst_structure_is_subset (structure, structure1)) {
         unique = FALSE;
         break;
       }
@@ -1147,7 +1089,7 @@ gst_caps_is_subset (const GstCaps * subset, const GstCaps * superset)
     for (j = superset->structs->len - 1; j >= 0; j--) {
       s1 = gst_caps_get_structure_unchecked (subset, i);
       s2 = gst_caps_get_structure_unchecked (superset, j);
-      if (gst_caps_structure_is_subset (s2, s1)) {
+      if (gst_structure_is_subset (s1, s2)) {
         /* If we found a superset, continue with the next
          * subset structure */
         break;

gst/gststructure.c

@@ -3099,3 +3099,74 @@ gst_structure_can_intersect (const GstStructure * struct1,
 
   return TRUE;
 }
+
+static gboolean
+gst_caps_structure_is_subset_field (GQuark field_id, const GValue * value,
+    gpointer user_data)
+{
+  GstStructure *superset = user_data;
+  GValue subtraction = { 0, };
+  const GValue *other;
+
+  if (!(other = gst_structure_id_get_value (superset, field_id)))
+    /* field is missing in the superset => is subset */
+    return TRUE;
+
+  /* equal values are subset */
+  if (gst_value_compare (other, value) == GST_VALUE_EQUAL)
+    return TRUE;
+
+  /*
+   * 1 - [1,2] = empty
+   * -> !subset
+   *
+   * [1,2] - 1 = 2
+   *  -> 1 - [1,2] = empty
+   *  -> subset
+   *
+   * [1,3] - [1,2] = 3
+   * -> [1,2] - [1,3] = empty
+   * -> subset
+   *
+   * {1,2} - {1,3} = 2
+   * -> {1,3} - {1,2} = 3
+   * -> !subset
+   *
+   *  First caps subtraction needs to return a non-empty set, second
+   *  subtractions needs to give en empty set.
+   */
+  if (gst_value_subtract (&subtraction, other, value)) {
+    g_value_unset (&subtraction);
+    /* !empty result, swapping must be empty */
+    if (!gst_value_subtract (&subtraction, value, other))
+      return TRUE;
+
+    g_value_unset (&subtraction);
+  }
+  return FALSE;
+}
+
+/**
+ * gst_structure_is_subset:
+ * @subset: a #GstStructure
+ * @superset: a potentially greater #GstStructure
+ *
+ * Checks if @subset is a subset of @superset, i.e. has the same
+ * structure name and for all fields that are existing in @superset,
+ * @subset has a value that is a subset of the value in @superset.
+ *
+ * Returns: %TRUE if @subset is a subset of @superset
+ *
+ * Since: 0.10.35
+ */
+gboolean
+gst_structure_is_subset (const GstStructure * subset,
+    const GstStructure * superset)
+{
+  if ((superset->name != subset->name) ||
+      (gst_structure_n_fields (superset) > gst_structure_n_fields (subset)))
+    return FALSE;
+
+  return gst_structure_foreach ((GstStructure *) subset,
+      gst_caps_structure_is_subset_field, (gpointer) superset);
+}

gst/gststructure.h

@@ -250,6 +250,8 @@ gboolean                 gst_structure_fixate_field_nearest_fraction (GstStructu
 
 gboolean                 gst_structure_is_equal(const GstStructure *structure1,
 						const GstStructure *structure2);
+gboolean                 gst_structure_is_subset(const GstStructure *subset,
+                                                 const GstStructure *superset);
 gboolean                 gst_structure_can_intersect(const GstStructure *struct1,
 						     const GstStructure *struct2);
 GstStructure*            gst_structure_intersect (const GstStructure *struct1,

win32/common/libgstreamer.def

@@ -1010,6 +1010,7 @@ EXPORTS
 	gst_structure_id_take_value
 	gst_structure_intersect
 	gst_structure_is_equal
+	gst_structure_is_subset
 	gst_structure_map_in_place
 	gst_structure_n_fields
 	gst_structure_new