From 0cf2dfd0ba7dc835a43c05d1b043e59021c18852 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian.droege@collabora.co.uk>
Date: Fri, 27 May 2011 13:37:06 +0200
Subject: [PATCH] caps: Fix subset check in gst_caps_merge()

Caps A are a subset of caps B even if caps B doesn't
have all fields of caps A.

Also add a unit test for this.
---
 gst/gstcaps.c             | 22 ++++++++++------------
 tests/check/gst/gstcaps.c | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/gst/gstcaps.c b/gst/gstcaps.c
index 3010d29d2e..10dbff7c00 100644
--- a/gst/gstcaps.c
+++ b/gst/gstcaps.c
@@ -569,13 +569,13 @@ static gboolean
 gst_caps_structure_is_subset_field (GQuark field_id, const GValue * value,
     gpointer user_data)
 {
-  GstStructure *subtract_from = user_data;
+  GstStructure *superset = user_data;
   GValue subtraction = { 0, };
   const GValue *other;
 
-  if (!(other = gst_structure_id_get_value (subtract_from, field_id)))
-    /* field is missing in one set */
-    return FALSE;
+  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)
@@ -612,17 +612,15 @@ gst_caps_structure_is_subset_field (GQuark field_id, const GValue * value,
 }
 
 static gboolean
-gst_caps_structure_is_subset (const GstStructure * minuend,
-    const GstStructure * subtrahend)
+gst_caps_structure_is_subset (const GstStructure * superset,
+    const GstStructure * subset)
 {
-  if ((minuend->name != subtrahend->name) ||
-      (gst_structure_n_fields (minuend) !=
-          gst_structure_n_fields (subtrahend))) {
+  if ((superset->name != subset->name) ||
+      (gst_structure_n_fields (superset) > gst_structure_n_fields (subset)))
     return FALSE;
-  }
 
-  return gst_structure_foreach ((GstStructure *) subtrahend,
-      gst_caps_structure_is_subset_field, (gpointer) minuend);
+  return gst_structure_foreach ((GstStructure *) subset,
+      gst_caps_structure_is_subset_field, (gpointer) superset);
 }
 
 /**
diff --git a/tests/check/gst/gstcaps.c b/tests/check/gst/gstcaps.c
index a22c15f0d2..12e9e44e4f 100644
--- a/tests/check/gst/gstcaps.c
+++ b/tests/check/gst/gstcaps.c
@@ -573,6 +573,26 @@ GST_START_TEST (test_merge_subset)
   fail_unless (gst_caps_is_subset (test, c2));
   gst_caps_unref (test);
   gst_caps_unref (c2);
+
+  c2 = gst_caps_from_string ("audio/x-raw-int");
+  c1 = gst_caps_from_string ("audio/x-raw-int,channels=1");
+  gst_caps_merge (c2, c1);
+  GST_DEBUG ("merged: (%d) %" GST_PTR_FORMAT, gst_caps_get_size (c2), c2);
+  fail_unless (gst_caps_get_size (c2) == 1, NULL);
+  test = gst_caps_from_string ("audio/x-raw-int");
+  fail_unless (gst_caps_is_equal (c2, test));
+  gst_caps_unref (c2);
+  gst_caps_unref (test);
+
+  c2 = gst_caps_from_string ("audio/x-raw-int,channels=1");
+  c1 = gst_caps_from_string ("audio/x-raw-int");
+  gst_caps_merge (c2, c1);
+  GST_DEBUG ("merged: (%d) %" GST_PTR_FORMAT, gst_caps_get_size (c2), c2);
+  fail_unless (gst_caps_get_size (c2) == 2, NULL);
+  test = gst_caps_from_string ("audio/x-raw-int,channels=1; audio/x-raw-int");
+  fail_unless (gst_caps_is_equal (c2, test));
+  gst_caps_unref (c2);
+  gst_caps_unref (test);
 }
 
 GST_END_TEST;