bufferpool: Add an helper to validate config

When we call gst_buffer_pool_set_config() the pool may return FALSE and
slightly change the parameters. This helper is useful to do the minial required
validation before accepting the modified configuration.

https://bugzilla.gnome.org/show_bug.cgi?id=727916

docs/gst/gstreamer-sections.txt

@@ -308,6 +308,7 @@ gst_buffer_pool_new
 
 gst_buffer_pool_config_get_params
 gst_buffer_pool_config_set_params
+gst_buffer_pool_config_validate_params
 gst_buffer_pool_config_get_allocator
 gst_buffer_pool_config_set_allocator
 

gst/gstbufferpool.c

@@ -1006,6 +1006,44 @@ gst_buffer_pool_config_get_allocator (GstStructure * config,
   return TRUE;
 }
 
+/**
+ * gst_buffer_pool_config_validate_params:
+ * @config: (transfer none): a #GstBufferPool configuration
+ * @caps: (transfer none): the excepted caps of buffers
+ * @size: the expected size of each buffer, not including prefix and padding
+ * @min_buffers: the expected minimum amount of buffers to allocate.
+ * @max_buffers: the expect maximum amount of buffers to allocate or 0 for unlimited.
+ *
+ * Validate that changes made to @config are still valid in the context of the
+ * expected parameters. This function is a helper that can be used to validate
+ * changes made by a pool to a config when gst_buffer_pool_set_config()
+ * returns %FALSE. This expects that @caps and @size haven't changed, and that
+ * @min_buffers aren't lower then what we initially expected. This does not check
+ * if options or allocator parameters.
+ *
+ * Since: 1.4
+ *
+ * Returns: %TRUE, if the parameters are valid in this context.
+ */
+gboolean
+gst_buffer_pool_config_validate_params (GstStructure * config, GstCaps * caps,
+    guint size, guint min_buffers, G_GNUC_UNUSED guint max_buffers)
+{
+  GstCaps *newcaps;
+  guint newsize, newmin;
+  gboolean ret = FALSE;
+
+  g_return_val_if_fail (config != NULL, FALSE);
+
+  gst_buffer_pool_config_get_params (config, &newcaps, &newsize, &newmin, NULL);
+
+  if (gst_caps_is_equal (caps, newcaps) && (size == newsize)
+      && (newmin >= min_buffers))
+    ret = TRUE;
+
+  return ret;
+}
+
 static GstFlowReturn
 default_acquire_buffer (GstBufferPool * pool, GstBuffer ** buffer,
     GstBufferPoolAcquireParams * params)

gst/gstbufferpool.h

@@ -201,6 +201,8 @@ guint            gst_buffer_pool_config_n_options   (GstStructure *config);
 void             gst_buffer_pool_config_add_option  (GstStructure *config, const gchar *option);
 const gchar *    gst_buffer_pool_config_get_option  (GstStructure *config, guint index);
 gboolean         gst_buffer_pool_config_has_option  (GstStructure *config, const gchar *option);
+gboolean         gst_buffer_pool_config_validate_params (GstStructure *config, GstCaps *caps,
+                                                         guint size, guint min_buffers, guint max_buffers);
 
 /* buffer management */
 GstFlowReturn    gst_buffer_pool_acquire_buffer  (GstBufferPool *pool, GstBuffer **buffer,

tests/check/gst/gstbufferpool.c

@@ -220,6 +220,28 @@ GST_START_TEST (test_pool_activation_and_config)
 
 GST_END_TEST;
 
+GST_START_TEST (test_pool_config_validate)
+{
+  GstBufferPool *pool = create_pool (5, 4, 30);
+  GstStructure *config = gst_buffer_pool_get_config (pool);
+  GstCaps *caps = gst_caps_new_empty_simple ("test/data");
+
+  fail_unless (gst_buffer_pool_config_validate_params (config, caps, 5, 4, 0));
+  fail_unless (gst_buffer_pool_config_validate_params (config, caps, 5, 2, 0));
+  fail_if (gst_buffer_pool_config_validate_params (config, caps, 5, 6, 0));
+  fail_if (gst_buffer_pool_config_validate_params (config, caps, 4, 4, 0));
+
+  gst_caps_unref (caps);
+  caps = gst_caps_new_empty_simple ("test/data2");
+  fail_if (gst_buffer_pool_config_validate_params (config, caps, 5, 4, 0));
+
+  gst_caps_unref (caps);
+  gst_structure_free (config);
+  gst_object_unref (pool);
+}
+
+GST_END_TEST;
+
 static Suite *
 gst_buffer_pool_suite (void)
 {
@@ -236,6 +258,7 @@ gst_buffer_pool_suite (void)
   tcase_add_test (tc_chain, test_inactive_pool_returns_flushing);
   tcase_add_test (tc_chain, test_buffer_modify_discard);
   tcase_add_test (tc_chain, test_pool_activation_and_config);
+  tcase_add_test (tc_chain, test_pool_config_validate);
 
   return s;
 }

win32/common/libgstreamer.def

@@ -148,6 +148,7 @@ EXPORTS
 	gst_buffer_pool_config_n_options
 	gst_buffer_pool_config_set_allocator
 	gst_buffer_pool_config_set_params
+	gst_buffer_pool_config_validate_params
 	gst_buffer_pool_get_config
 	gst_buffer_pool_get_options
 	gst_buffer_pool_get_type