gstsample: new API

gst_sample_set_buffer
gst_sample_set_caps
gst_sample_set_segment
gst_sample_set_info
gst_sample_is_writable
gst_sample_make_writable

This commit makes it possible to reuse a sample object and avoid
unnecessary memory allocations, for example in appsink.

In addition, writability is now required to set the buffer list.

https://bugzilla.gnome.org/show_bug.cgi?id=795144

docs/gst/gstreamer-sections.txt

@@ -560,11 +560,17 @@ gst_sample_get_buffer_list
 gst_sample_get_caps
 gst_sample_get_info
 gst_sample_get_segment
+gst_sample_set_buffer
 gst_sample_set_buffer_list
+gst_sample_set_caps
+gst_sample_set_segment
+gst_sample_set_info
 gst_sample_new
 gst_sample_ref
 gst_sample_unref
 gst_sample_copy
+gst_buffer_is_writable
+gst_buffer_make_writable
 <SUBSECTION Standard>
 GST_IS_SAMPLE
 GST_SAMPLE

gst/gstsample.c

@@ -123,6 +123,7 @@ gst_sample_new (GstBuffer * buffer, GstCaps * caps, const GstSegment * segment,
   sample->buffer = buffer ? gst_buffer_ref (buffer) : NULL;
   sample->caps = caps ? gst_caps_ref (caps) : NULL;
 
+  /* FIXME 2.0: initialize with GST_FORMAT_UNDEFINED by default */
   if (segment)
     gst_segment_copy_into (segment, &sample->segment);
   else
@@ -244,7 +245,7 @@ gst_sample_get_buffer_list (GstSample * sample)
  * @sample: a #GstSample
  * @buffer_list: a #GstBufferList
  *
- * Set the buffer list associated with @sample
+ * Set the buffer list associated with @sample. @sample must be writable.
  *
  * Since: 1.6
  */
@@ -253,10 +254,98 @@ gst_sample_set_buffer_list (GstSample * sample, GstBufferList * buffer_list)
 {
   GstBufferList *old = NULL;
   g_return_if_fail (GST_IS_SAMPLE (sample));
+  g_return_if_fail (gst_sample_is_writable (sample));
+
   old = sample->buffer_list;
-  sample->buffer_list = (GstBufferList *)
+  sample->buffer_list = buffer_list ? (GstBufferList *)
-      gst_mini_object_ref (GST_MINI_OBJECT_CAST (buffer_list));
+      gst_mini_object_ref (GST_MINI_OBJECT_CAST (buffer_list)) : NULL;
 
   if (old)
     gst_mini_object_unref (GST_MINI_OBJECT_CAST (old));
 }
+
+/**
+ * gst_sample_set_buffer:
+ *
+ * Set the buffer associated with @sample. @sample must be writable.
+ *
+ * Since: 1.16
+ */
+void
+gst_sample_set_buffer (GstSample * sample, GstBuffer * buffer)
+{
+  g_return_if_fail (GST_IS_SAMPLE (sample));
+  g_return_if_fail (gst_sample_is_writable (sample));
+
+  gst_buffer_replace (&sample->buffer, buffer);
+}
+
+/**
+ * gst_sample_set_caps:
+ *
+ * Set the caps associated with @sample. @sample must be writable.
+ *
+ * Since: 1.16
+ */
+void
+gst_sample_set_caps (GstSample * sample, GstCaps * caps)
+{
+  g_return_if_fail (GST_IS_SAMPLE (sample));
+  g_return_if_fail (gst_sample_is_writable (sample));
+
+  gst_caps_replace (&sample->caps, caps);
+}
+
+/**
+ * gst_sample_set_segment:
+ *
+ * Set the segment associated with @sample. @sample must be writable.
+ *
+ * Since: 1.16
+ */
+void
+gst_sample_set_segment (GstSample * sample, const GstSegment * segment)
+{
+  g_return_if_fail (GST_IS_SAMPLE (sample));
+  g_return_if_fail (gst_sample_is_writable (sample));
+
+  /* FIXME 2.0: initialize with GST_FORMAT_UNDEFINED by default */
+  if (segment)
+    gst_segment_copy_into (segment, &sample->segment);
+  else
+    gst_segment_init (&sample->segment, GST_FORMAT_TIME);
+}
+
+/**
+ * gst_sample_set_info:
+ *
+ * Set the info structure associated with @sample. @sample must be writable,
+ * and @info must not have a parent set already.
+ *
+ * Since: 1.16
+ */
+gboolean
+gst_sample_set_info (GstSample * sample, GstStructure * info)
+{
+  g_return_val_if_fail (GST_IS_SAMPLE (sample), FALSE);
+  g_return_val_if_fail (gst_sample_is_writable (sample), FALSE);
+
+  if (info) {
+    if (!gst_structure_set_parent_refcount (info,
+            &sample->mini_object.refcount))
+      goto had_parent;
+  }
+
+  if (sample->info) {
+    gst_structure_set_parent_refcount (sample->info, NULL);
+    gst_structure_free (sample->info);
+  }
+
+  sample->info = info;
+
+  return TRUE;
+
+had_parent:
+  g_warning ("structure is already owned by another object");
+  return FALSE;
+}

gst/gstsample.h

@@ -75,6 +75,18 @@ GstBufferList *      gst_sample_get_buffer_list (GstSample *sample);
 GST_API
 void                 gst_sample_set_buffer_list (GstSample *sample, GstBufferList *buffer_list);
 
+GST_API
+void                 gst_sample_set_buffer    (GstSample *sample, GstBuffer *buffer);
+
+GST_API
+void                 gst_sample_set_caps      (GstSample *sample, GstCaps *caps);
+
+GST_API
+void                 gst_sample_set_segment   (GstSample * sample, const GstSegment *segment);
+
+GST_API
+gboolean             gst_sample_set_info      (GstSample *sample, GstStructure *info);
+
 /* refcounting */
 /**
  * gst_sample_ref:
@@ -104,6 +116,44 @@ gst_sample_unref (GstSample * sample)
   gst_mini_object_unref (GST_MINI_OBJECT_CAST (sample));
 }
 
+/**
+ * gst_sample_is_writable:
+ *
+ * Tests if you can safely set the buffer and / or buffer list of @sample.
+ *
+ * Since: 1.16
+ */
+#define         gst_sample_is_writable(sample)     gst_mini_object_is_writable (GST_MINI_OBJECT_CAST (sample))
+
+/**
+ * gst_sample_make_writable:
+ * @sample: (transfer full):
+ *
+ * Returns a writable copy of @sample. If the source sample is
+ * already writable, this will simply return the same sample.
+ *
+ * Use this function to ensure that a sample can be safely modified before
+ * making changes to it, for example before calling gst_sample_set_buffer()
+ *
+ * If the reference count of the source sample @sample is exactly one, the caller
+ * is the sole owner and this function will return the sample object unchanged.
+ *
+ * If there is more than one reference on the object, a copy will be made using
+ * gst_sample_copy(). The passed-in @sample will be unreffed in that case, and the
+ * caller will now own a reference to the new returned sample object.
+ *
+ * In short, this function unrefs the sample in the argument and refs the sample
+ * that it returns. Don't access the argument after calling this function unless
+ * you have an additional reference to it.
+ *
+ * Returns: (transfer full): a writable sample which may or may not be the
+ *     same as @sample
+ *
+ * Since: 1.16
+ */
+#define         gst_sample_make_writable(sample)   GST_SAMPLE_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (sample)))
+
+
 /* copy sample */
 /**
  * gst_sample_copy:

win32/common/libgstreamer.def

@@ -1235,7 +1235,11 @@ EXPORTS
 	gst_sample_get_segment
 	gst_sample_get_type
 	gst_sample_new
+	gst_sample_set_buffer
 	gst_sample_set_buffer_list
+	gst_sample_set_caps
+	gst_sample_set_info
+	gst_sample_set_segment
 	gst_scheduling_flags_get_type
 	gst_search_mode_get_type
 	gst_seek_flags_get_type