bufferlist: add bufferlist code

Buffer lists are a means to manage disjoint buffers as one buffer. It's also
possible to put many of those buffers into a list.

The idea is that when support is added to various elements, we will be able to
more efficiently slice and dice buffers, reduce the amount of memcpy and also
reduce data passing overhead.

The implementation is kept simple on purpose, reusing all of the memory
management features we have for miniobjects and buffers.

Access to the bufferlist object is done with an iterator, which allows for
efficient iteration and modification of the list.

See #572285

gst/gstbufferlist.c

@@ -0,0 +1,717 @@
+/* GStreamer
+ * Copyright (C) 2009 Axis Communications <dev-gstreamer at axis dot com>
+ * @author Jonas Holmberg <jonas dot holmberg at axis dot com>
+ *
+ * gstbufferlist.c: Buffer list
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/**
+ * SECTION:gstbufferlist
+ * @short_description: Grouped scatter data buffer type for data-passing
+ * @see_also: #GstPad, #GstMiniObject
+ *
+ * Buffer lists are units of grouped scatter/gather data transfer in
+ * GStreamer.
+ *
+ * Buffer lists are created with gst_buffer_list_new() and filled with data
+ * using a #GstBufferListIterator. The iterator has no current buffer; its
+ * cursor position lies between buffers, immediately before the buffer that
+ * would be returned by gst_buffer_list_iterator_next(). After iterating to the
+ * end of a group the iterator must be advanced to the next group by a call to
+ * gst_buffer_list_iterator_next_group() before any further calls to
+ * gst_buffer_list_iterator_next() can return buffers again. The cursor position
+ * of a newly created iterator lies before the first group; a call to
+ * gst_buffer_list_iterator_next_group() is necessary before calls to
+ * gst_buffer_list_iterator_next() can return buffers.
+ *
+ * <informalexample>
+ *   <programlisting>
+ *      +--- group0 ----------------------+--- group1 ------------+
+ *      |   buffer0   buffer1   buffer2   |   buffer3   buffer4   |
+ *    ^   ^         ^         ^         ^   ^         ^         ^
+ *    Iterator positions
+ *   </programlisting>
+ * </informalexample>
+ *
+ * The gst_buffer_list_iterator_remove(), gst_buffer_list_iterator_steal(),
+ * gst_buffer_list_iterator_take(), gst_buffer_list_iterator_do() and
+ * gst_buffer_list_iterator_do_data() functions are not defined in terms of the
+ * cursor position; they operate on the last element returned from
+ * gst_buffer_list_iterator_next().
+ *
+ * The basic use pattern of creating a buffer list with an iterator is as
+ * follows:
+ *
+ * <example>
+ * <title>Creating a buffer list</title>
+ *   <programlisting>
+ *    GstBufferList *list;
+ *    GstBufferListIterator *it;
+ *
+ *    list = gst_buffer_list_new ();
+ *    it = gst_buffer_list_iterate (list);
+ *    gst_buffer_list_iterator_add_group (it);
+ *    gst_buffer_list_iterator_add (it, header1);
+ *    gst_buffer_list_iterator_add (it, data1);
+ *    gst_buffer_list_iterator_add_group (it);
+ *    gst_buffer_list_iterator_add (it, header2);
+ *    gst_buffer_list_iterator_add (it, data2);
+ *    gst_buffer_list_iterator_add_group (it);
+ *    gst_buffer_list_iterator_add (it, header3);
+ *    gst_buffer_list_iterator_add (it, data3);
+ *    ...
+ *    gst_buffer_list_iterator_free (it);
+ *   </programlisting>
+ * </example>
+ *
+ * The basic use pattern of iterating over a buffer list is as follows:
+ *
+ * <example>
+ * <title>Iterating a buffer list</title>
+ *   <programlisting>
+ *    GstBufferListIterator *it;
+ *
+ *    it = gst_buffer_list_iterate (list);
+ *    while (gst_buffer_list_iterator_next_group (it)) {
+ *      while ((buffer = gst_buffer_list_iterator_next (it)) != NULL) {
+ *        do_something_with_buffer (buffer);
+ *      }
+ *    }
+ *    gst_buffer_list_iterator_free (it);
+ *   </programlisting>
+ * </example>
+ *
+ * The basic use pattern of modifying a buffer in a list is as follows:
+ *
+ * <example>
+ * <title>Modifying the data of the first buffer in a list</title>
+ *   <programlisting>
+ *    GstBufferListIterator *it;
+ *
+ *    list = gst_buffer_list_make_writable (list);
+ *    it = gst_buffer_list_iterate (list);
+ *    if (gst_buffer_list_iterator_next_group (it)) {
+ *      GstBuffer *buf
+ *
+ *      buf = gst_buffer_list_iterator_next (it);
+ *      if (buf != NULL) {
+ *        buf = gst_buffer_list_iterator_do (it,
+ *            (GstBufferListDoFunction) gst_mini_object_make_writable);
+ *        modify_data (GST_BUFFER_DATA (buf));
+ *      }
+ *    }
+ *    gst_buffer_list_iterator_free (it);
+ *   </programlisting>
+ * </example>
+ *
+ * Since: 0.10.24
+ */
+#include "gst_private.h"
+
+#include "gstbuffer.h"
+#include "gstbufferlist.h"
+
+#define GST_CAT_DEFAULT GST_CAT_BUFFER_LIST
+
+#define GROUP_START NULL
+static const gpointer STOLEN = "";
+
+/**
+ * GstBufferListIterator:
+ *
+ * Iterator for a #GstBufferList.
+ */
+struct _GstBufferListIterator
+{
+  GstBufferList *list;
+  GList *next;
+  GList *last_returned;
+};
+
+static GType _gst_buffer_list_type = 0;
+static GstMiniObjectClass *parent_class = NULL;
+
+void
+_gst_buffer_list_initialize (void)
+{
+  g_type_class_ref (gst_buffer_list_get_type ());
+}
+
+static void
+gst_buffer_list_init (GTypeInstance * instance, gpointer g_class)
+{
+  GstBufferList *list;
+
+  list = (GstBufferList *) instance;
+  list->buffers = NULL;
+
+  GST_LOG ("init %p", list);
+}
+
+static void
+gst_buffer_list_finalize (GstBufferList * list)
+{
+  GList *tmp;
+
+  g_return_if_fail (list != NULL);
+
+  GST_LOG ("finalize %p", list);
+
+  tmp = list->buffers;
+  while (tmp) {
+    if (tmp->data != GROUP_START && tmp->data != STOLEN) {
+      gst_buffer_unref (GST_BUFFER_CAST (tmp->data));
+    }
+    tmp = tmp->next;
+  }
+  g_list_free (list->buffers);
+
+  parent_class->finalize (GST_MINI_OBJECT_CAST (list));
+}
+
+static GstBufferList *
+_gst_buffer_list_copy (GstBufferList * list)
+{
+  GstBufferList *list_copy;
+  GList *tmp;
+
+  g_return_val_if_fail (list != NULL, NULL);
+
+  list_copy = gst_buffer_list_new ();
+
+  /* shallow copy of list and pointers */
+  list_copy->buffers = g_list_copy (list->buffers);
+
+  /* copy all buffers in the list */
+  tmp = list_copy->buffers;
+  while (tmp) {
+    if (tmp->data != GROUP_START && tmp->data != STOLEN) {
+      tmp->data = gst_buffer_ref (GST_BUFFER_CAST (tmp->data));
+    }
+    tmp = g_list_next (tmp);
+  }
+
+  return list_copy;
+}
+
+static void
+gst_buffer_list_class_init (gpointer g_class, gpointer class_data)
+{
+  GstBufferListClass *list_class = GST_BUFFER_LIST_CLASS (g_class);
+
+  parent_class = g_type_class_peek_parent (g_class);
+
+  list_class->mini_object_class.copy =
+      (GstMiniObjectCopyFunction) _gst_buffer_list_copy;
+  list_class->mini_object_class.finalize =
+      (GstMiniObjectFinalizeFunction) gst_buffer_list_finalize;
+}
+
+/**
+ * gst_buffer_list_new:
+ *
+ * Creates a new, empty #GstBufferList. The caller is responsible for unreffing
+ * the returned #GstBufferList.
+ *
+ * Returns: the new #GstBufferList. gst_buffer_list_unref() after usage.
+ */
+GstBufferList *
+gst_buffer_list_new (void)
+{
+  GstBufferList *list;
+
+  list = (GstBufferList *) gst_mini_object_new (_gst_buffer_list_type);
+
+  GST_LOG ("new %p", list);
+
+  return list;
+}
+
+/**
+ * gst_buffer_list_n_groups:
+ * @list: a #GstBufferList
+ *
+ * Returns the number of groups in @list.
+ *
+ * Returns: the number of groups in the buffer list
+ */
+guint
+gst_buffer_list_n_groups (GstBufferList * list)
+{
+  GList *tmp;
+  guint n;
+
+  g_return_val_if_fail (list != NULL, 0);
+
+  tmp = list->buffers;
+  n = 0;
+  while (tmp) {
+    if (tmp->data == GROUP_START) {
+      n++;
+    }
+    tmp = g_list_next (tmp);
+  }
+
+  return n;
+}
+
+GType
+gst_buffer_list_get_type (void)
+{
+  if (G_UNLIKELY (_gst_buffer_list_type == 0)) {
+    static const GTypeInfo buffer_list_info = {
+      sizeof (GstBufferListClass),
+      NULL,
+      NULL,
+      gst_buffer_list_class_init,
+      NULL,
+      NULL,
+      sizeof (GstBufferList),
+      0,
+      gst_buffer_list_init,
+      NULL
+    };
+
+    _gst_buffer_list_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
+        "GstBufferList", &buffer_list_info, 0);
+  }
+
+  return _gst_buffer_list_type;
+}
+
+/**
+ * gst_buffer_list_iterate:
+ * @list: a #GstBufferList
+ *
+ * Iterate the buffers in @list. The owner of the iterator must also be the
+ * owner of a reference to @list while the returned iterator is in use.
+ *
+ * Returns: a new #GstBufferListIterator of the buffers in @list.
+ * gst_buffer_list_iterator_free() after usage
+ */
+GstBufferListIterator *
+gst_buffer_list_iterate (GstBufferList * list)
+{
+  GstBufferListIterator *it;
+
+  g_return_val_if_fail (list != NULL, NULL);
+
+  it = g_slice_new (GstBufferListIterator);
+  it->list = list;
+  it->next = list->buffers;
+  it->last_returned = NULL;
+
+  return it;
+}
+
+/**
+ * gst_buffer_list_iterator_free:
+ * @it: the #GstBufferListIterator to free
+ *
+ * Free the iterator.
+ */
+void
+gst_buffer_list_iterator_free (GstBufferListIterator * it)
+{
+  g_return_if_fail (it != NULL);
+
+  g_slice_free (GstBufferListIterator, it);
+}
+
+/**
+ * gst_buffer_list_iterator_n_buffers:
+ * @it: a #GstBufferListIterator
+ *
+ * Returns the number of buffers left to iterate in the current group. I.e. the
+ * number of calls that can be made to gst_buffer_list_iterator_next() before
+ * it returns NULL.
+ *
+ * This function will not move the implicit cursor or in any other way affect
+ * the state of the iterator @it.
+ *
+ * Returns: the number of buffers left to iterate in the current group
+ */
+guint
+gst_buffer_list_iterator_n_buffers (const GstBufferListIterator * it)
+{
+  GList *tmp;
+  guint n;
+
+  g_return_val_if_fail (it != NULL, 0);
+
+  tmp = it->next;
+  n = 0;
+  while (tmp && tmp->data != GROUP_START) {
+    if (tmp->data != STOLEN) {
+      n++;
+    }
+    tmp = g_list_next (tmp);
+  }
+
+  return n;
+}
+
+/**
+ * gst_buffer_list_iterator_add:
+ * @it: a #GstBufferListIterator
+ * @buffer: a #GstBuffer
+ *
+ * Inserts @buffer into the #GstBufferList iterated with @it. The buffer is
+ * inserted into the current group, immediately before the buffer that would be
+ * returned by gst_buffer_list_iterator_next(). The buffer is inserted before
+ * the implicit cursor, a subsequent call to gst_buffer_list_iterator_next()
+ * will return the buffer after the inserted buffer, if any.
+ *
+ * This function takes ownership of @buffer.
+ */
+void
+gst_buffer_list_iterator_add (GstBufferListIterator * it, GstBuffer * buffer)
+{
+  g_return_if_fail (it != NULL);
+  g_return_if_fail (buffer != NULL);
+
+  /* adding before the first group start is not allowed */
+  g_return_if_fail (it->next != it->list->buffers);
+
+  /* cheap insert into the GList */
+  it->list->buffers = g_list_insert_before (it->list->buffers, it->next,
+      buffer);
+}
+
+/**
+ * gst_buffer_list_iterator_add_group:
+ * @it: a #GstBufferListIterator
+ *
+ * Inserts a new, empty group into the #GstBufferList iterated with @it. The
+ * group is inserted immediately before the group that would be returned by
+ * gst_buffer_list_iterator_next_group(). A subsequent call to
+ * gst_buffer_list_iterator_next_group() will advance the iterator to the group
+ * after the inserted group, if any.
+ */
+void
+gst_buffer_list_iterator_add_group (GstBufferListIterator * it)
+{
+  g_return_if_fail (it != NULL);
+
+  /* advance iterator to next group start */
+  while (it->next != NULL && it->next->data != GROUP_START) {
+    it->next = g_list_next (it->next);
+  }
+
+  /* cheap insert of a group start into the GList */
+  it->list->buffers = g_list_insert_before (it->list->buffers, it->next,
+      GROUP_START);
+}
+
+/**
+ * gst_buffer_list_iterator_next:
+ * @it: a #GstBufferListIterator
+ *
+ * Returns the next buffer in the list iterated with @it. If the iterator is at
+ * the end of a group, NULL will be returned. This function may be called
+ * repeatedly to iterate through the current group.
+ *
+ * The caller will not get a new ref to the returned #GstBuffer and must not
+ * unref it.
+ *
+ * Returns: the next buffer in the current group of the buffer list, or NULL
+ */
+GstBuffer *
+gst_buffer_list_iterator_next (GstBufferListIterator * it)
+{
+  GstBuffer *buffer;
+
+  g_return_val_if_fail (it != NULL, NULL);
+
+  while (it->next != NULL && it->next->data != GROUP_START &&
+      it->next->data == STOLEN) {
+    it->next = g_list_next (it->next);
+  }
+
+  if (it->next == NULL || it->next->data == GROUP_START) {
+    goto no_buffer;
+  }
+
+  buffer = GST_BUFFER_CAST (it->next->data);
+
+  it->last_returned = it->next;
+  it->next = g_list_next (it->next);
+
+  return buffer;
+
+no_buffer:
+  it->last_returned = NULL;
+
+  return NULL;
+}
+
+/**
+ * gst_buffer_list_iterator_next_group:
+ * @it: a #GstBufferListIterator
+ *
+ * Advance the iterator @it to the first buffer in the next group. If the
+ * iterator is at the last group, FALSE will be returned. This function may be
+ * called repeatedly to iterate through the groups in a buffer list.
+ *
+ * Returns: TRUE if the iterator could be advanced to the next group, FALSE if
+ * the iterator was already at the last group
+ */
+gboolean
+gst_buffer_list_iterator_next_group (GstBufferListIterator * it)
+{
+  g_return_val_if_fail (it != NULL, FALSE);
+
+  /* advance iterator to next group start */
+  while (it->next != NULL && it->next->data != GROUP_START) {
+    it->next = g_list_next (it->next);
+  }
+
+  if (it->next) {
+    /* move one step beyond the group start */
+    it->next = g_list_next (it->next);
+  }
+
+  it->last_returned = NULL;
+
+  return (it->next != NULL);
+}
+
+/**
+ * gst_buffer_list_iterator_remove:
+ * @it: a #GstBufferListIterator
+ *
+ * Removes the last buffer returned by gst_buffer_list_iterator_next() from
+ * the #GstBufferList iterated with @it. gst_buffer_list_iterator_next() must
+ * have been called on @it before this function is called. This function can
+ * only be called once per call to gst_buffer_list_iterator_next().
+ *
+ * The removed buffer is unreffed.
+ */
+void
+gst_buffer_list_iterator_remove (GstBufferListIterator * it)
+{
+  g_return_if_fail (it != NULL);
+  g_return_if_fail (it->last_returned != NULL);
+  g_assert (it->last_returned->data != GROUP_START);
+
+  if (it->last_returned->data != STOLEN) {
+    gst_buffer_unref (it->last_returned->data);
+  }
+  it->list->buffers = g_list_delete_link (it->list->buffers, it->last_returned);
+  it->last_returned = NULL;
+}
+
+/**
+ * gst_buffer_list_iterator_take:
+ * @it: a #GstBufferListIterator
+ * @buffer: a #GstBuffer
+ *
+ * Replaces the last buffer returned by gst_buffer_list_iterator_next() with
+ * @buffer in the #GstBufferList iterated with @it and takes ownership of
+ * @buffer. gst_buffer_list_iterator_next() must have been called on @it before
+ * this function is called. gst_buffer_list_iterator_remove() must not have been
+ * called since the last call to gst_buffer_list_iterator_next().
+ *
+ * This function unrefs the replaced buffer if it has not been stolen with
+ * gst_buffer_list_iterator_steal() and takes ownership of @buffer (i.e. the
+ * refcount of @buffer is not increased).
+ */
+void
+gst_buffer_list_iterator_take (GstBufferListIterator * it, GstBuffer * buffer)
+{
+  g_return_if_fail (it != NULL);
+  g_return_if_fail (it->last_returned != NULL);
+  g_return_if_fail (buffer != NULL);
+  g_assert (it->last_returned->data != GROUP_START);
+
+  if (it->last_returned->data != STOLEN) {
+    gst_buffer_unref (it->last_returned->data);
+  }
+  it->last_returned->data = buffer;
+}
+
+/**
+ * gst_buffer_list_iterator_steal:
+ * @it: a #GstBufferListIterator
+ *
+ * Returns the last buffer returned by gst_buffer_list_iterator_next() without
+ * modifying the refcount of the buffer.
+ *
+ * Returns: the last buffer returned by gst_buffer_list_iterator_next()
+ */
+GstBuffer *
+gst_buffer_list_iterator_steal (GstBufferListIterator * it)
+{
+  GstBuffer *buffer;
+
+  g_return_val_if_fail (it != NULL, NULL);
+  g_return_val_if_fail (it->last_returned != NULL, NULL);
+  g_return_val_if_fail (it->last_returned->data != STOLEN, NULL);
+  g_assert (it->last_returned->data != GROUP_START);
+
+  buffer = it->last_returned->data;
+  it->last_returned->data = STOLEN;
+
+  return buffer;
+}
+
+/**
+ * gst_buffer_list_iterator_do_data:
+ * @it: a #GstBufferListIterator
+ * @do_func: the function to be called
+ * @data: the gpointer to optional user data.
+ * @data_notify: function to be called when @data is no longer used
+ *
+ * Calls the given function for the last buffer returned by
+ * gst_buffer_list_iterator_next(). gst_buffer_list_iterator_next() must have
+ * been called on @it before this function is called.
+ * gst_buffer_list_iterator_remove() and gst_buffer_list_iterator_steal() must
+ * not have been called since the last call to gst_buffer_list_iterator_next().
+ *
+ * See #GstBufferListDoFunction for more details.
+ *
+ * The @data_notify function is called after @do_func has returned, before this
+ * function returns, usually used to free @data.
+ *
+ * Returns: the return value from @do_func
+ */
+GstBuffer *
+gst_buffer_list_iterator_do_data (GstBufferListIterator * it,
+    GstBufferListDoDataFunction do_func, gpointer data,
+    GDestroyNotify data_notify)
+{
+  GstBuffer *buffer;
+
+  g_return_val_if_fail (it != NULL, NULL);
+  g_return_val_if_fail (it->last_returned != NULL, NULL);
+  g_return_val_if_fail (it->last_returned->data != STOLEN, NULL);
+  g_return_val_if_fail (do_func != NULL, NULL);
+  g_return_val_if_fail (gst_buffer_list_is_writable (it->list), NULL);
+  g_assert (it->last_returned->data != GROUP_START);
+
+  buffer = gst_buffer_list_iterator_steal (it);
+  buffer = do_func (buffer, data);
+  if (buffer == NULL) {
+    gst_buffer_list_iterator_remove (it);
+  } else {
+    gst_buffer_list_iterator_take (it, buffer);
+  }
+
+  if (data_notify != NULL) {
+    data_notify (data);
+  }
+
+  return buffer;
+}
+
+static GstBuffer *
+do_func_no_data (GstBuffer * buffer, GstBufferListDoFunction do_func)
+{
+  return do_func (buffer);
+}
+
+/**
+ * gst_buffer_list_iterator_do:
+ * @it: a #GstBufferListIterator
+ * @do_func: the function to be called
+ *
+ * Calls the given function for the last buffer returned by
+ * gst_buffer_list_iterator_next(). gst_buffer_list_iterator_next() must have
+ * been called on @it before this function is called.
+ * gst_buffer_list_iterator_remove() or gst_buffer_list_iterator_steal() must
+ * not have been called since the last call to gst_buffer_list_iterator_next().
+ *
+ * See #GstBufferListDoFunction for more details.
+ *
+ * Returns: the return value from @do_func
+ */
+GstBuffer *
+gst_buffer_list_iterator_do (GstBufferListIterator * it,
+    GstBufferListDoFunction do_func)
+{
+  g_return_val_if_fail (it != NULL, NULL);
+  g_return_val_if_fail (it->last_returned != NULL, NULL);
+  g_return_val_if_fail (it->last_returned->data != STOLEN, NULL);
+  g_return_val_if_fail (do_func != NULL, NULL);
+  g_return_val_if_fail (gst_buffer_list_is_writable (it->list), NULL);
+  g_assert (it->last_returned->data != GROUP_START);
+
+  return gst_buffer_list_iterator_do_data (it,
+      (GstBufferListDoDataFunction) do_func_no_data, do_func, NULL);
+}
+
+/**
+ * gst_buffer_list_iterator_merge_group:
+ * @it: a #GstBufferListIterator
+ *
+ * Merge a buffer list group into a normal #GstBuffer by copying its metadata
+ * and memcpying its data into consecutive memory. All buffers in the current
+ * group after the implicit cursor will be merged into one new buffer. The
+ * metadata of the new buffer will be a copy of the metadata of the buffer that
+ * would be returned by gst_buffer_list_iterator_next(). If there is no buffer
+ * in the current group after the implicit cursor, NULL will be returned.
+ *
+ * This function will not move the implicit cursor or in any other way affect
+ * the state of the iterator @it or the list.
+ *
+ * Returns: a new #GstBuffer, gst_buffer_unref() after usage, or NULL
+ */
+GstBuffer *
+gst_buffer_list_iterator_merge_group (const GstBufferListIterator * it)
+{
+  GList *tmp;
+  guint size;
+  GstBuffer *buf;
+  guint8 *ptr;
+
+  g_return_val_if_fail (it != NULL, NULL);
+
+  /* calculate size of merged buffer */
+  size = 0;
+  tmp = it->next;
+  while (tmp && tmp->data != GROUP_START) {
+    if (tmp->data != STOLEN) {
+      size += GST_BUFFER_SIZE (tmp->data);
+    }
+    tmp = g_list_next (tmp);
+  }
+
+  if (size == 0) {
+    return NULL;
+  }
+
+  /* allocate a new buffer */
+  buf = gst_buffer_new_and_alloc (size);
+
+  /* copy metadata from the next buffer after the implicit cursor */
+  gst_buffer_copy_metadata (buf, GST_BUFFER_CAST (it->next->data),
+      GST_BUFFER_COPY_ALL);
+
+  /* copy data of all buffers before the next group start into the new buffer */
+  ptr = GST_BUFFER_DATA (buf);
+  tmp = it->next;
+  do {
+    if (tmp->data != STOLEN) {
+      memcpy (ptr, GST_BUFFER_DATA (tmp->data), GST_BUFFER_SIZE (tmp->data));
+      ptr += GST_BUFFER_SIZE (tmp->data);
+    }
+    tmp = g_list_next (tmp);
+  } while (tmp && tmp->data != GROUP_START);
+
+  return buf;
+}

gst/gstbufferlist.h

@@ -0,0 +1,215 @@
+/* GStreamer
+ * Copyright (C) 2009 Axis Communications <dev-gstreamer at axis dot com>
+ * @author Jonas Holmberg <jonas dot holmberg at axis dot com>
+ *
+ * gstbufferlist.h: Header for GstBufferList object
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __GST_BUFFER_LIST_H__
+#define __GST_BUFFER_LIST_H__
+
+#include <gst/gstbuffer.h>
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_BUFFER_LIST (gst_buffer_list_get_type ())
+#define GST_IS_BUFFER_LIST(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_BUFFER_LIST))
+#define GST_IS_BUFFER_LIST_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), GST_TYPE_BUFFER_LIST))
+#define GST_BUFFER_LIST_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), GST_TYPE_BUFFER_LIST, GstBufferListClass))
+#define GST_BUFFER_LIST(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_BUFFER_LIST, GstBufferList))
+#define GST_BUFFER_LIST_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST ((klass), GST_TYPE_BUFFER_LIST, GstBufferListClass))
+#define GST_BUFFER_LIST_CAST(obj) ((GstBufferList *)obj)
+
+typedef struct _GstBufferList GstBufferList;
+typedef struct _GstBufferListClass GstBufferListClass;
+typedef struct _GstBufferListIterator GstBufferListIterator;
+
+/**
+ * GstBufferListDoFunction:
+ * @buffer: the #GstBuffer
+ *
+ * A function for accessing the last buffer returned by
+ * gst_buffer_list_iterator_next(). The function can leave @buffer in the list,
+ * replace @buffer in the list or remove @buffer from the list, depending on
+ * the return value. If the function returns NULL, @buffer will be removed from
+ * the list, otherwise @buffer will be replaced with the returned buffer.
+ *
+ * The last buffer returned by gst_buffer_list_iterator_next() will be replaced
+ * with the buffer returned from the function. The function takes ownership of
+ * @buffer and if a different value than @buffer is returned, @buffer must be
+ * unreffed. If NULL is returned, the buffer will be removed from the list. The
+ * list must be writable.
+ *
+ * Returns: the buffer to replace @buffer in the list, or NULL to remove @buffer
+ * from the list
+ */
+typedef GstBuffer* (*GstBufferListDoFunction) (GstBuffer * buffer);
+
+/**
+ * GstBufferListDoDataFunction:
+ * @buffer: the #GstBuffer
+ * @data: the gpointer to optional user data.
+ *
+ * A function for accessing the last buffer returned by
+ * gst_buffer_list_iterator_next(). The function can leave @buffer in the list,
+ * replace @buffer in the list or remove @buffer from the list, depending on
+ * the return value. If the function returns NULL, @buffer will be removed from
+ * the list, otherwise @buffer will be replaced with the returned buffer.
+ *
+ * The last buffer returned by gst_buffer_list_iterator_next() will be replaced
+ * with the buffer returned from the function. The function takes ownership of
+ * @buffer and if a different value than @buffer is returned, @buffer must be
+ * unreffed. If NULL is returned, the buffer will be removed from the list. The
+ * list must be writable.
+ *
+ * Returns: the buffer to replace @buffer in the list, or NULL to remove @buffer
+ * from the list
+ */
+typedef GstBuffer* (*GstBufferListDoDataFunction) (GstBuffer * buffer, gpointer data);
+
+/**
+ * GstBufferList:
+ * @mini_object: the parent structure
+ *
+ * List of grouped buffers.
+ */
+struct _GstBufferList {
+  GstMiniObject mini_object;
+
+  /*< private >*/
+  GList *buffers;
+
+  gpointer _gst_reserved[GST_PADDING];
+};
+
+struct _GstBufferListClass {
+  GstMiniObjectClass mini_object_class;
+};
+
+GType gst_buffer_list_get_type (void);
+
+/* allocation */
+GstBufferList *gst_buffer_list_new (void);
+
+/* refcounting */
+/**
+ * gst_buffer_list_ref:
+ * @list: a #GstBufferList
+ *
+ * Increases the refcount of the given buffer list by one.
+ *
+ * Note that the refcount affects the writeability of @list and its data, see
+ * gst_buffer_list_make_writable(). It is important to note that keeping
+ * additional references to GstBufferList instances can potentially increase
+ * the number of memcpy operations in a pipeline.
+ *
+ * Returns: @list
+ */
+#ifdef _FOOL_GTK_DOC_
+G_INLINE_FUNC GstBufferList * gst_buffer_list_ref (GstBufferList * list);
+#endif
+
+static inline GstBufferList *
+gst_buffer_list_ref (GstBufferList * list)
+{
+  return GST_BUFFER_LIST_CAST (gst_mini_object_ref (GST_MINI_OBJECT_CAST (
+      list)));
+}
+
+/**
+ * gst_buffer_list_unref:
+ * @list: a #GstBufferList
+ *
+ * Decreases the refcount of the buffer list. If the refcount reaches 0, the
+ * buffer list will be freed.
+ */
+#ifdef _FOOL_GTK_DOC_
+G_INLINE_FUNC void gst_buffer_list_unref (GstBufferList * list);
+#endif
+
+static inline void
+gst_buffer_list_unref (GstBufferList * list)
+{
+  gst_mini_object_unref (GST_MINI_OBJECT_CAST (list));
+}
+
+/* copy */
+/**
+ * gst_buffer_list_copy:
+ * @list: a #GstBufferList
+ *
+ * Create a shallow copy of the given buffer list. This will make a newly
+ * allocated copy of the source list with copies of buffer pointers. The
+ * refcount of buffers pointed to will be increased by one.
+ *
+ * Returns: a new copy of @list.
+ */
+#ifdef _FOOL_GTK_DOC_
+G_INLINE_FUNC GstBufferList * gst_buffer_list_copy (const GstBufferList * list);
+#endif
+
+static inline GstBufferList *
+gst_buffer_list_copy (const GstBufferList * list)
+{
+  return GST_BUFFER_LIST (gst_mini_object_copy (GST_MINI_OBJECT_CAST (list)));
+}
+
+/**
+ * gst_buffer_list_is_writable:
+ * @list: a #GstBufferList
+ *
+ * Tests if you can safely add buffers and groups into a buffer list.
+ */
+#define gst_buffer_list_is_writable(list) gst_mini_object_is_writable (GST_MINI_OBJECT_CAST (list))
+
+/**
+ * gst_buffer_list_make_writable:
+ * @list: a #GstBufferList
+ *
+ * Makes a writable buffer list from the given buffer list. If the source buffer
+ * list is already writable, this will simply return the same buffer list. A
+ * copy will otherwise be made using gst_buffer_list_copy().
+ */
+#define gst_buffer_list_make_writable(list) GST_BUFFER_LIST_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (list)))
+
+guint                    gst_buffer_list_n_groups              (GstBufferList *list);
+
+/* iterator */
+GstBufferListIterator *  gst_buffer_list_iterate               (GstBufferList *list);
+void                     gst_buffer_list_iterator_free         (GstBufferListIterator *it);
+
+guint                    gst_buffer_list_iterator_n_buffers    (const GstBufferListIterator *it);
+GstBuffer *              gst_buffer_list_iterator_next         (GstBufferListIterator *it);
+gboolean                 gst_buffer_list_iterator_next_group   (GstBufferListIterator *it);
+
+void                     gst_buffer_list_iterator_add          (GstBufferListIterator *it, GstBuffer *buffer);
+void                     gst_buffer_list_iterator_add_group    (GstBufferListIterator *it);
+void                     gst_buffer_list_iterator_remove       (GstBufferListIterator *it);
+GstBuffer *              gst_buffer_list_iterator_steal        (GstBufferListIterator *it);
+void                     gst_buffer_list_iterator_take         (GstBufferListIterator *it, GstBuffer *buffer);
+
+GstBuffer *              gst_buffer_list_iterator_do           (GstBufferListIterator *it, GstBufferListDoFunction do_func);
+GstBuffer *              gst_buffer_list_iterator_do_data      (GstBufferListIterator *it, GstBufferListDoDataFunction do_func,
+                                                                gpointer data, GDestroyNotify data_notify);
+
+/* conversion */
+GstBuffer *              gst_buffer_list_iterator_merge_group  (const GstBufferListIterator *it);
+
+G_END_DECLS
+
+#endif /* __GST_BUFFER_LIST_H__ */