--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gstreamer_core/gst/gstbuffer.c	Thu Dec 17 08:53:32 2009 +0200
@@ -0,0 +1,791 @@
+/* GStreamer
+ * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
+ *                    2000 Wim Taymans <wtay@chello.be>
+ *
+ * gstbuffer.c: Buffer operations
+ *
+ * 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:gstbuffer
+ * @short_description: Data-passing buffer type, supporting sub-buffers.
+ * @see_also: #GstPad, #GstMiniObject
+ *
+ * Buffers are the basic unit of data transfer in GStreamer.  The #GstBuffer
+ * type provides all the state necessary to define a region of memory as part
+ * of a stream.  Sub-buffers are also supported, allowing a smaller region of a
+ * buffer to become its own buffer, with mechanisms in place to ensure that
+ * neither memory space goes away prematurely.
+ *
+ * Buffers are usually created with gst_buffer_new(). After a buffer has been
+ * created one will typically allocate memory for it and set the size of the
+ * buffer data.  The following example creates a buffer that can hold a given
+ * video frame with a given width, height and bits per plane.
+ * <example>
+ * <title>Creating a buffer for a video frame</title>
+ *   <programlisting>
+ *   GstBuffer *buffer;
+ *   gint size, width, height, bpp;
+ *   ...
+ *   size = width * height * bpp;
+ *   buffer = gst_buffer_new ();
+ *   GST_BUFFER_SIZE (buffer) = size;
+ *   GST_BUFFER_MALLOCDATA (buffer) = g_malloc (size);
+ *   GST_BUFFER_DATA (buffer) = GST_BUFFER_MALLOCDATA (buffer);
+ *   ...
+ *   </programlisting>
+ * </example>
+ *
+ * Alternatively, use gst_buffer_new_and_alloc()
+ * to create a buffer with preallocated data of a given size.
+ *
+ * The data pointed to by the buffer can be retrieved with the GST_BUFFER_DATA()
+ * macro. The size of the data can be found with GST_BUFFER_SIZE(). For buffers
+ * of size 0, the data pointer is undefined (usually NULL) and should never be used.
+ *
+ * If an element knows what pad you will push the buffer out on, it should use
+ * gst_pad_alloc_buffer() instead to create a buffer.  This allows downstream
+ * elements to provide special buffers to write in, like hardware buffers.
+ *
+ * A buffer has a pointer to a #GstCaps describing the media type of the data
+ * in the buffer. Attach caps to the buffer with gst_buffer_set_caps(); this
+ * is typically done before pushing out a buffer using gst_pad_push() so that
+ * the downstream element knows the type of the buffer.
+ *
+ * A buffer will usually have a timestamp, and a duration, but neither of these
+ * are guaranteed (they may be set to #GST_CLOCK_TIME_NONE). Whenever a
+ * meaningful value can be given for these, they should be set. The timestamp
+ * and duration are measured in nanoseconds (they are #GstClockTime values).
+ *
+ * A buffer can also have one or both of a start and an end offset. These are
+ * media-type specific. For video buffers, the start offset will generally be
+ * the frame number. For audio buffers, it will be the number of samples
+ * produced so far. For compressed data, it could be the byte offset in a
+ * source or destination file. Likewise, the end offset will be the offset of
+ * the end of the buffer. These can only be meaningfully interpreted if you
+ * know the media type of the buffer (the #GstCaps set on it). Either or both
+ * can be set to #GST_BUFFER_OFFSET_NONE.
+ *
+ * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
+ * done when you want to keep a handle to the buffer after pushing it to the
+ * next element.
+ *
+ * To efficiently create a smaller buffer out of an existing one, you can
+ * use gst_buffer_create_sub().
+ *
+ * If a plug-in wants to modify the buffer data in-place, it should first obtain
+ * a buffer that is safe to modify by using gst_buffer_make_writable().  This
+ * function is optimized so that a copy will only be made when it is necessary.
+ *
+ * A plugin that only wishes to modify the metadata of a buffer, such as the
+ * offset, timestamp or caps, should use gst_buffer_make_metadata_writable(),
+ * which will create a subbuffer of the original buffer to ensure the caller
+ * has sole ownership, and not copy the buffer data.
+ *
+ * Several flags of the buffer can be set and unset with the
+ * GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use
+ * GST_BUFFER_FLAG_IS_SET() to test if a certain #GstBufferFlag is set.
+ *
+ * Buffers can be efficiently merged into a larger buffer with
+ * gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
+ * function returns TRUE.
+ *
+ * An element should either unref the buffer or push it out on a src pad
+ * using gst_pad_push() (see #GstPad).
+ *
+ * Buffers are usually freed by unreffing them with gst_buffer_unref(). When
+ * the refcount drops to 0, any data pointed to by GST_BUFFER_MALLOCDATA() will
+ * also be freed.
+ *
+ * Last reviewed on August 11th, 2006 (0.10.10)
+ */
+#include "gst_private.h"
+
+#include "gstbuffer.h"
+#include "gstinfo.h"
+#include "gstutils.h"
+#include "gstminiobject.h"
+
+static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
+static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
+static void gst_buffer_finalize (GstBuffer * buffer);
+static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
+static GType gst_subbuffer_get_type (void);
+
+static GType _gst_subbuffer_type = 0;
+static GType _gst_buffer_type = 0;
+
+static GstMiniObjectClass *parent_class = NULL;
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+
+void
+_gst_buffer_initialize (void)
+{
+  /* the GstMiniObject types need to be class_ref'd once before it can be
+   * done from multiple threads;
+   * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
+  g_type_class_ref (gst_buffer_get_type ());
+  g_type_class_ref (gst_subbuffer_get_type ());
+}
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+
+GType
+gst_buffer_get_type (void)
+{
+  if (G_UNLIKELY (_gst_buffer_type == 0)) {
+    static const GTypeInfo buffer_info = {
+      sizeof (GstBufferClass),
+      NULL,
+      NULL,
+      gst_buffer_class_init,
+      NULL,
+      NULL,
+      sizeof (GstBuffer),
+      0,
+      gst_buffer_init,
+      NULL
+    };
+
+    _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
+        "GstBuffer", &buffer_info, 0);
+  }
+  return _gst_buffer_type;
+}
+
+static void
+gst_buffer_class_init (gpointer g_class, gpointer class_data)
+{
+  GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
+
+  parent_class = g_type_class_peek_parent (g_class);
+
+  buffer_class->mini_object_class.copy =
+      (GstMiniObjectCopyFunction) _gst_buffer_copy;
+  buffer_class->mini_object_class.finalize =
+      (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
+
+}
+
+static void
+gst_buffer_finalize (GstBuffer * buffer)
+{
+  g_return_if_fail (buffer != NULL);
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
+
+  /* free our data */
+  g_free (buffer->malloc_data);
+
+  gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
+
+  GST_MINI_OBJECT_CLASS (parent_class)->finalize (GST_MINI_OBJECT (buffer));
+}
+
+/**
+ * gst_buffer_copy_metadata:
+ * @dest: a destination #GstBuffer
+ * @src: a source #GstBuffer
+ * @flags: flags indicating what metadata fields should be copied.
+ *
+ * Copies the metadata from @src into @dest. The data, size and mallocdata
+ * fields are not copied.
+ *
+ * @flags indicate which fields will be copied. Use #GST_BUFFER_COPY_ALL to copy
+ * all the metadata fields.
+ *
+ * This function is typically called from a custom buffer copy function after
+ * creating @dest and setting the data, size, mallocdata.
+ *
+ * Since: 0.10.13
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+void
+gst_buffer_copy_metadata (GstBuffer * dest, const GstBuffer * src,
+    GstBufferCopyFlags flags)
+{
+  g_return_if_fail (dest != NULL);
+  g_return_if_fail (src != NULL);
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", src, dest);
+
+  if (flags & GST_BUFFER_COPY_FLAGS) {
+    guint mask;
+
+    /* copy relevant flags */
+    mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
+        GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
+        GST_BUFFER_FLAG_GAP;
+    GST_MINI_OBJECT_FLAGS (dest) |= GST_MINI_OBJECT_FLAGS (src) & mask;
+  }
+
+  if (flags & GST_BUFFER_COPY_TIMESTAMPS) {
+    GST_BUFFER_TIMESTAMP (dest) = GST_BUFFER_TIMESTAMP (src);
+    GST_BUFFER_DURATION (dest) = GST_BUFFER_DURATION (src);
+    GST_BUFFER_OFFSET (dest) = GST_BUFFER_OFFSET (src);
+    GST_BUFFER_OFFSET_END (dest) = GST_BUFFER_OFFSET_END (src);
+  }
+
+  if (flags & GST_BUFFER_COPY_CAPS) {
+    if (GST_BUFFER_CAPS (src))
+      GST_BUFFER_CAPS (dest) = gst_caps_ref (GST_BUFFER_CAPS (src));
+    else
+      GST_BUFFER_CAPS (dest) = NULL;
+  }
+}
+
+static GstBuffer *
+_gst_buffer_copy (GstBuffer * buffer)
+{
+  GstBuffer *copy;
+
+  g_return_val_if_fail (buffer != NULL, NULL);
+
+  /* create a fresh new buffer */
+  copy = gst_buffer_new ();
+
+  /* we simply copy everything from our parent */
+  copy->data = g_memdup (buffer->data, buffer->size);
+  /* make sure it gets freed (even if the parent is subclassed, we return a
+     normal buffer) */
+  copy->malloc_data = copy->data;
+  copy->size = buffer->size;
+
+  gst_buffer_copy_metadata (copy, buffer, GST_BUFFER_COPY_ALL);
+
+  return copy;
+}
+
+static void
+gst_buffer_init (GTypeInstance * instance, gpointer g_class)
+{
+  GstBuffer *buffer;
+
+  buffer = (GstBuffer *) instance;
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
+
+  GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
+  GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
+  GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
+  GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
+}
+
+/**
+ * gst_buffer_new:
+ *
+ * Creates a newly allocated buffer without any data.
+ *
+ * MT safe.
+ * Returns: the new #GstBuffer.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBuffer *
+gst_buffer_new (void)
+{
+  GstBuffer *newbuf;
+
+  newbuf = (GstBuffer *) gst_mini_object_new (_gst_buffer_type);
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
+
+  return newbuf;
+}
+
+/**
+ * gst_buffer_new_and_alloc:
+ * @size: the size of the new buffer's data.
+ *
+ * Creates a newly allocated buffer with data of the given size.
+ * The buffer memory is not cleared. If the requested amount of
+ * memory can't be allocated, the program will abort. Use
+ * gst_buffer_try_new_and_alloc() if you want to handle this case
+ * gracefully or have gotten the size to allocate from an untrusted
+ * source such as a media stream.
+ * 
+ *
+ * Note that when @size == 0, the buffer data pointer will be NULL.
+ *
+ * MT safe.
+ * Returns: the new #GstBuffer.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBuffer *
+gst_buffer_new_and_alloc (guint size)
+{
+  GstBuffer *newbuf;
+
+  newbuf = gst_buffer_new ();
+
+  newbuf->malloc_data = g_malloc (size);
+  GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
+  GST_BUFFER_SIZE (newbuf) = size;
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
+
+  return newbuf;
+}
+
+/**
+ * gst_buffer_try_new_and_alloc:
+ * @size: the size of the new buffer's data.
+ *
+ * Tries to create a newly allocated buffer with data of the given size. If
+ * the requested amount of memory can't be allocated, NULL will be returned.
+ * The buffer memory is not cleared.
+ *
+ * Note that when @size == 0, the buffer data pointer will be NULL.
+ *
+ * MT safe.
+ *
+ * Returns: a new #GstBuffer, or NULL if the memory couldn't be allocated.
+ *
+ * Since: 0.10.13
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBuffer *
+gst_buffer_try_new_and_alloc (guint size)
+{
+  GstBuffer *newbuf;
+  guint8 *malloc_data;
+
+  malloc_data = g_try_malloc (size);
+
+  if (G_UNLIKELY (malloc_data == NULL && size != 0)) {
+    GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
+    return NULL;
+  }
+
+  /* FIXME: there's no g_type_try_create_instance() in GObject yet, so this
+   * will still abort if a new GstBuffer structure can't be allocated */
+  newbuf = gst_buffer_new ();
+
+  GST_BUFFER_MALLOCDATA (newbuf) = malloc_data;
+  GST_BUFFER_DATA (newbuf) = malloc_data;
+  GST_BUFFER_SIZE (newbuf) = size;
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
+
+  return newbuf;
+}
+
+/**
+ * gst_buffer_get_caps:
+ * @buffer: a #GstBuffer.
+ *
+ * Gets the media type of the buffer. This can be NULL if there
+ * is no media type attached to this buffer.
+ *
+ * Returns: a reference to the #GstCaps. unref after usage.
+ * Returns NULL if there were no caps on this buffer.
+ */
+/* this is not made atomic because if the buffer were reffed from multiple
+ * threads, it would have a refcount > 2 and thus be immutable.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstCaps *
+gst_buffer_get_caps (GstBuffer * buffer)
+{
+  GstCaps *ret;
+
+  g_return_val_if_fail (buffer != NULL, NULL);
+
+  ret = GST_BUFFER_CAPS (buffer);
+
+  if (ret)
+    gst_caps_ref (ret);
+
+  return ret;
+}
+
+/**
+ * gst_buffer_set_caps:
+ * @buffer: a #GstBuffer.
+ * @caps: a #GstCaps.
+ *
+ * Sets the media type on the buffer. The refcount of the caps will
+ * be increased and any previous caps on the buffer will be
+ * unreffed.
+ */
+/* this is not made atomic because if the buffer were reffed from multiple
+ * threads, it would have a refcount > 2 and thus be immutable.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+void
+gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
+{
+  g_return_if_fail (buffer != NULL);
+
+  gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
+}
+
+/**
+ * gst_buffer_is_metadata_writable:
+ * @buf: a #GstBuffer
+ *
+ * Similar to gst_buffer_is_writable, but this only ensures that the
+ * refcount of the buffer is 1, indicating that the caller is the sole
+ * owner and can change the buffer metadata, such as caps and timestamps.
+ *
+ * Returns: TRUE if the metadata is writable.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+gboolean
+gst_buffer_is_metadata_writable (GstBuffer * buf)
+{
+  return (GST_MINI_OBJECT_REFCOUNT_VALUE (GST_MINI_OBJECT_CAST (buf)) == 1);
+}
+
+/**
+ * gst_buffer_make_metadata_writable:
+ * @buf: a #GstBuffer
+ *
+ * Similar to gst_buffer_make_writable, but does not ensure that the buffer
+ * data array is writable. Instead, this just ensures that the returned buffer
+ * is solely owned by the caller, by creating a subbuffer of the original
+ * buffer if necessary.
+ * 
+ * After calling this function, @buf should not be referenced anymore. The
+ * result of this function has guaranteed writable metadata.
+ *
+ * Returns: A new #GstBuffer with writable metadata.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBuffer *
+gst_buffer_make_metadata_writable (GstBuffer * buf)
+{
+  GstBuffer *ret;
+
+  if (gst_buffer_is_metadata_writable (buf)) {
+    ret = buf;
+  } else {
+    ret = gst_buffer_create_sub (buf, 0, GST_BUFFER_SIZE (buf));
+
+    gst_buffer_unref (buf);
+  }
+
+  return ret;
+}
+
+typedef struct _GstSubBuffer GstSubBuffer;
+typedef struct _GstSubBufferClass GstSubBufferClass;
+
+#define GST_IS_SUBBUFFER(obj)   (G_TYPE_CHECK_INSTANCE_TYPE ((obj), _gst_subbuffer_type))
+#define GST_SUBBUFFER_CAST(obj) ((GstSubBuffer *)(obj))
+
+struct _GstSubBuffer
+{
+  GstBuffer buffer;
+
+  GstBuffer *parent;
+};
+
+struct _GstSubBufferClass
+{
+  GstBufferClass buffer_class;
+};
+
+static GstBufferClass *sub_parent_class;
+
+static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
+static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
+static void gst_subbuffer_finalize (GstSubBuffer * buffer);
+
+static GType
+gst_subbuffer_get_type (void)
+{
+  if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
+    static const GTypeInfo subbuffer_info = {
+      sizeof (GstSubBufferClass),
+      NULL,
+      NULL,
+      gst_subbuffer_class_init,
+      NULL,
+      NULL,
+      sizeof (GstSubBuffer),
+      0,
+      gst_subbuffer_init,
+      NULL
+    };
+
+    _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
+        "GstSubBuffer", &subbuffer_info, 0);
+  }
+  return _gst_subbuffer_type;
+}
+
+static void
+gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
+{
+  GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
+
+  sub_parent_class = g_type_class_peek_parent (g_class);
+
+  buffer_class->mini_object_class.finalize =
+      (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
+}
+
+static void
+gst_subbuffer_finalize (GstSubBuffer * buffer)
+{
+  gst_buffer_unref (buffer->parent);
+
+  GST_MINI_OBJECT_CLASS (sub_parent_class)->
+      finalize (GST_MINI_OBJECT_CAST (buffer));
+}
+
+static void
+gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
+{
+  GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
+}
+
+/**
+ * gst_buffer_create_sub:
+ * @parent: a #GstBuffer.
+ * @offset: the offset into parent #GstBuffer at which the new sub-buffer 
+ *          begins.
+ * @size: the size of the new #GstBuffer sub-buffer, in bytes.
+ *
+ * Creates a sub-buffer from @parent at @offset and @size.
+ * This sub-buffer uses the actual memory space of the parent buffer.
+ * This function will copy the offset and timestamp fields when the
+ * offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and 
+ * #GST_BUFFER_OFFSET_NONE.
+ * If @offset equals 0 and @size equals the total size of @buffer, the
+ * duration and offset end fields are also copied. If not they will be set
+ * to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
+ *
+ * MT safe.
+ * Returns: the new #GstBuffer.
+ * Returns NULL if the arguments were invalid.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBuffer *
+gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
+{
+  GstSubBuffer *subbuffer;
+  GstBuffer *parent;
+  gboolean complete;
+
+  g_return_val_if_fail (buffer != NULL, NULL);
+  g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
+  g_return_val_if_fail (buffer->size >= offset + size, NULL);
+
+  /* find real parent */
+  if (GST_IS_SUBBUFFER (buffer)) {
+    parent = GST_SUBBUFFER_CAST (buffer)->parent;
+  } else {
+    parent = buffer;
+  }
+  gst_buffer_ref (parent);
+
+  /* create the new buffer */
+  subbuffer = (GstSubBuffer *) gst_mini_object_new (_gst_subbuffer_type);
+  subbuffer->parent = parent;
+
+  GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
+      parent);
+
+  /* set the right values in the child */
+  GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
+  GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
+
+  if ((offset == 0) && (size == GST_BUFFER_SIZE (buffer))) {
+    /* copy all the flags except IN_CAPS */
+    GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAGS (buffer));
+    GST_BUFFER_FLAG_UNSET (subbuffer, GST_BUFFER_FLAG_IN_CAPS);
+  } else {
+    /* copy only PREROLL & GAP flags */
+    GST_BUFFER_FLAG_SET (subbuffer, (GST_BUFFER_FLAGS (buffer) &
+            (GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_GAP)));
+  }
+
+  /* we can copy the timestamp and offset if the new buffer starts at
+   * offset 0 */
+  if (offset == 0) {
+    GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
+    GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
+    complete = (buffer->size == size);
+  } else {
+    GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
+    GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
+    complete = FALSE;
+  }
+
+  if (complete) {
+    GstCaps *caps;
+
+    /* if we copied the complete buffer we can copy the duration,
+     * offset_end and caps as well */
+    GST_BUFFER_DURATION (subbuffer) = GST_BUFFER_DURATION (buffer);
+    GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_END (buffer);
+    if ((caps = GST_BUFFER_CAPS (buffer)))
+      gst_caps_ref (caps);
+    GST_BUFFER_CAPS (subbuffer) = caps;
+  } else {
+    GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
+    GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
+    GST_BUFFER_CAPS (subbuffer) = NULL;
+  }
+  return GST_BUFFER_CAST (subbuffer);
+}
+
+/**
+ * gst_buffer_is_span_fast:
+ * @buf1: the first #GstBuffer.
+ * @buf2: the second #GstBuffer.
+ *
+ * Determines whether a gst_buffer_span() can be done without copying
+ * the contents, that is, whether the data areas are contiguous sub-buffers of 
+ * the same buffer.
+ *
+ * MT safe.
+ * Returns: TRUE if the buffers are contiguous,
+ * FALSE if a copy would be required.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+gboolean
+gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
+{
+  g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
+  g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
+  g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
+
+  /* it's only fast if we have subbuffers of the same parent */
+  return (GST_IS_SUBBUFFER (buf1) &&
+      GST_IS_SUBBUFFER (buf2) &&
+      (GST_SUBBUFFER_CAST (buf1)->parent == GST_SUBBUFFER_CAST (buf2)->parent)
+      && ((buf1->data + buf1->size) == buf2->data));
+}
+
+/**
+ * gst_buffer_span:
+ * @buf1: the first source #GstBuffer to merge.
+ * @offset: the offset in the first buffer from where the new
+ * buffer should start.
+ * @buf2: the second source #GstBuffer to merge.
+ * @len: the total length of the new buffer.
+ *
+ * Creates a new buffer that consists of part of buf1 and buf2.
+ * Logically, buf1 and buf2 are concatenated into a single larger
+ * buffer, and a new buffer is created at the given offset inside
+ * this space, with a given length.
+ *
+ * If the two source buffers are children of the same larger buffer,
+ * and are contiguous, the new buffer will be a child of the shared
+ * parent, and thus no copying is necessary. you can use
+ * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
+ *
+ * MT safe.
+ * Returns: the new #GstBuffer that spans the two source buffers.
+ * Returns NULL if the arguments are invalid.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBuffer *
+gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
+    guint32 len)
+{
+  GstBuffer *newbuf;
+
+  g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
+  g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
+  g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
+  g_return_val_if_fail (len > 0, NULL);
+  g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
+
+  /* if the two buffers have the same parent and are adjacent */
+  if (gst_buffer_is_span_fast (buf1, buf2)) {
+    GstBuffer *parent = GST_SUBBUFFER_CAST (buf1)->parent;
+
+    /* we simply create a subbuffer of the common parent */
+    newbuf = gst_buffer_create_sub (parent,
+        buf1->data - parent->data + offset, len);
+  } else {
+    GST_CAT_DEBUG (GST_CAT_BUFFER,
+        "slow path taken while spanning buffers %p and %p", buf1, buf2);
+    /* otherwise we simply have to brute-force copy the buffers */
+    newbuf = gst_buffer_new_and_alloc (len);
+
+    /* copy the first buffer's data across */
+    memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
+    /* copy the second buffer's data across */
+    memcpy (newbuf->data + (buf1->size - offset), buf2->data,
+        len - (buf1->size - offset));
+  }
+  /* if the offset is 0, the new buffer has the same timestamp as buf1 */
+  if (offset == 0) {
+    GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
+    GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
+
+    /* if we completely merged the two buffers (appended), we can
+     * calculate the duration too. Also make sure we's not messing with
+     * invalid DURATIONS */
+    if (buf1->size + buf2->size == len) {
+      if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
+          GST_BUFFER_DURATION_IS_VALID (buf2)) {
+        /* add duration */
+        GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
+            GST_BUFFER_DURATION (buf2);
+      }
+      if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
+        /* add offset_end */
+        GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);
+      }
+    }
+  }
+
+  return newbuf;
+}