gstreamer/libs/gst/base/gstadapter.c
Andy Wingo ecbae942c5 gst/base/gstadapter.*: New function, like peek() but you own the data. Not terribly efficient atm.
Original commit message from CVS:
2005-08-16  Andy Wingo  <wingo@pobox.com>

* gst/base/gstadapter.h:
* gst/base/gstadapter.c (gst_adapter_take): New function, like
peek() but you own the data. Not terribly efficient atm.
2005-08-16 17:23:55 +00:00

332 lines
9.3 KiB
C

/* GStreamer
* Copyright (C) 2004 Benjamin Otte <otte@gnome.org>
*
* 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:gstadapter
* @short_description: object to splice and merge buffers to desired size
* @see_also: #GstBytestream, #GstFilePad
*
* This class is for elements that receive buffers in an undesired size.
* While for example raw video contains one image per buffer, the same is not
* true for a lot of other formats, especially those that come directly from
* a file. So if you have undefined buffer sizes and require a specific size,
* this object is for you.
*
* The theory of operation is like this: All buffers received are put
* into the adapter using gst_adapter_push() and the data is then read back
* in chunks of the desired size using gst_adapter_peek(). After the data is
* processed, it is freed using gst_adapter_flush(). An example function that
* needs to process data in 10 byte chunks could look like this:
* <programlisting>
* void
* process_buffer (GstAdapter *adapter, GstBuffer *buffer)
* {
* guint8 *data;
* // put buffer into adapter
* #gst_adapter_push (adapter, buffer);
* // while we can read out 10 bytes, process them
* while ((data = #gst_adapter_peek (adapter, 10))) {
* // process the 10 bytes here
* // after processing the data, flush it
* #gst_adapter_flush (adapter, 10);
* }
* }
* </programlisting>
* For another example, a simple element inside GStreamer that uses GstAdapter
* is the libvisual element.
*
* A last thing to note is that while GstAdapter is pretty optimized,
* merging buffers still might be an operation that requires a memcpy()
* operation, and this operation is not the fastest. Because of this, some
* functions like gst_adapter_available_fast() are provided to help speed up
* such cases should you want to.
*/
#include <string.h>
#include "gstadapter.h"
/* default size for the assembled data buffer */
#define DEFAULT_SIZE 16
GST_DEBUG_CATEGORY_STATIC (gst_adapter_debug);
#define GST_CAT_DEFAULT gst_adapter_debug
#define _do_init(thing) \
GST_DEBUG_CATEGORY_INIT (gst_adapter_debug, "GstAdapter", 0, "object to splice and merge buffers to desired size")
GST_BOILERPLATE_FULL (GstAdapter, gst_adapter, GObject, G_TYPE_OBJECT, _do_init)
static void gst_adapter_dispose (GObject * object);
static void gst_adapter_finalize (GObject * object);
static void gst_adapter_base_init (gpointer g_class)
{
}
static void
gst_adapter_class_init (GstAdapterClass * klass)
{
GObjectClass *object = G_OBJECT_CLASS (klass);
object->dispose = gst_adapter_dispose;
object->finalize = gst_adapter_finalize;
}
static void
gst_adapter_init (GstAdapter * adapter)
{
adapter->assembled_data = g_malloc (DEFAULT_SIZE);
adapter->assembled_size = DEFAULT_SIZE;
}
static void
gst_adapter_dispose (GObject * object)
{
GstAdapter *adapter = GST_ADAPTER (object);
gst_adapter_clear (adapter);
GST_CALL_PARENT (G_OBJECT_CLASS, dispose, (object));
}
static void
gst_adapter_finalize (GObject * object)
{
GstAdapter *adapter = GST_ADAPTER (object);
g_free (adapter->assembled_data);
GST_CALL_PARENT (G_OBJECT_CLASS, finalize, (object));
}
/**
* gst_adapter_new:
*
* Creates a new #GstAdapter.
*
* Returns: a new #GstAdapter
*/
GstAdapter *
gst_adapter_new (void)
{
return g_object_new (GST_TYPE_ADAPTER, NULL);
}
/**
* gst_adapter_clear:
* @adapter: the #GstAdapter to clear
*
* Removes all buffers from the @adapter.
*/
void
gst_adapter_clear (GstAdapter * adapter)
{
g_return_if_fail (GST_IS_ADAPTER (adapter));
g_slist_foreach (adapter->buflist, (GFunc) gst_mini_object_unref, NULL);
g_slist_free (adapter->buflist);
adapter->buflist = NULL;
adapter->size = 0;
adapter->skip = 0;
adapter->assembled_len = 0;
}
/**
* gst_adapter_push:
* @adapter: a #GstAdapter
* @buf: the #GstBuffer to queue into the adapter
*
* Adds the data from @buf to the data stored inside @adapter and takes
* ownership of the buffer.
*/
void
gst_adapter_push (GstAdapter * adapter, GstBuffer * buf)
{
g_return_if_fail (GST_IS_ADAPTER (adapter));
g_return_if_fail (GST_IS_BUFFER (buf));
adapter->size += GST_BUFFER_SIZE (buf);
adapter->buflist = g_slist_append (adapter->buflist, buf);
}
/**
* gst_adapter_peek:
* @adapter: a #GstAdapter
* @size: number of bytes to peek
*
* Gets the first @size bytes stored in the @adapter. If this many bytes are
* not available, it returns NULL. The returned pointer is valid until the next
* function is called on the adapter.
*
* Returns: a pointer to the first @size bytes of data or NULL
*/
const guint8 *
gst_adapter_peek (GstAdapter * adapter, guint size)
{
GstBuffer *cur;
GSList *cur_list;
guint copied;
g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);
g_return_val_if_fail (size > 0, NULL);
/* we don't have enough data, return NULL */
if (size > adapter->size)
return NULL;
/* we have enough assembled data, return it */
if (adapter->assembled_len >= size)
return adapter->assembled_data;
/* our head buffer has enough data left, return it */
cur = adapter->buflist->data;
if (GST_BUFFER_SIZE (cur) >= size + adapter->skip)
return GST_BUFFER_DATA (cur) + adapter->skip;
if (adapter->assembled_size < size) {
adapter->assembled_size = (size / DEFAULT_SIZE + 1) * DEFAULT_SIZE;
GST_DEBUG_OBJECT (adapter, "setting size of internal buffer to %u",
adapter->assembled_size);
adapter->assembled_data =
g_realloc (adapter->assembled_data, adapter->assembled_size);
}
adapter->assembled_len = size;
copied = GST_BUFFER_SIZE (cur) - adapter->skip;
memcpy (adapter->assembled_data, GST_BUFFER_DATA (cur) + adapter->skip,
copied);
cur_list = g_slist_next (adapter->buflist);
while (copied < size) {
g_assert (cur_list);
cur = cur_list->data;
cur_list = g_slist_next (cur_list);
memcpy (adapter->assembled_data + copied, GST_BUFFER_DATA (cur),
MIN (GST_BUFFER_SIZE (cur), size - copied));
copied = MIN (size, copied + GST_BUFFER_SIZE (cur));
}
return adapter->assembled_data;
}
/**
* gst_adapter_flush:
* @adapter: a #GstAdapter
* @flush: number of bytes to flush
*
* Flushes the first @flush bytes of the @adapter.
*/
void
gst_adapter_flush (GstAdapter * adapter, guint flush)
{
GstBuffer *cur;
g_return_if_fail (GST_IS_ADAPTER (adapter));
g_return_if_fail (flush > 0);
g_return_if_fail (flush <= adapter->size);
GST_LOG_OBJECT (adapter, "flushing %u bytes", flush);
adapter->size -= flush;
adapter->assembled_len = 0;
while (flush > 0) {
cur = adapter->buflist->data;
if (GST_BUFFER_SIZE (cur) <= flush + adapter->skip) {
/* can skip whole buffer */
flush -= GST_BUFFER_SIZE (cur) - adapter->skip;
adapter->skip = 0;
adapter->buflist = g_slist_remove (adapter->buflist, cur);
gst_buffer_unref (cur);
} else {
adapter->skip += flush;
break;
}
}
}
/**
* gst_adapter_take:
* @adapter: a #GstAdapter
* @nbytes: number of bytes to take
*
* Returns a freshly allocated buffer containing the first @nbytes bytes of the
* @adapter. g_free() the return value after use.
*
* Returns: oven-fresh hot data, or NULL if @nbytes bytes are not available
*/
guint8 *
gst_adapter_take (GstAdapter * adapter, guint nbytes)
{
const guint8 *cdata;
guint8 *data;
g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);
g_return_val_if_fail (nbytes > 0, NULL);
GST_LOG_OBJECT (adapter, "taking %u bytes", nbytes);
cdata = gst_adapter_peek (adapter, nbytes);
if (!cdata)
return NULL;
data = g_malloc (nbytes);
memcpy (data, cdata, nbytes);
gst_adapter_flush (adapter, nbytes);
return data;
}
/**
* gst_adapter_available:
* @adapter: a #GstAdapter
*
* Gets the maximum amount of bytes available, that is it returns the maximum
* value that can be supplied to gst_adapter_peek() without that function
* returning NULL.
*
* Returns: amount of bytes available in @adapter
*/
guint
gst_adapter_available (GstAdapter * adapter)
{
g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);
return adapter->size;
}
/**
* gst_adapter_available_fast:
* @adapter: a #GstAdapter
*
* Gets the maximum amount of bytes available without the need to do expensive
* operations (like copying the data into a temporary buffer).
*
* Returns: amount of bytes available in @adapter without expensive operations
*/
guint
gst_adapter_available_fast (GstAdapter * adapter)
{
g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);
if (!adapter->buflist)
return 0;
if (adapter->assembled_len)
return adapter->assembled_len;
g_assert (GST_BUFFER_SIZE (adapter->buflist->data) > adapter->skip);
return GST_BUFFER_SIZE (adapter->buflist->data) - adapter->skip;
}