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b2ff4bd747
Original commit message from CVS: * docs/gst/gstreamer-sections.txt: Added some docs for GstCollectData. * gst/base/gstadapter.c: Some small code example fix. * gst/base/gstcollectpads.c: * gst/base/gstcollectpads.h: Document some more.
372 lines
11 KiB
C
372 lines
11 KiB
C
/* GStreamer
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* Copyright (C) 2004 Benjamin Otte <otte@gnome.org>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/**
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* SECTION:gstadapter
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* @short_description: adapts incoming data on a sink pad into chunks of N bytes
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*
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* This class is for elements that receive buffers in an undesired size.
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* While for example raw video contains one image per buffer, the same is not
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* true for a lot of other formats, especially those that come directly from
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* a file. So if you have undefined buffer sizes and require a specific size,
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* this object is for you.
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*
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* The theory of operation is like this: All buffers received are put
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* into the adapter using gst_adapter_push() and the data is then read back
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* in chunks of the desired size using gst_adapter_peek(). After the data is
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* processed, it is freed using gst_adapter_flush().
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*
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* For example, a sink pad's chain function that needs to pass data to a library
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* in 512-byte chunks could be implemented like this:
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* <programlisting>
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* static GstFlowReturn
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* sink_pad_chain (GstPad *pad, GstBuffer *buffer)
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* {
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* MyElement *this;
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* GstAdapter *adapter;
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* GstFlowReturn ret = GST_FLOW_OK;
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*
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* // will give the element an extra ref; remember to drop it
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* this = MY_ELEMENT (gst_pad_get_parent (pad));
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* adapter = this->adapter;
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*
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* // put buffer into adapter
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* #gst_adapter_push (adapter, buffer);
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* // while we can read out 512 bytes, process them
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* while (#gst_adapter_available (adapter) >= 512 && ret == GST_FLOW_OK) {
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* // use flowreturn as an error value
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* ret = my_library_foo (#gst_adapter_peek (adapter, 512));
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* #gst_adapter_flush (adapter, 512);
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* }
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*
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* gst_object_unref (this);
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* return ret;
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* }
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* </programlisting>
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* For another example, a simple element inside GStreamer that uses GstAdapter
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* is the libvisual element.
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*
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* An element using GstAdapter in its sink pad chain function should ensure that
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* when the FLUSH_STOP event is received, that any queued data is cleared using
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* gst_adapter_clear(). Data should also be cleared or processed on EOS and
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* when changing state from #GST_STATE_PAUSED to #GST_STATE_READY.
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*
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* A last thing to note is that while GstAdapter is pretty optimized,
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* merging buffers still might be an operation that requires a memcpy()
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* operation, and this operation is not the fastest. Because of this, some
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* functions like gst_adapter_available_fast() are provided to help speed up
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* such cases should you want to.
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*
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* GstAdapter is not MT safe. All operations on an adapter must be serialized by
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* the caller. This is not normally a problem, however, as the normal use case
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* of GstAdapter is inside one pad's chain function, in which case access is
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* serialized via the pad's stream lock.
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*
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* Last reviewed on 2005-11-08 (0.9.5).
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*/
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#include <string.h>
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#include "gstadapter.h"
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/* default size for the assembled data buffer */
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#define DEFAULT_SIZE 16
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GST_DEBUG_CATEGORY_STATIC (gst_adapter_debug);
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#define GST_CAT_DEFAULT gst_adapter_debug
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#define _do_init(thing) \
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GST_DEBUG_CATEGORY_INIT (gst_adapter_debug, "adapter", 0, "object to splice and merge buffers to desired size")
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GST_BOILERPLATE_FULL (GstAdapter, gst_adapter, GObject, G_TYPE_OBJECT,
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_do_init);
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static void gst_adapter_dispose (GObject * object);
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static void gst_adapter_finalize (GObject * object);
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static void
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gst_adapter_base_init (gpointer g_class)
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{
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/* nop */
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}
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static void
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gst_adapter_class_init (GstAdapterClass * klass)
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{
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GObjectClass *object = G_OBJECT_CLASS (klass);
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object->dispose = gst_adapter_dispose;
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object->finalize = gst_adapter_finalize;
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}
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static void
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gst_adapter_init (GstAdapter * adapter, GstAdapterClass * g_class)
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{
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adapter->assembled_data = g_malloc (DEFAULT_SIZE);
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adapter->assembled_size = DEFAULT_SIZE;
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}
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static void
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gst_adapter_dispose (GObject * object)
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{
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GstAdapter *adapter = GST_ADAPTER (object);
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gst_adapter_clear (adapter);
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GST_CALL_PARENT (G_OBJECT_CLASS, dispose, (object));
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}
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static void
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gst_adapter_finalize (GObject * object)
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{
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GstAdapter *adapter = GST_ADAPTER (object);
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g_free (adapter->assembled_data);
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GST_CALL_PARENT (G_OBJECT_CLASS, finalize, (object));
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}
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/**
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* gst_adapter_new:
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*
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* Creates a new #GstAdapter.
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*
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* Returns: a new #GstAdapter
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*/
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GstAdapter *
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gst_adapter_new (void)
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{
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return g_object_new (GST_TYPE_ADAPTER, NULL);
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}
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/**
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* gst_adapter_clear:
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* @adapter: a #GstAdapter
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*
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* Removes all buffers from @adapter.
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*/
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void
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gst_adapter_clear (GstAdapter * adapter)
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{
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g_return_if_fail (GST_IS_ADAPTER (adapter));
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g_slist_foreach (adapter->buflist, (GFunc) gst_mini_object_unref, NULL);
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g_slist_free (adapter->buflist);
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adapter->buflist = NULL;
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adapter->size = 0;
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adapter->skip = 0;
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adapter->assembled_len = 0;
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}
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/**
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* gst_adapter_push:
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* @adapter: a #GstAdapter
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* @buf: a #GstBuffer to add to queue in the adapter
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*
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* Adds the data from @buf to the data stored inside @adapter and takes
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* ownership of the buffer.
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*/
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void
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gst_adapter_push (GstAdapter * adapter, GstBuffer * buf)
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{
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g_return_if_fail (GST_IS_ADAPTER (adapter));
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g_return_if_fail (GST_IS_BUFFER (buf));
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adapter->size += GST_BUFFER_SIZE (buf);
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adapter->buflist = g_slist_append (adapter->buflist, buf);
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}
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/**
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* gst_adapter_peek:
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* @adapter: a #GstAdapter
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* @size: the number of bytes to peek
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*
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* Gets the first @size bytes stored in the @adapter. The returned pointer is
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* valid until the next function is called on the adapter.
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*
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* Note that setting the returned pointer as the data of a #GstBuffer is
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* incorrect for general-purpose plugins. The reason is that if a downstream
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* element stores the buffer so that it has access to it outside of the bounds
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* of its chain function, the buffer will have an invalid data pointer after
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* your element flushes the bytes. In that case you should use
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* gst_adapter_take(), which returns a freshly-allocated buffer that you can set
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* as #GstBuffer malloc_data.
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*
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* Returns #NULL if @size bytes are not available.
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*
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* Returns: a pointer to the first @size bytes of data, or NULL.
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*/
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const guint8 *
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gst_adapter_peek (GstAdapter * adapter, guint size)
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{
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GstBuffer *cur;
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GSList *cur_list;
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guint copied;
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g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);
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g_return_val_if_fail (size > 0, NULL);
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/* we don't have enough data, return NULL */
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if (size > adapter->size)
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return NULL;
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/* we have enough assembled data, return it */
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if (adapter->assembled_len >= size)
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return adapter->assembled_data;
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/* our head buffer has enough data left, return it */
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cur = adapter->buflist->data;
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if (GST_BUFFER_SIZE (cur) >= size + adapter->skip)
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return GST_BUFFER_DATA (cur) + adapter->skip;
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if (adapter->assembled_size < size) {
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adapter->assembled_size = (size / DEFAULT_SIZE + 1) * DEFAULT_SIZE;
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GST_DEBUG_OBJECT (adapter, "setting size of internal buffer to %u",
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adapter->assembled_size);
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adapter->assembled_data =
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g_realloc (adapter->assembled_data, adapter->assembled_size);
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}
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adapter->assembled_len = size;
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copied = GST_BUFFER_SIZE (cur) - adapter->skip;
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memcpy (adapter->assembled_data, GST_BUFFER_DATA (cur) + adapter->skip,
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copied);
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cur_list = g_slist_next (adapter->buflist);
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while (copied < size) {
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g_assert (cur_list);
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cur = cur_list->data;
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cur_list = g_slist_next (cur_list);
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memcpy (adapter->assembled_data + copied, GST_BUFFER_DATA (cur),
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MIN (GST_BUFFER_SIZE (cur), size - copied));
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copied = MIN (size, copied + GST_BUFFER_SIZE (cur));
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}
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return adapter->assembled_data;
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}
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/**
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* gst_adapter_flush:
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* @adapter: a #GstAdapter
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* @flush: the number of bytes to flush
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*
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* Flushes the first @flush bytes in the @adapter. The caller must ensure that
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* at least this many bytes are available.
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*
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* See also: gst_adapter_peek().
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*/
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void
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gst_adapter_flush (GstAdapter * adapter, guint flush)
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{
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GstBuffer *cur;
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g_return_if_fail (GST_IS_ADAPTER (adapter));
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g_return_if_fail (flush >= 0);
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g_return_if_fail (flush <= adapter->size);
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GST_LOG_OBJECT (adapter, "flushing %u bytes", flush);
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adapter->size -= flush;
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adapter->assembled_len = 0;
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while (flush > 0) {
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cur = adapter->buflist->data;
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if (GST_BUFFER_SIZE (cur) <= flush + adapter->skip) {
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/* can skip whole buffer */
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flush -= GST_BUFFER_SIZE (cur) - adapter->skip;
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adapter->skip = 0;
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adapter->buflist = g_slist_remove (adapter->buflist, cur);
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gst_buffer_unref (cur);
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} else {
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adapter->skip += flush;
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break;
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}
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}
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}
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/**
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* gst_adapter_take:
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* @adapter: a #GstAdapter
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* @nbytes: the number of bytes to take
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*
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* Returns a freshly allocated buffer containing the first @nbytes bytes of the
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* @adapter.
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*
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* Caller owns returned value.
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*
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* Returns: oven-fresh hot data, or #NULL if @nbytes bytes are not available
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*/
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guint8 *
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gst_adapter_take (GstAdapter * adapter, guint nbytes)
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{
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const guint8 *cdata;
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guint8 *data;
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g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);
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g_return_val_if_fail (nbytes > 0, NULL);
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GST_LOG_OBJECT (adapter, "taking %u bytes", nbytes);
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cdata = gst_adapter_peek (adapter, nbytes);
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if (!cdata)
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return NULL;
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data = g_malloc (nbytes);
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memcpy (data, cdata, nbytes);
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gst_adapter_flush (adapter, nbytes);
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return data;
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}
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/**
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* gst_adapter_available:
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* @adapter: a #GstAdapter
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*
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* Gets the maximum amount of bytes available, that is it returns the maximum
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* value that can be supplied to gst_adapter_peek() without that function
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* returning NULL.
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*
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* Returns: number of bytes available in @adapter
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*/
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guint
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gst_adapter_available (GstAdapter * adapter)
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{
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g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);
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return adapter->size;
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}
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/**
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* gst_adapter_available_fast:
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* @adapter: a #GstAdapter
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*
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* Gets the maximum number of bytes available without the need to do expensive
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* operations (like copying the data into a temporary buffer).
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*
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* Returns: number of bytes available in @adapter without expensive operations
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*/
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guint
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gst_adapter_available_fast (GstAdapter * adapter)
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{
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g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);
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if (!adapter->buflist)
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return 0;
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if (adapter->assembled_len)
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return adapter->assembled_len;
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g_assert (GST_BUFFER_SIZE (adapter->buflist->data) > adapter->skip);
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return GST_BUFFER_SIZE (adapter->buflist->data) - adapter->skip;
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}
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