gstreamer/gst/gstbuffer.c
Wim Taymans d16ce65df7 gst/gstbuffer.c: Small docs update.
Original commit message from CVS:
* gst/gstbuffer.c:
Small docs update.

* gst/gstcaps.c: (gst_caps_is_equal):
Don't assert on NULL <--> X. Fixes #323260

* gst/gstminiobject.c: (gst_mini_object_replace):
If we're doing atomic operations, we might just as well use
the proper way to get an atomic pointer.

* libs/gst/base/gstbasesink.c: (gst_base_sink_get_position):
Clean up debugging.
2005-12-07 15:16:43 +00:00

578 lines
18 KiB
C

/* 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_alloc (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.
*
* 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 the plug-in wants to modify the buffer 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.
*
* 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 November 23th, 2005 (0.9.5)
*/
#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);
void
_gst_buffer_initialize (void)
{
gpointer ptr;
gst_buffer_get_type ();
/* 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 */
ptr = g_type_class_ref (GST_TYPE_BUFFER);
g_type_class_unref (ptr);
}
GType
gst_buffer_get_type (void)
{
static GType _gst_buffer_type;
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);
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 */
if (buffer->malloc_data) {
g_free (buffer->malloc_data);
}
gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
}
static GstBuffer *
_gst_buffer_copy (GstBuffer * buffer)
{
GstBuffer *copy;
guint mask;
g_return_val_if_fail (buffer != NULL, NULL);
/* create a fresh new buffer */
copy = gst_buffer_new ();
GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
/* 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 (copy)->flags |= GST_MINI_OBJECT (buffer)->flags & mask;
/* 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_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
if (GST_BUFFER_CAPS (buffer))
GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
else
GST_BUFFER_CAPS (copy) = NULL;
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.
*/
GstBuffer *
gst_buffer_new (void)
{
GstBuffer *newbuf;
newbuf = (GstBuffer *) gst_mini_object_new (GST_TYPE_BUFFER);
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.
*
* MT safe.
* Returns: the new #GstBuffer.
*/
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_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.
*/
/* FIXME can we make this threadsafe without a lock on the buffer?
* We can use compare and swap and atomic reads. */
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.
*/
/* FIXME can we make this threadsafe without a lock on the buffer?
* We can use compare and swap and atomic reads. Another idea is to
* not attach the caps to the buffer but use an event to signal a caps
* change. */
void
gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
{
g_return_if_fail (buffer != NULL);
gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
}
typedef struct _GstSubBuffer GstSubBuffer;
typedef struct _GstSubBufferClass GstSubBufferClass;
#define GST_TYPE_SUBBUFFER (gst_subbuffer_get_type())
#define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_SUBBUFFER))
#define GST_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_SUBBUFFER, GstSubBuffer))
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)
{
static GType _gst_subbuffer_type = 0;
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_ref (GST_TYPE_BUFFER);
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 (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 (with size > 0).
*
* 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, else they are set to #GST_CLOCK_TIME_NONE/#GST_BUFFER_OFFSET_NONE.
* The duration field of the new buffer is set to #GST_CLOCK_TIME_NONE.
*
* MT safe.
* Returns: the new #GstBuffer.
* Returns NULL if the arguments were invalid.
*/
GstBuffer *
gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
{
GstSubBuffer *subbuffer;
GstBuffer *parent;
g_return_val_if_fail (buffer != NULL, NULL);
g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
g_return_val_if_fail (size > 0, NULL);
g_return_val_if_fail (buffer->size >= offset + size, NULL);
/* find real parent */
if (GST_IS_SUBBUFFER (buffer)) {
parent = GST_SUBBUFFER (buffer)->parent;
} else {
parent = buffer;
}
gst_buffer_ref (parent);
/* create the new buffer */
subbuffer = (GstSubBuffer *) gst_mini_object_new (GST_TYPE_SUBBUFFER);
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;
/* 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);
} else {
GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
}
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.
*/
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 (buf1)->parent == GST_SUBBUFFER (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.
*/
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 (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 (offset == 0 && 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;
}