/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- aligned_malloc
- _gst_buffer_initialize
- gst_buffer_class_init
- gst_buffer_finalize
- gst_buffer_copy_metadata
- _gst_buffer_copy
- gst_buffer_init
- gst_buffer_new
- gst_buffer_new_and_alloc
- gst_buffer_try_new_and_alloc
- gst_buffer_get_caps
- gst_buffer_set_caps
- gst_buffer_is_metadata_writable
- gst_buffer_make_metadata_writable
- gst_buffer_create_sub
- gst_buffer_is_span_fast
- gst_buffer_span
/* 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"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include "gstbuffer.h"
#include "gstinfo.h"
#include "gstutils.h"
#include "gstminiobject.h"
#include "gstversion.h"
static void gst_buffer_finalize (GstBuffer * buffer);
static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
static GType _gst_buffer_type = 0;
/* buffer alignment in bytes
* an alignment of 8 would be the same as malloc() guarantees
*/
#ifdef HAVE_POSIX_MEMALIGN
#if defined(BUFFER_ALIGNMENT_MALLOC)
static size_t _gst_buffer_data_alignment = 8;
#elif defined(BUFFER_ALIGNMENT_PAGESIZE)
static size_t _gst_buffer_data_alignment = 0;
#elif defined(BUFFER_ALIGNMENT)
static size_t _gst_buffer_data_alignment = BUFFER_ALIGNMENT;
#else
#error "No buffer alignment configured"
#endif
static inline gboolean
aligned_malloc (gpointer * memptr, guint size)
{
gint res;
res = posix_memalign (memptr, _gst_buffer_data_alignment, size);
return (res == 0);
}
#endif /* HAVE_POSIX_MEMALIGN */
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 ());
#ifdef HAVE_GETPAGESIZE
#ifdef BUFFER_ALIGNMENT_PAGESIZE
_gst_buffer_data_alignment = getpagesize ();
#endif
#endif
}
#define _do_init \
{ \
_gst_buffer_type = g_define_type_id; \
}
G_DEFINE_TYPE_WITH_CODE (GstBuffer, gst_buffer, GST_TYPE_MINI_OBJECT, _do_init);
static void
gst_buffer_class_init (GstBufferClass * klass)
{
klass->mini_object_class.copy = (GstMiniObjectCopyFunction) _gst_buffer_copy;
klass->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 (G_LIKELY (buffer->malloc_data))
buffer->free_func (buffer->malloc_data);
gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
if (buffer->parent)
gst_buffer_unref (buffer->parent);
/* ((GstMiniObjectClass *) */
/* gst_buffer_parent_class)->finalize (GST_MINI_OBJECT_CAST (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
*/
void
gst_buffer_copy_metadata (GstBuffer * dest, const GstBuffer * src,
GstBufferCopyFlags flags)
{
g_return_if_fail (dest != NULL);
g_return_if_fail (src != NULL);
/* nothing to copy if the buffers are the same */
if (G_UNLIKELY (dest == src))
return;
#if GST_VERSION_NANO == 1
/* we enable this extra debugging in git versions only for now */
g_warn_if_fail (gst_buffer_is_metadata_writable (dest));
#endif
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_BUFFER_FLAG_MEDIA1 |
GST_BUFFER_FLAG_MEDIA2 | GST_BUFFER_FLAG_MEDIA3;
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) {
gst_caps_replace (&GST_BUFFER_CAPS (dest), GST_BUFFER_CAPS (src));
}
}
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 */
#ifdef HAVE_POSIX_MEMALIGN
{
gpointer memptr = NULL;
if (G_LIKELY (buffer->size)) {
if (G_UNLIKELY (!aligned_malloc (&memptr, buffer->size))) {
/* terminate on error like g_memdup() would */
g_error ("%s: failed to allocate %u bytes", G_STRLOC, buffer->size);
} else {
memcpy (memptr, buffer->data, buffer->size);
}
}
copy->data = (guint8 *) memptr;
GST_BUFFER_FREE_FUNC (copy) = free;
}
#else
copy->data = g_memdup (buffer->data, buffer->size);
#endif
/* 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 (GstBuffer * buffer)
{
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_FREE_FUNC (buffer) = g_free;
}
/**
* 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_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.
*/
GstBuffer *
gst_buffer_new_and_alloc (guint size)
{
GstBuffer *newbuf;
newbuf = gst_buffer_new ();
#ifdef HAVE_POSIX_MEMALIGN
{
gpointer memptr = NULL;
if (G_LIKELY (size)) {
if (G_UNLIKELY (!aligned_malloc (&memptr, size))) {
/* terminate on error like g_memdup() would */
g_error ("%s: failed to allocate %u bytes", G_STRLOC, size);
}
}
newbuf->malloc_data = (guint8 *) memptr;
GST_BUFFER_FREE_FUNC (newbuf) = free;
}
#else
newbuf->malloc_data = g_malloc (size);
#endif
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
*/
GstBuffer *
gst_buffer_try_new_and_alloc (guint size)
{
GstBuffer *newbuf;
guint8 *malloc_data;
#ifdef HAVE_POSIX_MEMALIGN
gpointer memptr = NULL;
if (G_LIKELY (size)) {
if (G_UNLIKELY (!aligned_malloc (&memptr, size))) {
GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
return NULL;
}
}
malloc_data = (guint8 *) memptr;
#else
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;
}
#endif
/* 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;
#ifdef HAVE_POSIX_MEMALIGN
GST_BUFFER_FREE_FUNC (newbuf) = free;
#endif
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.
*/
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.
*/
void
gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
{
g_return_if_fail (buffer != NULL);
#if GST_VERSION_NANO == 1
/* we enable this extra debugging in git versions only for now */
g_warn_if_fail (gst_buffer_is_metadata_writable (buffer));
#endif
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.
*/
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.
*/
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;
}
#define GST_IS_SUBBUFFER(obj) (GST_BUFFER_CAST(obj)->parent != NULL)
/**
* 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.
*/
GstBuffer *
gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
{
GstBuffer *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 = buffer->parent;
} else {
parent = buffer;
}
gst_buffer_ref (parent);
/* create the new buffer */
subbuffer = gst_buffer_new ();
subbuffer->parent = parent;
GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAG_READONLY);
GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
parent);
/* set the right values in the child */
GST_BUFFER_DATA (subbuffer) = buffer->data + offset;
GST_BUFFER_SIZE (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 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) && (buf1->parent == 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 = 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;
}