2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2000 Wim Taymans <wtay@chello.be>
5 * gstbuffer.c: Buffer operations
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 * Boston, MA 02111-1307, USA.
25 * @short_description: Data-passing buffer type, supporting sub-buffers.
26 * @see_also: #GstPad, #GstMiniObject
28 * Buffers are the basic unit of data transfer in GStreamer. The #GstBuffer
29 * type provides all the state necessary to define a region of memory as part
30 * of a stream. Sub-buffers are also supported, allowing a smaller region of a
31 * buffer to become its own buffer, with mechanisms in place to ensure that
32 * neither memory space goes away prematurely.
34 * Buffers are usually created with gst_buffer_new(). After a buffer has been
35 * created one will typically allocate memory for it and set the size of the
36 * buffer data. The following example creates a buffer that can hold a given
37 * video frame with a given width, height and bits per plane.
39 * <title>Creating a buffer for a video frame</title>
42 * gint size, width, height, bpp;
44 * size = width * height * bpp;
45 * buffer = gst_buffer_new ();
46 * GST_BUFFER_SIZE (buffer) = size;
47 * GST_BUFFER_MALLOCDATA (buffer) = g_malloc (size);
48 * GST_BUFFER_DATA (buffer) = GST_BUFFER_MALLOCDATA (buffer);
53 * Alternatively, use gst_buffer_new_and_alloc()
54 * to create a buffer with preallocated data of a given size.
56 * The data pointed to by the buffer can be retrieved with the GST_BUFFER_DATA()
57 * macro. The size of the data can be found with GST_BUFFER_SIZE(). For buffers
58 * of size 0, the data pointer is undefined (usually NULL) and should never be used.
60 * If an element knows what pad you will push the buffer out on, it should use
61 * gst_pad_alloc_buffer() instead to create a buffer. This allows downstream
62 * elements to provide special buffers to write in, like hardware buffers.
64 * A buffer has a pointer to a #GstCaps describing the media type of the data
65 * in the buffer. Attach caps to the buffer with gst_buffer_set_caps(); this
66 * is typically done before pushing out a buffer using gst_pad_push() so that
67 * the downstream element knows the type of the buffer.
69 * A buffer will usually have a timestamp, and a duration, but neither of these
70 * are guaranteed (they may be set to #GST_CLOCK_TIME_NONE). Whenever a
71 * meaningful value can be given for these, they should be set. The timestamp
72 * and duration are measured in nanoseconds (they are #GstClockTime values).
74 * A buffer can also have one or both of a start and an end offset. These are
75 * media-type specific. For video buffers, the start offset will generally be
76 * the frame number. For audio buffers, it will be the number of samples
77 * produced so far. For compressed data, it could be the byte offset in a
78 * source or destination file. Likewise, the end offset will be the offset of
79 * the end of the buffer. These can only be meaningfully interpreted if you
80 * know the media type of the buffer (the #GstCaps set on it). Either or both
81 * can be set to #GST_BUFFER_OFFSET_NONE.
83 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
84 * done when you want to keep a handle to the buffer after pushing it to the
87 * To efficiently create a smaller buffer out of an existing one, you can
88 * use gst_buffer_create_sub().
90 * If a plug-in wants to modify the buffer data in-place, it should first obtain
91 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
92 * function is optimized so that a copy will only be made when it is necessary.
94 * A plugin that only wishes to modify the metadata of a buffer, such as the
95 * offset, timestamp or caps, should use gst_buffer_make_metadata_writable(),
96 * which will create a subbuffer of the original buffer to ensure the caller
97 * has sole ownership, and not copy the buffer data.
99 * Several flags of the buffer can be set and unset with the
100 * GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use
101 * GST_BUFFER_FLAG_IS_SET() to test if a certain #GstBufferFlag is set.
103 * Buffers can be efficiently merged into a larger buffer with
104 * gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
105 * function returns TRUE.
107 * An element should either unref the buffer or push it out on a src pad
108 * using gst_pad_push() (see #GstPad).
110 * Buffers are usually freed by unreffing them with gst_buffer_unref(). When
111 * the refcount drops to 0, any data pointed to by GST_BUFFER_MALLOCDATA() will
114 * Last reviewed on August 11th, 2006 (0.10.10)
116 #include "gst_private.h"
125 #include "gstbuffer.h"
126 #include "gstbufferpool.h"
128 #include "gstutils.h"
129 #include "gstminiobject.h"
130 #include "gstversion.h"
132 GType _gst_buffer_type = 0;
134 typedef struct _GstMetaItem GstMetaItem;
142 #define ITEM_SIZE(info) ((info)->size + sizeof (GstMetaItem))
144 /* buffer alignment in bytes
145 * an alignment of 8 would be the same as malloc() guarantees
147 #ifdef HAVE_POSIX_MEMALIGN
148 #if defined(BUFFER_ALIGNMENT_MALLOC)
149 static size_t _gst_buffer_data_alignment = 8;
150 #elif defined(BUFFER_ALIGNMENT_PAGESIZE)
151 static size_t _gst_buffer_data_alignment = 0;
152 #elif defined(BUFFER_ALIGNMENT)
153 static size_t _gst_buffer_data_alignment = BUFFER_ALIGNMENT;
155 #error "No buffer alignment configured"
158 static inline gboolean
159 aligned_malloc (gpointer * memptr, guint size)
163 res = posix_memalign (memptr, _gst_buffer_data_alignment, size);
167 #endif /* HAVE_POSIX_MEMALIGN */
170 _gst_buffer_initialize (void)
172 if (G_LIKELY (_gst_buffer_type == 0)) {
173 _gst_buffer_type = gst_mini_object_register ("GstBuffer");
174 #ifdef HAVE_GETPAGESIZE
175 #ifdef BUFFER_ALIGNMENT_PAGESIZE
176 _gst_buffer_data_alignment = getpagesize ();
183 * gst_buffer_copy_metadata:
184 * @dest: a destination #GstBuffer
185 * @src: a source #GstBuffer
186 * @flags: flags indicating what metadata fields should be copied.
188 * Copies the metadata from @src into @dest. The data, size and mallocdata
189 * fields are not copied.
191 * @flags indicate which fields will be copied. Use #GST_BUFFER_COPY_ALL to copy
192 * all the metadata fields.
194 * This function is typically called from a custom buffer copy function after
195 * creating @dest and setting the data, size, mallocdata.
200 gst_buffer_copy_metadata (GstBuffer * dest, const GstBuffer * src,
201 GstBufferCopyFlags flags)
205 g_return_if_fail (dest != NULL);
206 g_return_if_fail (src != NULL);
208 /* nothing to copy if the buffers are the same */
209 if (G_UNLIKELY (dest == src))
212 #if GST_VERSION_NANO == 1
213 /* we enable this extra debugging in git versions only for now */
214 g_warn_if_fail (gst_buffer_is_metadata_writable (dest));
217 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", src, dest);
219 if (flags & GST_BUFFER_COPY_FLAGS) {
222 /* copy relevant flags */
223 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
224 GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
225 GST_BUFFER_FLAG_GAP | GST_BUFFER_FLAG_MEDIA1 |
226 GST_BUFFER_FLAG_MEDIA2 | GST_BUFFER_FLAG_MEDIA3;
227 GST_MINI_OBJECT_FLAGS (dest) |= GST_MINI_OBJECT_FLAGS (src) & mask;
230 if (flags & GST_BUFFER_COPY_TIMESTAMPS) {
231 GST_BUFFER_TIMESTAMP (dest) = GST_BUFFER_TIMESTAMP (src);
232 GST_BUFFER_DURATION (dest) = GST_BUFFER_DURATION (src);
233 GST_BUFFER_OFFSET (dest) = GST_BUFFER_OFFSET (src);
234 GST_BUFFER_OFFSET_END (dest) = GST_BUFFER_OFFSET_END (src);
237 if (flags & GST_BUFFER_COPY_CAPS) {
238 gst_caps_replace (&GST_BUFFER_CAPS (dest), GST_BUFFER_CAPS (src));
241 for (walk = src->priv; walk; walk = walk->next) {
242 GstMeta *meta = &walk->meta;
243 const GstMetaInfo *info = meta->info;
246 info->copy_func (dest, meta, src);
251 _gst_buffer_copy (GstBuffer * buffer)
255 g_return_val_if_fail (buffer != NULL, NULL);
257 /* create a fresh new buffer */
258 copy = gst_buffer_new ();
260 /* we simply copy everything from our parent */
261 #ifdef HAVE_POSIX_MEMALIGN
263 gpointer memptr = NULL;
265 if (G_LIKELY (buffer->size)) {
266 if (G_UNLIKELY (!aligned_malloc (&memptr, buffer->size))) {
267 /* terminate on error like g_memdup() would */
268 g_error ("%s: failed to allocate %u bytes", G_STRLOC, buffer->size);
270 memcpy (memptr, buffer->data, buffer->size);
273 copy->data = (guint8 *) memptr;
274 GST_BUFFER_FREE_FUNC (copy) = free;
277 copy->data = g_memdup (buffer->data, buffer->size);
280 /* make sure it gets freed (even if the parent is subclassed, we return a
282 copy->malloc_data = copy->data;
283 copy->size = buffer->size;
285 gst_buffer_copy_metadata (copy, buffer, GST_BUFFER_COPY_ALL);
290 /* the default dispose function revives the buffer and returns it to the
291 * pool when there is a pool */
293 _gst_buffer_dispose (GstBuffer * buffer)
297 if ((pool = buffer->pool) != NULL) {
298 /* keep the buffer alive */
299 gst_buffer_ref (buffer);
300 /* return the buffer to the pool */
301 gst_buffer_pool_release_buffer (pool, buffer);
306 _gst_buffer_free (GstBuffer * buffer)
308 GstMetaItem *walk, *next;
310 g_return_if_fail (buffer != NULL);
312 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
315 if (G_LIKELY (buffer->malloc_data))
316 buffer->free_func (buffer->malloc_data);
318 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
321 gst_buffer_unref (buffer->parent);
324 for (walk = buffer->priv; walk; walk = next) {
325 GstMeta *meta = &walk->meta;
326 const GstMetaInfo *info = meta->info;
328 /* call free_func if any */
330 info->free_func (meta, buffer);
331 /* and free the slice */
333 g_slice_free (GstMetaItem, walk);
336 g_slice_free1 (GST_MINI_OBJECT_SIZE (buffer), buffer);
340 gst_buffer_init (GstBuffer * buffer, gsize size)
342 gst_mini_object_init (GST_MINI_OBJECT_CAST (buffer), _gst_buffer_type, size);
344 buffer->mini_object.copy = (GstMiniObjectCopyFunction) _gst_buffer_copy;
345 buffer->mini_object.dispose =
346 (GstMiniObjectDisposeFunction) _gst_buffer_dispose;
347 buffer->mini_object.free = (GstMiniObjectFreeFunction) _gst_buffer_free;
349 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
350 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
351 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
352 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
353 GST_BUFFER_FREE_FUNC (buffer) = g_free;
359 * Creates a newly allocated buffer without any data.
363 * Returns: (transfer full): the new #GstBuffer.
366 gst_buffer_new (void)
370 newbuf = g_slice_new0 (GstBuffer);
371 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
373 gst_buffer_init (newbuf, sizeof (GstBuffer));
379 * gst_buffer_new_and_alloc:
380 * @size: the size in bytes of the new buffer's data.
382 * Creates a newly allocated buffer with data of the given size.
383 * The buffer memory is not cleared. If the requested amount of
384 * memory can't be allocated, the program will abort. Use
385 * gst_buffer_try_new_and_alloc() if you want to handle this case
386 * gracefully or have gotten the size to allocate from an untrusted
387 * source such as a media stream.
389 * Note that when @size == 0, the buffer data pointer will be NULL.
393 * Returns: (transfer full): the new #GstBuffer.
396 gst_buffer_new_and_alloc (guint size)
400 newbuf = gst_buffer_new ();
402 #ifdef HAVE_POSIX_MEMALIGN
404 gpointer memptr = NULL;
406 if (G_LIKELY (size)) {
407 if (G_UNLIKELY (!aligned_malloc (&memptr, size))) {
408 /* terminate on error like g_memdup() would */
409 g_error ("%s: failed to allocate %u bytes", G_STRLOC, size);
412 newbuf->malloc_data = (guint8 *) memptr;
413 GST_BUFFER_FREE_FUNC (newbuf) = free;
416 newbuf->malloc_data = g_malloc (size);
418 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
419 GST_BUFFER_SIZE (newbuf) = size;
421 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
427 * gst_buffer_try_new_and_alloc:
428 * @size: the size in bytes of the new buffer's data.
430 * Tries to create a newly allocated buffer with data of the given size. If
431 * the requested amount of memory can't be allocated, NULL will be returned.
432 * The buffer memory is not cleared.
434 * Note that when @size == 0, the buffer data pointer will be NULL.
438 * Returns: (transfer full): a new #GstBuffer, or NULL if the memory couldn't
444 gst_buffer_try_new_and_alloc (guint size)
448 #ifdef HAVE_POSIX_MEMALIGN
449 gpointer memptr = NULL;
451 if (G_LIKELY (size)) {
452 if (G_UNLIKELY (!aligned_malloc (&memptr, size))) {
453 GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
457 malloc_data = (guint8 *) memptr;
459 malloc_data = g_try_malloc (size);
461 if (G_UNLIKELY (malloc_data == NULL && size != 0)) {
462 GST_CAT_WARNING (GST_CAT_BUFFER, "failed to allocate %d bytes", size);
467 /* FIXME: there's no g_type_try_create_instance() in GObject yet, so this
468 * will still abort if a new GstBuffer structure can't be allocated */
469 newbuf = gst_buffer_new ();
471 GST_BUFFER_MALLOCDATA (newbuf) = malloc_data;
472 GST_BUFFER_DATA (newbuf) = malloc_data;
473 GST_BUFFER_SIZE (newbuf) = size;
474 #ifdef HAVE_POSIX_MEMALIGN
475 GST_BUFFER_FREE_FUNC (newbuf) = free;
478 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
484 * gst_buffer_get_caps:
485 * @buffer: a #GstBuffer.
487 * Gets the media type of the buffer. This can be NULL if there
488 * is no media type attached to this buffer.
490 * Returns: (transfer full): a reference to the #GstCaps. unref after usage.
491 * Returns NULL if there were no caps on this buffer.
493 /* this is not made atomic because if the buffer were reffed from multiple
494 * threads, it would have a refcount > 2 and thus be immutable.
497 gst_buffer_get_caps (GstBuffer * buffer)
501 g_return_val_if_fail (buffer != NULL, NULL);
503 ret = GST_BUFFER_CAPS (buffer);
512 * gst_buffer_set_caps:
513 * @buffer: a #GstBuffer.
514 * @caps: (transfer none): a #GstCaps.
516 * Sets the media type on the buffer. The refcount of the caps will
517 * be increased and any previous caps on the buffer will be
520 /* this is not made atomic because if the buffer were reffed from multiple
521 * threads, it would have a refcount > 2 and thus be immutable.
524 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
526 g_return_if_fail (buffer != NULL);
527 g_return_if_fail (caps == NULL || GST_CAPS_IS_SIMPLE (caps));
529 #if GST_VERSION_NANO == 1
530 /* we enable this extra debugging in git versions only for now */
531 g_warn_if_fail (gst_buffer_is_metadata_writable (buffer));
532 /* FIXME: would be nice to also check if caps are fixed here, but expensive */
535 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
539 * gst_buffer_is_metadata_writable:
542 * Similar to gst_buffer_is_writable, but this only ensures that the
543 * refcount of the buffer is 1, indicating that the caller is the sole
544 * owner and can change the buffer metadata, such as caps and timestamps.
546 * Returns: TRUE if the metadata is writable.
549 gst_buffer_is_metadata_writable (GstBuffer * buf)
551 return (GST_MINI_OBJECT_REFCOUNT_VALUE (GST_MINI_OBJECT_CAST (buf)) == 1);
555 * gst_buffer_make_metadata_writable:
556 * @buf: (transfer full): a #GstBuffer
558 * Similar to gst_buffer_make_writable, but does not ensure that the buffer
559 * data array is writable. Instead, this just ensures that the returned buffer
560 * is solely owned by the caller, by creating a subbuffer of the original
561 * buffer if necessary.
563 * After calling this function, @buf should not be referenced anymore. The
564 * result of this function has guaranteed writable metadata.
566 * Returns: (transfer full): a new #GstBuffer with writable metadata, which
567 * may or may not be the same as @buf.
570 gst_buffer_make_metadata_writable (GstBuffer * buf)
574 if (gst_buffer_is_metadata_writable (buf)) {
577 ret = gst_buffer_create_sub (buf, 0, GST_BUFFER_SIZE (buf));
579 gst_buffer_unref (buf);
585 #define GST_IS_SUBBUFFER(obj) (GST_BUFFER_CAST(obj)->parent != NULL)
588 * gst_buffer_create_sub:
589 * @parent: a #GstBuffer.
590 * @offset: the offset into parent #GstBuffer at which the new sub-buffer
592 * @size: the size of the new #GstBuffer sub-buffer, in bytes.
594 * Creates a sub-buffer from @parent at @offset and @size.
595 * This sub-buffer uses the actual memory space of the parent buffer.
596 * This function will copy the offset and timestamp fields when the
597 * offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and
598 * #GST_BUFFER_OFFSET_NONE.
599 * If @offset equals 0 and @size equals the total size of @buffer, the
600 * duration and offset end fields are also copied. If not they will be set
601 * to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
605 * Returns: (transfer full): the new #GstBuffer or NULL if the arguments were
609 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
611 GstBuffer *subbuffer;
616 g_return_val_if_fail (buffer != NULL, NULL);
617 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
618 g_return_val_if_fail (buffer->size >= offset + size, NULL);
620 /* find real parent */
621 if (GST_IS_SUBBUFFER (buffer)) {
622 parent = buffer->parent;
626 gst_buffer_ref (parent);
628 /* create the new buffer */
629 subbuffer = gst_buffer_new ();
630 subbuffer->parent = parent;
631 GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAG_READONLY);
633 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
636 /* set the right values in the child */
637 GST_BUFFER_DATA (subbuffer) = buffer->data + offset;
638 GST_BUFFER_SIZE (subbuffer) = size;
640 if ((offset == 0) && (size == GST_BUFFER_SIZE (buffer))) {
641 /* copy all the flags except IN_CAPS */
642 GST_BUFFER_FLAG_SET (subbuffer, GST_BUFFER_FLAGS (buffer));
643 GST_BUFFER_FLAG_UNSET (subbuffer, GST_BUFFER_FLAG_IN_CAPS);
645 /* copy only PREROLL & GAP flags */
646 GST_BUFFER_FLAG_SET (subbuffer, (GST_BUFFER_FLAGS (buffer) &
647 (GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_GAP)));
650 /* we can copy the timestamp and offset if the new buffer starts at
653 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
654 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
655 complete = (buffer->size == size);
657 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
658 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
665 /* if we copied the complete buffer we can copy the duration,
666 * offset_end and caps as well */
667 GST_BUFFER_DURATION (subbuffer) = GST_BUFFER_DURATION (buffer);
668 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_END (buffer);
669 if ((caps = GST_BUFFER_CAPS (buffer)))
671 GST_BUFFER_CAPS (subbuffer) = caps;
673 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
674 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
675 GST_BUFFER_CAPS (subbuffer) = NULL;
677 /* call subbuffer functions for metadata */
678 for (walk = buffer->priv; walk; walk = walk->next) {
679 GstMeta *meta = &walk->meta;
680 const GstMetaInfo *info = meta->info;
683 info->sub_func (subbuffer, meta, buffer, offset, size);
689 * gst_buffer_is_span_fast:
690 * @buf1: the first #GstBuffer.
691 * @buf2: the second #GstBuffer.
693 * Determines whether a gst_buffer_span() can be done without copying
694 * the contents, that is, whether the data areas are contiguous sub-buffers of
698 * Returns: TRUE if the buffers are contiguous,
699 * FALSE if a copy would be required.
702 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
704 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
705 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
706 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
708 /* it's only fast if we have subbuffers of the same parent */
709 return (GST_IS_SUBBUFFER (buf1) &&
710 GST_IS_SUBBUFFER (buf2) && (buf1->parent == buf2->parent)
711 && ((buf1->data + buf1->size) == buf2->data));
716 * @buf1: the first source #GstBuffer to merge.
717 * @offset: the offset in the first buffer from where the new
718 * buffer should start.
719 * @buf2: the second source #GstBuffer to merge.
720 * @len: the total length of the new buffer.
722 * Creates a new buffer that consists of part of buf1 and buf2.
723 * Logically, buf1 and buf2 are concatenated into a single larger
724 * buffer, and a new buffer is created at the given offset inside
725 * this space, with a given length.
727 * If the two source buffers are children of the same larger buffer,
728 * and are contiguous, the new buffer will be a child of the shared
729 * parent, and thus no copying is necessary. you can use
730 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
734 * Returns: (transfer full): the new #GstBuffer that spans the two source
735 * buffers, or NULL if the arguments are invalid.
738 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
743 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
744 g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
745 g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
746 g_return_val_if_fail (len > 0, NULL);
747 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
749 /* if the two buffers have the same parent and are adjacent */
750 if (gst_buffer_is_span_fast (buf1, buf2)) {
751 GstBuffer *parent = buf1->parent;
753 /* we simply create a subbuffer of the common parent */
754 newbuf = gst_buffer_create_sub (parent,
755 buf1->data - parent->data + offset, len);
757 GST_CAT_DEBUG (GST_CAT_BUFFER,
758 "slow path taken while spanning buffers %p and %p", buf1, buf2);
759 /* otherwise we simply have to brute-force copy the buffers */
760 newbuf = gst_buffer_new_and_alloc (len);
762 /* copy the first buffer's data across */
763 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
764 /* copy the second buffer's data across */
765 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
766 len - (buf1->size - offset));
768 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
770 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
771 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
773 /* if we completely merged the two buffers (appended), we can
774 * calculate the duration too. Also make sure we's not messing with
775 * invalid DURATIONS */
776 if (buf1->size + buf2->size == len) {
777 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
778 GST_BUFFER_DURATION_IS_VALID (buf2)) {
780 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
781 GST_BUFFER_DURATION (buf2);
783 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
785 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);
794 * gst_buffer_get_meta:
795 * @buffer: a #GstBuffer
796 * @info: a #GstMetaInfo
798 * Get the metadata for the api in @info on buffer. When there is no such
799 * metadata, NULL is returned.
801 * Note that the result metadata might not be of the implementation @info.
803 * Returns: the metadata for the api in @info on @buffer.
806 gst_buffer_get_meta (GstBuffer * buffer, const GstMetaInfo * info)
809 GstMeta *result = NULL;
811 g_return_val_if_fail (buffer != NULL, NULL);
812 g_return_val_if_fail (info != NULL, NULL);
814 /* find GstMeta of the requested API */
815 for (item = buffer->priv; item; item = item->next) {
816 GstMeta *meta = &item->meta;
817 if (meta->info->api == info->api) {
826 * gst_buffer_add_meta:
827 * @buffer: a #GstBuffer
828 * @info: a #GstMetaInfo
829 * @params: params for @info
831 * Add metadata for @info to @buffer using the parameters in @params.
833 * Returns: the metadata for the api in @info on @buffer.
836 gst_buffer_add_meta (GstBuffer * buffer, const GstMetaInfo * info,
840 GstMeta *result = NULL;
843 g_return_val_if_fail (buffer != NULL, NULL);
844 g_return_val_if_fail (info != NULL, NULL);
846 /* create a new slice */
847 GST_DEBUG ("alloc metadata of size %" G_GSIZE_FORMAT, info->size);
849 size = ITEM_SIZE (info);
850 item = g_slice_alloc (size);
851 result = &item->meta;
854 /* call the init_func when needed */
856 if (!info->init_func (result, params, buffer))
859 /* and add to the list of metadata */
860 item->next = buffer->priv;
867 g_slice_free1 (size, item);
873 * gst_buffer_remove_meta:
874 * @buffer: a #GstBuffer
875 * @info: a #GstMetaInfo
877 * Remove the metadata for @info on @buffer.
879 * Returns: %TRUE if the metadata existed and was removed, %FALSE if no such
880 * metadata was on @buffer.
883 gst_buffer_remove_meta (GstBuffer * buffer, GstMeta * meta)
885 GstMetaItem *walk, *prev;
887 g_return_val_if_fail (buffer != NULL, FALSE);
888 g_return_val_if_fail (meta != NULL, FALSE);
890 /* find the metadata and delete */
892 for (walk = prev; walk; walk = walk->next) {
893 GstMeta *m = &walk->meta;
895 const GstMetaInfo *info = meta->info;
897 /* remove from list */
898 if (buffer->priv == walk)
899 buffer->priv = walk->next;
901 prev->next = walk->next;
902 /* call free_func if any */
904 info->free_func (m, buffer);
906 /* and free the slice */
907 g_slice_free1 (ITEM_SIZE (info), walk);
916 * gst_buffer_iterate_meta:
917 * @buffer: a #GstBuffer
918 * @state: an opaque state pointer
920 * Retrieve the next #GstMeta after @current. If @state points
921 * to %NULL, the first metadata is returned.
923 * @state will be updated with an opage state pointer
925 * Returns: The next #GstMeta or %NULL when there are no more items.
928 gst_buffer_iterate_meta (GstBuffer * buffer, gpointer * state)
932 g_return_val_if_fail (buffer != NULL, NULL);
933 g_return_val_if_fail (state != NULL, NULL);
935 meta = (GstMetaItem **) state;
937 /* state NULL, move to first item */
938 *meta = buffer->priv;
940 /* state !NULL, move to next item in list */
941 *meta = (*meta)->next;
944 return &(*meta)->meta;