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.
24 * @short_description: Data-passing buffer type, supporting sub-buffers.
25 * @see_also: #GstPad, #GstMiniObject
27 * Buffers are the basic unit of data transfer in GStreamer. The GstBuffer type
28 * provides all the state necessary to define a region of memory as part of a
29 * stream. Sub-buffers are also supported, allowing a smaller region of a
30 * buffer to become its own buffer, with mechanisms in place to ensure that
31 * neither memory space goes away.
33 * Buffers are usually created with gst_buffer_new(). After a buffer has been
34 * created one will typically allocate memory for it and set the size of the
35 * buffer data. The following example creates a buffer that can hold a given
36 * video frame with a given width, height and bits per plane.
38 * <title>Creating a buffer for a video frame</title>
41 * gint size, width, height, bpp;
45 * size = width * height * bpp;
47 * buffer = gst_buffer_new ();
48 * GST_BUFFER_SIZE (buffer) = size;
49 * GST_BUFFER_MALLOCDATA (buffer) = g_alloc (size);
50 * GST_BUFFER_DATA (buffer) = GST_BUFFER_MALLOCDATA (buffer);
55 * Alternatively, use gst_buffer_new_and_alloc()
56 * to create a buffer with preallocated data of a given size.
58 * If an element knows what pad you will push the buffer out on, it should use
59 * gst_pad_alloc_buffer() instead to create a buffer. This allows downstream
60 * elements to provide special buffers to write in, like hardware buffers.
62 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
63 * done when you want to keep a handle to the buffer after pushing it to the
66 * To efficiently create a smaller buffer out of an existing one, you can
67 * use gst_buffer_create_sub().
69 * If the plug-in wants to modify the buffer in-place, it should first obtain
70 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
71 * function is optimized so that a copy will only be made when it is necessary.
73 * Several flags of the buffer can be set and unset with the GST_BUFFER_FLAG_SET()
74 * and GST_BUFFER_FLAG_UNSET() macros. Use GST_BUFFER_FLAG_IS_SET() to test it
75 * a certain #GstBufferFlag is set.
77 * Buffers can be efficiently merged into a larger buffer with gst_buffer_merge()
78 * and gst_buffer_span() if the gst_buffer_is_span_fast() function returns TRUE.
80 * An element should either unref the buffer or push it out on a src pad
81 * using gst_pad_push() (see #GstPad).
83 * Buffers usually are freed by unreffing them with gst_buffer_unref().
84 * Do not use gst_buffer_free() : this function effectively frees the buffer
85 * regardless of the refcount, which is dangerous.
87 * Last reviewed on August 12th, 2004 (0.8.5)
90 #include "gst_private.h"
92 #include "gstbuffer.h"
95 #include "gstminiobject.h"
98 static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
99 static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
100 static void gst_buffer_finalize (GstBuffer * buffer);
101 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
105 _gst_buffer_initialize (void)
109 gst_buffer_get_type ();
111 /* the GstMiniObject types need to be class_ref'd once before it can be
112 * done from multiple threads;
113 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
114 ptr = g_type_class_ref (GST_TYPE_BUFFER);
115 g_type_class_unref (ptr);
119 gst_buffer_get_type (void)
121 static GType _gst_buffer_type;
123 if (G_UNLIKELY (_gst_buffer_type == 0)) {
124 static const GTypeInfo buffer_info = {
125 sizeof (GstBufferClass),
128 gst_buffer_class_init,
137 _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
138 "GstBuffer", &buffer_info, 0);
140 return _gst_buffer_type;
144 gst_buffer_class_init (gpointer g_class, gpointer class_data)
146 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
148 buffer_class->mini_object_class.copy =
149 (GstMiniObjectCopyFunction) _gst_buffer_copy;
150 buffer_class->mini_object_class.finalize =
151 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
156 gst_buffer_finalize (GstBuffer * buffer)
158 g_return_if_fail (buffer != NULL);
161 if (buffer->malloc_data) {
162 g_free (buffer->malloc_data);
165 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
169 _gst_buffer_copy (GstBuffer * buffer)
174 g_return_val_if_fail (buffer != NULL, NULL);
176 /* create a fresh new buffer */
177 copy = gst_buffer_new ();
179 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
181 /* copy relevant flags */
182 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
183 GST_BUFFER_FLAG_DELTA_UNIT;
184 GST_MINI_OBJECT (copy)->flags |= GST_MINI_OBJECT (buffer)->flags & mask;
186 /* we simply copy everything from our parent */
187 copy->data = g_memdup (buffer->data, buffer->size);
188 /* make sure it gets freed (even if the parent is subclassed, we return a
190 copy->malloc_data = copy->data;
192 copy->size = buffer->size;
194 GST_BUFFER_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
195 GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
196 GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
197 GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
199 if (GST_BUFFER_CAPS (buffer))
200 GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
202 GST_BUFFER_CAPS (copy) = NULL;
208 gst_buffer_init (GTypeInstance * instance, gpointer g_class)
212 buffer = (GstBuffer *) instance;
214 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
216 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
217 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
218 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
219 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
225 * Creates a newly allocated buffer without any data.
227 * Returns: the new #GstBuffer.
232 gst_buffer_new (void)
236 newbuf = (GstBuffer *) gst_mini_object_new (GST_TYPE_BUFFER);
238 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
244 * gst_buffer_new_and_alloc:
245 * @size: the size of the new buffer's data.
247 * Creates a newly allocated buffer with data of the given size.
249 * Returns: the new #GstBuffer.
254 gst_buffer_new_and_alloc (guint size)
258 newbuf = gst_buffer_new ();
260 newbuf->malloc_data = g_malloc (size);
261 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
262 GST_BUFFER_SIZE (newbuf) = size;
264 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
270 * gst_buffer_get_caps:
271 * @buffer: a #GstBuffer to get the caps of.
273 * Gets the media type of the buffer. This can be NULL if there
274 * is not media type attached to this buffer or when the media
275 * type is the same as the previous received buffer.
277 * Returns: a reference to the #GstCaps, or NULL if there were no caps on this
280 /* FIXME can we make this threadsafe without a lock on the buffer?
281 * We can use compare and swap and atomic reads. */
283 gst_buffer_get_caps (GstBuffer * buffer)
287 g_return_val_if_fail (buffer != NULL, NULL);
289 ret = GST_BUFFER_CAPS (buffer);
298 * gst_buffer_set_caps:
299 * @buffer: a #GstBuffer to set the caps of.
300 * @caps: a #GstCaps to set.
302 * Sets the media type on the buffer. The caps' refcount will
303 * be increased and any previous caps on the buffer will be
306 /* FIXME can we make this threadsafe without a lock on the buffer?
307 * We can use compare and swap and atomic reads. Another idea is to
308 * not attach the caps to the buffer but use an event to signal a caps
311 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
313 g_return_if_fail (buffer != NULL);
315 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
319 typedef struct _GstSubBuffer GstSubBuffer;
320 typedef struct _GstSubBufferClass GstSubBufferClass;
322 #define GST_TYPE_SUBBUFFER (gst_subbuffer_get_type())
324 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_SUBBUFFER))
325 #define GST_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_SUBBUFFER, GstSubBuffer))
334 struct _GstSubBufferClass
336 GstBufferClass buffer_class;
339 static GstBufferClass *sub_parent_class;
341 static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
342 static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
343 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
346 gst_subbuffer_get_type (void)
348 static GType _gst_subbuffer_type = 0;
350 if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
351 static const GTypeInfo subbuffer_info = {
352 sizeof (GstSubBufferClass),
355 gst_subbuffer_class_init,
358 sizeof (GstSubBuffer),
364 _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
365 "GstSubBuffer", &subbuffer_info, 0);
367 return _gst_subbuffer_type;
371 gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
373 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
375 sub_parent_class = g_type_class_ref (GST_TYPE_BUFFER);
377 buffer_class->mini_object_class.finalize =
378 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
382 gst_subbuffer_finalize (GstSubBuffer * buffer)
384 gst_buffer_unref (buffer->parent);
386 GST_MINI_OBJECT_CLASS (sub_parent_class)->finalize (GST_MINI_OBJECT (buffer));
390 gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
395 * gst_buffer_create_sub:
396 * @parent: a parent #GstBuffer to create a subbuffer from.
397 * @offset: the offset into parent #GstBuffer.
398 * @size: the size of the new #GstBuffer sub-buffer (with size > 0).
400 * Creates a sub-buffer from the parent at a given offset.
401 * This sub-buffer uses the actual memory space of the parent buffer.
402 * This function will copy the offset and timestamp field when the
403 * offset is 0, else they are set to _NONE.
404 * The duration field of the new buffer are set to GST_CLOCK_TIME_NONE.
406 * Returns: the new #GstBuffer, or NULL if there was an error.
411 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
413 GstSubBuffer *subbuffer;
416 g_return_val_if_fail (buffer != NULL, NULL);
417 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
418 g_return_val_if_fail (size > 0, NULL);
419 g_return_val_if_fail (buffer->size >= offset + size, NULL);
421 /* find real parent */
422 if (GST_IS_SUBBUFFER (buffer)) {
423 parent = GST_SUBBUFFER (buffer)->parent;
427 gst_buffer_ref (parent);
429 /* create the new buffer */
430 subbuffer = (GstSubBuffer *) gst_mini_object_new (GST_TYPE_SUBBUFFER);
431 subbuffer->parent = parent;
433 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
436 /* set the right values in the child */
437 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
438 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
440 /* we can copy the timestamp and offset if the new buffer starts at
443 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
444 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
446 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
447 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
450 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
451 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
453 GST_BUFFER_CAPS (subbuffer) = NULL;
455 return GST_BUFFER_CAST (subbuffer);
459 * gst_buffer_is_span_fast:
460 * @buf1: a first source #GstBuffer.
461 * @buf2: the second source #GstBuffer.
463 * Determines whether a gst_buffer_span() can be done without copying
464 * the contents, that is, whether the data areas are contiguous.
466 * Returns: TRUE if the buffers are contiguous,
467 * FALSE if a copy would be required.
472 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
474 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
475 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
476 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
478 /* it's only fast if we have subbuffers of the same parent */
479 return (GST_IS_SUBBUFFER (buf1) &&
480 GST_IS_SUBBUFFER (buf2) &&
481 (GST_SUBBUFFER (buf1)->parent == GST_SUBBUFFER (buf2)->parent) &&
482 ((buf1->data + buf1->size) == buf2->data));
487 * @buf1: a first source #GstBuffer to merge.
488 * @offset: the offset in the first buffer from where the new
489 * buffer should start.
490 * @buf2: the second source #GstBuffer to merge.
491 * @len: the total length of the new buffer.
493 * Creates a new buffer that consists of part of buf1 and buf2.
494 * Logically, buf1 and buf2 are concatenated into a single larger
495 * buffer, and a new buffer is created at the given offset inside
496 * this space, with a given length.
498 * If the two source buffers are children of the same larger buffer,
499 * and are contiguous, the new buffer will be a child of the shared
500 * parent, and thus no copying is necessary. you can use
501 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
503 * Returns: the new #GstBuffer that spans the two source buffers.
508 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
513 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
514 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
515 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
516 g_return_val_if_fail (len > 0, NULL);
517 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
519 /* if the two buffers have the same parent and are adjacent */
520 if (gst_buffer_is_span_fast (buf1, buf2)) {
521 GstBuffer *parent = GST_SUBBUFFER (buf1)->parent;
523 /* we simply create a subbuffer of the common parent */
524 newbuf = gst_buffer_create_sub (parent,
525 buf1->data - parent->data + offset, len);
527 GST_CAT_DEBUG (GST_CAT_BUFFER,
528 "slow path taken while spanning buffers %p and %p", buf1, buf2);
529 /* otherwise we simply have to brute-force copy the buffers */
530 newbuf = gst_buffer_new_and_alloc (len);
532 /* copy the first buffer's data across */
533 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
534 /* copy the second buffer's data across */
535 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
536 len - (buf1->size - offset));
537 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
539 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
540 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
543 /* if we completely merged the two buffers (appended), we can
544 * calculate the duration too. Also make sure we's not messing with
545 * invalid DURATIONS */
546 if (offset == 0 && buf1->size + buf2->size == len) {
547 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
548 GST_BUFFER_DURATION_IS_VALID (buf2)) {
550 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
551 GST_BUFFER_DURATION (buf2);
553 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
555 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);