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 * A buffer has a pointer to a #GstCaps describing the media type of the data
63 * in the buffer. Attach caps to the buffer with gst_buffer_set_caps(); this
64 * is typically done before pushing out a buffer using gst_pad_push() so that
65 * the downstream element knows the type of the buffer.
67 * gst_buffer_ref() is used to increase the refcount of a buffer. This must be
68 * done when you want to keep a handle to the buffer after pushing it to the
71 * To efficiently create a smaller buffer out of an existing one, you can
72 * use gst_buffer_create_sub().
74 * If the plug-in wants to modify the buffer in-place, it should first obtain
75 * a buffer that is safe to modify by using gst_buffer_make_writable(). This
76 * function is optimized so that a copy will only be made when it is necessary.
78 * Several flags of the buffer can be set and unset with the GST_BUFFER_FLAG_SET()
79 * and GST_BUFFER_FLAG_UNSET() macros. Use GST_BUFFER_FLAG_IS_SET() to test it
80 * a certain #GstBufferFlag is set.
82 * Buffers can be efficiently merged into a larger buffer with gst_buffer_merge()
83 * and gst_buffer_span() if the gst_buffer_is_span_fast() function returns TRUE.
85 * An element should either unref the buffer or push it out on a src pad
86 * using gst_pad_push() (see #GstPad).
88 * Buffers usually are freed by unreffing them with gst_buffer_unref(). When
89 * the refcount drops to 0, the buffer memory will be freed again.
91 * Last reviewed on September 24th, 2005 (0.9.0)
93 #include "gst_private.h"
95 #include "gstbuffer.h"
98 #include "gstminiobject.h"
101 static void gst_buffer_init (GTypeInstance * instance, gpointer g_class);
102 static void gst_buffer_class_init (gpointer g_class, gpointer class_data);
103 static void gst_buffer_finalize (GstBuffer * buffer);
104 static GstBuffer *_gst_buffer_copy (GstBuffer * buffer);
108 _gst_buffer_initialize (void)
112 gst_buffer_get_type ();
114 /* the GstMiniObject types need to be class_ref'd once before it can be
115 * done from multiple threads;
116 * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
117 ptr = g_type_class_ref (GST_TYPE_BUFFER);
118 g_type_class_unref (ptr);
122 gst_buffer_get_type (void)
124 static GType _gst_buffer_type;
126 if (G_UNLIKELY (_gst_buffer_type == 0)) {
127 static const GTypeInfo buffer_info = {
128 sizeof (GstBufferClass),
131 gst_buffer_class_init,
140 _gst_buffer_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
141 "GstBuffer", &buffer_info, 0);
143 return _gst_buffer_type;
147 gst_buffer_class_init (gpointer g_class, gpointer class_data)
149 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
151 buffer_class->mini_object_class.copy =
152 (GstMiniObjectCopyFunction) _gst_buffer_copy;
153 buffer_class->mini_object_class.finalize =
154 (GstMiniObjectFinalizeFunction) gst_buffer_finalize;
159 gst_buffer_finalize (GstBuffer * buffer)
161 g_return_if_fail (buffer != NULL);
163 GST_CAT_LOG (GST_CAT_BUFFER, "finalize %p", buffer);
166 if (buffer->malloc_data) {
167 g_free (buffer->malloc_data);
170 gst_caps_replace (&GST_BUFFER_CAPS (buffer), NULL);
174 _gst_buffer_copy (GstBuffer * buffer)
179 g_return_val_if_fail (buffer != NULL, NULL);
181 /* create a fresh new buffer */
182 copy = gst_buffer_new ();
184 GST_CAT_LOG (GST_CAT_BUFFER, "copy %p to %p", buffer, copy);
186 /* copy relevant flags */
187 mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
188 GST_BUFFER_FLAG_DELTA_UNIT;
189 GST_MINI_OBJECT (copy)->flags |= GST_MINI_OBJECT (buffer)->flags & mask;
191 /* we simply copy everything from our parent */
192 copy->data = g_memdup (buffer->data, buffer->size);
193 /* make sure it gets freed (even if the parent is subclassed, we return a
195 copy->malloc_data = copy->data;
197 copy->size = buffer->size;
199 GST_BUFFER_TIMESTAMP (copy) = GST_BUFFER_TIMESTAMP (buffer);
200 GST_BUFFER_DURATION (copy) = GST_BUFFER_DURATION (buffer);
201 GST_BUFFER_OFFSET (copy) = GST_BUFFER_OFFSET (buffer);
202 GST_BUFFER_OFFSET_END (copy) = GST_BUFFER_OFFSET_END (buffer);
204 if (GST_BUFFER_CAPS (buffer))
205 GST_BUFFER_CAPS (copy) = gst_caps_ref (GST_BUFFER_CAPS (buffer));
207 GST_BUFFER_CAPS (copy) = NULL;
213 gst_buffer_init (GTypeInstance * instance, gpointer g_class)
217 buffer = (GstBuffer *) instance;
219 GST_CAT_LOG (GST_CAT_BUFFER, "init %p", buffer);
221 GST_BUFFER_TIMESTAMP (buffer) = GST_CLOCK_TIME_NONE;
222 GST_BUFFER_DURATION (buffer) = GST_CLOCK_TIME_NONE;
223 GST_BUFFER_OFFSET (buffer) = GST_BUFFER_OFFSET_NONE;
224 GST_BUFFER_OFFSET_END (buffer) = GST_BUFFER_OFFSET_NONE;
230 * Creates a newly allocated buffer without any data.
232 * Returns: the new #GstBuffer.
237 gst_buffer_new (void)
241 newbuf = (GstBuffer *) gst_mini_object_new (GST_TYPE_BUFFER);
243 GST_CAT_LOG (GST_CAT_BUFFER, "new %p", newbuf);
249 * gst_buffer_new_and_alloc:
250 * @size: the size of the new buffer's data.
252 * Creates a newly allocated buffer with data of the given size.
254 * Returns: the new #GstBuffer.
259 gst_buffer_new_and_alloc (guint size)
263 newbuf = gst_buffer_new ();
265 newbuf->malloc_data = g_malloc (size);
266 GST_BUFFER_DATA (newbuf) = newbuf->malloc_data;
267 GST_BUFFER_SIZE (newbuf) = size;
269 GST_CAT_LOG (GST_CAT_BUFFER, "new %p of size %d", newbuf, size);
275 * gst_buffer_get_caps:
276 * @buffer: a #GstBuffer to get the caps of.
278 * Gets the media type of the buffer. This can be NULL if there
279 * is not media type attached to this buffer or when the media
280 * type is the same as the previous received buffer.
282 * Returns: a reference to the #GstCaps, or NULL if there were no caps on this
285 /* FIXME can we make this threadsafe without a lock on the buffer?
286 * We can use compare and swap and atomic reads. */
288 gst_buffer_get_caps (GstBuffer * buffer)
292 g_return_val_if_fail (buffer != NULL, NULL);
294 ret = GST_BUFFER_CAPS (buffer);
303 * gst_buffer_set_caps:
304 * @buffer: a #GstBuffer to set the caps of.
305 * @caps: a #GstCaps to set.
307 * Sets the media type on the buffer. The caps' refcount will
308 * be increased and any previous caps on the buffer will be
311 /* FIXME can we make this threadsafe without a lock on the buffer?
312 * We can use compare and swap and atomic reads. Another idea is to
313 * not attach the caps to the buffer but use an event to signal a caps
316 gst_buffer_set_caps (GstBuffer * buffer, GstCaps * caps)
318 g_return_if_fail (buffer != NULL);
320 gst_caps_replace (&GST_BUFFER_CAPS (buffer), caps);
324 typedef struct _GstSubBuffer GstSubBuffer;
325 typedef struct _GstSubBufferClass GstSubBufferClass;
327 #define GST_TYPE_SUBBUFFER (gst_subbuffer_get_type())
329 #define GST_IS_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_SUBBUFFER))
330 #define GST_SUBBUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_SUBBUFFER, GstSubBuffer))
339 struct _GstSubBufferClass
341 GstBufferClass buffer_class;
344 static GstBufferClass *sub_parent_class;
346 static void gst_subbuffer_init (GTypeInstance * instance, gpointer g_class);
347 static void gst_subbuffer_class_init (gpointer g_class, gpointer class_data);
348 static void gst_subbuffer_finalize (GstSubBuffer * buffer);
351 gst_subbuffer_get_type (void)
353 static GType _gst_subbuffer_type = 0;
355 if (G_UNLIKELY (_gst_subbuffer_type == 0)) {
356 static const GTypeInfo subbuffer_info = {
357 sizeof (GstSubBufferClass),
360 gst_subbuffer_class_init,
363 sizeof (GstSubBuffer),
369 _gst_subbuffer_type = g_type_register_static (GST_TYPE_BUFFER,
370 "GstSubBuffer", &subbuffer_info, 0);
372 return _gst_subbuffer_type;
376 gst_subbuffer_class_init (gpointer g_class, gpointer class_data)
378 GstBufferClass *buffer_class = GST_BUFFER_CLASS (g_class);
380 sub_parent_class = g_type_class_ref (GST_TYPE_BUFFER);
382 buffer_class->mini_object_class.finalize =
383 (GstMiniObjectFinalizeFunction) gst_subbuffer_finalize;
387 gst_subbuffer_finalize (GstSubBuffer * buffer)
389 gst_buffer_unref (buffer->parent);
391 GST_MINI_OBJECT_CLASS (sub_parent_class)->finalize (GST_MINI_OBJECT (buffer));
395 gst_subbuffer_init (GTypeInstance * instance, gpointer g_class)
397 GST_BUFFER_FLAG_SET (GST_BUFFER_CAST (instance), GST_BUFFER_FLAG_READONLY);
401 * gst_buffer_create_sub:
402 * @parent: a parent #GstBuffer to create a subbuffer from.
403 * @offset: the offset into parent #GstBuffer.
404 * @size: the size of the new #GstBuffer sub-buffer (with size > 0).
406 * Creates a sub-buffer from the parent at a given offset.
407 * This sub-buffer uses the actual memory space of the parent buffer.
408 * This function will copy the offset and timestamp field when the
409 * offset is 0, else they are set to _NONE.
410 * The duration field of the new buffer are set to GST_CLOCK_TIME_NONE.
412 * Returns: the new #GstBuffer, or NULL if there was an error.
417 gst_buffer_create_sub (GstBuffer * buffer, guint offset, guint size)
419 GstSubBuffer *subbuffer;
422 g_return_val_if_fail (buffer != NULL, NULL);
423 g_return_val_if_fail (buffer->mini_object.refcount > 0, NULL);
424 g_return_val_if_fail (size > 0, NULL);
425 g_return_val_if_fail (buffer->size >= offset + size, NULL);
427 /* find real parent */
428 if (GST_IS_SUBBUFFER (buffer)) {
429 parent = GST_SUBBUFFER (buffer)->parent;
433 gst_buffer_ref (parent);
435 /* create the new buffer */
436 subbuffer = (GstSubBuffer *) gst_mini_object_new (GST_TYPE_SUBBUFFER);
437 subbuffer->parent = parent;
439 GST_CAT_LOG (GST_CAT_BUFFER, "new subbuffer %p (parent %p)", subbuffer,
442 /* set the right values in the child */
443 GST_BUFFER_DATA (GST_BUFFER_CAST (subbuffer)) = buffer->data + offset;
444 GST_BUFFER_SIZE (GST_BUFFER_CAST (subbuffer)) = size;
446 /* we can copy the timestamp and offset if the new buffer starts at
449 GST_BUFFER_TIMESTAMP (subbuffer) = GST_BUFFER_TIMESTAMP (buffer);
450 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET (buffer);
452 GST_BUFFER_TIMESTAMP (subbuffer) = GST_CLOCK_TIME_NONE;
453 GST_BUFFER_OFFSET (subbuffer) = GST_BUFFER_OFFSET_NONE;
456 GST_BUFFER_DURATION (subbuffer) = GST_CLOCK_TIME_NONE;
457 GST_BUFFER_OFFSET_END (subbuffer) = GST_BUFFER_OFFSET_NONE;
459 GST_BUFFER_CAPS (subbuffer) = NULL;
461 return GST_BUFFER_CAST (subbuffer);
465 * gst_buffer_is_span_fast:
466 * @buf1: a first source #GstBuffer.
467 * @buf2: the second source #GstBuffer.
469 * Determines whether a gst_buffer_span() can be done without copying
470 * the contents, that is, whether the data areas are contiguous.
472 * Returns: TRUE if the buffers are contiguous,
473 * FALSE if a copy would be required.
478 gst_buffer_is_span_fast (GstBuffer * buf1, GstBuffer * buf2)
480 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, FALSE);
481 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
482 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
484 /* it's only fast if we have subbuffers of the same parent */
485 return (GST_IS_SUBBUFFER (buf1) &&
486 GST_IS_SUBBUFFER (buf2) &&
487 (GST_SUBBUFFER (buf1)->parent == GST_SUBBUFFER (buf2)->parent) &&
488 ((buf1->data + buf1->size) == buf2->data));
493 * @buf1: a first source #GstBuffer to merge.
494 * @offset: the offset in the first buffer from where the new
495 * buffer should start.
496 * @buf2: the second source #GstBuffer to merge.
497 * @len: the total length of the new buffer.
499 * Creates a new buffer that consists of part of buf1 and buf2.
500 * Logically, buf1 and buf2 are concatenated into a single larger
501 * buffer, and a new buffer is created at the given offset inside
502 * this space, with a given length.
504 * If the two source buffers are children of the same larger buffer,
505 * and are contiguous, the new buffer will be a child of the shared
506 * parent, and thus no copying is necessary. you can use
507 * gst_buffer_is_span_fast() to determine if a memcpy will be needed.
509 * Returns: the new #GstBuffer that spans the two source buffers.
514 gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
519 g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
520 g_return_val_if_fail (buf1->mini_object.refcount > 0, FALSE);
521 g_return_val_if_fail (buf2->mini_object.refcount > 0, FALSE);
522 g_return_val_if_fail (len > 0, NULL);
523 g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
525 /* if the two buffers have the same parent and are adjacent */
526 if (gst_buffer_is_span_fast (buf1, buf2)) {
527 GstBuffer *parent = GST_SUBBUFFER (buf1)->parent;
529 /* we simply create a subbuffer of the common parent */
530 newbuf = gst_buffer_create_sub (parent,
531 buf1->data - parent->data + offset, len);
533 GST_CAT_DEBUG (GST_CAT_BUFFER,
534 "slow path taken while spanning buffers %p and %p", buf1, buf2);
535 /* otherwise we simply have to brute-force copy the buffers */
536 newbuf = gst_buffer_new_and_alloc (len);
538 /* copy the first buffer's data across */
539 memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
540 /* copy the second buffer's data across */
541 memcpy (newbuf->data + (buf1->size - offset), buf2->data,
542 len - (buf1->size - offset));
543 /* if the offset is 0, the new buffer has the same timestamp as buf1 */
545 GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
546 GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
549 /* if we completely merged the two buffers (appended), we can
550 * calculate the duration too. Also make sure we's not messing with
551 * invalid DURATIONS */
552 if (offset == 0 && buf1->size + buf2->size == len) {
553 if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
554 GST_BUFFER_DURATION_IS_VALID (buf2)) {
556 GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
557 GST_BUFFER_DURATION (buf2);
559 if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
561 GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);