2 * Copyright (C) 2011 Wim Taymans <wim.taymans@gmail.be>
4 * gstmemory.c: memory block handling
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
24 * @short_description: refcounted wrapper for memory blocks
25 * @see_also: #GstBuffer
27 * GstMemory is a lightweight refcounted object that wraps a region of memory.
28 * They are typically used to manage the data of a #GstBuffer.
30 * A GstMemory object has an allocated region of memory of maxsize. The maximum
31 * size does not change during the lifetime of the memory object. The memory
32 * also has an offset and size property that specifies the valid range of memory
33 * in the allocated region.
35 * Memory is usually created by allocators with a gst_allocator_alloc()
36 * method call. When NULL is used as the allocator, the default allocator will
39 * New allocators can be registered with gst_allocator_register().
40 * Allocators are identified by name and can be retrieved with
41 * gst_allocator_find().
43 * New memory can be created with gst_memory_new_wrapped() that wraps the memory
44 * allocated elsewhere.
46 * Refcounting of the memory block is performed with gst_memory_ref() and
49 * The size of the memory can be retrieved and changed with
50 * gst_memory_get_sizes() and gst_memory_resize() respectively.
52 * Getting access to the data of the memory is performed with gst_memory_map().
53 * The call will return a pointer to offset bytes into the region of memory.
54 * After the memory access is completed, gst_memory_unmap() should be called.
56 * Memory can be copied with gst_memory_copy(), which will returnn a writable
57 * copy. gst_memory_share() will create a new memory block that shares the
58 * memory with an existing memory block at a custom offset and with a custom
61 * Memory can be efficiently merged when gst_memory_is_span() returns TRUE.
63 * Last reviewed on 2011-06-08 (0.11.0)
70 #include "gst_private.h"
71 #include "gstmemory.h"
73 G_DEFINE_BOXED_TYPE (GstMemory, gst_memory, (GBoxedCopyFunc) gst_memory_ref,
74 (GBoxedFreeFunc) gst_memory_unref);
77 * gst_memory_alignment:
79 * The default memory alignment in bytes - 1
80 * an alignment of 7 would be the same as what malloc() guarantees.
82 #if defined(MEMORY_ALIGNMENT_MALLOC)
83 size_t gst_memory_alignment = 7;
84 #elif defined(MEMORY_ALIGNMENT_PAGESIZE)
85 /* we fill this in in the _init method */
86 size_t gst_memory_alignment = 0;
87 #elif defined(MEMORY_ALIGNMENT)
88 size_t gst_memory_alignment = MEMORY_ALIGNMENT - 1;
90 #error "No memory alignment configured"
91 size_t gst_memory_alignment = 0;
101 /* default memory implementation */
113 /* the default allocator */
114 static const GstAllocator *_default_allocator;
116 /* our predefined allocators */
117 static const GstAllocator *_default_mem_impl;
119 /* initialize the fields */
121 _default_mem_init (GstMemoryDefault * mem, GstMemoryFlags flags,
122 GstMemory * parent, gsize slice_size, gpointer data,
123 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
125 mem->mem.allocator = _default_mem_impl;
126 mem->mem.flags = flags;
127 mem->mem.refcount = 1;
128 mem->mem.parent = parent ? gst_memory_ref (parent) : NULL;
130 mem->slice_size = slice_size;
132 mem->free_func = free_func;
133 mem->maxsize = maxsize;
134 mem->offset = offset;
138 /* create a new memory block that manages the given memory */
139 static GstMemoryDefault *
140 _default_mem_new (GstMemoryFlags flags, GstMemory * parent, gpointer data,
141 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
143 GstMemoryDefault *mem;
146 slice_size = sizeof (GstMemoryDefault);
148 mem = g_slice_alloc (slice_size);
149 _default_mem_init (mem, flags, parent, slice_size,
150 data, free_func, maxsize, offset, size);
155 /* allocate the memory and structure in one block */
156 static GstMemoryDefault *
157 _default_mem_new_block (gsize maxsize, gsize align, gsize offset, gsize size)
159 GstMemoryDefault *mem;
160 gsize aoffset, slice_size;
163 /* ensure configured alignment */
164 align |= gst_memory_alignment;
165 /* allocate more to compensate for alignment */
167 /* alloc header and data in one block */
168 slice_size = sizeof (GstMemoryDefault) + maxsize;
170 mem = g_slice_alloc (slice_size);
174 data = (guint8 *) mem + sizeof (GstMemoryDefault);
176 if ((aoffset = ((guintptr) data & align)))
177 aoffset = (align + 1) - aoffset;
179 _default_mem_init (mem, 0, NULL, slice_size, data, NULL, maxsize,
180 aoffset + offset, size);
186 _default_mem_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
188 return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
192 _default_mem_get_sizes (GstMemoryDefault * mem, gsize * offset, gsize * maxsize)
195 *offset = mem->offset;
197 *maxsize = mem->maxsize;
203 _default_mem_resize (GstMemoryDefault * mem, gssize offset, gsize size)
205 g_return_if_fail (offset >= 0 || mem->offset >= -offset);
206 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
208 mem->offset += offset;
213 _default_mem_map (GstMemoryDefault * mem, gsize * size, gsize * maxsize,
219 *maxsize = mem->maxsize - mem->offset;
221 return mem->data + mem->offset;
225 _default_mem_unmap (GstMemoryDefault * mem, gpointer data, gsize size)
227 GST_DEBUG ("mem: %p, data %p, size %" G_GSIZE_FORMAT, mem, data, size);
228 GST_DEBUG ("mem: %p, data %p, offset %" G_GSIZE_FORMAT ", size %"
229 G_GSIZE_FORMAT ", maxsize %" G_GSIZE_FORMAT, mem, mem->data, mem->offset,
230 mem->size, mem->maxsize);
232 g_return_val_if_fail ((guint8 *) data >= mem->data
233 && (guint8 *) data < mem->data + mem->maxsize, FALSE);
235 if (mem->data + mem->offset != data) {
236 gsize newoffset = (guint8 *) data - mem->data;
238 size = mem->offset + mem->size - newoffset;
239 mem->offset = newoffset;
243 g_return_val_if_fail (mem->offset + size <= mem->maxsize, FALSE);
251 _default_mem_free (GstMemoryDefault * mem)
254 gst_memory_unref (mem->mem.parent);
257 mem->free_func (mem->data);
259 g_slice_free1 (mem->slice_size, mem);
262 static GstMemoryDefault *
263 _default_mem_copy (GstMemoryDefault * mem, gssize offset, gsize size)
265 GstMemoryDefault *copy;
268 size = mem->size > offset ? mem->size - offset : 0;
270 copy = _default_mem_new_block (mem->maxsize, 0, mem->offset + offset, size);
271 memcpy (copy->data, mem->data, mem->maxsize);
276 static GstMemoryDefault *
277 _default_mem_share (GstMemoryDefault * mem, gssize offset, gsize size)
279 GstMemoryDefault *sub;
282 /* find the real parent */
283 if ((parent = mem->mem.parent) == NULL)
284 parent = (GstMemory *) mem;
287 size = mem->size - offset;
289 sub = _default_mem_new (parent->flags, parent, mem->data, NULL, mem->maxsize,
290 mem->offset + offset, size);
296 _default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
301 GstMemoryDefault *parent;
303 parent = (GstMemoryDefault *) mem1->mem.parent;
305 *offset = mem1->offset - parent->offset;
308 /* and memory is contiguous */
309 return mem1->data + mem1->offset + mem1->size == mem2->data + mem2->offset;
313 _fallback_copy (GstMemory * mem, gssize offset, gssize size)
319 data = gst_memory_map (mem, &msize, NULL, GST_MAP_READ);
321 size = msize > offset ? msize - offset : 0;
322 /* use the same allocator as the memory we copy, FIXME, alignment? */
323 copy = gst_allocator_alloc (mem->allocator, size, 0);
324 dest = gst_memory_map (copy, NULL, NULL, GST_MAP_WRITE);
325 memcpy (dest, data + offset, size);
326 gst_memory_unmap (copy, dest, size);
328 gst_memory_unmap (mem, data, msize);
330 return (GstMemory *) copy;
334 _fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
340 static GHashTable *allocators;
343 _priv_gst_memory_initialize (void)
345 static const GstMemoryInfo _mem_info = {
346 (GstMemoryAllocFunction) _default_mem_alloc,
347 (GstMemoryGetSizesFunction) _default_mem_get_sizes,
348 (GstMemoryResizeFunction) _default_mem_resize,
349 (GstMemoryMapFunction) _default_mem_map,
350 (GstMemoryUnmapFunction) _default_mem_unmap,
351 (GstMemoryFreeFunction) _default_mem_free,
352 (GstMemoryCopyFunction) _default_mem_copy,
353 (GstMemoryShareFunction) _default_mem_share,
354 (GstMemoryIsSpanFunction) _default_mem_is_span,
358 g_rw_lock_init (&lock);
359 allocators = g_hash_table_new (g_str_hash, g_str_equal);
361 #ifdef HAVE_GETPAGESIZE
362 #ifdef MEMORY_ALIGNMENT_PAGESIZE
363 gst_memory_alignment = getpagesize () - 1;
367 GST_DEBUG ("memory alignment: %" G_GSIZE_FORMAT, gst_memory_alignment);
369 _default_mem_impl = gst_allocator_register (GST_ALLOCATOR_SYSMEM, &_mem_info);
371 _default_allocator = _default_mem_impl;
375 * gst_memory_new_wrapped:
376 * @flags: #GstMemoryFlags
377 * @data: data to wrap
378 * @free_func: function to free @data
379 * @maxsize: allocated size of @data
380 * @offset: offset in @data
381 * @size: size of valid data
383 * Allocate a new memory block that wraps the given @data.
385 * Returns: a new #GstMemory.
388 gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
389 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
391 GstMemoryDefault *mem;
393 g_return_val_if_fail (data != NULL, NULL);
394 g_return_val_if_fail (offset + size <= maxsize, NULL);
396 mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
398 return (GstMemory *) mem;
405 * Increases the refcount of @mem.
407 * Returns: @mem with increased refcount
410 gst_memory_ref (GstMemory * mem)
412 g_return_val_if_fail (mem != NULL, NULL);
414 g_atomic_int_inc (&mem->refcount);
423 * Decreases the refcount of @mem. When the refcount reaches 0, the free
424 * function of @mem will be called.
427 gst_memory_unref (GstMemory * mem)
429 g_return_if_fail (mem != NULL);
430 g_return_if_fail (mem->allocator != NULL);
432 if (g_atomic_int_dec_and_test (&mem->refcount))
433 mem->allocator->info.free (mem);
437 * gst_memory_get_sizes:
439 * @offset: pointer to offset
440 * @maxsize: pointer to maxsize
442 * Get the current @size, @offset and @maxsize of @mem.
444 * Returns: the current sizes of @mem
447 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
449 g_return_val_if_fail (mem != NULL, 0);
451 return mem->allocator->info.get_sizes (mem, offset, maxsize);
457 * @offset: a new offset
460 * Resize the memory region. @mem should be writable and offset + size should be
461 * less than the maxsize of @mem.
464 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
466 g_return_if_fail (mem != NULL);
467 g_return_if_fail (gst_memory_is_writable (mem));
469 mem->allocator->info.resize (mem, offset, size);
473 * gst_memory_is_writable:
476 * Check if @mem is writable.
478 * Returns: %TRUE is @mem is writable.
481 gst_memory_is_writable (GstMemory * mem)
483 g_return_val_if_fail (mem != NULL, FALSE);
485 return (mem->refcount == 1) &&
486 ((mem->parent == NULL) || (mem->parent->refcount == 1)) &&
487 ((mem->flags & GST_MEMORY_FLAG_READONLY) == 0);
493 * @size: (out) (allow-none): pointer for size
494 * @maxsize: (out) (allow-none): pointer for maxsize
495 * @flags: mapping flags
497 * Get a pointer to the memory of @mem that can be accessed according to @flags.
499 * @size and @maxsize will contain the size of the memory and the maximum
500 * allocated memory of @mem respectively. They can be set to NULL.
502 * Returns: (transfer none): a pointer to the memory of @mem.
505 gst_memory_map (GstMemory * mem, gsize * size, gsize * maxsize,
509 gint access_mode, state, newstate;
511 g_return_val_if_fail (mem != NULL, NULL);
512 access_mode = flags & 3;
513 g_return_val_if_fail (!(access_mode & GST_MAP_WRITE)
514 || gst_memory_is_writable (mem), NULL);
517 state = g_atomic_int_get (&mem->state);
519 /* nothing mapped, set access_mode and refcount */
520 newstate = 4 | access_mode;
522 /* access_mode must match */
523 g_return_val_if_fail ((state & access_mode) == access_mode, NULL);
524 /* increase refcount */
525 newstate = state + 4;
527 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
529 res = mem->allocator->info.map (mem, size, maxsize, flags);
531 if (G_UNLIKELY (res == NULL)) {
532 /* something went wrong, restore the orginal state again */
534 state = g_atomic_int_get (&mem->state);
535 /* there must be a ref */
536 g_return_val_if_fail (state >= 4, NULL);
537 /* decrease the refcount */
538 newstate = state - 4;
539 /* last refcount, unset access_mode */
542 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
550 * @data: data to unmap
551 * @size: new size of @mem, or -1
553 * Release the memory pointer obtained with gst_memory_map() and set the size of
554 * the memory to @size. @size can be set to -1 when the size should not be
557 * It is possible to pass a different @data than that obtained from
558 * gst_memory_map() in which case the offset of @mem will be updated.
560 * Returns: TRUE when the memory was release successfully.
563 gst_memory_unmap (GstMemory * mem, gpointer data, gssize size)
565 gboolean need_unmap = TRUE;
566 gint state, newstate;
568 g_return_val_if_fail (mem != NULL, FALSE);
571 state = g_atomic_int_get (&mem->state);
573 /* there must be a ref */
574 g_return_val_if_fail (state >= 4, FALSE);
577 /* try to unmap, only do this once */
578 if (!mem->allocator->info.unmap (mem, data, size))
582 /* success, try to decrease the refcount */
583 newstate = state - 4;
584 /* last refcount, unset access_mode */
587 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
595 * @offset: an offset to copy
596 * @size: size to copy or -1 to copy all bytes from offset
598 * Return a copy of @size bytes from @mem starting from @offset. This copy is
599 * guaranteed to be writable. @size can be set to -1 to return a copy all bytes
602 * Returns: a new #GstMemory.
605 gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
607 g_return_val_if_fail (mem != NULL, NULL);
609 return mem->allocator->info.copy (mem, offset, size);
615 * @offset: an offset to share
616 * @size: size to share or -1 to share bytes from offset
618 * Return a shared copy of @size bytes from @mem starting from @offset. No
619 * memory copy is performed and the memory region is simply shared. The result
620 * is guaranteed to be not-writable. @size can be set to -1 to return a share
621 * all bytes from @offset.
623 * Returns: a new #GstMemory.
626 gst_memory_share (GstMemory * mem, gssize offset, gssize size)
628 g_return_val_if_fail (mem != NULL, NULL);
630 return mem->allocator->info.share (mem, offset, size);
634 * gst_memory_is_span:
635 * @mem1: a #GstMemory
636 * @mem2: a #GstMemory
637 * @offset: a pointer to a result offset
639 * Check if @mem1 and mem2 share the memory with a common parent memory object
640 * and that the memory is contiguous.
642 * If this is the case, the memory of @mem1 and @mem2 can be merged
643 * efficiently by performing gst_memory_share() on the parent object from
644 * the returned @offset.
646 * Returns: %TRUE if the memory is contiguous and of a common parent.
649 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
651 g_return_val_if_fail (mem1 != NULL, FALSE);
652 g_return_val_if_fail (mem2 != NULL, FALSE);
654 /* need to have the same allocators */
655 if (mem1->allocator != mem2->allocator)
658 /* need to have the same parent */
659 if (mem1->parent == NULL || mem1->parent != mem2->parent)
662 /* and memory is contiguous */
663 if (!mem1->allocator->info.is_span (mem1, mem2, offset))
670 * gst_allocator_register:
671 * @name: the name of the allocator
672 * @info: #GstMemoryInfo
674 * Registers the memory allocator with @name and implementation functions
677 * All functions in @info are mandatory exept the copy and is_span
678 * functions, which will have a default implementation when left NULL.
680 * The user_data field in @info will be passed to all calls of the alloc
683 * Returns: a new #GstAllocator.
686 gst_allocator_register (const gchar * name, const GstMemoryInfo * info)
688 GstAllocator *allocator;
690 #define INSTALL_FALLBACK(_t) \
691 if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
693 g_return_val_if_fail (name != NULL, NULL);
694 g_return_val_if_fail (info != NULL, NULL);
695 g_return_val_if_fail (info->alloc != NULL, NULL);
696 g_return_val_if_fail (info->get_sizes != NULL, NULL);
697 g_return_val_if_fail (info->resize != NULL, NULL);
698 g_return_val_if_fail (info->map != NULL, NULL);
699 g_return_val_if_fail (info->unmap != NULL, NULL);
700 g_return_val_if_fail (info->free != NULL, NULL);
701 g_return_val_if_fail (info->share != NULL, NULL);
703 allocator = g_slice_new (GstAllocator);
704 allocator->name = g_quark_from_string (name);
705 allocator->info = *info;
706 INSTALL_FALLBACK (copy);
707 INSTALL_FALLBACK (is_span);
708 #undef INSTALL_FALLBACK
710 GST_DEBUG ("registering allocator \"%s\"", name);
712 g_rw_lock_writer_lock (&lock);
713 g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
714 g_rw_lock_writer_unlock (&lock);
720 * gst_allocator_find:
721 * @name: the name of the allocator
723 * Find a previously registered allocator with @name. When @name is NULL, the
724 * default allocator will be returned.
726 * Returns: a #GstAllocator or NULL when the allocator with @name was not
730 gst_allocator_find (const gchar * name)
732 const GstAllocator *allocator;
734 g_rw_lock_reader_lock (&lock);
736 allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
738 allocator = _default_allocator;
740 g_rw_lock_reader_unlock (&lock);
746 * gst_allocator_set_default:
747 * @allocator: a #GstAllocator
749 * Set the default allocator.
752 gst_allocator_set_default (const GstAllocator * allocator)
754 g_return_if_fail (allocator != NULL);
756 g_rw_lock_writer_lock (&lock);
757 _default_allocator = allocator;
758 g_rw_lock_writer_unlock (&lock);
762 * gst_allocator_alloc:
763 * @allocator: (transfer none) (allow-none): a #GstAllocator to use
764 * @maxsize: allocated size of @data
765 * @align: alignment for the data
767 * Use @allocator to allocate a new memory block with memory that is at least
768 * @maxsize big and has the given alignment.
770 * When @allocator is NULL, the default allocator will be used.
772 * @align is given as a bitmask so that @align + 1 equals the amount of bytes to
773 * align to. For example, to align to 8 bytes, use an alignment of 7.
775 * Returns: (transfer full): a new #GstMemory.
778 gst_allocator_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
780 g_return_val_if_fail (((align + 1) & align) == 0, NULL);
782 if (allocator == NULL)
783 allocator = _default_allocator;
785 return allocator->info.alloc (allocator, maxsize, align,
786 allocator->info.user_data);