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)
67 #include "gst_private.h"
68 #include "gstmemory.h"
70 G_DEFINE_BOXED_TYPE (GstMemory, gst_memory, (GBoxedCopyFunc) gst_memory_ref,
71 (GBoxedFreeFunc) gst_memory_unref);
74 * gst_memory_alignment:
76 * The default memory alignment in bytes - 1
77 * an alignment of 7 would be the same as what malloc() guarantees.
79 #if defined(MEMORY_ALIGNMENT_MALLOC)
80 size_t gst_memory_alignment = 7;
81 #elif defined(MEMORY_ALIGNMENT_PAGESIZE)
82 /* we fill this in in the _init method */
83 size_t gst_memory_alignment = 0;
84 #elif defined(MEMORY_ALIGNMENT)
85 size_t gst_memory_alignment = MEMORY_ALIGNMENT - 1;
87 #error "No memory alignment configured"
88 size_t gst_memory_alignment = 0;
98 /* default memory implementation */
110 /* the default allocator */
111 static const GstAllocator *_default_allocator;
113 /* our predefined allocators */
114 static const GstAllocator *_default_mem_impl;
116 /* initialize the fields */
118 _default_mem_init (GstMemoryDefault * mem, GstMemoryFlags flags,
119 GstMemory * parent, gsize slice_size, gpointer data,
120 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
122 mem->mem.allocator = _default_mem_impl;
123 mem->mem.flags = flags;
124 mem->mem.refcount = 1;
125 mem->mem.parent = parent ? gst_memory_ref (parent) : NULL;
127 mem->slice_size = slice_size;
129 mem->free_func = free_func;
130 mem->maxsize = maxsize;
131 mem->offset = offset;
135 /* create a new memory block that manages the given memory */
136 static GstMemoryDefault *
137 _default_mem_new (GstMemoryFlags flags, GstMemory * parent, gpointer data,
138 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
140 GstMemoryDefault *mem;
143 slice_size = sizeof (GstMemoryDefault);
145 mem = g_slice_alloc (slice_size);
146 _default_mem_init (mem, flags, parent, slice_size,
147 data, free_func, maxsize, offset, size);
152 /* allocate the memory and structure in one block */
153 static GstMemoryDefault *
154 _default_mem_new_block (gsize maxsize, gsize align, gsize offset, gsize size)
156 GstMemoryDefault *mem;
157 gsize aoffset, slice_size;
160 /* ensure configured alignment */
161 align |= gst_memory_alignment;
162 /* allocate more to compensate for alignment */
164 /* alloc header and data in one block */
165 slice_size = sizeof (GstMemoryDefault) + maxsize;
167 mem = g_slice_alloc (slice_size);
171 data = (guint8 *) mem + sizeof (GstMemoryDefault);
173 if ((aoffset = ((guintptr) data & align)))
174 aoffset = (align + 1) - aoffset;
176 _default_mem_init (mem, 0, NULL, slice_size, data, NULL, maxsize,
177 aoffset + offset, size);
183 _default_mem_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
185 return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
189 _default_mem_get_sizes (GstMemoryDefault * mem, gsize * offset, gsize * maxsize)
192 *offset = mem->offset;
194 *maxsize = mem->maxsize;
200 _default_mem_resize (GstMemoryDefault * mem, gssize offset, gsize size)
202 g_return_if_fail (offset >= 0 || mem->offset >= -offset);
203 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
205 mem->offset += offset;
210 _default_mem_map (GstMemoryDefault * mem, gsize * size, gsize * maxsize,
216 *maxsize = mem->maxsize - mem->offset;
218 return mem->data + mem->offset;
222 _default_mem_unmap (GstMemoryDefault * mem, gpointer data, gsize size)
224 GST_DEBUG ("mem: %p, data %p, size %" G_GSIZE_FORMAT, mem, data, size);
225 GST_DEBUG ("mem: %p, data %p, offset %" G_GSIZE_FORMAT ", size %"
226 G_GSIZE_FORMAT ", maxsize %" G_GSIZE_FORMAT, mem, mem->data, mem->offset,
227 mem->size, mem->maxsize);
229 g_return_val_if_fail ((guint8 *) data >= mem->data
230 && (guint8 *) data < mem->data + mem->maxsize, FALSE);
232 if (mem->data + mem->offset != data) {
233 gsize newoffset = (guint8 *) data - mem->data;
235 size = mem->offset + mem->size - newoffset;
236 mem->offset = newoffset;
240 g_return_val_if_fail (mem->offset + size <= mem->maxsize, FALSE);
248 _default_mem_free (GstMemoryDefault * mem)
251 gst_memory_unref (mem->mem.parent);
254 mem->free_func (mem->data);
256 g_slice_free1 (mem->slice_size, mem);
259 static GstMemoryDefault *
260 _default_mem_copy (GstMemoryDefault * mem, gssize offset, gsize size)
262 GstMemoryDefault *copy;
265 size = mem->size > offset ? mem->size - offset : 0;
267 copy = _default_mem_new_block (mem->maxsize, 0, mem->offset + offset, size);
268 memcpy (copy->data, mem->data, mem->maxsize);
273 static GstMemoryDefault *
274 _default_mem_share (GstMemoryDefault * mem, gssize offset, gsize size)
276 GstMemoryDefault *sub;
279 /* find the real parent */
280 if ((parent = mem->mem.parent) == NULL)
281 parent = (GstMemory *) mem;
284 size = mem->size - offset;
286 sub = _default_mem_new (parent->flags, parent, mem->data, NULL, mem->maxsize,
287 mem->offset + offset, size);
293 _default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
298 GstMemoryDefault *parent;
300 parent = (GstMemoryDefault *) mem1->mem.parent;
302 *offset = mem1->offset - parent->offset;
305 /* and memory is contiguous */
306 return mem1->data + mem1->offset + mem1->size == mem2->data + mem2->offset;
310 _fallback_copy (GstMemory * mem, gssize offset, gssize size)
316 data = gst_memory_map (mem, &msize, NULL, GST_MAP_READ);
318 size = msize > offset ? msize - offset : 0;
319 /* use the same allocator as the memory we copy, FIXME, alignment? */
320 copy = gst_allocator_alloc (mem->allocator, size, 0);
321 dest = gst_memory_map (copy, NULL, NULL, GST_MAP_WRITE);
322 memcpy (dest, data + offset, size);
323 gst_memory_unmap (copy, dest, size);
325 gst_memory_unmap (mem, data, msize);
327 return (GstMemory *) copy;
331 _fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
336 static GStaticRWLock lock = G_STATIC_RW_LOCK_INIT;
337 static GHashTable *allocators;
340 _priv_gst_memory_initialize (void)
342 static const GstMemoryInfo _mem_info = {
343 (GstMemoryAllocFunction) _default_mem_alloc,
344 (GstMemoryGetSizesFunction) _default_mem_get_sizes,
345 (GstMemoryResizeFunction) _default_mem_resize,
346 (GstMemoryMapFunction) _default_mem_map,
347 (GstMemoryUnmapFunction) _default_mem_unmap,
348 (GstMemoryFreeFunction) _default_mem_free,
349 (GstMemoryCopyFunction) _default_mem_copy,
350 (GstMemoryShareFunction) _default_mem_share,
351 (GstMemoryIsSpanFunction) _default_mem_is_span,
355 allocators = g_hash_table_new (g_str_hash, g_str_equal);
357 #ifdef HAVE_GETPAGESIZE
358 #ifdef MEMORY_ALIGNMENT_PAGESIZE
359 gst_memory_alignment = getpagesize () - 1;
363 GST_DEBUG ("memory alignment: %" G_GSIZE_FORMAT, gst_memory_alignment);
365 _default_mem_impl = gst_allocator_register (GST_ALLOCATOR_SYSMEM, &_mem_info);
367 _default_allocator = _default_mem_impl;
371 * gst_memory_new_wrapped:
372 * @flags: #GstMemoryFlags
373 * @data: data to wrap
374 * @free_func: function to free @data
375 * @maxsize: allocated size of @data
376 * @offset: offset in @data
377 * @size: size of valid data
379 * Allocate a new memory block that wraps the given @data.
381 * Returns: a new #GstMemory.
384 gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
385 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
387 GstMemoryDefault *mem;
389 g_return_val_if_fail (data != NULL, NULL);
390 g_return_val_if_fail (offset + size <= maxsize, NULL);
392 mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
394 return (GstMemory *) mem;
401 * Increases the refcount of @mem.
403 * Returns: @mem with increased refcount
406 gst_memory_ref (GstMemory * mem)
408 g_return_val_if_fail (mem != NULL, NULL);
410 g_atomic_int_inc (&mem->refcount);
419 * Decreases the refcount of @mem. When the refcount reaches 0, the free
420 * function of @mem will be called.
423 gst_memory_unref (GstMemory * mem)
425 g_return_if_fail (mem != NULL);
426 g_return_if_fail (mem->allocator != NULL);
428 if (g_atomic_int_dec_and_test (&mem->refcount))
429 mem->allocator->info.free (mem);
433 * gst_memory_get_sizes:
435 * @offset: pointer to offset
436 * @maxsize: pointer to maxsize
438 * Get the current @size, @offset and @maxsize of @mem.
440 * Returns: the current sizes of @mem
443 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
445 g_return_val_if_fail (mem != NULL, 0);
447 return mem->allocator->info.get_sizes (mem, offset, maxsize);
453 * @offset: a new offset
456 * Resize the memory region. @mem should be writable and offset + size should be
457 * less than the maxsize of @mem.
460 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
462 g_return_if_fail (mem != NULL);
463 g_return_if_fail (GST_MEMORY_IS_WRITABLE (mem));
465 mem->allocator->info.resize (mem, offset, size);
471 * @size: (out) (allow-none): pointer for size
472 * @maxsize: (out) (allow-none): pointer for maxsize
473 * @flags: mapping flags
475 * Get a pointer to the memory of @mem that can be accessed according to @flags.
477 * @size and @maxsize will contain the size of the memory and the maximum
478 * allocated memory of @mem respectively. They can be set to NULL.
480 * Returns: (transfer none): a pointer to the memory of @mem.
483 gst_memory_map (GstMemory * mem, gsize * size, gsize * maxsize,
487 gint access_mode, state, newstate;
489 g_return_val_if_fail (mem != NULL, NULL);
490 access_mode = flags & 3;
491 g_return_val_if_fail (!(access_mode & GST_MAP_WRITE)
492 || GST_MEMORY_IS_WRITABLE (mem), NULL);
495 state = g_atomic_int_get (&mem->state);
497 /* nothing mapped, set access_mode and refcount */
498 newstate = 4 | access_mode;
500 /* access_mode must match */
501 g_return_val_if_fail ((state & access_mode) == access_mode, NULL);
502 /* increase refcount */
503 newstate = state + 4;
505 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
507 res = mem->allocator->info.map (mem, size, maxsize, flags);
509 if (G_UNLIKELY (res == NULL)) {
510 /* something went wrong, restore the orginal state again */
512 state = g_atomic_int_get (&mem->state);
513 /* there must be a ref */
514 g_return_val_if_fail (state >= 4, NULL);
515 /* decrease the refcount */
516 newstate = state - 4;
517 /* last refcount, unset access_mode */
520 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
528 * @data: data to unmap
529 * @size: new size of @mem, or -1
531 * Release the memory pointer obtained with gst_memory_map() and set the size of
532 * the memory to @size. @size can be set to -1 when the size should not be
535 * It is possible to pass a different @data than that obtained from
536 * gst_memory_map() in which case the offset of @mem will be updated.
538 * Returns: TRUE when the memory was release successfully.
541 gst_memory_unmap (GstMemory * mem, gpointer data, gssize size)
543 gboolean need_unmap = TRUE;
544 gint state, newstate;
546 g_return_val_if_fail (mem != NULL, FALSE);
549 state = g_atomic_int_get (&mem->state);
551 /* there must be a ref */
552 g_return_val_if_fail (state >= 4, FALSE);
555 /* try to unmap, only do this once */
556 if (!mem->allocator->info.unmap (mem, data, size))
560 /* success, try to decrease the refcount */
561 newstate = state - 4;
562 /* last refcount, unset access_mode */
565 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
573 * @offset: an offset to copy
574 * @size: size to copy or -1 to copy all bytes from offset
576 * Return a copy of @size bytes from @mem starting from @offset. This copy is
577 * guaranteed to be writable. @size can be set to -1 to return a copy all bytes
580 * Returns: a new #GstMemory.
583 gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
585 g_return_val_if_fail (mem != NULL, NULL);
587 return mem->allocator->info.copy (mem, offset, size);
593 * @offset: an offset to share
594 * @size: size to share or -1 to share bytes from offset
596 * Return a shared copy of @size bytes from @mem starting from @offset. No
597 * memory copy is performed and the memory region is simply shared. The result
598 * is guaranteed to be not-writable. @size can be set to -1 to return a share
599 * all bytes from @offset.
601 * Returns: a new #GstMemory.
604 gst_memory_share (GstMemory * mem, gssize offset, gssize size)
606 g_return_val_if_fail (mem != NULL, NULL);
608 return mem->allocator->info.share (mem, offset, size);
612 * gst_memory_is_span:
613 * @mem1: a #GstMemory
614 * @mem2: a #GstMemory
615 * @offset: a pointer to a result offset
617 * Check if @mem1 and mem2 share the memory with a common parent memory object
618 * and that the memory is contiguous.
620 * If this is the case, the memory of @mem1 and @mem2 can be merged
621 * efficiently by performing gst_memory_share() on the parent object from
622 * the returned @offset.
624 * Returns: %TRUE if the memory is contiguous and of a common parent.
627 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
629 g_return_val_if_fail (mem1 != NULL, FALSE);
630 g_return_val_if_fail (mem2 != NULL, FALSE);
632 /* need to have the same allocators */
633 if (mem1->allocator != mem2->allocator)
636 /* need to have the same parent */
637 if (mem1->parent == NULL || mem1->parent != mem2->parent)
640 /* and memory is contiguous */
641 if (!mem1->allocator->info.is_span (mem1, mem2, offset))
648 * gst_allocator_register:
649 * @name: the name of the allocator
650 * @info: #GstMemoryInfo
652 * Registers the memory allocator with @name and implementation functions
655 * All functions in @info are mandatory exept the copy and is_span
656 * functions, which will have a default implementation when left NULL.
658 * The user_data field in @info will be passed to all calls of the alloc
661 * Returns: a new #GstAllocator.
664 gst_allocator_register (const gchar * name, const GstMemoryInfo * info)
666 GstAllocator *allocator;
668 #define INSTALL_FALLBACK(_t) \
669 if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
671 g_return_val_if_fail (name != NULL, NULL);
672 g_return_val_if_fail (info != NULL, NULL);
673 g_return_val_if_fail (info->alloc != NULL, NULL);
674 g_return_val_if_fail (info->get_sizes != NULL, NULL);
675 g_return_val_if_fail (info->resize != NULL, NULL);
676 g_return_val_if_fail (info->map != NULL, NULL);
677 g_return_val_if_fail (info->unmap != NULL, NULL);
678 g_return_val_if_fail (info->free != NULL, NULL);
679 g_return_val_if_fail (info->share != NULL, NULL);
681 allocator = g_slice_new (GstAllocator);
682 allocator->name = g_quark_from_string (name);
683 allocator->info = *info;
684 INSTALL_FALLBACK (copy);
685 INSTALL_FALLBACK (is_span);
686 #undef INSTALL_FALLBACK
688 GST_DEBUG ("registering allocator \"%s\"", name);
690 g_static_rw_lock_writer_lock (&lock);
691 g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
692 g_static_rw_lock_writer_unlock (&lock);
698 * gst_allocator_find:
699 * @name: the name of the allocator
701 * Find a previously registered allocator with @name. When @name is NULL, the
702 * default allocator will be returned.
704 * Returns: a #GstAllocator or NULL when the allocator with @name was not
708 gst_allocator_find (const gchar * name)
710 const GstAllocator *allocator;
712 g_static_rw_lock_reader_lock (&lock);
714 allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
716 allocator = _default_allocator;
718 g_static_rw_lock_reader_unlock (&lock);
724 * gst_allocator_set_default:
725 * @allocator: a #GstAllocator
727 * Set the default allocator.
730 gst_allocator_set_default (const GstAllocator * allocator)
732 g_return_if_fail (allocator != NULL);
734 g_static_rw_lock_writer_lock (&lock);
735 _default_allocator = allocator;
736 g_static_rw_lock_writer_unlock (&lock);
740 * gst_allocator_alloc:
741 * @allocator: (transfer none) (allow-none): a #GstAllocator to use
742 * @maxsize: allocated size of @data
743 * @align: alignment for the data
745 * Use @allocator to allocate a new memory block with memory that is at least
746 * @maxsize big and has the given alignment.
748 * When @allocator is NULL, the default allocator will be used.
750 * @align is given as a bitmask so that @align + 1 equals the amount of bytes to
751 * align to. For example, to align to 8 bytes, use an alignment of 7.
753 * Returns: (transfer full): a new #GstMemory.
756 gst_allocator_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
758 g_return_val_if_fail (((align + 1) & align) == 0, NULL);
760 if (allocator == NULL)
761 allocator = _default_allocator;
763 return allocator->info.alloc (allocator, maxsize, align,
764 allocator->info.user_data);