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 /* FIXME 0.11: suppress warnings for deprecated API such as GStaticRecMutex
71 * with newer GLib versions (>= 2.31.0) */
72 #define GLIB_DISABLE_DEPRECATION_WARNINGS
73 #include "gst_private.h"
74 #include "gstmemory.h"
76 G_DEFINE_BOXED_TYPE (GstMemory, gst_memory, (GBoxedCopyFunc) gst_memory_ref,
77 (GBoxedFreeFunc) gst_memory_unref);
80 * gst_memory_alignment:
82 * The default memory alignment in bytes - 1
83 * an alignment of 7 would be the same as what malloc() guarantees.
85 #if defined(MEMORY_ALIGNMENT_MALLOC)
86 size_t gst_memory_alignment = 7;
87 #elif defined(MEMORY_ALIGNMENT_PAGESIZE)
88 /* we fill this in in the _init method */
89 size_t gst_memory_alignment = 0;
90 #elif defined(MEMORY_ALIGNMENT)
91 size_t gst_memory_alignment = MEMORY_ALIGNMENT - 1;
93 #error "No memory alignment configured"
94 size_t gst_memory_alignment = 0;
104 /* default memory implementation */
116 /* the default allocator */
117 static const GstAllocator *_default_allocator;
119 /* our predefined allocators */
120 static const GstAllocator *_default_mem_impl;
122 /* initialize the fields */
124 _default_mem_init (GstMemoryDefault * mem, GstMemoryFlags flags,
125 GstMemory * parent, gsize slice_size, gpointer data,
126 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
128 mem->mem.allocator = _default_mem_impl;
129 mem->mem.flags = flags;
130 mem->mem.refcount = 1;
131 mem->mem.parent = parent ? gst_memory_ref (parent) : NULL;
133 mem->slice_size = slice_size;
135 mem->free_func = free_func;
136 mem->maxsize = maxsize;
137 mem->offset = offset;
141 /* create a new memory block that manages the given memory */
142 static GstMemoryDefault *
143 _default_mem_new (GstMemoryFlags flags, GstMemory * parent, gpointer data,
144 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
146 GstMemoryDefault *mem;
149 slice_size = sizeof (GstMemoryDefault);
151 mem = g_slice_alloc (slice_size);
152 _default_mem_init (mem, flags, parent, slice_size,
153 data, free_func, maxsize, offset, size);
158 /* allocate the memory and structure in one block */
159 static GstMemoryDefault *
160 _default_mem_new_block (gsize maxsize, gsize align, gsize offset, gsize size)
162 GstMemoryDefault *mem;
163 gsize aoffset, slice_size;
166 /* ensure configured alignment */
167 align |= gst_memory_alignment;
168 /* allocate more to compensate for alignment */
170 /* alloc header and data in one block */
171 slice_size = sizeof (GstMemoryDefault) + maxsize;
173 mem = g_slice_alloc (slice_size);
177 data = (guint8 *) mem + sizeof (GstMemoryDefault);
179 if ((aoffset = ((guintptr) data & align)))
180 aoffset = (align + 1) - aoffset;
182 _default_mem_init (mem, 0, NULL, slice_size, data, NULL, maxsize,
183 aoffset + offset, size);
189 _default_mem_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
191 return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
195 _default_mem_get_sizes (GstMemoryDefault * mem, gsize * offset, gsize * maxsize)
198 *offset = mem->offset;
200 *maxsize = mem->maxsize;
206 _default_mem_resize (GstMemoryDefault * mem, gssize offset, gsize size)
208 g_return_if_fail (offset >= 0 || mem->offset >= -offset);
209 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
211 mem->offset += offset;
216 _default_mem_map (GstMemoryDefault * mem, gsize * size, gsize * maxsize,
222 *maxsize = mem->maxsize - mem->offset;
224 return mem->data + mem->offset;
228 _default_mem_unmap (GstMemoryDefault * mem, gpointer data, gsize size)
230 GST_DEBUG ("mem: %p, data %p, size %" G_GSIZE_FORMAT, mem, data, size);
231 GST_DEBUG ("mem: %p, data %p, offset %" G_GSIZE_FORMAT ", size %"
232 G_GSIZE_FORMAT ", maxsize %" G_GSIZE_FORMAT, mem, mem->data, mem->offset,
233 mem->size, mem->maxsize);
235 g_return_val_if_fail ((guint8 *) data >= mem->data
236 && (guint8 *) data < mem->data + mem->maxsize, FALSE);
238 if (mem->data + mem->offset != data) {
239 gsize newoffset = (guint8 *) data - mem->data;
241 size = mem->offset + mem->size - newoffset;
242 mem->offset = newoffset;
246 g_return_val_if_fail (mem->offset + size <= mem->maxsize, FALSE);
254 _default_mem_free (GstMemoryDefault * mem)
257 gst_memory_unref (mem->mem.parent);
260 mem->free_func (mem->data);
262 g_slice_free1 (mem->slice_size, mem);
265 static GstMemoryDefault *
266 _default_mem_copy (GstMemoryDefault * mem, gssize offset, gsize size)
268 GstMemoryDefault *copy;
271 size = mem->size > offset ? mem->size - offset : 0;
273 copy = _default_mem_new_block (mem->maxsize, 0, mem->offset + offset, size);
274 memcpy (copy->data, mem->data, mem->maxsize);
279 static GstMemoryDefault *
280 _default_mem_share (GstMemoryDefault * mem, gssize offset, gsize size)
282 GstMemoryDefault *sub;
285 /* find the real parent */
286 if ((parent = mem->mem.parent) == NULL)
287 parent = (GstMemory *) mem;
290 size = mem->size - offset;
292 sub = _default_mem_new (parent->flags, parent, mem->data, NULL, mem->maxsize,
293 mem->offset + offset, size);
299 _default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
304 GstMemoryDefault *parent;
306 parent = (GstMemoryDefault *) mem1->mem.parent;
308 *offset = mem1->offset - parent->offset;
311 /* and memory is contiguous */
312 return mem1->data + mem1->offset + mem1->size == mem2->data + mem2->offset;
316 _fallback_copy (GstMemory * mem, gssize offset, gssize size)
322 data = gst_memory_map (mem, &msize, NULL, GST_MAP_READ);
324 size = msize > offset ? msize - offset : 0;
325 /* use the same allocator as the memory we copy, FIXME, alignment? */
326 copy = gst_allocator_alloc (mem->allocator, size, 0);
327 dest = gst_memory_map (copy, NULL, NULL, GST_MAP_WRITE);
328 memcpy (dest, data + offset, size);
329 gst_memory_unmap (copy, dest, size);
331 gst_memory_unmap (mem, data, msize);
333 return (GstMemory *) copy;
337 _fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
342 static GStaticRWLock lock = G_STATIC_RW_LOCK_INIT;
343 static GHashTable *allocators;
346 _priv_gst_memory_initialize (void)
348 static const GstMemoryInfo _mem_info = {
349 (GstMemoryAllocFunction) _default_mem_alloc,
350 (GstMemoryGetSizesFunction) _default_mem_get_sizes,
351 (GstMemoryResizeFunction) _default_mem_resize,
352 (GstMemoryMapFunction) _default_mem_map,
353 (GstMemoryUnmapFunction) _default_mem_unmap,
354 (GstMemoryFreeFunction) _default_mem_free,
355 (GstMemoryCopyFunction) _default_mem_copy,
356 (GstMemoryShareFunction) _default_mem_share,
357 (GstMemoryIsSpanFunction) _default_mem_is_span,
361 allocators = g_hash_table_new (g_str_hash, g_str_equal);
363 #ifdef HAVE_GETPAGESIZE
364 #ifdef MEMORY_ALIGNMENT_PAGESIZE
365 gst_memory_alignment = getpagesize () - 1;
369 GST_DEBUG ("memory alignment: %" G_GSIZE_FORMAT, gst_memory_alignment);
371 _default_mem_impl = gst_allocator_register (GST_ALLOCATOR_SYSMEM, &_mem_info);
373 _default_allocator = _default_mem_impl;
377 * gst_memory_new_wrapped:
378 * @flags: #GstMemoryFlags
379 * @data: data to wrap
380 * @free_func: function to free @data
381 * @maxsize: allocated size of @data
382 * @offset: offset in @data
383 * @size: size of valid data
385 * Allocate a new memory block that wraps the given @data.
387 * Returns: a new #GstMemory.
390 gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
391 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
393 GstMemoryDefault *mem;
395 g_return_val_if_fail (data != NULL, NULL);
396 g_return_val_if_fail (offset + size <= maxsize, NULL);
398 mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
400 return (GstMemory *) mem;
407 * Increases the refcount of @mem.
409 * Returns: @mem with increased refcount
412 gst_memory_ref (GstMemory * mem)
414 g_return_val_if_fail (mem != NULL, NULL);
416 g_atomic_int_inc (&mem->refcount);
425 * Decreases the refcount of @mem. When the refcount reaches 0, the free
426 * function of @mem will be called.
429 gst_memory_unref (GstMemory * mem)
431 g_return_if_fail (mem != NULL);
432 g_return_if_fail (mem->allocator != NULL);
434 if (g_atomic_int_dec_and_test (&mem->refcount))
435 mem->allocator->info.free (mem);
439 * gst_memory_get_sizes:
441 * @offset: pointer to offset
442 * @maxsize: pointer to maxsize
444 * Get the current @size, @offset and @maxsize of @mem.
446 * Returns: the current sizes of @mem
449 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
451 g_return_val_if_fail (mem != NULL, 0);
453 return mem->allocator->info.get_sizes (mem, offset, maxsize);
459 * @offset: a new offset
462 * Resize the memory region. @mem should be writable and offset + size should be
463 * less than the maxsize of @mem.
466 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
468 g_return_if_fail (mem != NULL);
469 g_return_if_fail (gst_memory_is_writable (mem));
471 mem->allocator->info.resize (mem, offset, size);
475 * gst_memory_is_writable:
478 * Check if @mem is writable.
480 * Returns: %TRUE is @mem is writable.
483 gst_memory_is_writable (GstMemory * mem)
485 g_return_val_if_fail (mem != NULL, FALSE);
487 return (mem->refcount == 1) &&
488 ((mem->parent == NULL) || (mem->parent->refcount == 1)) &&
489 ((mem->flags & GST_MEMORY_FLAG_READONLY) == 0);
495 * @size: (out) (allow-none): pointer for size
496 * @maxsize: (out) (allow-none): pointer for maxsize
497 * @flags: mapping flags
499 * Get a pointer to the memory of @mem that can be accessed according to @flags.
501 * @size and @maxsize will contain the size of the memory and the maximum
502 * allocated memory of @mem respectively. They can be set to NULL.
504 * Returns: (transfer none): a pointer to the memory of @mem.
507 gst_memory_map (GstMemory * mem, gsize * size, gsize * maxsize,
511 gint access_mode, state, newstate;
513 g_return_val_if_fail (mem != NULL, NULL);
514 access_mode = flags & 3;
515 g_return_val_if_fail (!(access_mode & GST_MAP_WRITE)
516 || gst_memory_is_writable (mem), NULL);
519 state = g_atomic_int_get (&mem->state);
521 /* nothing mapped, set access_mode and refcount */
522 newstate = 4 | access_mode;
524 /* access_mode must match */
525 g_return_val_if_fail ((state & access_mode) == access_mode, NULL);
526 /* increase refcount */
527 newstate = state + 4;
529 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
531 res = mem->allocator->info.map (mem, size, maxsize, flags);
533 if (G_UNLIKELY (res == NULL)) {
534 /* something went wrong, restore the orginal state again */
536 state = g_atomic_int_get (&mem->state);
537 /* there must be a ref */
538 g_return_val_if_fail (state >= 4, NULL);
539 /* decrease the refcount */
540 newstate = state - 4;
541 /* last refcount, unset access_mode */
544 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
552 * @data: data to unmap
553 * @size: new size of @mem, or -1
555 * Release the memory pointer obtained with gst_memory_map() and set the size of
556 * the memory to @size. @size can be set to -1 when the size should not be
559 * It is possible to pass a different @data than that obtained from
560 * gst_memory_map() in which case the offset of @mem will be updated.
562 * Returns: TRUE when the memory was release successfully.
565 gst_memory_unmap (GstMemory * mem, gpointer data, gssize size)
567 gboolean need_unmap = TRUE;
568 gint state, newstate;
570 g_return_val_if_fail (mem != NULL, FALSE);
573 state = g_atomic_int_get (&mem->state);
575 /* there must be a ref */
576 g_return_val_if_fail (state >= 4, FALSE);
579 /* try to unmap, only do this once */
580 if (!mem->allocator->info.unmap (mem, data, size))
584 /* success, try to decrease the refcount */
585 newstate = state - 4;
586 /* last refcount, unset access_mode */
589 } while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
597 * @offset: an offset to copy
598 * @size: size to copy or -1 to copy all bytes from offset
600 * Return a copy of @size bytes from @mem starting from @offset. This copy is
601 * guaranteed to be writable. @size can be set to -1 to return a copy all bytes
604 * Returns: a new #GstMemory.
607 gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
609 g_return_val_if_fail (mem != NULL, NULL);
611 return mem->allocator->info.copy (mem, offset, size);
617 * @offset: an offset to share
618 * @size: size to share or -1 to share bytes from offset
620 * Return a shared copy of @size bytes from @mem starting from @offset. No
621 * memory copy is performed and the memory region is simply shared. The result
622 * is guaranteed to be not-writable. @size can be set to -1 to return a share
623 * all bytes from @offset.
625 * Returns: a new #GstMemory.
628 gst_memory_share (GstMemory * mem, gssize offset, gssize size)
630 g_return_val_if_fail (mem != NULL, NULL);
632 return mem->allocator->info.share (mem, offset, size);
636 * gst_memory_is_span:
637 * @mem1: a #GstMemory
638 * @mem2: a #GstMemory
639 * @offset: a pointer to a result offset
641 * Check if @mem1 and mem2 share the memory with a common parent memory object
642 * and that the memory is contiguous.
644 * If this is the case, the memory of @mem1 and @mem2 can be merged
645 * efficiently by performing gst_memory_share() on the parent object from
646 * the returned @offset.
648 * Returns: %TRUE if the memory is contiguous and of a common parent.
651 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
653 g_return_val_if_fail (mem1 != NULL, FALSE);
654 g_return_val_if_fail (mem2 != NULL, FALSE);
656 /* need to have the same allocators */
657 if (mem1->allocator != mem2->allocator)
660 /* need to have the same parent */
661 if (mem1->parent == NULL || mem1->parent != mem2->parent)
664 /* and memory is contiguous */
665 if (!mem1->allocator->info.is_span (mem1, mem2, offset))
672 * gst_allocator_register:
673 * @name: the name of the allocator
674 * @info: #GstMemoryInfo
676 * Registers the memory allocator with @name and implementation functions
679 * All functions in @info are mandatory exept the copy and is_span
680 * functions, which will have a default implementation when left NULL.
682 * The user_data field in @info will be passed to all calls of the alloc
685 * Returns: a new #GstAllocator.
688 gst_allocator_register (const gchar * name, const GstMemoryInfo * info)
690 GstAllocator *allocator;
692 #define INSTALL_FALLBACK(_t) \
693 if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
695 g_return_val_if_fail (name != NULL, NULL);
696 g_return_val_if_fail (info != NULL, NULL);
697 g_return_val_if_fail (info->alloc != NULL, NULL);
698 g_return_val_if_fail (info->get_sizes != NULL, NULL);
699 g_return_val_if_fail (info->resize != NULL, NULL);
700 g_return_val_if_fail (info->map != NULL, NULL);
701 g_return_val_if_fail (info->unmap != NULL, NULL);
702 g_return_val_if_fail (info->free != NULL, NULL);
703 g_return_val_if_fail (info->share != NULL, NULL);
705 allocator = g_slice_new (GstAllocator);
706 allocator->name = g_quark_from_string (name);
707 allocator->info = *info;
708 INSTALL_FALLBACK (copy);
709 INSTALL_FALLBACK (is_span);
710 #undef INSTALL_FALLBACK
712 GST_DEBUG ("registering allocator \"%s\"", name);
714 g_static_rw_lock_writer_lock (&lock);
715 g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
716 g_static_rw_lock_writer_unlock (&lock);
722 * gst_allocator_find:
723 * @name: the name of the allocator
725 * Find a previously registered allocator with @name. When @name is NULL, the
726 * default allocator will be returned.
728 * Returns: a #GstAllocator or NULL when the allocator with @name was not
732 gst_allocator_find (const gchar * name)
734 const GstAllocator *allocator;
736 g_static_rw_lock_reader_lock (&lock);
738 allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
740 allocator = _default_allocator;
742 g_static_rw_lock_reader_unlock (&lock);
748 * gst_allocator_set_default:
749 * @allocator: a #GstAllocator
751 * Set the default allocator.
754 gst_allocator_set_default (const GstAllocator * allocator)
756 g_return_if_fail (allocator != NULL);
758 g_static_rw_lock_writer_lock (&lock);
759 _default_allocator = allocator;
760 g_static_rw_lock_writer_unlock (&lock);
764 * gst_allocator_alloc:
765 * @allocator: (transfer none) (allow-none): a #GstAllocator to use
766 * @maxsize: allocated size of @data
767 * @align: alignment for the data
769 * Use @allocator to allocate a new memory block with memory that is at least
770 * @maxsize big and has the given alignment.
772 * When @allocator is NULL, the default allocator will be used.
774 * @align is given as a bitmask so that @align + 1 equals the amount of bytes to
775 * align to. For example, to align to 8 bytes, use an alignment of 7.
777 * Returns: (transfer full): a new #GstMemory.
780 gst_allocator_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
782 g_return_val_if_fail (((align + 1) & align) == 0, NULL);
784 if (allocator == NULL)
785 allocator = _default_allocator;
787 return allocator->info.alloc (allocator, maxsize, align,
788 allocator->info.user_data);