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;
126 mem->slice_size = slice_size;
128 mem->free_func = free_func;
129 mem->maxsize = maxsize;
130 mem->offset = offset;
134 /* create a new memory block that manages the given memory */
135 static GstMemoryDefault *
136 _default_mem_new (GstMemoryFlags flags, GstMemory * parent, gpointer data,
137 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
139 GstMemoryDefault *mem;
142 slice_size = sizeof (GstMemoryDefault);
144 mem = g_slice_alloc (slice_size);
145 _default_mem_init (mem, flags, parent, slice_size,
146 data, free_func, maxsize, offset, size);
151 /* allocate the memory and structure in one block */
152 static GstMemoryDefault *
153 _default_mem_new_block (gsize maxsize, gsize align, gsize offset, gsize size)
155 GstMemoryDefault *mem;
156 gsize aoffset, slice_size;
159 /* ensure configured alignment */
160 align |= gst_memory_alignment;
161 /* allocate more to compensate for alignment */
163 /* alloc header and data in one block */
164 slice_size = sizeof (GstMemoryDefault) + maxsize;
166 mem = g_slice_alloc (slice_size);
170 data = (guint8 *) mem + sizeof (GstMemoryDefault);
172 if ((aoffset = ((guintptr) data & align)))
173 aoffset = (align + 1) - aoffset;
175 _default_mem_init (mem, 0, NULL, slice_size, data, NULL, maxsize,
176 aoffset + offset, size);
182 _default_mem_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
184 return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
188 _default_mem_get_sizes (GstMemoryDefault * mem, gsize * offset, gsize * maxsize)
191 *offset = mem->offset;
193 *maxsize = mem->maxsize;
199 _default_mem_resize (GstMemoryDefault * mem, gssize offset, gsize size)
201 g_return_if_fail (offset >= 0 || mem->offset >= -offset);
202 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
204 mem->offset += offset;
209 _default_mem_map (GstMemoryDefault * mem, gsize * size, gsize * maxsize,
215 *maxsize = mem->maxsize - mem->offset;
217 return mem->data + mem->offset;
221 _default_mem_unmap (GstMemoryDefault * mem, gpointer data, gsize size)
223 g_return_val_if_fail ((guint8 *) data >= mem->data
224 && (guint8 *) data < mem->data + mem->maxsize, FALSE);
226 if (mem->data + mem->offset != data) {
227 gsize newoffset = (guint8 *) data - mem->data;
229 size = mem->offset + mem->size - newoffset;
230 mem->offset = newoffset;
234 g_return_val_if_fail (mem->offset + size <= mem->maxsize, FALSE);
242 _default_mem_free (GstMemoryDefault * mem)
245 gst_memory_unref (mem->mem.parent);
248 mem->free_func (mem->data);
250 g_slice_free1 (mem->slice_size, mem);
253 static GstMemoryDefault *
254 _default_mem_copy (GstMemoryDefault * mem, gssize offset, gsize size)
256 GstMemoryDefault *copy;
259 size = mem->size > offset ? mem->size - offset : 0;
261 copy = _default_mem_new_block (mem->maxsize, 0, mem->offset + offset, size);
262 memcpy (copy->data, mem->data, mem->maxsize);
267 static GstMemoryDefault *
268 _default_mem_share (GstMemoryDefault * mem, gssize offset, gsize size)
270 GstMemoryDefault *sub;
273 /* find the real parent */
274 if ((parent = mem->mem.parent) == NULL)
275 parent = (GstMemory *) mem;
278 size = mem->size - offset;
280 sub = _default_mem_new (parent->flags, parent, mem->data, NULL, mem->maxsize,
281 mem->offset + offset, size);
287 _default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
292 GstMemoryDefault *parent;
294 parent = (GstMemoryDefault *) mem1->mem.parent;
296 *offset = mem1->offset - parent->offset;
299 /* and memory is contiguous */
300 return mem1->data + mem1->offset + mem1->size == mem2->data + mem2->offset;
304 _fallback_copy (GstMemory * mem, gssize offset, gssize size)
310 data = gst_memory_map (mem, &msize, NULL, GST_MAP_READ);
312 size = msize > offset ? msize - offset : 0;
313 /* use the same allocator as the memory we copy, FIXME, alignment? */
314 copy = gst_allocator_alloc (mem->allocator, size, 0);
315 dest = gst_memory_map (copy, NULL, NULL, GST_MAP_WRITE);
316 memcpy (dest, data + offset, size);
317 gst_memory_unmap (copy, dest, size);
319 gst_memory_unmap (mem, data, msize);
321 return (GstMemory *) copy;
325 _fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
330 static GStaticRWLock lock = G_STATIC_RW_LOCK_INIT;
331 static GHashTable *allocators;
334 _priv_gst_memory_initialize (void)
336 static const GstMemoryInfo _mem_info = {
337 (GstMemoryAllocFunction) _default_mem_alloc,
338 (GstMemoryGetSizesFunction) _default_mem_get_sizes,
339 (GstMemoryResizeFunction) _default_mem_resize,
340 (GstMemoryMapFunction) _default_mem_map,
341 (GstMemoryUnmapFunction) _default_mem_unmap,
342 (GstMemoryFreeFunction) _default_mem_free,
343 (GstMemoryCopyFunction) _default_mem_copy,
344 (GstMemoryShareFunction) _default_mem_share,
345 (GstMemoryIsSpanFunction) _default_mem_is_span,
349 allocators = g_hash_table_new (g_str_hash, g_str_equal);
351 #ifdef HAVE_GETPAGESIZE
352 #ifdef MEMORY_ALIGNMENT_PAGESIZE
353 gst_memory_alignment = getpagesize () - 1;
357 GST_DEBUG ("memory alignment: %" G_GSIZE_FORMAT, gst_memory_alignment);
359 _default_mem_impl = gst_allocator_register (GST_ALLOCATOR_SYSMEM, &_mem_info);
361 _default_allocator = _default_mem_impl;
365 * gst_memory_new_wrapped:
366 * @flags: #GstMemoryFlags
367 * @data: data to wrap
368 * @free_func: function to free @data
369 * @maxsize: allocated size of @data
370 * @offset: offset in @data
371 * @size: size of valid data
373 * Allocate a new memory block that wraps the given @data.
375 * Returns: a new #GstMemory.
378 gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
379 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
381 GstMemoryDefault *mem;
383 g_return_val_if_fail (data != NULL, NULL);
384 g_return_val_if_fail (offset + size <= maxsize, NULL);
386 mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
388 return (GstMemory *) mem;
395 * Increases the refcount of @mem.
397 * Returns: @mem with increased refcount
400 gst_memory_ref (GstMemory * mem)
402 g_return_val_if_fail (mem != NULL, NULL);
404 g_atomic_int_inc (&mem->refcount);
413 * Decreases the refcount of @mem. When the refcount reaches 0, the free
414 * function of @mem will be called.
417 gst_memory_unref (GstMemory * mem)
419 g_return_if_fail (mem != NULL);
420 g_return_if_fail (mem->allocator != NULL);
422 if (g_atomic_int_dec_and_test (&mem->refcount))
423 mem->allocator->info.free (mem);
427 * gst_memory_get_sizes:
429 * @offset: pointer to offset
430 * @maxsize: pointer to maxsize
432 * Get the current @size, @offset and @maxsize of @mem.
434 * Returns: the current sizes of @mem
437 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
439 g_return_val_if_fail (mem != NULL, 0);
441 return mem->allocator->info.get_sizes (mem, offset, maxsize);
447 * @offset: a new offset
450 * Resize the memory region. @mem should be writable and offset + size should be
451 * less than the maxsize of @mem.
454 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
456 g_return_if_fail (mem != NULL);
457 g_return_if_fail (GST_MEMORY_IS_WRITABLE (mem));
459 mem->allocator->info.resize (mem, offset, size);
465 * @size: (out) (allow-none): pointer for size
466 * @maxsize: (out) (allow-none): pointer for maxsize
467 * @flags: mapping flags
469 * Get a pointer to the memory of @mem that can be accessed according to @flags.
471 * @size and @maxsize will contain the size of the memory and the maximum
472 * allocated memory of @mem respectively. They can be set to NULL.
474 * Returns: (transfer none): a pointer to the memory of @mem.
477 gst_memory_map (GstMemory * mem, gsize * size, gsize * maxsize,
480 g_return_val_if_fail (mem != NULL, NULL);
481 g_return_val_if_fail (!(flags & GST_MAP_WRITE) ||
482 GST_MEMORY_IS_WRITABLE (mem), NULL);
484 return mem->allocator->info.map (mem, size, maxsize, flags);
490 * @data: data to unmap
491 * @size: new size of @mem, or -1
493 * Release the memory pointer obtained with gst_memory_map() and set the size of
494 * the memory to @size. @size can be set to -1 when the size should not be
497 * It is possible to pass a different @data than that obtained from
498 * gst_memory_map() in which case the offset of @mem will be updated.
500 * Returns: TRUE when the memory was release successfully.
503 gst_memory_unmap (GstMemory * mem, gpointer data, gssize size)
505 g_return_val_if_fail (mem != NULL, FALSE);
507 return mem->allocator->info.unmap (mem, data, size);
513 * @offset: an offset to copy
514 * @size: size to copy or -1 to copy all bytes from offset
516 * Return a copy of @size bytes from @mem starting from @offset. This copy is
517 * guaranteed to be writable. @size can be set to -1 to return a copy all bytes
520 * Returns: a new #GstMemory.
523 gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
525 g_return_val_if_fail (mem != NULL, NULL);
527 return mem->allocator->info.copy (mem, offset, size);
533 * @offset: an offset to share
534 * @size: size to share or -1 to share bytes from offset
536 * Return a shared copy of @size bytes from @mem starting from @offset. No
537 * memory copy is performed and the memory region is simply shared. The result
538 * is guaranteed to be not-writable. @size can be set to -1 to return a share
539 * all bytes from @offset.
541 * Returns: a new #GstMemory.
544 gst_memory_share (GstMemory * mem, gssize offset, gssize size)
546 g_return_val_if_fail (mem != NULL, NULL);
548 return mem->allocator->info.share (mem, offset, size);
552 * gst_memory_is_span:
553 * @mem1: a #GstMemory
554 * @mem2: a #GstMemory
555 * @offset: a pointer to a result offset
557 * Check if @mem1 and mem2 share the memory with a common parent memory object
558 * and that the memory is contiguous.
560 * If this is the case, the memory of @mem1 and @mem2 can be merged
561 * efficiently by performing gst_memory_share() on the parent object from
562 * the returned @offset.
564 * Returns: %TRUE if the memory is contiguous and of a common parent.
567 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
569 g_return_val_if_fail (mem1 != NULL, FALSE);
570 g_return_val_if_fail (mem2 != NULL, FALSE);
572 /* need to have the same allocators */
573 if (mem1->allocator != mem2->allocator)
576 /* need to have the same parent */
577 if (mem1->parent == NULL || mem1->parent != mem2->parent)
580 /* and memory is contiguous */
581 if (!mem1->allocator->info.is_span (mem1, mem2, offset))
588 * gst_allocator_register:
589 * @name: the name of the allocator
590 * @info: #GstMemoryInfo
592 * Registers the memory allocator with @name and implementation functions
595 * All functions in @info are mandatory exept the copy and is_span
596 * functions, which will have a default implementation when left NULL.
598 * The user_data field in @info will be passed to all calls of the alloc
601 * Returns: a new #GstAllocator.
604 gst_allocator_register (const gchar * name, const GstMemoryInfo * info)
606 GstAllocator *allocator;
608 #define INSTALL_FALLBACK(_t) \
609 if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
611 g_return_val_if_fail (name != NULL, NULL);
612 g_return_val_if_fail (info != NULL, NULL);
613 g_return_val_if_fail (info->alloc != NULL, NULL);
614 g_return_val_if_fail (info->get_sizes != NULL, NULL);
615 g_return_val_if_fail (info->resize != NULL, NULL);
616 g_return_val_if_fail (info->map != NULL, NULL);
617 g_return_val_if_fail (info->unmap != NULL, NULL);
618 g_return_val_if_fail (info->free != NULL, NULL);
619 g_return_val_if_fail (info->share != NULL, NULL);
621 allocator = g_slice_new (GstAllocator);
622 allocator->name = g_quark_from_string (name);
623 allocator->info = *info;
624 INSTALL_FALLBACK (copy);
625 INSTALL_FALLBACK (is_span);
626 #undef INSTALL_FALLBACK
628 GST_DEBUG ("registering allocator \"%s\"", name);
630 g_static_rw_lock_writer_lock (&lock);
631 g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
632 g_static_rw_lock_writer_unlock (&lock);
638 * gst_allocator_find:
639 * @name: the name of the allocator
641 * Find a previously registered allocator with @name. When @name is NULL, the
642 * default allocator will be returned.
644 * Returns: a #GstAllocator or NULL when the allocator with @name was not
648 gst_allocator_find (const gchar * name)
650 const GstAllocator *allocator;
652 g_static_rw_lock_reader_lock (&lock);
654 allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
656 allocator = _default_allocator;
658 g_static_rw_lock_reader_unlock (&lock);
664 * gst_allocator_set_default:
665 * @allocator: a #GstAllocator
667 * Set the default allocator.
670 gst_allocator_set_default (const GstAllocator * allocator)
672 g_return_if_fail (allocator != NULL);
674 g_static_rw_lock_writer_lock (&lock);
675 _default_allocator = allocator;
676 g_static_rw_lock_writer_unlock (&lock);
680 * gst_allocator_alloc:
681 * @allocator: (transfer none) (allow-none): a #GstAllocator to use
682 * @maxsize: allocated size of @data
683 * @align: alignment for the data
685 * Use @allocator to allocate a new memory block with memory that is at least
686 * @maxsize big and has the given alignment.
688 * When @allocator is NULL, the default allocator will be used.
690 * @align is given as a bitmask so that @align + 1 equals the amount of bytes to
691 * align to. For example, to align to 8 bytes, use an alignment of 7.
693 * Returns: (transfer full): a new #GstMemory.
696 gst_allocator_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
698 g_return_val_if_fail (((align + 1) & align) == 0, NULL);
700 if (allocator == NULL)
701 allocator = _default_allocator;
703 return allocator->info.alloc (allocator, maxsize, align,
704 allocator->info.user_data);