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 * Memory is usually created by allocators with a gst_allocator_alloc()
31 * method call. When NULL is used as the allocator, the default allocator will
34 * New allocators can be registered with gst_allocator_register().
35 * Allocators are identified by name and can be retrieved with
36 * gst_allocator_find().
38 * New memory can be created with gst_memory_new_wrapped() that wraps the memory
39 * allocated elsewhere.
41 * Refcounting of the memory block is performed with gst_memory_ref() and
44 * The size of the memory can be retrieved and changed with
45 * gst_memory_get_sizes() and gst_memory_resize() respectively.
47 * Getting access to the data of the memory is performed with gst_memory_map().
48 * After the memory access is completed, gst_memory_unmap() should be called.
50 * Memory can be copied with gst_memory_copy(), which will returnn a writable
51 * copy. gst_memory_share() will create a new memory block that shares the
52 * memory with an existing memory block at a custom offset and with a custom
55 * Memory can be efficiently merged when gst_memory_is_span() returns TRUE.
57 * Last reviewed on 2011-06-08 (0.11.0)
61 #include "gst_private.h"
62 #include "gstmemory.h"
64 G_DEFINE_BOXED_TYPE (GstMemory, gst_memory, (GBoxedCopyFunc) gst_memory_ref,
65 (GBoxedFreeFunc) gst_memory_unref);
67 /* buffer alignment in bytes - 1
68 * an alignment of 7 would be the same as malloc() guarantees
70 #if defined(MEMORY_ALIGNMENT_MALLOC)
71 size_t gst_memory_alignment = 7;
72 #elif defined(MEMORY_ALIGNMENT_PAGESIZE)
73 /* we fill this in in the _init method */
74 size_t gst_memory_alignment = 0;
75 #elif defined(MEMORY_ALIGNMENT)
76 size_t gst_memory_alignment = MEMORY_ALIGNMENT - 1;
78 #error "No memory alignment configured"
79 size_t gst_memory_alignment = 0;
89 /* default memory implementation */
101 /* the default allocator */
102 static const GstAllocator *_default_allocator;
104 /* our predefined allocators */
105 static const GstAllocator *_default_mem_impl;
107 /* initialize the fields */
109 _default_mem_init (GstMemoryDefault * mem, GstMemoryFlags flags,
110 GstMemory * parent, gsize slice_size, gpointer data,
111 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
113 mem->mem.allocator = _default_mem_impl;
114 mem->mem.flags = flags;
115 mem->mem.refcount = 1;
116 mem->mem.parent = parent ? gst_memory_ref (parent) : NULL;
117 mem->slice_size = slice_size;
119 mem->free_func = free_func;
120 mem->maxsize = maxsize;
121 mem->offset = offset;
125 /* create a new memory block that manages the given memory */
126 static GstMemoryDefault *
127 _default_mem_new (GstMemoryFlags flags, GstMemory * parent, gpointer data,
128 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
130 GstMemoryDefault *mem;
133 slice_size = sizeof (GstMemoryDefault);
135 mem = g_slice_alloc (slice_size);
136 _default_mem_init (mem, flags, parent, slice_size,
137 data, free_func, maxsize, offset, size);
142 /* allocate the memory and structure in one block */
143 static GstMemoryDefault *
144 _default_mem_new_block (gsize maxsize, gsize align, gsize offset, gsize size)
146 GstMemoryDefault *mem;
147 gsize aoffset, slice_size;
150 /* ensure configured alignment */
151 align |= gst_memory_alignment;
152 /* allocate more to compensate for alignment */
154 /* alloc header and data in one block */
155 slice_size = sizeof (GstMemoryDefault) + maxsize;
157 mem = g_slice_alloc (slice_size);
161 data = (guint8 *) mem + sizeof (GstMemoryDefault);
163 if ((aoffset = ((guintptr) data & align)))
164 aoffset = (align + 1) - aoffset;
166 _default_mem_init (mem, 0, NULL, slice_size, data, NULL, maxsize,
167 aoffset + offset, size);
173 _default_mem_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
175 return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
179 _default_mem_get_sizes (GstMemoryDefault * mem, gsize * offset, gsize * maxsize)
182 *offset = mem->offset;
184 *maxsize = mem->maxsize;
190 _default_mem_resize (GstMemoryDefault * mem, gssize offset, gsize size)
192 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
194 mem->offset += offset;
199 _default_mem_map (GstMemoryDefault * mem, gsize * size, gsize * maxsize,
205 *maxsize = mem->maxsize;
207 return mem->data + mem->offset;
211 _default_mem_unmap (GstMemoryDefault * mem, gpointer data, gsize size)
219 _default_mem_free (GstMemoryDefault * mem)
222 gst_memory_unref (mem->mem.parent);
225 mem->free_func (mem->data);
227 g_slice_free1 (mem->slice_size, mem);
230 static GstMemoryDefault *
231 _default_mem_copy (GstMemoryDefault * mem, gssize offset, gsize size)
233 GstMemoryDefault *copy;
236 size = mem->size > offset ? mem->size - offset : 0;
238 copy = _default_mem_new_block (mem->maxsize, 0, mem->offset + offset, size);
239 memcpy (copy->data, mem->data, mem->maxsize);
244 static GstMemoryDefault *
245 _default_mem_share (GstMemoryDefault * mem, gssize offset, gsize size)
247 GstMemoryDefault *sub;
250 /* find the real parent */
251 if ((parent = mem->mem.parent) == NULL)
252 parent = (GstMemory *) mem;
255 size = mem->size - offset;
257 sub = _default_mem_new (parent->flags, parent, mem->data, NULL, mem->maxsize,
258 mem->offset + offset, size);
264 _default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
269 GstMemoryDefault *parent;
271 parent = (GstMemoryDefault *) mem1->mem.parent;
273 *offset = mem1->offset - parent->offset;
276 /* and memory is contiguous */
277 return mem1->data + mem1->offset + mem1->size == mem2->data + mem2->offset;
281 _fallback_copy (GstMemory * mem, gssize offset, gsize size)
287 data = gst_memory_map (mem, &msize, NULL, GST_MAP_READ);
289 size = msize > offset ? msize - offset : 0;
290 /* use the same allocator as the memory we copy, FIXME, alignment? */
291 copy = gst_allocator_alloc (mem->allocator, size, 0);
292 dest = gst_memory_map (copy, NULL, NULL, GST_MAP_WRITE);
293 memcpy (dest, data + offset, size);
294 gst_memory_unmap (copy, dest, size);
296 gst_memory_unmap (mem, data, msize);
298 return (GstMemory *) copy;
302 _fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
307 static GStaticRWLock lock = G_STATIC_RW_LOCK_INIT;
308 static GHashTable *allocators;
311 _priv_gst_memory_initialize (void)
313 static const GstMemoryInfo _mem_info = {
314 (GstMemoryAllocFunction) _default_mem_alloc,
315 (GstMemoryGetSizesFunction) _default_mem_get_sizes,
316 (GstMemoryResizeFunction) _default_mem_resize,
317 (GstMemoryMapFunction) _default_mem_map,
318 (GstMemoryUnmapFunction) _default_mem_unmap,
319 (GstMemoryFreeFunction) _default_mem_free,
320 (GstMemoryCopyFunction) _default_mem_copy,
321 (GstMemoryShareFunction) _default_mem_share,
322 (GstMemoryIsSpanFunction) _default_mem_is_span,
326 allocators = g_hash_table_new (g_str_hash, g_str_equal);
328 #ifdef HAVE_GETPAGESIZE
329 #ifdef MEMORY_ALIGNMENT_PAGESIZE
330 gst_memory_alignment = getpagesize () - 1;
334 GST_DEBUG ("memory alignment: %" G_GSIZE_FORMAT, gst_memory_alignment);
336 _default_mem_impl = gst_allocator_register (GST_ALLOCATOR_SYSMEM, &_mem_info);
338 _default_allocator = _default_mem_impl;
342 * gst_memory_new_wrapped:
343 * @flags: #GstMemoryFlags
344 * @data: data to wrap
345 * @free_func: function to free @data
346 * @maxsize: allocated size of @data
347 * @offset: offset in @data
348 * @size: size of valid data
350 * Allocate a new memory block that wraps the given @data.
352 * Returns: a new #GstMemory.
355 gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
356 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
358 GstMemoryDefault *mem;
360 g_return_val_if_fail (data != NULL, NULL);
361 g_return_val_if_fail (offset + size <= maxsize, NULL);
363 mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
365 return (GstMemory *) mem;
372 * Increases the refcount of @mem.
374 * Returns: @mem with increased refcount
377 gst_memory_ref (GstMemory * mem)
379 g_return_val_if_fail (mem != NULL, NULL);
381 g_atomic_int_inc (&mem->refcount);
390 * Decreases the refcount of @mem. When the refcount reaches 0, the free
391 * function of @mem will be called.
394 gst_memory_unref (GstMemory * mem)
396 g_return_if_fail (mem != NULL);
397 g_return_if_fail (mem->allocator != NULL);
399 if (g_atomic_int_dec_and_test (&mem->refcount))
400 mem->allocator->info.free (mem);
404 * gst_memory_get_sizes:
406 * @offset: pointer to offset
407 * @maxsize: pointer to maxsize
409 * Get the current @size, @offset and @maxsize of @mem.
411 * Returns: the current sizes of @mem
414 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
416 g_return_val_if_fail (mem != NULL, 0);
418 return mem->allocator->info.get_sizes (mem, offset, maxsize);
424 * @offset: a new offset
427 * Resize the memory region. @mem should be writable and offset + size should be
428 * less than the maxsize of @mem.
431 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
433 g_return_if_fail (mem != NULL);
434 g_return_if_fail (GST_MEMORY_IS_WRITABLE (mem));
436 mem->allocator->info.resize (mem, offset, size);
442 * @size: (out) (allow-none): pointer for size
443 * @maxsize: (out) (allow-none): pointer for maxsize
444 * @flags: mapping flags
446 * Get a pointer to the memory of @mem that can be accessed according to @flags.
448 * @size and @maxsize will contain the size of the memory and the maximum
449 * allocated memory of @mem respectively. They can be set to NULL.
451 * Returns: (transfer none): a pointer to the memory of @mem.
454 gst_memory_map (GstMemory * mem, gsize * size, gsize * maxsize,
457 g_return_val_if_fail (mem != NULL, NULL);
458 g_return_val_if_fail (!(flags & GST_MAP_WRITE) ||
459 GST_MEMORY_IS_WRITABLE (mem), NULL);
461 return mem->allocator->info.map (mem, size, maxsize, flags);
467 * @data: data to unmap
468 * @size: new size of @mem
470 * Release the memory pointer obtained with gst_memory_map() and set the size of
471 * the memory to @size. @size can be set to -1 when the size should not be
474 * Returns: TRUE when the memory was release successfully.
477 gst_memory_unmap (GstMemory * mem, gpointer data, gsize size)
479 g_return_val_if_fail (mem != NULL, FALSE);
481 return mem->allocator->info.unmap (mem, data, size);
487 * @offset: an offset to copy
488 * @size: size to copy
490 * Return a copy of @size bytes from @mem starting from @offset. This copy is
491 * guaranteed to be writable. @size can be set to -1 to return a copy all bytes
494 * Returns: a new #GstMemory.
497 gst_memory_copy (GstMemory * mem, gssize offset, gsize size)
499 g_return_val_if_fail (mem != NULL, NULL);
501 return mem->allocator->info.copy (mem, offset, size);
507 * @offset: an offset to share
508 * @size: size to share
510 * Return a shared copy of @size bytes from @mem starting from @offset. No memory
511 * copy is performed and the memory region is simply shared. The result is
512 * guaranteed to be not-writable. @size can be set to -1 to return a share all bytes
515 * Returns: a new #GstMemory.
518 gst_memory_share (GstMemory * mem, gssize offset, gsize size)
520 g_return_val_if_fail (mem != NULL, NULL);
522 return mem->allocator->info.share (mem, offset, size);
526 * gst_memory_is_span:
527 * @mem1: a #GstMemory
528 * @mem2: a #GstMemory
529 * @offset: a pointer to a result offset
531 * Check if @mem1 and mem2 share the memory with a common parent memory object
532 * and that the memory is contiguous.
534 * If this is the case, the memory of @mem1 and @mem2 can be merged
535 * efficiently by performing gst_memory_share() on the parent object from
536 * the returned @offset.
538 * Returns: %TRUE if the memory is contiguous and of a common parent.
541 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
543 g_return_val_if_fail (mem1 != NULL, FALSE);
544 g_return_val_if_fail (mem2 != NULL, FALSE);
546 /* need to have the same allocators */
547 if (mem1->allocator != mem2->allocator)
550 /* need to have the same parent */
551 if (mem1->parent == NULL || mem1->parent != mem2->parent)
554 /* and memory is contiguous */
555 if (!mem1->allocator->info.is_span (mem1, mem2, offset))
562 * gst_allocator_register:
563 * @name: the name of the allocator
564 * @info: #GstMemoryInfo
566 * Registers the memory allocator with @name and implementation functions
569 * All functions in @info are mandatory exept the copy and is_span
570 * functions, which will have a default implementation when left NULL.
572 * The user_data field in @info will be passed to all calls of the alloc
575 * Returns: a new #GstAllocator.
578 gst_allocator_register (const gchar * name, const GstMemoryInfo * info)
580 GstAllocator *allocator;
582 #define INSTALL_FALLBACK(_t) \
583 if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
585 g_return_val_if_fail (name != NULL, NULL);
586 g_return_val_if_fail (info != NULL, NULL);
587 g_return_val_if_fail (info->alloc != NULL, NULL);
588 g_return_val_if_fail (info->get_sizes != NULL, NULL);
589 g_return_val_if_fail (info->resize != NULL, NULL);
590 g_return_val_if_fail (info->map != NULL, NULL);
591 g_return_val_if_fail (info->unmap != NULL, NULL);
592 g_return_val_if_fail (info->free != NULL, NULL);
593 g_return_val_if_fail (info->share != NULL, NULL);
595 allocator = g_slice_new (GstAllocator);
596 allocator->name = g_quark_from_string (name);
597 allocator->info = *info;
598 INSTALL_FALLBACK (copy);
599 INSTALL_FALLBACK (is_span);
600 #undef INSTALL_FALLBACK
602 GST_DEBUG ("registering allocator \"%s\"", name);
604 g_static_rw_lock_writer_lock (&lock);
605 g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
606 g_static_rw_lock_writer_unlock (&lock);
612 * gst_allocator_find:
613 * @name: the name of the allocator
615 * Find a previously registered allocator with @name. When @name is NULL, the
616 * default allocator will be returned.
618 * Returns: a #GstAllocator or NULL when the allocator with @name was not
622 gst_allocator_find (const gchar * name)
624 const GstAllocator *allocator;
626 g_static_rw_lock_reader_lock (&lock);
628 allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
630 allocator = _default_allocator;
632 g_static_rw_lock_reader_unlock (&lock);
638 * gst_allocator_set_default:
639 * @allocator: a #GstAllocator
641 * Set the default allocator.
644 gst_allocator_set_default (const GstAllocator * allocator)
646 g_return_if_fail (allocator != NULL);
648 g_static_rw_lock_writer_lock (&lock);
649 _default_allocator = allocator;
650 g_static_rw_lock_writer_unlock (&lock);
654 * gst_allocator_alloc:
655 * @allocator: (transfer none) (allow-none): a #GstAllocator to use
656 * @maxsize: allocated size of @data
657 * @align: alignment for the data
659 * Use @allocator to allocate a new memory block with memory that is at least
660 * @maxsize big and has the given alignment.
662 * When @allocator is NULL, the default allocator will be used.
664 * @align is given as a bitmask so that @align + 1 equals the amount of bytes to
665 * align to. For example, to align to 8 bytes, use an alignment of 7.
667 * Returns: (transfer full): a new #GstMemory.
670 gst_allocator_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
672 g_return_val_if_fail (((align + 1) & align) == 0, NULL);
674 if (allocator == NULL)
675 allocator = _default_allocator;
677 return allocator->info.alloc (allocator, maxsize, align,
678 allocator->info.user_data);