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_memory_allocator_alloc()
31 * method call. When NULL is used as the allocator, the default allocator will
34 * New allocators can be registered with gst_memory_allocator_register().
35 * Allocators are identified by name and can be retrieved with
36 * gst_memory_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 and
56 * with the function gst_memory_span().
58 * Last reviewed on 2011-06-08 (0.11.0)
62 #include "gst_private.h"
63 #include "gstmemory.h"
66 /* buffer alignment in bytes - 1
67 * an alignment of 7 would be the same as malloc() guarantees
69 #ifdef HAVE_POSIX_MEMALIGN
70 #if defined(MEMORY_ALIGNMENT_MALLOC)
71 size_t gst_memory_alignment = 7;
72 #elif defined(MEMORY_ALIGNMENT_PAGESIZE)
73 size_t gst_memory_alignment = 0;
74 #elif defined(MEMORY_ALIGNMENT)
75 size_t gst_memory_alignment = MEMORY_ALIGNMENT - 1;
77 #error "No memory alignment configured"
78 size_t gst_memory_alignment = 0;
80 #endif /* HAVE_POSIX_MEMALIGN */
82 struct _GstMemoryAllocator
89 /* default memory implementation */
101 /* the default allocator */
102 static const GstMemoryAllocator *_default_allocator;
104 /* our predefined allocators */
105 static const GstMemoryAllocator *_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 GstMemoryAllocator * allocator, gsize maxsize,
176 return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
180 _default_mem_get_sizes (GstMemoryDefault * mem, gsize * maxsize)
183 *maxsize = mem->maxsize;
189 _default_mem_resize (GstMemoryDefault * mem, gsize offset, gsize size)
191 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
193 mem->offset += offset;
198 _default_mem_map (GstMemoryDefault * mem, gsize * size, gsize * maxsize,
204 *maxsize = mem->maxsize;
206 return mem->data + mem->offset;
210 _default_mem_unmap (GstMemoryDefault * mem, gpointer data, gsize size)
218 _default_mem_free (GstMemoryDefault * mem)
221 gst_memory_unref (mem->mem.parent);
224 mem->free_func (mem->data);
226 g_slice_free1 (mem->slice_size, mem);
229 static GstMemoryDefault *
230 _default_mem_copy (GstMemoryDefault * mem, gsize offset, gsize size)
232 GstMemoryDefault *copy;
235 size = mem->size > offset ? mem->size - offset : 0;
237 copy = _default_mem_new_block (mem->maxsize, 0, mem->offset + offset, size);
238 memcpy (copy->data, mem->data, mem->maxsize);
243 static GstMemoryDefault *
244 _default_mem_share (GstMemoryDefault * mem, gsize offset, gsize size)
246 GstMemoryDefault *sub;
249 /* find the real parent */
250 if ((parent = mem->mem.parent) == NULL)
251 parent = (GstMemory *) mem;
254 size = mem->size - offset;
256 sub = _default_mem_new (parent->flags, parent, mem->data, NULL, mem->maxsize,
257 mem->offset + offset, size);
263 _default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
268 GstMemoryDefault *parent;
270 parent = (GstMemoryDefault *) mem1->mem.parent;
272 *offset = mem1->offset - parent->offset;
275 /* and memory is contiguous */
276 return mem1->data + mem1->offset + mem1->size == mem2->data + mem2->offset;
280 _fallback_copy (GstMemory * mem, gsize offset, gsize size)
286 data = gst_memory_map (mem, &msize, NULL, GST_MAP_READ);
288 size = msize > offset ? msize - offset : 0;
289 /* use the same allocator as the memory we copy, FIXME, alignment? */
290 copy = gst_memory_allocator_alloc (mem->allocator, size, 1);
291 dest = gst_memory_map (copy, NULL, NULL, GST_MAP_WRITE);
292 memcpy (dest, data + offset, size);
293 gst_memory_unmap (copy, dest, size);
295 gst_memory_unmap (mem, data, msize);
297 return (GstMemory *) copy;
301 _fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
306 static GStaticRWLock lock = G_STATIC_RW_LOCK_INIT;
307 static GHashTable *allocators;
310 _gst_memory_init (void)
312 static const GstMemoryInfo _mem_info = {
313 (GstMemoryAllocFunction) _default_mem_alloc,
314 (GstMemoryGetSizesFunction) _default_mem_get_sizes,
315 (GstMemoryResizeFunction) _default_mem_resize,
316 (GstMemoryMapFunction) _default_mem_map,
317 (GstMemoryUnmapFunction) _default_mem_unmap,
318 (GstMemoryFreeFunction) _default_mem_free,
319 (GstMemoryCopyFunction) _default_mem_copy,
320 (GstMemoryShareFunction) _default_mem_share,
321 (GstMemoryIsSpanFunction) _default_mem_is_span,
325 allocators = g_hash_table_new (g_str_hash, g_str_equal);
327 #ifdef HAVE_GETPAGESIZE
328 #ifdef MEMORY_ALIGNMENT_PAGESIZE
329 gst_memory_alignment = getpagesize () - 1;
334 gst_memory_allocator_register ("GstMemoryDefault", &_mem_info);
336 _default_allocator = _default_mem_impl;
340 * gst_memory_new_wrapped:
341 * @flags: #GstMemoryFlags
342 * @data: data to wrap
343 * @free_func: function to free @data
344 * @maxsize: allocated size of @data
345 * @offset: offset in @data
346 * @size: size of valid data
348 * Allocate a new memory block that wraps the given @data.
350 * Returns: a new #GstMemory.
353 gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
354 GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
356 GstMemoryDefault *mem;
358 g_return_val_if_fail (data != NULL, NULL);
359 g_return_val_if_fail (offset + size <= maxsize, NULL);
361 mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
363 return (GstMemory *) mem;
370 * Increases the refcount of @mem.
372 * Returns: @mem with increased refcount
375 gst_memory_ref (GstMemory * mem)
377 g_return_val_if_fail (mem != NULL, NULL);
379 g_atomic_int_inc (&mem->refcount);
388 * Decreases the refcount of @mem. When the refcount reaches 0, the free
389 * function of @mem will be called.
392 gst_memory_unref (GstMemory * mem)
394 g_return_if_fail (mem != NULL);
395 g_return_if_fail (mem->allocator != NULL);
397 if (g_atomic_int_dec_and_test (&mem->refcount))
398 mem->allocator->info.free (mem);
402 * gst_memory_get_sizes:
404 * @maxsize: pointer to maxsize
406 * Get the current @size and @maxsize of @mem.
408 * Returns: the current sizes of @mem
411 gst_memory_get_sizes (GstMemory * mem, gsize * maxsize)
413 g_return_val_if_fail (mem != NULL, 0);
415 return mem->allocator->info.get_sizes (mem, maxsize);
421 * @offset: a new offset
424 * Resize the memory region. @mem should be writable and offset + size should be
425 * less than the maxsize of @mem.
428 gst_memory_resize (GstMemory * mem, gsize offset, gsize size)
430 g_return_if_fail (mem != NULL);
431 g_return_if_fail (GST_MEMORY_IS_WRITABLE (mem));
433 mem->allocator->info.resize (mem, offset, size);
439 * @size: pointer for size
440 * @maxsize: pointer for maxsize
441 * @flags: mapping flags
443 * Get a pointer to the memory of @mem that can be accessed according to @flags.
445 * @size and @maxsize will contain the size of the memory and the maximum
446 * allocated memory of @mem respectively. They can be set to NULL.
448 * Returns: a pointer to the memory of @mem.
451 gst_memory_map (GstMemory * mem, gsize * size, gsize * maxsize,
454 g_return_val_if_fail (mem != NULL, NULL);
455 g_return_val_if_fail (!(flags & GST_MAP_WRITE) ||
456 GST_MEMORY_IS_WRITABLE (mem), NULL);
458 return mem->allocator->info.map (mem, size, maxsize, flags);
464 * @data: data to unmap
465 * @size: new size of @mem
467 * Release the memory pointer obtained with gst_memory_map() and set the size of
468 * the memory to @size. @size can be set to -1 when the size should not be
471 * Returns: TRUE when the memory was release successfully.
474 gst_memory_unmap (GstMemory * mem, gpointer data, gsize size)
476 g_return_val_if_fail (mem != NULL, FALSE);
478 return mem->allocator->info.unmap (mem, data, size);
484 * @offset: an offset to copy
485 * @size: size to copy
487 * Return a copy of @size bytes from @mem starting from @offset. This copy is
488 * guaranteed to be writable. @size can be set to -1 to return a copy all bytes
491 * Returns: a new #GstMemory.
494 gst_memory_copy (GstMemory * mem, gsize offset, gsize size)
496 g_return_val_if_fail (mem != NULL, NULL);
498 return mem->allocator->info.copy (mem, offset, size);
504 * @offset: an offset to share
505 * @size: size to share
507 * Return a shared copy of @size bytes from @mem starting from @offset. No memory
508 * copy is performed and the memory region is simply shared. The result is
509 * guaranteed to be not-writable. @size can be set to -1 to return a share all bytes
512 * Returns: a new #GstMemory.
515 gst_memory_share (GstMemory * mem, gsize offset, gsize size)
517 g_return_val_if_fail (mem != NULL, NULL);
519 return mem->allocator->info.share (mem, offset, size);
523 * gst_memory_is_span:
524 * @mem1: a #GstMemory
525 * @mem2: a #GstMemory
526 * @offset: a pointer to a result offset
528 * Check if @mem1 and mem2 share the memory with a common parent memory object
529 * and that the memory is contiguous.
531 * If this is the case, the memory of @mem1 and @mem2 can be merged
532 * efficiently by performing gst_memory_share() on the parent object from
533 * the returned @offset.
535 * Returns: %TRUE if the memory is contiguous and of a common parent.
538 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
540 g_return_val_if_fail (mem1 != NULL, FALSE);
541 g_return_val_if_fail (mem2 != NULL, FALSE);
543 /* need to have the same allocators */
544 if (mem1->allocator != mem2->allocator)
547 /* need to have the same parent */
548 if (mem1->parent == NULL || mem1->parent != mem2->parent)
551 /* and memory is contiguous */
552 if (!mem1->allocator->info.is_span (mem1, mem2, offset))
559 * gst_memory_allocator_register:
560 * @name: the name of the allocator
561 * @info: #GstMemoryInfo
563 * Registers the memory allocator with @name and implementation functions
566 * All functions in @info are mandatory exept the copy and is_span
567 * functions, which will have a default implementation when left NULL.
569 * The user_data field in @info will be passed to all calls of the alloc
572 * Returns: a new #GstMemoryAllocator.
574 const GstMemoryAllocator *
575 gst_memory_allocator_register (const gchar * name, const GstMemoryInfo * info)
577 GstMemoryAllocator *allocator;
579 #define INSTALL_FALLBACK(_t) \
580 if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
582 g_return_val_if_fail (name != NULL, NULL);
583 g_return_val_if_fail (info != NULL, NULL);
584 g_return_val_if_fail (info->alloc != NULL, NULL);
585 g_return_val_if_fail (info->get_sizes != NULL, NULL);
586 g_return_val_if_fail (info->resize != NULL, NULL);
587 g_return_val_if_fail (info->map != NULL, NULL);
588 g_return_val_if_fail (info->unmap != NULL, NULL);
589 g_return_val_if_fail (info->free != NULL, NULL);
590 g_return_val_if_fail (info->share != NULL, NULL);
592 allocator = g_slice_new (GstMemoryAllocator);
593 allocator->name = g_quark_from_string (name);
594 allocator->info = *info;
595 INSTALL_FALLBACK (copy);
596 INSTALL_FALLBACK (is_span);
597 #undef INSTALL_FALLBACK
599 GST_DEBUG ("register \"%s\" of size %" G_GSIZE_FORMAT, name);
601 g_static_rw_lock_writer_lock (&lock);
602 g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
603 g_static_rw_lock_writer_unlock (&lock);
609 * gst_memory_allocator_find:
610 * @name: the name of the allocator
612 * Find a previously registered allocator with @name. When @name is NULL, the
613 * default allocator will be returned.
615 * Returns: a #GstMemoryAllocator or NULL when the allocator with @name was not
618 const GstMemoryAllocator *
619 gst_memory_allocator_find (const gchar * name)
621 const GstMemoryAllocator *allocator;
623 g_static_rw_lock_reader_lock (&lock);
625 allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
627 allocator = _default_allocator;
629 g_static_rw_lock_reader_unlock (&lock);
635 * gst_memory_allocator_set_default:
636 * @allocator: a ##GstMemoryAllocator
638 * Set the default allocator.
641 gst_memory_allocator_set_default (const GstMemoryAllocator * allocator)
643 g_return_if_fail (allocator != NULL);
645 g_static_rw_lock_writer_lock (&lock);
646 _default_allocator = allocator;
647 g_static_rw_lock_writer_unlock (&lock);
651 * gst_memory_allocator_alloc:
652 * @allocator: a #GstMemoryAllocator to use
653 * @maxsize: allocated size of @data
654 * @align: alignment for the data
656 * Use @allocator to allocate a new memory block with memory that is at least
657 * @maxsize big and has the given alignment.
659 * When @allocator is NULL, the default allocator will be used.
661 * @align is given as a bitmask so that @align + 1 equals the amount of bytes to
662 * align to. For example, to align to 8 bytes, use an alignment of 7.
664 * Returns: a new #GstMemory.
667 gst_memory_allocator_alloc (const GstMemoryAllocator * allocator,
668 gsize maxsize, gsize align)
670 g_return_val_if_fail (((align + 1) & align) == 0, NULL);
672 if (allocator == NULL)
673 allocator = _default_allocator;
675 return allocator->info.alloc (allocator, maxsize, align,
676 allocator->info.user_data);