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., 51 Franklin St, Fifth Floor,
19 * Boston, MA 02110-1301, USA.
25 * @short_description: refcounted wrapper for memory blocks
26 * @see_also: #GstBuffer
28 * GstMemory is a lightweight refcounted object that wraps a region of memory.
29 * They are typically used to manage the data of a #GstBuffer.
31 * A GstMemory object has an allocated region of memory of maxsize. The maximum
32 * size does not change during the lifetime of the memory object. The memory
33 * also has an offset and size property that specifies the valid range of memory
34 * in the allocated region.
36 * Memory is usually created by allocators with a gst_allocator_alloc()
37 * method call. When %NULL is used as the allocator, the default allocator will
40 * New allocators can be registered with gst_allocator_register().
41 * Allocators are identified by name and can be retrieved with
42 * gst_allocator_find(). gst_allocator_set_default() can be used to change the
45 * New memory can be created with gst_memory_new_wrapped() that wraps the memory
46 * allocated elsewhere.
48 * Refcounting of the memory block is performed with gst_memory_ref() and
51 * The size of the memory can be retrieved and changed with
52 * gst_memory_get_sizes() and gst_memory_resize() respectively.
54 * Getting access to the data of the memory is performed with gst_memory_map().
55 * The call will return a pointer to offset bytes into the region of memory.
56 * After the memory access is completed, gst_memory_unmap() should be called.
58 * Memory can be copied with gst_memory_copy(), which will return a writable
59 * copy. gst_memory_share() will create a new memory block that shares the
60 * memory with an existing memory block at a custom offset and with a custom
63 * Memory can be efficiently merged when gst_memory_is_span() returns %TRUE.
70 #define GST_DISABLE_MINIOBJECT_INLINE_FUNCTIONS
71 #include "gst_private.h"
72 #include "gstmemory.h"
74 GType _gst_memory_type = 0;
75 GST_DEFINE_MINI_OBJECT_TYPE (GstMemory, gst_memory);
78 _gst_memory_copy (GstMemory * mem)
80 GST_CAT_DEBUG (GST_CAT_MEMORY, "copy memory %p", mem);
81 return gst_memory_copy (mem, 0, -1);
85 _gst_memory_free (GstMemory * mem)
87 GstAllocator *allocator;
89 GST_CAT_DEBUG (GST_CAT_MEMORY, "free memory %p", mem);
92 gst_memory_unlock (mem->parent, GST_LOCK_FLAG_EXCLUSIVE);
93 gst_memory_unref (mem->parent);
96 allocator = mem->allocator;
98 gst_allocator_free (allocator, mem);
100 gst_object_unref (allocator);
104 * gst_memory_init: (skip)
106 * @flags: #GstMemoryFlags
107 * @allocator: the #GstAllocator
108 * @parent: the parent of @mem
109 * @maxsize: the total size of the memory
110 * @align: the alignment of the memory
111 * @offset: The offset in the memory
112 * @size: the size of valid data in the memory
114 * Initializes a newly allocated @mem with the given parameters. This function
115 * will call gst_mini_object_init() with the default memory parameters.
118 gst_memory_init (GstMemory * mem, GstMemoryFlags flags,
119 GstAllocator * allocator, GstMemory * parent, gsize maxsize, gsize align,
120 gsize offset, gsize size)
122 gst_mini_object_init (GST_MINI_OBJECT_CAST (mem),
123 flags | GST_MINI_OBJECT_FLAG_LOCKABLE, GST_TYPE_MEMORY,
124 (GstMiniObjectCopyFunction) _gst_memory_copy, NULL,
125 (GstMiniObjectFreeFunction) _gst_memory_free);
127 mem->allocator = gst_object_ref (allocator);
129 /* FIXME 2.0: this can fail if the memory is already write locked */
130 gst_memory_lock (parent, GST_LOCK_FLAG_EXCLUSIVE);
131 gst_memory_ref (parent);
133 mem->parent = parent;
134 mem->maxsize = maxsize;
136 mem->offset = offset;
139 GST_CAT_DEBUG (GST_CAT_MEMORY, "new memory %p, maxsize:%" G_GSIZE_FORMAT
140 " offset:%" G_GSIZE_FORMAT " size:%" G_GSIZE_FORMAT, mem, maxsize,
145 * gst_memory_is_type:
147 * @mem_type: a memory type
149 * Check if @mem if allocated with an allocator for @mem_type.
151 * Returns: %TRUE if @mem was allocated from an allocator for @mem_type.
156 gst_memory_is_type (GstMemory * mem, const gchar * mem_type)
158 g_return_val_if_fail (mem != NULL, FALSE);
159 g_return_val_if_fail (mem->allocator != NULL, FALSE);
160 g_return_val_if_fail (mem_type != NULL, FALSE);
162 return (g_strcmp0 (mem->allocator->mem_type, mem_type) == 0);
166 * gst_memory_get_sizes:
168 * @offset: (out) (allow-none): pointer to offset
169 * @maxsize: (out) (allow-none): pointer to maxsize
171 * Get the current @size, @offset and @maxsize of @mem.
173 * Returns: the current size of @mem
176 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
178 g_return_val_if_fail (mem != NULL, 0);
181 *offset = mem->offset;
183 *maxsize = mem->maxsize;
191 * @offset: a new offset
194 * Resize the memory region. @mem should be writable and offset + size should be
195 * less than the maxsize of @mem.
197 * #GST_MEMORY_FLAG_ZERO_PREFIXED and #GST_MEMORY_FLAG_ZERO_PADDED will be
198 * cleared when offset or padding is increased respectively.
201 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
203 g_return_if_fail (mem != NULL);
204 g_return_if_fail (gst_memory_is_writable (mem));
205 g_return_if_fail (offset >= 0 || mem->offset >= -offset);
206 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
208 /* if we increase the prefix, we can't guarantee it is still 0 filled */
209 if ((offset > 0) && GST_MEMORY_IS_ZERO_PREFIXED (mem))
210 GST_MEMORY_FLAG_UNSET (mem, GST_MEMORY_FLAG_ZERO_PREFIXED);
212 /* if we increase the padding, we can't guarantee it is still 0 filled */
213 if ((offset + size < mem->size) && GST_MEMORY_IS_ZERO_PADDED (mem))
214 GST_MEMORY_FLAG_UNSET (mem, GST_MEMORY_FLAG_ZERO_PADDED);
216 mem->offset += offset;
221 * gst_memory_make_mapped:
222 * @mem: (transfer full): a #GstMemory
223 * @info: (out caller-allocates): pointer for info
224 * @flags: mapping flags
226 * Create a #GstMemory object that is mapped with @flags. If @mem is mappable
227 * with @flags, this function returns the mapped @mem directly. Otherwise a
228 * mapped copy of @mem is returned.
230 * This function takes ownership of old @mem and returns a reference to a new
233 * Returns: (transfer full) (nullable): a #GstMemory object mapped
234 * with @flags or %NULL when a mapping is not possible.
237 gst_memory_make_mapped (GstMemory * mem, GstMapInfo * info, GstMapFlags flags)
241 if (gst_memory_map (mem, info, flags)) {
244 result = gst_memory_copy (mem, 0, -1);
245 gst_memory_unref (mem);
250 if (!gst_memory_map (result, info, flags))
258 GST_CAT_DEBUG (GST_CAT_MEMORY, "cannot copy memory %p", mem);
263 GST_CAT_DEBUG (GST_CAT_MEMORY, "cannot map memory %p with flags %d", mem,
265 gst_memory_unref (result);
273 * @info: (out caller-allocates): pointer for info
274 * @flags: mapping flags
276 * Fill @info with the pointer and sizes of the memory in @mem that can be
277 * accessed according to @flags.
279 * This function can return %FALSE for various reasons:
280 * - the memory backed by @mem is not accessible with the given @flags.
281 * - the memory was already mapped with a different mapping.
283 * @info and its contents remain valid for as long as @mem is valid and
284 * until gst_memory_unmap() is called.
286 * For each gst_memory_map() call, a corresponding gst_memory_unmap() call
289 * Returns: %TRUE if the map operation was successful.
292 gst_memory_map (GstMemory * mem, GstMapInfo * info, GstMapFlags flags)
294 g_return_val_if_fail (mem != NULL, FALSE);
295 g_return_val_if_fail (info != NULL, FALSE);
297 if (!gst_memory_lock (mem, (GstLockFlags) flags))
302 info->size = mem->size;
303 info->maxsize = mem->maxsize - mem->offset;
305 if (mem->allocator->mem_map_full)
306 info->data = mem->allocator->mem_map_full (mem, info, mem->maxsize);
308 info->data = mem->allocator->mem_map (mem, mem->maxsize, flags);
310 if (G_UNLIKELY (info->data == NULL))
313 info->data = info->data + mem->offset;
320 GST_CAT_DEBUG (GST_CAT_MEMORY, "mem %p: lock %d failed", mem, flags);
321 memset (info, 0, sizeof (GstMapInfo));
326 /* something went wrong, restore the original state again
327 * it is up to the subclass to log an error if needed. */
328 GST_CAT_INFO (GST_CAT_MEMORY, "mem %p: subclass map failed", mem);
329 gst_memory_unlock (mem, (GstLockFlags) flags);
330 memset (info, 0, sizeof (GstMapInfo));
338 * @info: a #GstMapInfo
340 * Release the memory obtained with gst_memory_map()
343 gst_memory_unmap (GstMemory * mem, GstMapInfo * info)
345 g_return_if_fail (mem != NULL);
346 g_return_if_fail (info != NULL);
347 g_return_if_fail (info->memory == mem);
349 if (mem->allocator->mem_unmap_full)
350 mem->allocator->mem_unmap_full (mem, info);
352 mem->allocator->mem_unmap (mem);
353 gst_memory_unlock (mem, (GstLockFlags) info->flags);
359 * @offset: offset to copy from
360 * @size: size to copy, or -1 to copy to the end of the memory region
362 * Return a copy of @size bytes from @mem starting from @offset. This copy is
363 * guaranteed to be writable. @size can be set to -1 to return a copy
364 * from @offset to the end of the memory region.
366 * Returns: a new #GstMemory.
369 gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
373 g_return_val_if_fail (mem != NULL, NULL);
375 copy = mem->allocator->mem_copy (mem, offset, size);
383 * @offset: offset to share from
384 * @size: size to share, or -1 to share to the end of the memory region
386 * Return a shared copy of @size bytes from @mem starting from @offset. No
387 * memory copy is performed and the memory region is simply shared. The result
388 * is guaranteed to be non-writable. @size can be set to -1 to return a shared
389 * copy from @offset to the end of the memory region.
391 * Returns: a new #GstMemory.
394 gst_memory_share (GstMemory * mem, gssize offset, gssize size)
398 g_return_val_if_fail (mem != NULL, NULL);
399 g_return_val_if_fail (!GST_MEMORY_FLAG_IS_SET (mem, GST_MEMORY_FLAG_NO_SHARE),
402 /* whether we can lock the memory exclusively */
403 /* in order to maintain backwards compatibility by not requiring subclasses
404 * to lock the memory themselves and propagate the possible failure in their
405 * mem_share implementation */
406 /* FIXME 2.0: remove and fix gst_memory_init() and/or all memory subclasses
407 * to propagate this failure case */
408 if (!gst_memory_lock (mem, GST_LOCK_FLAG_EXCLUSIVE))
411 /* double lock to ensure we are not mapped writable without an
413 if (!gst_memory_lock (mem, GST_LOCK_FLAG_EXCLUSIVE)) {
414 gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
418 shared = mem->allocator->mem_share (mem, offset, size);
420 /* unlocking before calling the subclass would be racy */
421 gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
422 gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
428 * gst_memory_is_span:
429 * @mem1: a #GstMemory
430 * @mem2: a #GstMemory
431 * @offset: (out): a pointer to a result offset
433 * Check if @mem1 and mem2 share the memory with a common parent memory object
434 * and that the memory is contiguous.
436 * If this is the case, the memory of @mem1 and @mem2 can be merged
437 * efficiently by performing gst_memory_share() on the parent object from
438 * the returned @offset.
440 * Returns: %TRUE if the memory is contiguous and of a common parent.
443 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
445 g_return_val_if_fail (mem1 != NULL, FALSE);
446 g_return_val_if_fail (mem2 != NULL, FALSE);
448 /* need to have the same allocators */
449 if (mem1->allocator != mem2->allocator)
452 /* need to have the same parent */
453 if (mem1->parent == NULL || mem1->parent != mem2->parent)
456 /* and memory is contiguous */
457 if (!mem1->allocator->mem_is_span (mem1, mem2, offset))
464 _priv_gst_memory_initialize (void)
466 _gst_memory_type = gst_memory_get_type ();
470 * gst_memory_ref: (skip)
471 * @memory: The memory to refcount
473 * Increase the refcount of this memory.
475 * Returns: (transfer full): @memory (for convenience when doing assignments)
478 gst_memory_ref (GstMemory * memory)
480 return (GstMemory *) gst_mini_object_ref (GST_MINI_OBJECT_CAST (memory));
484 * gst_memory_unref: (skip)
485 * @memory: (transfer full): the memory to refcount
487 * Decrease the refcount of a memory, freeing it if the refcount reaches 0.
490 gst_memory_unref (GstMemory * memory)
492 gst_mini_object_unref (GST_MINI_OBJECT_CAST (memory));