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 #include "gst_private.h"
71 #include "gstmemory.h"
73 GType _gst_memory_type = 0;
74 GST_DEFINE_MINI_OBJECT_TYPE (GstMemory, gst_memory);
77 _gst_memory_copy (GstMemory * mem)
79 GST_CAT_DEBUG (GST_CAT_MEMORY, "copy memory %p", mem);
80 return gst_memory_copy (mem, 0, -1);
84 _gst_memory_free (GstMemory * mem)
86 GstAllocator *allocator;
88 GST_CAT_DEBUG (GST_CAT_MEMORY, "free memory %p", mem);
91 gst_memory_unlock (mem->parent, GST_LOCK_FLAG_EXCLUSIVE);
92 gst_memory_unref (mem->parent);
95 allocator = mem->allocator;
97 gst_allocator_free (allocator, mem);
99 gst_object_unref (allocator);
103 * gst_memory_init: (skip)
105 * @flags: #GstMemoryFlags
106 * @allocator: the #GstAllocator
107 * @parent: the parent of @mem
108 * @maxsize: the total size of the memory
109 * @align: the alignment of the memory
110 * @offset: The offset in the memory
111 * @size: the size of valid data in the memory
113 * Initializes a newly allocated @mem with the given parameters. This function
114 * will call gst_mini_object_init() with the default memory parameters.
117 gst_memory_init (GstMemory * mem, GstMemoryFlags flags,
118 GstAllocator * allocator, GstMemory * parent, gsize maxsize, gsize align,
119 gsize offset, gsize size)
121 gst_mini_object_init (GST_MINI_OBJECT_CAST (mem),
122 flags | GST_MINI_OBJECT_FLAG_LOCKABLE, GST_TYPE_MEMORY,
123 (GstMiniObjectCopyFunction) _gst_memory_copy, NULL,
124 (GstMiniObjectFreeFunction) _gst_memory_free);
126 mem->allocator = gst_object_ref (allocator);
128 /* FIXME 2.0: this can fail if the memory is already write locked */
129 gst_memory_lock (parent, GST_LOCK_FLAG_EXCLUSIVE);
130 gst_memory_ref (parent);
132 mem->parent = parent;
133 mem->maxsize = maxsize;
135 mem->offset = offset;
138 GST_CAT_DEBUG (GST_CAT_MEMORY, "new memory %p, maxsize:%" G_GSIZE_FORMAT
139 " offset:%" G_GSIZE_FORMAT " size:%" G_GSIZE_FORMAT, mem, maxsize,
144 * gst_memory_is_type:
146 * @mem_type: a memory type
148 * Check if @mem if allocated with an allocator for @mem_type.
150 * Returns: %TRUE if @mem was allocated from an allocator for @mem_type.
155 gst_memory_is_type (GstMemory * mem, const gchar * mem_type)
157 g_return_val_if_fail (mem != NULL, FALSE);
158 g_return_val_if_fail (mem->allocator != NULL, FALSE);
159 g_return_val_if_fail (mem_type != NULL, FALSE);
161 return (g_strcmp0 (mem->allocator->mem_type, mem_type) == 0);
165 * gst_memory_get_sizes:
167 * @offset: (out) (allow-none): pointer to offset
168 * @maxsize: (out) (allow-none): pointer to maxsize
170 * Get the current @size, @offset and @maxsize of @mem.
172 * Returns: the current sizes of @mem
175 gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
177 g_return_val_if_fail (mem != NULL, 0);
180 *offset = mem->offset;
182 *maxsize = mem->maxsize;
190 * @offset: a new offset
193 * Resize the memory region. @mem should be writable and offset + size should be
194 * less than the maxsize of @mem.
196 * #GST_MEMORY_FLAG_ZERO_PREFIXED and #GST_MEMORY_FLAG_ZERO_PADDED will be
197 * cleared when offset or padding is increased respectively.
200 gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
202 g_return_if_fail (mem != NULL);
203 g_return_if_fail (gst_memory_is_writable (mem));
204 g_return_if_fail (offset >= 0 || mem->offset >= -offset);
205 g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
207 /* if we increase the prefix, we can't guarantee it is still 0 filled */
208 if ((offset > 0) && GST_MEMORY_IS_ZERO_PREFIXED (mem))
209 GST_MEMORY_FLAG_UNSET (mem, GST_MEMORY_FLAG_ZERO_PREFIXED);
211 /* if we increase the padding, we can't guarantee it is still 0 filled */
212 if ((offset + size < mem->size) && GST_MEMORY_IS_ZERO_PADDED (mem))
213 GST_MEMORY_FLAG_UNSET (mem, GST_MEMORY_FLAG_ZERO_PADDED);
215 mem->offset += offset;
220 * gst_memory_make_mapped:
221 * @mem: (transfer full): a #GstMemory
222 * @info: (out): pointer for info
223 * @flags: mapping flags
225 * Create a #GstMemory object that is mapped with @flags. If @mem is mappable
226 * with @flags, this function returns the mapped @mem directly. Otherwise a
227 * mapped copy of @mem is returned.
229 * This function takes ownership of old @mem and returns a reference to a new
232 * Returns: (transfer full) (nullable): a #GstMemory object mapped
233 * with @flags or %NULL when a mapping is not possible.
236 gst_memory_make_mapped (GstMemory * mem, GstMapInfo * info, GstMapFlags flags)
240 if (gst_memory_map (mem, info, flags)) {
243 result = gst_memory_copy (mem, 0, -1);
244 gst_memory_unref (mem);
249 if (!gst_memory_map (result, info, flags))
257 GST_CAT_DEBUG (GST_CAT_MEMORY, "cannot copy memory %p", mem);
262 GST_CAT_DEBUG (GST_CAT_MEMORY, "cannot map memory %p with flags %d", mem,
264 gst_memory_unref (result);
272 * @info: (out): pointer for info
273 * @flags: mapping flags
275 * Fill @info with the pointer and sizes of the memory in @mem that can be
276 * accessed according to @flags.
278 * This function can return %FALSE for various reasons:
279 * - the memory backed by @mem is not accessible with the given @flags.
280 * - the memory was already mapped with a different mapping.
282 * @info and its contents remain valid for as long as @mem is valid and
283 * until gst_memory_unmap() is called.
285 * For each gst_memory_map() call, a corresponding gst_memory_unmap() call
288 * Returns: %TRUE if the map operation was successful.
291 gst_memory_map (GstMemory * mem, GstMapInfo * info, GstMapFlags flags)
293 g_return_val_if_fail (mem != NULL, FALSE);
294 g_return_val_if_fail (info != NULL, FALSE);
296 if (!gst_memory_lock (mem, (GstLockFlags) flags))
301 info->size = mem->size;
302 info->maxsize = mem->maxsize - mem->offset;
304 if (mem->allocator->mem_map_full)
305 info->data = mem->allocator->mem_map_full (mem, info, mem->maxsize);
307 info->data = mem->allocator->mem_map (mem, mem->maxsize, flags);
309 if (G_UNLIKELY (info->data == NULL))
312 info->data = info->data + mem->offset;
319 GST_CAT_DEBUG (GST_CAT_MEMORY, "mem %p: lock %d failed", mem, flags);
320 memset (info, 0, sizeof (GstMapInfo));
325 /* something went wrong, restore the original state again
326 * it is up to the subclass to log an error if needed. */
327 GST_CAT_INFO (GST_CAT_MEMORY, "mem %p: subclass map failed", mem);
328 gst_memory_unlock (mem, (GstLockFlags) flags);
329 memset (info, 0, sizeof (GstMapInfo));
337 * @info: a #GstMapInfo
339 * Release the memory obtained with gst_memory_map()
342 gst_memory_unmap (GstMemory * mem, GstMapInfo * info)
344 g_return_if_fail (mem != NULL);
345 g_return_if_fail (info != NULL);
346 g_return_if_fail (info->memory == mem);
348 if (mem->allocator->mem_unmap_full)
349 mem->allocator->mem_unmap_full (mem, info);
351 mem->allocator->mem_unmap (mem);
352 gst_memory_unlock (mem, (GstLockFlags) info->flags);
358 * @offset: offset to copy from
359 * @size: size to copy, or -1 to copy to the end of the memory region
361 * Return a copy of @size bytes from @mem starting from @offset. This copy is
362 * guaranteed to be writable. @size can be set to -1 to return a copy
363 * from @offset to the end of the memory region.
365 * Returns: a new #GstMemory.
368 gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
372 g_return_val_if_fail (mem != NULL, NULL);
374 copy = mem->allocator->mem_copy (mem, offset, size);
382 * @offset: offset to share from
383 * @size: size to share, or -1 to share to the end of the memory region
385 * Return a shared copy of @size bytes from @mem starting from @offset. No
386 * memory copy is performed and the memory region is simply shared. The result
387 * is guaranteed to be non-writable. @size can be set to -1 to return a shared
388 * copy from @offset to the end of the memory region.
390 * Returns: a new #GstMemory.
393 gst_memory_share (GstMemory * mem, gssize offset, gssize size)
397 g_return_val_if_fail (mem != NULL, NULL);
398 g_return_val_if_fail (!GST_MEMORY_FLAG_IS_SET (mem, GST_MEMORY_FLAG_NO_SHARE),
401 /* whether we can lock the memory exclusively */
402 /* in order to maintain backwards compatibility by not requiring subclasses
403 * to lock the memory themselves and propagate the possible failure in their
404 * mem_share implementation */
405 /* FIXME 2.0: remove and fix gst_memory_init() and/or all memory subclasses
406 * to propagate this failure case */
407 if (!gst_memory_lock (mem, GST_LOCK_FLAG_EXCLUSIVE))
410 /* double lock to ensure we are not mapped writable without an
412 if (!gst_memory_lock (mem, GST_LOCK_FLAG_EXCLUSIVE)) {
413 gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
417 shared = mem->allocator->mem_share (mem, offset, size);
419 /* unlocking before calling the subclass would be racy */
420 gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
421 gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
427 * gst_memory_is_span:
428 * @mem1: a #GstMemory
429 * @mem2: a #GstMemory
430 * @offset: (out): a pointer to a result offset
432 * Check if @mem1 and mem2 share the memory with a common parent memory object
433 * and that the memory is contiguous.
435 * If this is the case, the memory of @mem1 and @mem2 can be merged
436 * efficiently by performing gst_memory_share() on the parent object from
437 * the returned @offset.
439 * Returns: %TRUE if the memory is contiguous and of a common parent.
442 gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
444 g_return_val_if_fail (mem1 != NULL, FALSE);
445 g_return_val_if_fail (mem2 != NULL, FALSE);
447 /* need to have the same allocators */
448 if (mem1->allocator != mem2->allocator)
451 /* need to have the same parent */
452 if (mem1->parent == NULL || mem1->parent != mem2->parent)
455 /* and memory is contiguous */
456 if (!mem1->allocator->mem_is_span (mem1, mem2, offset))
463 _priv_gst_memory_initialize (void)
465 _gst_memory_type = gst_memory_get_type ();