gstreamer/gst/gstmemory.c

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/* GStreamer
* Copyright (C) 2011 Wim Taymans <wim.taymans@gmail.be>
*
* gstmemory.c: memory block handling
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
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*/
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/**
* SECTION:gstmemory
* @title: GstMemory
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* @short_description: refcounted wrapper for memory blocks
* @see_also: #GstBuffer
*
* GstMemory is a lightweight refcounted object that wraps a region of memory.
* They are typically used to manage the data of a #GstBuffer.
*
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* A GstMemory object has an allocated region of memory of maxsize. The maximum
* size does not change during the lifetime of the memory object. The memory
* also has an offset and size property that specifies the valid range of memory
* in the allocated region.
*
* Memory is usually created by allocators with a gst_allocator_alloc()
* method call. When %NULL is used as the allocator, the default allocator will
* be used.
*
* New allocators can be registered with gst_allocator_register().
* Allocators are identified by name and can be retrieved with
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* gst_allocator_find(). gst_allocator_set_default() can be used to change the
* default allocator.
*
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* New memory can be created with gst_memory_new_wrapped() that wraps the memory
* allocated elsewhere.
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*
* Refcounting of the memory block is performed with gst_memory_ref() and
* gst_memory_unref().
*
* The size of the memory can be retrieved and changed with
* gst_memory_get_sizes() and gst_memory_resize() respectively.
*
* Getting access to the data of the memory is performed with gst_memory_map().
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* The call will return a pointer to offset bytes into the region of memory.
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* After the memory access is completed, gst_memory_unmap() should be called.
*
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* Memory can be copied with gst_memory_copy(), which will return a writable
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* copy. gst_memory_share() will create a new memory block that shares the
* memory with an existing memory block at a custom offset and with a custom
* size.
*
* Memory can be efficiently merged when gst_memory_is_span() returns %TRUE.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
#endif
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#include "gst_private.h"
#include "gstmemory.h"
GType _gst_memory_type = 0;
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GST_DEFINE_MINI_OBJECT_TYPE (GstMemory, gst_memory);
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static GstMemory *
_gst_memory_copy (GstMemory * mem)
{
GST_CAT_DEBUG (GST_CAT_MEMORY, "copy memory %p", mem);
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return gst_memory_copy (mem, 0, -1);
}
static void
_gst_memory_free (GstMemory * mem)
{
GstAllocator *allocator;
GST_CAT_DEBUG (GST_CAT_MEMORY, "free memory %p", mem);
if (mem->parent) {
gst_memory_unlock (mem->parent, GST_LOCK_FLAG_EXCLUSIVE);
gst_memory_unref (mem->parent);
}
allocator = mem->allocator;
gst_allocator_free (allocator, mem);
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gst_object_unref (allocator);
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}
/**
* gst_memory_init: (skip)
* @mem: a #GstMemory
* @flags: #GstMemoryFlags
* @allocator: the #GstAllocator
* @parent: the parent of @mem
* @maxsize: the total size of the memory
* @align: the alignment of the memory
* @offset: The offset in the memory
* @size: the size of valid data in the memory
* Initializes a newly allocated @mem with the given parameters. This function
* will call gst_mini_object_init() with the default memory parameters.
*/
void
gst_memory_init (GstMemory * mem, GstMemoryFlags flags,
GstAllocator * allocator, GstMemory * parent, gsize maxsize, gsize align,
gsize offset, gsize size)
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{
gst_mini_object_init (GST_MINI_OBJECT_CAST (mem),
flags | GST_MINI_OBJECT_FLAG_LOCKABLE, GST_TYPE_MEMORY,
(GstMiniObjectCopyFunction) _gst_memory_copy, NULL,
(GstMiniObjectFreeFunction) _gst_memory_free);
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mem->allocator = gst_object_ref (allocator);
if (parent) {
/* FIXME 2.0: this can fail if the memory is already write locked */
gst_memory_lock (parent, GST_LOCK_FLAG_EXCLUSIVE);
gst_memory_ref (parent);
}
mem->parent = parent;
mem->maxsize = maxsize;
mem->align = align;
mem->offset = offset;
mem->size = size;
GST_CAT_DEBUG (GST_CAT_MEMORY, "new memory %p, maxsize:%" G_GSIZE_FORMAT
" offset:%" G_GSIZE_FORMAT " size:%" G_GSIZE_FORMAT, mem, maxsize,
offset, size);
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}
/**
* gst_memory_is_type:
* @mem: a #GstMemory
* @mem_type: a memory type
*
* Check if @mem if allocated with an allocator for @mem_type.
*
* Returns: %TRUE if @mem was allocated from an allocator for @mem_type.
*
* Since: 1.2
*/
gboolean
gst_memory_is_type (GstMemory * mem, const gchar * mem_type)
{
g_return_val_if_fail (mem != NULL, FALSE);
g_return_val_if_fail (mem->allocator != NULL, FALSE);
g_return_val_if_fail (mem_type != NULL, FALSE);
return (g_strcmp0 (mem->allocator->mem_type, mem_type) == 0);
}
/**
* gst_memory_get_sizes:
* @mem: a #GstMemory
* @offset: (out) (allow-none): pointer to offset
* @maxsize: (out) (allow-none): pointer to maxsize
*
* Get the current @size, @offset and @maxsize of @mem.
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*
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* Returns: the current size of @mem
*/
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gsize
gst_memory_get_sizes (GstMemory * mem, gsize * offset, gsize * maxsize)
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{
g_return_val_if_fail (mem != NULL, 0);
if (offset)
*offset = mem->offset;
if (maxsize)
*maxsize = mem->maxsize;
return mem->size;
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}
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/**
* gst_memory_resize:
* @mem: a #GstMemory
* @offset: a new offset
* @size: a new size
*
* Resize the memory region. @mem should be writable and offset + size should be
* less than the maxsize of @mem.
*
* #GST_MEMORY_FLAG_ZERO_PREFIXED and #GST_MEMORY_FLAG_ZERO_PADDED will be
* cleared when offset or padding is increased respectively.
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*/
void
gst_memory_resize (GstMemory * mem, gssize offset, gsize size)
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{
g_return_if_fail (mem != NULL);
g_return_if_fail (gst_memory_is_writable (mem));
g_return_if_fail (offset >= 0 || mem->offset >= -offset);
g_return_if_fail (size + mem->offset + offset <= mem->maxsize);
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/* if we increase the prefix, we can't guarantee it is still 0 filled */
if ((offset > 0) && GST_MEMORY_IS_ZERO_PREFIXED (mem))
GST_MEMORY_FLAG_UNSET (mem, GST_MEMORY_FLAG_ZERO_PREFIXED);
/* if we increase the padding, we can't guarantee it is still 0 filled */
if ((offset + size < mem->size) && GST_MEMORY_IS_ZERO_PADDED (mem))
GST_MEMORY_FLAG_UNSET (mem, GST_MEMORY_FLAG_ZERO_PADDED);
mem->offset += offset;
mem->size = size;
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}
/**
* gst_memory_make_mapped:
* @mem: (transfer full): a #GstMemory
* @info: (out): pointer for info
* @flags: mapping flags
*
* Create a #GstMemory object that is mapped with @flags. If @mem is mappable
* with @flags, this function returns the mapped @mem directly. Otherwise a
* mapped copy of @mem is returned.
*
* This function takes ownership of old @mem and returns a reference to a new
* #GstMemory.
*
* Returns: (transfer full) (nullable): a #GstMemory object mapped
* with @flags or %NULL when a mapping is not possible.
*/
GstMemory *
gst_memory_make_mapped (GstMemory * mem, GstMapInfo * info, GstMapFlags flags)
{
GstMemory *result;
if (gst_memory_map (mem, info, flags)) {
result = mem;
} else {
result = gst_memory_copy (mem, 0, -1);
gst_memory_unref (mem);
if (result == NULL)
goto cannot_copy;
if (!gst_memory_map (result, info, flags))
goto cannot_map;
}
return result;
/* ERRORS */
cannot_copy:
{
GST_CAT_DEBUG (GST_CAT_MEMORY, "cannot copy memory %p", mem);
return NULL;
}
cannot_map:
{
GST_CAT_DEBUG (GST_CAT_MEMORY, "cannot map memory %p with flags %d", mem,
flags);
gst_memory_unref (result);
return NULL;
}
}
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/**
* gst_memory_map:
* @mem: a #GstMemory
* @info: (out): pointer for info
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* @flags: mapping flags
*
* Fill @info with the pointer and sizes of the memory in @mem that can be
* accessed according to @flags.
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*
* This function can return %FALSE for various reasons:
* - the memory backed by @mem is not accessible with the given @flags.
* - the memory was already mapped with a different mapping.
*
* @info and its contents remain valid for as long as @mem is valid and
* until gst_memory_unmap() is called.
*
* For each gst_memory_map() call, a corresponding gst_memory_unmap() call
* should be done.
*
* Returns: %TRUE if the map operation was successful.
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*/
gboolean
gst_memory_map (GstMemory * mem, GstMapInfo * info, GstMapFlags flags)
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{
g_return_val_if_fail (mem != NULL, FALSE);
g_return_val_if_fail (info != NULL, FALSE);
if (!gst_memory_lock (mem, (GstLockFlags) flags))
goto lock_failed;
info->flags = flags;
info->memory = mem;
info->size = mem->size;
info->maxsize = mem->maxsize - mem->offset;
if (mem->allocator->mem_map_full)
info->data = mem->allocator->mem_map_full (mem, info, mem->maxsize);
else
info->data = mem->allocator->mem_map (mem, mem->maxsize, flags);
if (G_UNLIKELY (info->data == NULL))
goto error;
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info->data = info->data + mem->offset;
return TRUE;
/* ERRORS */
lock_failed:
{
GST_CAT_DEBUG (GST_CAT_MEMORY, "mem %p: lock %d failed", mem, flags);
memset (info, 0, sizeof (GstMapInfo));
return FALSE;
}
error:
{
/* something went wrong, restore the original state again
* it is up to the subclass to log an error if needed. */
GST_CAT_INFO (GST_CAT_MEMORY, "mem %p: subclass map failed", mem);
gst_memory_unlock (mem, (GstLockFlags) flags);
memset (info, 0, sizeof (GstMapInfo));
return FALSE;
}
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}
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/**
* gst_memory_unmap:
* @mem: a #GstMemory
* @info: a #GstMapInfo
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*
* Release the memory obtained with gst_memory_map()
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*/
void
gst_memory_unmap (GstMemory * mem, GstMapInfo * info)
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{
g_return_if_fail (mem != NULL);
g_return_if_fail (info != NULL);
g_return_if_fail (info->memory == mem);
if (mem->allocator->mem_unmap_full)
mem->allocator->mem_unmap_full (mem, info);
else
mem->allocator->mem_unmap (mem);
gst_memory_unlock (mem, (GstLockFlags) info->flags);
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}
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/**
* gst_memory_copy:
* @mem: a #GstMemory
* @offset: offset to copy from
* @size: size to copy, or -1 to copy to the end of the memory region
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*
* Return a copy of @size bytes from @mem starting from @offset. This copy is
* guaranteed to be writable. @size can be set to -1 to return a copy
* from @offset to the end of the memory region.
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*
* Returns: a new #GstMemory.
*/
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GstMemory *
gst_memory_copy (GstMemory * mem, gssize offset, gssize size)
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{
GstMemory *copy;
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g_return_val_if_fail (mem != NULL, NULL);
copy = mem->allocator->mem_copy (mem, offset, size);
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return copy;
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}
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/**
* gst_memory_share:
* @mem: a #GstMemory
* @offset: offset to share from
* @size: size to share, or -1 to share to the end of the memory region
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*
* Return a shared copy of @size bytes from @mem starting from @offset. No
* memory copy is performed and the memory region is simply shared. The result
* is guaranteed to be non-writable. @size can be set to -1 to return a shared
* copy from @offset to the end of the memory region.
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*
* Returns: a new #GstMemory.
*/
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GstMemory *
gst_memory_share (GstMemory * mem, gssize offset, gssize size)
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{
GstMemory *shared;
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g_return_val_if_fail (mem != NULL, NULL);
g_return_val_if_fail (!GST_MEMORY_FLAG_IS_SET (mem, GST_MEMORY_FLAG_NO_SHARE),
NULL);
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/* whether we can lock the memory exclusively */
/* in order to maintain backwards compatibility by not requiring subclasses
* to lock the memory themselves and propagate the possible failure in their
* mem_share implementation */
/* FIXME 2.0: remove and fix gst_memory_init() and/or all memory subclasses
* to propagate this failure case */
if (!gst_memory_lock (mem, GST_LOCK_FLAG_EXCLUSIVE))
return NULL;
/* double lock to ensure we are not mapped writable without an
* exclusive lock. */
if (!gst_memory_lock (mem, GST_LOCK_FLAG_EXCLUSIVE)) {
gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
return NULL;
}
shared = mem->allocator->mem_share (mem, offset, size);
/* unlocking before calling the subclass would be racy */
gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
gst_memory_unlock (mem, GST_LOCK_FLAG_EXCLUSIVE);
return shared;
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}
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/**
* gst_memory_is_span:
* @mem1: a #GstMemory
* @mem2: a #GstMemory
* @offset: (out): a pointer to a result offset
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*
* Check if @mem1 and mem2 share the memory with a common parent memory object
* and that the memory is contiguous.
*
* If this is the case, the memory of @mem1 and @mem2 can be merged
* efficiently by performing gst_memory_share() on the parent object from
* the returned @offset.
*
* Returns: %TRUE if the memory is contiguous and of a common parent.
*/
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gboolean
gst_memory_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
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{
g_return_val_if_fail (mem1 != NULL, FALSE);
g_return_val_if_fail (mem2 != NULL, FALSE);
/* need to have the same allocators */
if (mem1->allocator != mem2->allocator)
return FALSE;
/* need to have the same parent */
if (mem1->parent == NULL || mem1->parent != mem2->parent)
return FALSE;
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/* and memory is contiguous */
if (!mem1->allocator->mem_is_span (mem1, mem2, offset))
return FALSE;
return TRUE;
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}
void
_priv_gst_memory_initialize (void)
{
_gst_memory_type = gst_memory_get_type ();
}