gstreamer/gst/gstmemory.c

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2011-03-18 18:28:17 +00:00
/* 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., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
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/**
* SECTION:gstmemory
* @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
* gst_allocator_find().
*
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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.
*
* Memory can be copied with gst_memory_copy(), which will returnn a writable
* 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.
*
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* Memory can be efficiently merged when gst_memory_is_span() returns TRUE.
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*
* Last reviewed on 2011-06-08 (0.11.0)
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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"
G_DEFINE_BOXED_TYPE (GstMemory, gst_memory, (GBoxedCopyFunc) gst_memory_ref,
(GBoxedFreeFunc) gst_memory_unref);
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/**
* gst_memory_alignment:
*
* The default memory alignment in bytes - 1
* an alignment of 7 would be the same as what malloc() guarantees.
*/
#if defined(MEMORY_ALIGNMENT_MALLOC)
size_t gst_memory_alignment = 7;
#elif defined(MEMORY_ALIGNMENT_PAGESIZE)
/* we fill this in in the _init method */
size_t gst_memory_alignment = 0;
#elif defined(MEMORY_ALIGNMENT)
size_t gst_memory_alignment = MEMORY_ALIGNMENT - 1;
#else
#error "No memory alignment configured"
size_t gst_memory_alignment = 0;
#endif
struct _GstAllocator
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{
GQuark name;
GstMemoryInfo info;
};
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/* default memory implementation */
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typedef struct
{
GstMemory mem;
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gsize slice_size;
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guint8 *data;
GFreeFunc free_func;
} GstMemoryDefault;
/* the default allocator */
static const GstAllocator *_default_allocator;
/* our predefined allocators */
static const GstAllocator *_default_mem_impl;
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/* initialize the fields */
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static void
_default_mem_init (GstMemoryDefault * mem, GstMemoryFlags flags,
GstMemory * parent, gsize slice_size, gpointer data,
GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
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{
mem->mem.allocator = _default_mem_impl;
mem->mem.flags = flags;
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mem->mem.refcount = 1;
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mem->mem.parent = parent ? gst_memory_ref (parent) : NULL;
mem->mem.state = (flags & GST_MEMORY_FLAG_READONLY ? 0x5 : 0);
mem->mem.maxsize = maxsize;
mem->mem.offset = offset;
mem->mem.size = size;
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mem->slice_size = slice_size;
mem->data = data;
mem->free_func = free_func;
}
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/* create a new memory block that manages the given memory */
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static GstMemoryDefault *
_default_mem_new (GstMemoryFlags flags, GstMemory * parent, gpointer data,
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GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
{
GstMemoryDefault *mem;
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gsize slice_size;
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slice_size = sizeof (GstMemoryDefault);
mem = g_slice_alloc (slice_size);
_default_mem_init (mem, flags, parent, slice_size,
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data, free_func, maxsize, offset, size);
return mem;
}
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/* allocate the memory and structure in one block */
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static GstMemoryDefault *
_default_mem_new_block (gsize maxsize, gsize align, gsize offset, gsize size)
{
GstMemoryDefault *mem;
gsize aoffset, slice_size;
guint8 *data;
/* ensure configured alignment */
align |= gst_memory_alignment;
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/* allocate more to compensate for alignment */
maxsize += align;
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/* alloc header and data in one block */
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slice_size = sizeof (GstMemoryDefault) + maxsize;
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mem = g_slice_alloc (slice_size);
if (mem == NULL)
return NULL;
data = (guint8 *) mem + sizeof (GstMemoryDefault);
if ((aoffset = ((guintptr) data & align)))
aoffset = (align + 1) - aoffset;
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_default_mem_init (mem, 0, NULL, slice_size, data, NULL, maxsize,
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aoffset + offset, size);
return mem;
}
static GstMemory *
_default_mem_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
{
return (GstMemory *) _default_mem_new_block (maxsize, align, 0, maxsize);
}
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static gpointer
_default_mem_map (GstMemoryDefault * mem, GstMapFlags flags)
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{
return mem->data;
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}
static gboolean
_default_mem_unmap (GstMemoryDefault * mem)
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{
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return TRUE;
}
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static void
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_default_mem_free (GstMemoryDefault * mem)
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{
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if (mem->mem.parent)
gst_memory_unref (mem->mem.parent);
if (mem->free_func)
mem->free_func (mem->data);
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g_slice_free1 (mem->slice_size, mem);
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}
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static GstMemoryDefault *
_default_mem_copy (GstMemoryDefault * mem, gssize offset, gsize size)
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{
GstMemoryDefault *copy;
if (size == -1)
size = mem->mem.size > offset ? mem->mem.size - offset : 0;
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copy =
_default_mem_new_block (mem->mem.maxsize, 0, mem->mem.offset + offset,
size);
memcpy (copy->data, mem->data, mem->mem.maxsize);
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return copy;
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}
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static GstMemoryDefault *
_default_mem_share (GstMemoryDefault * mem, gssize offset, gsize size)
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{
GstMemoryDefault *sub;
GstMemory *parent;
/* find the real parent */
if ((parent = mem->mem.parent) == NULL)
parent = (GstMemory *) mem;
if (size == -1)
size = mem->mem.size - offset;
sub =
_default_mem_new (parent->flags, parent, mem->data, NULL,
mem->mem.maxsize, mem->mem.offset + offset, size);
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return sub;
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}
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static gboolean
_default_mem_is_span (GstMemoryDefault * mem1, GstMemoryDefault * mem2,
gsize * offset)
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{
if (offset) {
GstMemoryDefault *parent;
parent = (GstMemoryDefault *) mem1->mem.parent;
*offset = mem1->mem.offset - parent->mem.offset;
}
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/* and memory is contiguous */
return mem1->data + mem1->mem.offset + mem1->mem.size ==
mem2->data + mem2->mem.offset;
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}
static GstMemory *
_fallback_copy (GstMemory * mem, gssize offset, gssize size)
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{
GstMemory *copy;
GstMapInfo sinfo, dinfo;
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if (!gst_memory_map (mem, &sinfo, GST_MAP_READ))
return NULL;
if (size == -1)
size = sinfo.size > offset ? sinfo.size - offset : 0;
/* use the same allocator as the memory we copy */
copy = gst_allocator_alloc (mem->allocator, size, mem->align);
if (!gst_memory_map (copy, &dinfo, GST_MAP_WRITE)) {
GST_WARNING ("could not write map memory %p", copy);
gst_memory_unmap (mem, &sinfo);
return NULL;
}
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memcpy (dinfo.data, sinfo.data + offset, size);
gst_memory_unmap (copy, &dinfo);
gst_memory_unmap (mem, &sinfo);
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return copy;
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}
static gboolean
_fallback_is_span (GstMemory * mem1, GstMemory * mem2, gsize * offset)
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{
return FALSE;
}
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static GRWLock lock;
static GHashTable *allocators;
void
_priv_gst_memory_initialize (void)
{
static const GstMemoryInfo _mem_info = {
(GstMemoryAllocFunction) _default_mem_alloc,
(GstMemoryMapFunction) _default_mem_map,
(GstMemoryUnmapFunction) _default_mem_unmap,
(GstMemoryFreeFunction) _default_mem_free,
(GstMemoryCopyFunction) _default_mem_copy,
(GstMemoryShareFunction) _default_mem_share,
(GstMemoryIsSpanFunction) _default_mem_is_span,
NULL
};
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g_rw_lock_init (&lock);
allocators = g_hash_table_new (g_str_hash, g_str_equal);
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#ifdef HAVE_GETPAGESIZE
#ifdef MEMORY_ALIGNMENT_PAGESIZE
gst_memory_alignment = getpagesize () - 1;
#endif
#endif
GST_DEBUG ("memory alignment: %" G_GSIZE_FORMAT, gst_memory_alignment);
_default_mem_impl = gst_allocator_register (GST_ALLOCATOR_SYSMEM, &_mem_info);
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_default_allocator = _default_mem_impl;
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}
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/**
* gst_memory_new_wrapped:
* @flags: #GstMemoryFlags
* @data: data to wrap
* @free_func: function to free @data
* @maxsize: allocated size of @data
* @offset: offset in @data
* @size: size of valid data
*
* Allocate a new memory block that wraps the given @data.
*
* Returns: a new #GstMemory.
*/
GstMemory *
gst_memory_new_wrapped (GstMemoryFlags flags, gpointer data,
GFreeFunc free_func, gsize maxsize, gsize offset, gsize size)
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{
GstMemoryDefault *mem;
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g_return_val_if_fail (data != NULL, NULL);
g_return_val_if_fail (offset + size <= maxsize, NULL);
mem = _default_mem_new (flags, NULL, data, free_func, maxsize, offset, size);
return (GstMemory *) mem;
}
/**
* gst_memory_ref:
* @mem: a #GstMemory
*
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* Increases the refcount of @mem.
*
* Returns: @mem with increased refcount
*/
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GstMemory *
gst_memory_ref (GstMemory * mem)
{
g_return_val_if_fail (mem != NULL, NULL);
g_atomic_int_inc (&mem->refcount);
return mem;
}
/**
* gst_memory_unref:
* @mem: a #GstMemory
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*
* Decreases the refcount of @mem. When the refcount reaches 0, the free
* function of @mem will be called.
*/
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void
gst_memory_unref (GstMemory * mem)
{
g_return_if_fail (mem != NULL);
g_return_if_fail (mem->allocator != NULL);
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if (g_atomic_int_dec_and_test (&mem->refcount))
mem->allocator->info.free (mem);
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}
/**
* gst_memory_get_sizes:
* @mem: a #GstMemory
* @offset: pointer to offset
* @maxsize: pointer to maxsize
*
* Get the current @size, @offset and @maxsize of @mem.
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*
* Returns: the current sizes 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.
*/
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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mem->offset += offset;
mem->size = size;
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}
/**
* gst_memory_is_writable:
* @mem: a #GstMemory
*
* Check if @mem is writable.
*
* Returns: %TRUE is @mem is writable.
*/
gboolean
gst_memory_is_writable (GstMemory * mem)
{
g_return_val_if_fail (mem != NULL, FALSE);
return (mem->refcount == 1) &&
((mem->parent == NULL) || (mem->parent->refcount == 1)) &&
((mem->flags & GST_MEMORY_FLAG_READONLY) == 0);
}
static gboolean
gst_memory_lock (GstMemory * mem, GstMapFlags flags)
{
gint access_mode, state, newstate;
access_mode = flags & 3;
do {
state = g_atomic_int_get (&mem->state);
if (state == 0) {
/* nothing mapped, set access_mode and refcount */
newstate = 4 | access_mode;
} else {
/* access_mode must match */
if ((state & access_mode) != access_mode)
goto lock_failed;
/* increase refcount */
newstate = state + 4;
}
} while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
return TRUE;
lock_failed:
{
GST_DEBUG ("lock failed %p: state %d, access_mode %d", mem, state,
access_mode);
return FALSE;
}
}
static void
gst_memory_unlock (GstMemory * mem)
{
gint state, newstate;
do {
state = g_atomic_int_get (&mem->state);
/* decrease the refcount */
newstate = state - 4;
/* last refcount, unset access_mode */
if (newstate < 4)
newstate = 0;
} while (!g_atomic_int_compare_and_exchange (&mem->state, state, newstate));
}
/**
* 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): 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);
if (result == NULL)
goto cannot_copy;
if (!gst_memory_map (result, info, flags))
goto cannot_map;
}
return result;
/* ERRORS */
cannot_copy:
{
GST_DEBUG ("cannot copy memory %p", mem);
return NULL;
}
cannot_map:
{
GST_DEBUG ("cannot map memory %p with flags %d", mem, flags);
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 remains valid for as long as @mem is alive 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, flags))
goto lock_failed;
info->data = mem->allocator->info.map (mem, mem->maxsize, flags);
if (G_UNLIKELY (info->data == NULL))
goto error;
info->memory = mem;
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info->flags = flags;
info->size = mem->size;
info->maxsize = mem->maxsize - mem->offset;
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info->data = info->data + mem->offset;
return TRUE;
/* ERRORS */
lock_failed:
{
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GST_DEBUG ("mem %p: lock %d failed", mem, flags);
return FALSE;
}
error:
{
/* something went wrong, restore the orginal state again */
GST_ERROR ("mem %p: map failed", mem);
gst_memory_unlock (mem);
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);
/* there must be a ref */
g_return_if_fail (g_atomic_int_get (&mem->state) >= 4);
mem->allocator->info.unmap (mem);
gst_memory_unlock (mem);
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}
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/**
* gst_memory_copy:
* @mem: a #GstMemory
* @offset: an offset to copy
* @size: size to copy or -1 to copy all bytes from offset
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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 all bytes
* from @offset.
*
* 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);
g_return_val_if_fail (gst_memory_lock (mem, GST_MAP_READ), NULL);
copy = mem->allocator->info.copy (mem, offset, size);
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gst_memory_unlock (mem);
return copy;
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}
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/**
* gst_memory_share:
* @mem: a #GstMemory
* @offset: an offset to share
* @size: size to share or -1 to share bytes from offset
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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 not-writable. @size can be set to -1 to return a share
* all bytes from @offset.
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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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{
g_return_val_if_fail (mem != NULL, NULL);
return mem->allocator->info.share (mem, offset, size);
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}
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/**
* gst_memory_is_span:
* @mem1: a #GstMemory
* @mem2: a #GstMemory
* @offset: a pointer to a result offset
*
* 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->info.is_span (mem1, mem2, offset))
return FALSE;
return TRUE;
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}
/**
* gst_allocator_register:
* @name: the name of the allocator
* @info: #GstMemoryInfo
*
* Registers the memory allocator with @name and implementation functions
* @info.
*
* All functions in @info are mandatory exept the copy and is_span
* functions, which will have a default implementation when left NULL.
*
* The user_data field in @info will be passed to all calls of the alloc
* function.
*
* Returns: a new #GstAllocator.
*/
const GstAllocator *
gst_allocator_register (const gchar * name, const GstMemoryInfo * info)
{
GstAllocator *allocator;
#define INSTALL_FALLBACK(_t) \
if (allocator->info._t == NULL) allocator->info._t = _fallback_ ##_t;
g_return_val_if_fail (name != NULL, NULL);
g_return_val_if_fail (info != NULL, NULL);
g_return_val_if_fail (info->alloc != NULL, NULL);
g_return_val_if_fail (info->map != NULL, NULL);
g_return_val_if_fail (info->unmap != NULL, NULL);
g_return_val_if_fail (info->free != NULL, NULL);
g_return_val_if_fail (info->share != NULL, NULL);
allocator = g_slice_new (GstAllocator);
allocator->name = g_quark_from_string (name);
allocator->info = *info;
INSTALL_FALLBACK (copy);
INSTALL_FALLBACK (is_span);
#undef INSTALL_FALLBACK
GST_DEBUG ("registering allocator \"%s\"", name);
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g_rw_lock_writer_lock (&lock);
g_hash_table_insert (allocators, (gpointer) name, (gpointer) allocator);
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g_rw_lock_writer_unlock (&lock);
return allocator;
}
/**
* gst_allocator_find:
* @name: the name of the allocator
*
* Find a previously registered allocator with @name. When @name is NULL, the
* default allocator will be returned.
*
* Returns: a #GstAllocator or NULL when the allocator with @name was not
* registered.
*/
const GstAllocator *
gst_allocator_find (const gchar * name)
{
const GstAllocator *allocator;
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g_rw_lock_reader_lock (&lock);
if (name) {
allocator = g_hash_table_lookup (allocators, (gconstpointer) name);
} else {
allocator = _default_allocator;
}
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g_rw_lock_reader_unlock (&lock);
return allocator;
}
/**
* gst_allocator_set_default:
* @allocator: a #GstAllocator
*
* Set the default allocator.
*/
void
gst_allocator_set_default (const GstAllocator * allocator)
{
g_return_if_fail (allocator != NULL);
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g_rw_lock_writer_lock (&lock);
_default_allocator = allocator;
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g_rw_lock_writer_unlock (&lock);
}
/**
* gst_allocator_alloc:
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* @allocator: (transfer none) (allow-none): a #GstAllocator to use
* @maxsize: allocated size of @data
* @align: alignment for the data
*
* Use @allocator to allocate a new memory block with memory that is at least
* @maxsize big and has the given alignment.
*
* When @allocator is NULL, the default allocator will be used.
*
* @align is given as a bitmask so that @align + 1 equals the amount of bytes to
* align to. For example, to align to 8 bytes, use an alignment of 7.
*
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* Returns: (transfer full): a new #GstMemory.
*/
GstMemory *
gst_allocator_alloc (const GstAllocator * allocator, gsize maxsize, gsize align)
{
g_return_val_if_fail (((align + 1) & align) == 0, NULL);
if (allocator == NULL)
allocator = _default_allocator;
return allocator->info.alloc (allocator, maxsize, align,
allocator->info.user_data);
}