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GstAllocator

GstAllocator — allocate memory blocks

Object Hierarchy

    GBoxed
    ╰── GstAllocationParams
    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstAllocator

Includes

#include <gst/gst.h>

Description

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(). gst_allocator_set_default() can be used to change the default allocator.

New memory can be created with gst_memory_new_wrapped() that wraps the memory allocated elsewhere.

Functions

gst_allocator_find ()

GstAllocator *
gst_allocator_find (const gchar *name);

Find a previously registered allocator with name . When name is NULL, the default allocator will be returned.

Parameters

name

the name of the allocator.

[allow-none]

Returns

a GstAllocator or NULL when the allocator with name was not registered. Use gst_object_unref() to release the allocator after usage.

[transfer full][nullable]


gst_allocator_register ()

void
gst_allocator_register (const gchar *name,
                        GstAllocator *allocator);

Registers the memory allocator with name . This function takes ownership of allocator .

Parameters

name

the name of the allocator

 

allocator

GstAllocator.

[transfer full]

gst_allocator_set_default ()

void
gst_allocator_set_default (GstAllocator *allocator);

Set the default allocator. This function takes ownership of allocator .

Parameters

allocator

a GstAllocator.

[transfer full]

gst_allocation_params_init ()

void
gst_allocation_params_init (GstAllocationParams *params);

Initialize params to its default values

Parameters

params

a GstAllocationParams

 

gst_allocation_params_copy ()

GstAllocationParams *
gst_allocation_params_copy (const GstAllocationParams *params);

Create a copy of params .

Free-function: gst_allocation_params_free

Parameters

params

a GstAllocationParams.

[transfer none]

Returns

a new #GstAllocationParams, free with gst_allocation_params_free().

[transfer full]


gst_allocation_params_free ()

void
gst_allocation_params_free (GstAllocationParams *params);

Free params

Parameters

params

a GstAllocationParams.

[in][transfer full]

gst_allocator_alloc ()

GstMemory *
gst_allocator_alloc (GstAllocator *allocator,
                     gsize size,
                     GstAllocationParams *params);

Use allocator to allocate a new memory block with memory that is at least size big.

The optional params can specify the prefix and padding for the memory. If NULL is passed, no flags, no extra prefix/padding and a default alignment is used.

The prefix/padding will be filled with 0 if flags contains GST_MEMORY_FLAG_ZERO_PREFIXED and GST_MEMORY_FLAG_ZERO_PADDED respectively.

When allocator is NULL, the default allocator will be used.

The alignment in params 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.

Parameters

allocator

a GstAllocator to use.

[transfer none][allow-none]

size

size of the visible memory area

 

params

optional parameters.

[transfer none][allow-none]

Returns

a new GstMemory.

[transfer full]


gst_allocator_free ()

void
gst_allocator_free (GstAllocator *allocator,
                    GstMemory *memory);

Free memory that was previously allocated with gst_allocator_alloc().

Parameters

allocator

a GstAllocator to use.

[transfer none]

memory

the memory to free.

[transfer full]

gst_memory_new_wrapped ()

GstMemory *
gst_memory_new_wrapped (GstMemoryFlags flags,
                        gpointer data,
                        gsize maxsize,
                        gsize offset,
                        gsize size,
                        gpointer user_data,
                        GDestroyNotify notify);

Allocate a new memory block that wraps the given data .

The prefix/padding must be filled with 0 if flags contains GST_MEMORY_FLAG_ZERO_PREFIXED and GST_MEMORY_FLAG_ZERO_PADDED respectively.

Parameters

flags

GstMemoryFlags

 

data

data to wrap.

[array length=size][element-type guint8][transfer none]

maxsize

allocated size of data

 

offset

offset in data

 

size

size of valid data

 

user_data

user_data.

[allow-none]

notify

called with user_data when the memory is freed.

[allow-none][scope async][closure user_data]

Returns

a new GstMemory.

[transfer full]

Types and Values

gst_memory_alignment

GST_EXPORT gsize gst_memory_alignment;

The default memory alignment in bytes - 1 an alignment of 7 would be the same as what malloc() guarantees.


GstAllocator

typedef struct {
  GstMemoryMapFunction       mem_map;
  GstMemoryUnmapFunction     mem_unmap;

  GstMemoryCopyFunction      mem_copy;
  GstMemoryShareFunction     mem_share;
  GstMemoryIsSpanFunction    mem_is_span;

  GstMemoryMapFullFunction   mem_map_full;
  GstMemoryUnmapFullFunction mem_unmap_full;
} GstAllocator;

The GstAllocator is used to create new memory.

Members

GstMemoryMapFunction mem_map;

the implementation of the GstMemoryMapFunction

 

GstMemoryUnmapFunction mem_unmap;

the implementation of the GstMemoryUnmapFunction

 

GstMemoryCopyFunction mem_copy;

the implementation of the GstMemoryCopyFunction

 

GstMemoryShareFunction mem_share;

the implementation of the GstMemoryShareFunction

 

GstMemoryIsSpanFunction mem_is_span;

the implementation of the GstMemoryIsSpanFunction

 

GstMemoryMapFullFunction mem_map_full;

the implementation of the GstMemoryMapFullFunction. Will be used instead of mem_map if present. (Since 1.6)

 

GstMemoryUnmapFullFunction mem_unmap_full;

the implementation of the GstMemoryUnmapFullFunction. Will be used instead of mem_unmap if present. (Since 1.6)

 

struct GstAllocatorClass

struct GstAllocatorClass {
  GstObjectClass object_class;

  GstMemory *  (*alloc)      (GstAllocator *allocator, gsize size,
                              GstAllocationParams *params);
  void         (*free)       (GstAllocator *allocator, GstMemory *memory);
};

The GstAllocator is used to create new memory.

Members

GstObjectClass object_class;

Object parent class

 

alloc ()

implementation that acquires memory

 

free ()

implementation that releases memory

 

enum GstAllocatorFlags

Flags for allocators.

Members

GST_ALLOCATOR_FLAG_CUSTOM_ALLOC

The allocator has a custom alloc function.

 

GST_ALLOCATOR_FLAG_LAST

first flag that can be used for custom purposes

 

struct GstAllocationParams

struct GstAllocationParams {
  GstMemoryFlags flags;
  gsize          align;
  gsize          prefix;
  gsize          padding;
};

Parameters to control the allocation of memory

Members

GstMemoryFlags flags;

flags to control allocation

 

gsize align;

the desired alignment of the memory

 

gsize prefix;

the desired prefix

 

gsize padding;

the desired padding

 

GST_ALLOCATOR_SYSMEM

#define GST_ALLOCATOR_SYSMEM   "SystemMemory"

The allocator name for the default system memory allocator

See Also

GstMemory

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