World of Might and Magic  0.2.0
Open reimplementation of Might and Magic 6 7 8 game engine
Файлы | Классы | Определения типов | Функции
AVBuffer
libavutil » Data Structures
+ Граф связей класса AVBuffer:

Файлы

файл  buffer.h
 

Классы

struct  AVBufferRef
 

Определения типов

typedef struct AVBuffer AVBuffer
 
typedef struct AVBufferRef AVBufferRef
 

Функции

AVBufferRef * av_buffer_alloc (int size)
 
AVBufferRef * av_buffer_allocz (int size)
 
AVBufferRef * av_buffer_create (uint8_t *data, int size, void(*free)(void *opaque, uint8_t *data), void *opaque, int flags)
 
void av_buffer_default_free (void *opaque, uint8_t *data)
 
AVBufferRef * av_buffer_ref (AVBufferRef *buf)
 
void av_buffer_unref (AVBufferRef **buf)
 
int av_buffer_is_writable (const AVBufferRef *buf)
 
void * av_buffer_get_opaque (const AVBufferRef *buf)
 
int av_buffer_get_ref_count (const AVBufferRef *buf)
 
int av_buffer_make_writable (AVBufferRef **buf)
 
int av_buffer_realloc (AVBufferRef **buf, int size)
 

Подробное описание

AVBuffer is an API for reference-counted data buffers.

There are two core objects in this API – AVBuffer and AVBufferRef. AVBuffer represents the data buffer itself; it is opaque and not meant to be accessed by the caller directly, but only through AVBufferRef. However, the caller may e.g. compare two AVBuffer pointers to check whether two different references are describing the same data buffer. AVBufferRef represents a single reference to an AVBuffer and it is the object that may be manipulated by the caller directly.

There are two functions provided for creating a new AVBuffer with a single reference – av_buffer_alloc() to just allocate a new buffer, and av_buffer_create() to wrap an existing array in an AVBuffer. From an existing reference, additional references may be created with av_buffer_ref(). Use av_buffer_unref() to free a reference (this will automatically free the data once all the references are freed).

The convention throughout this API and the rest of FFmpeg is such that the buffer is considered writable if there exists only one reference to it (and it has not been marked as read-only). The av_buffer_is_writable() function is provided to check whether this is true and av_buffer_make_writable() will automatically create a new writable buffer when necessary. Of course nothing prevents the calling code from violating this convention, however that is safe only when all the existing references are under its control.

Заметки
Referencing and unreferencing the buffers is thread-safe and thus may be done from multiple threads simultaneously without any need for additional locking.
Two different references to the same buffer can point to different parts of the buffer (i.e. their AVBufferRef.data will not be equal).

Типы

◆ AVBuffer

typedef struct AVBuffer AVBuffer

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

A reference counted buffer type. It is opaque and is meant to be used through references (AVBufferRef).

См. определение в файле buffer.h строка 73

◆ AVBufferRef

typedef struct AVBufferRef AVBufferRef

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

A reference to a data buffer.

The size of this struct is not a part of the public ABI and it is not meant to be allocated directly.

Функции

◆ av_buffer_alloc()

AVBufferRef* av_buffer_alloc ( int  size)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Allocate an AVBuffer of the given size using av_malloc().

Возвращает
an AVBufferRef of given size or NULL when out of memory

◆ av_buffer_allocz()

AVBufferRef* av_buffer_allocz ( int  size)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Same as av_buffer_alloc(), except the returned buffer will be initialized to zero.

◆ av_buffer_create()

AVBufferRef* av_buffer_create ( uint8_t *  data,
int  size,
void(*)(void *opaque, uint8_t *data)  free,
void *  opaque,
int  flags 
)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Create an AVBuffer from an existing array.

If this function is successful, data is owned by the AVBuffer. The caller may only access data through the returned AVBufferRef and references derived from it. If this function fails, data is left untouched.

Аргументы
datadata array
sizesize of data in bytes
freea callback for freeing this buffer's data
opaqueparameter to be got for processing or passed to free
flagsa combination of AV_BUFFER_FLAG_*
Возвращает
an AVBufferRef referring to data on success, NULL on failure.

◆ av_buffer_default_free()

void av_buffer_default_free ( void *  opaque,
uint8_t *  data 
)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Default free callback, which calls av_free() on the buffer data. This function is meant to be passed to av_buffer_create(), not called directly.

◆ av_buffer_ref()

AVBufferRef* av_buffer_ref ( AVBufferRef *  buf)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Create a new reference to an AVBuffer.

Возвращает
a new AVBufferRef referring to the same AVBuffer as buf or NULL on failure.

◆ av_buffer_unref()

void av_buffer_unref ( AVBufferRef **  buf)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Free a given reference and automatically free the buffer if there are no more references to it.

Аргументы
bufthe reference to be freed. The pointer is set to NULL on return.

◆ av_buffer_is_writable()

int av_buffer_is_writable ( const AVBufferRef *  buf)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Возвращает
1 if the caller may write to the data referred to by buf (which is true if and only if buf is the only reference to the underlying AVBuffer). Return 0 otherwise. A positive answer is valid until av_buffer_ref() is called on buf.

◆ av_buffer_get_opaque()

void* av_buffer_get_opaque ( const AVBufferRef *  buf)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Возвращает
the opaque parameter set by av_buffer_create.

◆ av_buffer_get_ref_count()

int av_buffer_get_ref_count ( const AVBufferRef *  buf)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

◆ av_buffer_make_writable()

int av_buffer_make_writable ( AVBufferRef **  buf)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Create a writable reference from a given buffer reference, avoiding data copy if possible.

Аргументы
bufbuffer reference to make writable. On success, buf is either left untouched, or it is unreferenced and a new writable AVBufferRef is written in its place. On failure, buf is left untouched.
Возвращает
0 on success, a negative AVERROR on failure.

◆ av_buffer_realloc()

int av_buffer_realloc ( AVBufferRef **  buf,
int  size 
)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/buffer.h>

Reallocate a given buffer.

Аргументы
bufa buffer reference to reallocate. On success, buf will be unreferenced and a new reference with the required size will be written in its place. On failure buf will be left untouched. *buf may be NULL, then a new buffer is allocated.
sizerequired new buffer size.
Возвращает
0 on success, a negative AVERROR on failure.
Заметки
the buffer is actually reallocated with av_realloc() only if it was initially allocated through av_buffer_realloc(NULL) and there is only one reference to it (i.e. the one passed to this function). In all other cases a new buffer is allocated and the data is copied.