AVFifo

A generic FIFO API. More...

Files
file	fifo.h
	A generic FIFO API.

Macros
#define	AV_FIFO_FLAG_AUTO_GROW   (1 << 0)
	Automatically resize the FIFO on writes, so that the data fits.

Typedefs
typedef struct AVFifo	AVFifo
typedef int	AVFifoCB(void *opaque, void *buf, size_t *nb_elems)
	Callback for writing or reading from a FIFO, passed to (and invoked from) the av_fifo_*_cb() functions.

Functions
AVFifo *	av_fifo_alloc2 (size_t elems, size_t elem_size, unsigned int flags)
	Allocate and initialize an AVFifo with a given element size.
size_t	av_fifo_elem_size (const AVFifo *f)
void	av_fifo_auto_grow_limit (AVFifo *f, size_t max_elems)
	Set the maximum size (in elements) to which the FIFO can be resized automatically.
size_t	av_fifo_can_read (const AVFifo *f)
size_t	av_fifo_can_write (const AVFifo *f)
int	av_fifo_grow2 (AVFifo *f, size_t inc)
	Enlarge an AVFifo.
int	av_fifo_write (AVFifo *f, const void *buf, size_t nb_elems)
	Write data into a FIFO.
int	av_fifo_write_from_cb (AVFifo *f, AVFifoCB read_cb, void *opaque, size_t *nb_elems)
	Write data from a user-provided callback into a FIFO.
int	av_fifo_read (AVFifo *f, void *buf, size_t nb_elems)
	Read data from a FIFO.
int	av_fifo_read_to_cb (AVFifo *f, AVFifoCB write_cb, void *opaque, size_t *nb_elems)
	Feed data from a FIFO into a user-provided callback.
int	av_fifo_peek (const AVFifo *f, void *buf, size_t nb_elems, size_t offset)
	Read data from a FIFO without modifying FIFO state.
int	av_fifo_peek_to_cb (const AVFifo *f, AVFifoCB write_cb, void *opaque, size_t *nb_elems, size_t offset)
	Feed data from a FIFO into a user-provided callback.
void	av_fifo_drain2 (AVFifo *f, size_t size)
	Discard the specified amount of data from an AVFifo.
void	av_fifo_reset2 (AVFifo *f)
void	av_fifo_freep2 (AVFifo **f)
	Free an AVFifo and reset pointer to NULL.

Detailed Description

A generic FIFO API.

Macro Definition Documentation

AV_FIFO_FLAG_AUTO_GROW

#define AV_FIFO_FLAG_AUTO_GROW   (1 << 0)

Automatically resize the FIFO on writes, so that the data fits.

This automatic resizing happens up to a limit that can be modified with av_fifo_auto_grow_limit().

Definition at line 63 of file fifo.h.

Typedef Documentation

AVFifo

typedef struct AVFifo AVFifo

Definition at line 38 of file fifo.h.

AVFifoCB

typedef int AVFifoCB(void *opaque, void *buf, size_t *nb_elems)

Callback for writing or reading from a FIFO, passed to (and invoked from) the av_fifo_*_cb() functions.

It may be invoked multiple times from a single av_fifo_*_cb() call and may process less data than the maximum size indicated by nb_elems.

Parameters

opaque	the opaque pointer provided to the av_fifo_*_cb() function
buf	the buffer for reading or writing the data, depending on which av_fifo_*_cb function is called
nb_elems	On entry contains the maximum number of elements that can be read from / written into buf. On success, the callback should update it to contain the number of elements actually written.

Returns

0 on success, a negative error code on failure (will be returned from the invoking av_fifo_*_cb() function)

Definition at line 56 of file fifo.h.

Function Documentation

av_fifo_alloc2()

AVFifo * av_fifo_alloc2	(	size_t	elems,
		size_t	elem_size,
		unsigned int	flags )

Allocate and initialize an AVFifo with a given element size.

Parameters

elems	initial number of elements that can be stored in the FIFO
elem_size	Size in bytes of a single element. Further operations on the returned FIFO will implicitly use this element size.
flags	a combination of AV_FIFO_FLAG_*

Returns

newly-allocated AVFifo on success, a negative error code on failure

av_fifo_elem_size()

size_t av_fifo_elem_size

(

const AVFifo *

f

)

Returns

Element size for FIFO operations. This element size is set at FIFO allocation and remains constant during its lifetime

av_fifo_auto_grow_limit()

void av_fifo_auto_grow_limit	(	AVFifo *	f,
		size_t	max_elems )

Set the maximum size (in elements) to which the FIFO can be resized automatically.

Has no effect unless AV_FIFO_FLAG_AUTO_GROW is used.

av_fifo_can_read()

size_t av_fifo_can_read

(

const AVFifo *

f

)

Returns

number of elements available for reading from the given FIFO.

av_fifo_can_write()

size_t av_fifo_can_write

(

const AVFifo *

f

)

Returns

Number of elements that can be written into the given FIFO without growing it.

In other words, this number of elements or less is guaranteed to fit into the FIFO. More data may be written when the AV_FIFO_FLAG_AUTO_GROW flag was specified at FIFO creation, but this may involve memory allocation, which can fail.

av_fifo_grow2()

int av_fifo_grow2	(	AVFifo *	f,
		size_t	inc )

Enlarge an AVFifo.

On success, the FIFO will be large enough to hold exactly inc + av_fifo_can_read() + av_fifo_can_write() elements. In case of failure, the old FIFO is kept unchanged.

Parameters

f	AVFifo to resize
inc	number of elements to allocate for, in addition to the current allocated size

Returns

a non-negative number on success, a negative error code on failure

av_fifo_write()

int av_fifo_write	(	AVFifo *	f,
		const void *	buf,
		size_t	nb_elems )

Write data into a FIFO.

In case nb_elems > av_fifo_can_write(f) and the AV_FIFO_FLAG_AUTO_GROW flag was not specified at FIFO creation, nothing is written and an error is returned.

Calling function is guaranteed to succeed if nb_elems <= av_fifo_can_write(f).

Parameters

f	the FIFO buffer
buf	Data to be written. nb_elems * av_fifo_elem_size(f) bytes will be read from buf on success.
nb_elems	number of elements to write into FIFO

Returns

a non-negative number on success, a negative error code on failure

av_fifo_write_from_cb()

int av_fifo_write_from_cb	(	AVFifo *	f,
		AVFifoCB	read_cb,
		void *	opaque,
		size_t *	nb_elems )

Write data from a user-provided callback into a FIFO.

Parameters

f	the FIFO buffer
read_cb	Callback supplying the data to the FIFO. May be called multiple times.
opaque	opaque user data to be provided to read_cb
nb_elems	Should point to the maximum number of elements that can be written. Will be updated to contain the number of elements actually written.

Returns

non-negative number on success, a negative error code on failure

av_fifo_read()

int av_fifo_read	(	AVFifo *	f,
		void *	buf,
		size_t	nb_elems )

Read data from a FIFO.

In case nb_elems > av_fifo_can_read(f), nothing is read and an error is returned.

Parameters

f	the FIFO buffer
buf	Buffer to store the data. nb_elems * av_fifo_elem_size(f) bytes will be written into buf on success.
nb_elems	number of elements to read from FIFO

Returns

a non-negative number on success, a negative error code on failure

av_fifo_read_to_cb()

int av_fifo_read_to_cb	(	AVFifo *	f,
		AVFifoCB	write_cb,
		void *	opaque,
		size_t *	nb_elems )

Feed data from a FIFO into a user-provided callback.

Parameters

f	the FIFO buffer
write_cb	Callback the data will be supplied to. May be called multiple times.
opaque	opaque user data to be provided to write_cb
nb_elems	Should point to the maximum number of elements that can be read. Will be updated to contain the total number of elements actually sent to the callback.

Returns

non-negative number on success, a negative error code on failure

av_fifo_peek()

int av_fifo_peek	(	const AVFifo *	f,
		void *	buf,
		size_t	nb_elems,
		size_t	offset )

Read data from a FIFO without modifying FIFO state.

Returns an error if an attempt is made to peek to nonexistent elements (i.e. if offset + nb_elems is larger than av_fifo_can_read(f)).

Parameters

f	the FIFO buffer
buf	Buffer to store the data. nb_elems * av_fifo_elem_size(f) bytes will be written into buf.
nb_elems	number of elements to read from FIFO
offset	number of initial elements to skip.

Returns

a non-negative number on success, a negative error code on failure

av_fifo_peek_to_cb()

int av_fifo_peek_to_cb	(	const AVFifo *	f,
		AVFifoCB	write_cb,
		void *	opaque,
		size_t *	nb_elems,
		size_t	offset )

Feed data from a FIFO into a user-provided callback.

Parameters

f	the FIFO buffer
write_cb	Callback the data will be supplied to. May be called multiple times.
opaque	opaque user data to be provided to write_cb
nb_elems	Should point to the maximum number of elements that can be read. Will be updated to contain the total number of elements actually sent to the callback.
offset	number of initial elements to skip; offset + *nb_elems must not be larger than av_fifo_can_read(f).

Returns

a non-negative number on success, a negative error code on failure

av_fifo_drain2()

void av_fifo_drain2	(	AVFifo *	f,
		size_t	size )

Discard the specified amount of data from an AVFifo.

Parameters

size	number of elements to discard, MUST NOT be larger than av_fifo_can_read(f)

av_fifo_reset2()

void av_fifo_reset2

(

AVFifo *

f

)

av_fifo_freep2()

void av_fifo_freep2

(

AVFifo **

f

)

Free an AVFifo and reset pointer to NULL.

Parameters

f	Pointer to an AVFifo to free. *f == NULL is allowed.