Output Interface

Typedefs
typedef struct _snd_output	snd_output_t
	Internal structure for an output object. More...

Enumerations
enum	snd_output_type_t { SND_OUTPUT_STDIO , SND_OUTPUT_BUFFER }

Functions
int	snd_output_stdio_open (snd_output_t **outputp, const char *file, const char *mode)
	Creates a new output object writing to a file. More...
int	snd_output_stdio_attach (snd_output_t **outputp, FILE *fp, int _close)
	Creates a new output object using an existing stdio FILE pointer. More...
int	snd_output_buffer_open (snd_output_t **outputp)
	Creates a new output object with an auto-extending memory buffer. More...
size_t	snd_output_buffer_string (snd_output_t *output, char **buf)
	Returns the address of the buffer of a SND_OUTPUT_BUFFER output handle. More...
size_t	snd_output_buffer_steal (snd_output_t *output, char **buf)
	Returns the address of the buffer of a SND_OUTPUT_BUFFER output handle. More...
int	snd_output_close (snd_output_t *output)
	Closes an output handle. More...
int	snd_output_printf (snd_output_t *output, const char *format,...)
	Writes formatted output (like fprintf(3)) to an output handle. More...
int	snd_output_vprintf (snd_output_t *output, const char *format, va_list args)
	Writes formatted output (like fprintf(3)) to an output handle. More...
int	snd_output_puts (snd_output_t *output, const char *str)
	Writes a string to an output handle (like fputs(3)). More...
int	snd_output_putc (snd_output_t *output, int c)
	Writes a character to an output handle (like putc(3)). More...
int	snd_output_flush (snd_output_t *output)
	Flushes an output handle (like fflush(3)). More...

Detailed Description

The output functions present an interface similar to the stdio functions on top of different underlying output destinations.

Many PCM debugging functions (snd_pcm_xxx_dump_xxx) use such an output handle to be able to write not only to the screen but also to other destinations, e.g. to files or to memory buffers.

Typedef Documentation

snd_output_t

typedef struct _snd_output snd_output_t

Internal structure for an output object.

The ALSA library uses a pointer to this structure as a handle to an output object. Applications don't access its contents directly.

Enumeration Type Documentation

snd_output_type_t

enum snd_output_type_t

Output type.

Enumerator
SND_OUTPUT_STDIO	Output to a stdio stream.
SND_OUTPUT_BUFFER	Output to a memory buffer.

Function Documentation

snd_output_buffer_open()

int snd_output_buffer_open

(

snd_output_t **

outputp

)

Creates a new output object with an auto-extending memory buffer.

Parameters

outputp

The function puts the pointer to the new output object at the address specified by outputp.

Returns

Zero if successful, otherwise a negative error code.

snd_output_buffer_steal()

size_t snd_output_buffer_steal	(	snd_output_t *	output,
		char **	buf
	)

Returns the address of the buffer of a SND_OUTPUT_BUFFER output handle.

Parameters

output	The output handle.
buf	The functions puts the current address of the buffer at the address specified by buf.

Returns

The current size of valid data in the buffer.

The internal buffer is empty after this call. The caller has the responsibility to clean the buffer using the free() call.

snd_output_buffer_string()

size_t snd_output_buffer_string	(	snd_output_t *	output,
		char **	buf
	)

Returns the address of the buffer of a SND_OUTPUT_BUFFER output handle.

Parameters

output	The output handle.
buf	The functions puts the current address of the buffer at the address specified by buf.

Returns

The current size of valid data in the buffer.

The address of the buffer may become invalid when output functions or snd_output_close are called.

snd_output_close()

int snd_output_close

(

snd_output_t *

output

)

Closes an output handle.

Parameters

output

The output handle to be closed.

Returns

Zero if successful, otherwise a negative error code.

snd_output_flush()

int snd_output_flush

(

snd_output_t *

output

)

Flushes an output handle (like fflush(3)).

Parameters

output

The output handle.

Returns

Zero if successful, otherwise EOF.

If the underlying destination is a stdio stream, this function calls fflush. If the underlying destination is a memory buffer, the write position is reset to the beginning of the buffer. =:-o

snd_output_printf()

int snd_output_printf	(	snd_output_t *	output,
		const char *	format,
			...
	)

Writes formatted output (like fprintf(3)) to an output handle.

Parameters

output	The output handle.
format	Format string in fprintf format.
...	Other fprintf arguments.

Returns

The number of characters written, or a negative error code.

snd_output_putc()

int snd_output_putc	(	snd_output_t *	output,
		int	c
	)

Writes a character to an output handle (like putc(3)).

Parameters

output	The output handle.
c	The character.

Returns

Zero if successful, otherwise a negative error code or EOF.

snd_output_puts()

int snd_output_puts	(	snd_output_t *	output,
		const char *	str
	)

Writes a string to an output handle (like fputs(3)).

Parameters

output	The output handle.
str	Pointer to the string.

Returns

Zero if successful, otherwise a negative error code or EOF.

snd_output_stdio_attach()

int snd_output_stdio_attach	(	snd_output_t **	outputp,
		FILE *	fp,
		int	_close
	)

Creates a new output object using an existing stdio FILE pointer.

Parameters

outputp	The function puts the pointer to the new output object at the address specified by outputp.
fp	The FILE pointer to write to. Characters are written to the file starting at the current file position.
_close	Close flag. Set this to 1 if snd_output_close should close fp by calling fclose.

Returns

Zero if successful, otherwise a negative error code.

Examples

/test/latency.c, and /test/pcm.c.

snd_output_stdio_open()

int snd_output_stdio_open	(	snd_output_t **	outputp,
		const char *	file,
		const char *	mode
	)

Creates a new output object writing to a file.

Parameters

outputp	The function puts the pointer to the new output object at the address specified by outputp.
file	The name of the file to open.
mode	The open mode, like fopen(3).

Returns

Zero if successful, otherwise a negative error code.

snd_output_vprintf()

int snd_output_vprintf	(	snd_output_t *	output,
		const char *	format,
		va_list	args
	)

Writes formatted output (like fprintf(3)) to an output handle.

Parameters

output	The output handle.
format	Format string in fprintf format.
args	Other fprintf arguments.

Returns

The number of characters written, or a negative error code.