Global defines and functions

Macros
#define	__SND_DLSYM_VERSION(name, version)
	Helper macro for SND_DLSYM_BUILD_VERSION.
#define	SND_DLSYM_BUILD_VERSION(name, version)
	Appends the build version to the name of a versioned dynamic symbol.
#define	__STRING(x)   #x
	Return 'x' argument as string.
#define	SND_DLSYM_VERSION(version)   __STRING(version)
	Returns the version of a dynamic symbol as a string.
#define	__snd_alloca(ptr, type)   do { *ptr = (type##_t *) alloca(type##_sizeof()); memset(*ptr, 0, type##_sizeof()); } while (0)
	alloca helper macro.

Typedefs
typedef struct _snd_async_handler	snd_async_handler_t
	Internal structure for an async notification client handler. More...
typedef void(*	snd_async_callback_t) (snd_async_handler_t *handler)
	Async notification callback. More...
typedef struct timeval	snd_timestamp_t
typedef struct timespec	snd_htimestamp_t

Functions
const char *	snd_asoundlib_version (void)
	Returns the ALSA sound library version in ASCII format. More...
int	snd_dlpath (char *path, size_t path_len, const char *name)
	Compose the dynamic path. More...
void *	snd_dlopen (const char *file, int mode, char *errbuf, size_t errbuflen)
	Opens a dynamic library - ALSA wrapper for dlopen. More...
void *	snd_dlsym (void *handle, const char *name, const char *version)
	Resolves a symbol from a dynamic library - ALSA wrapper for dlsym. More...
int	snd_dlclose (void *handle)
	Closes a dynamic library - ALSA wrapper for dlclose. More...
int	snd_async_add_handler (snd_async_handler_t **handler, int fd, snd_async_callback_t callback, void *private_data)
	Registers an async handler. More...
int	snd_async_del_handler (snd_async_handler_t *handler)
	Deletes an async handler. More...
int	snd_async_handler_get_fd (snd_async_handler_t *handler)
	Returns the file descriptor assigned to an async handler. More...
int	snd_async_handler_get_signo (snd_async_handler_t *handler)
	Returns the signal number assigned to an async handler. More...
void *	snd_async_handler_get_callback_private (snd_async_handler_t *handler)
	Returns the private data assigned to an async handler. More...
struct snd_shm_area *	snd_shm_area_create (int shmid, void *ptr)
struct snd_shm_area *	snd_shm_area_share (struct snd_shm_area *area)
int	snd_shm_area_destroy (struct snd_shm_area *area)
int	snd_user_file (const char *file, char **result)
	Get the full file name. More...

Detailed Description

Global defines and functions.

The ALSA library implementation uses these macros and functions. Most applications probably do not need them.

Typedef Documentation

snd_async_callback_t

typedef void(* snd_async_callback_t) (snd_async_handler_t *handler)

Async notification callback.

See the snd_async_add_handler function for details.

snd_async_handler_t

typedef struct _snd_async_handler snd_async_handler_t

Internal structure for an async notification client handler.

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

snd_htimestamp_t

typedef struct timespec snd_htimestamp_t

Hi-res timestamp

snd_timestamp_t

typedef struct timeval snd_timestamp_t

Timestamp

Function Documentation

snd_asoundlib_version()

const char * snd_asoundlib_version

(

void

)

Returns the ALSA sound library version in ASCII format.

Returns

The ASCII description of the used ALSA sound library.

snd_async_add_handler()

int snd_async_add_handler	(	snd_async_handler_t **	handler,
		int	fd,
		snd_async_callback_t	callback,
		void *	private_data
	)

Registers an async handler.

Parameters

handler	The function puts the pointer to the new async handler object at the address specified by handler.
fd	The file descriptor to be associated with the callback.
callback	The async callback function.
private_data	Private data for the async callback function.

Returns

Zero if successful, otherwise a negative error code.

This function associates the callback function with the given file, and saves this association in a snd_async_handler_t object.

Whenever the SIGIO signal is raised for the file fd, the callback function will be called with its parameter pointing to the async handler object returned by this function.

The ALSA sigaction handler for the SIGIO signal automatically multiplexes the notifications to the registered async callbacks. However, the application is responsible for instructing the device driver to generate the SIGIO signal.

The SIGIO signal may have been replaced with another signal, see snd_async_handler_get_signo.

When the async handler isn't needed anymore, you must delete it with snd_async_del_handler.

See also

snd_async_add_pcm_handler, snd_async_add_ctl_handler

snd_async_del_handler()

int snd_async_del_handler

(

snd_async_handler_t *

handler

)

Deletes an async handler.

Parameters

handler

Handle of the async handler to delete.

Returns

Zero if successful, otherwise a negative error code.

snd_async_handler_get_callback_private()

void * snd_async_handler_get_callback_private

(

snd_async_handler_t *

handler

)

Returns the private data assigned to an async handler.

Parameters

handler

Handle to an async handler.

Returns

The private_data value registered with the async handler.

Examples

/test/pcm.c, and /test/timer.c.

snd_async_handler_get_fd()

int snd_async_handler_get_fd

(

snd_async_handler_t *

handler

)

Returns the file descriptor assigned to an async handler.

Parameters

handler

Handle to an async handler.

Returns

The file descriptor if successful, otherwise a negative error code.

snd_async_handler_get_signo()

int snd_async_handler_get_signo

(

snd_async_handler_t *

handler

)

Returns the signal number assigned to an async handler.

Parameters

handler

Handle to an async handler.

Returns

The signal number if successful, otherwise a negative error code.

The signal number for async handlers usually is SIGIO, but wizards can redefine it to a realtime signal when compiling the ALSA library.

snd_dlclose()

int snd_dlclose

(

void *

handle

)

Closes a dynamic library - ALSA wrapper for dlclose.

Parameters

handle

Library handle, similar to dlclose.

Returns

Zero if successful, otherwise an error code.

This function can emulate dynamic linking for the static build of the alsa-lib library.

snd_dlopen()

void * snd_dlopen	(	const char *	name,
		int	mode,
		char *	errbuf,
		size_t	errbuflen
	)

Opens a dynamic library - ALSA wrapper for dlopen.

Parameters

name	name of the library, similar to dlopen.
mode	mode flags, similar to dlopen.
errbuf	a string buffer for the error message dlerror.
errbuflen	a length of the string buffer for the error message.

Returns

Library handle if successful, otherwise NULL.

This function can emulate dynamic linking for the static build of the alsa-lib library. In that case, name is set to NULL.

snd_dlpath()

int snd_dlpath	(	char *	path,
		size_t	path_len,
		const char *	name
	)

Compose the dynamic path.

Parameters

path	Returned path (string)
path_len	Returned path max size (with trailing zero)
name	Plugin name (relative)

Returns

Zero on success, otherwise a negative error code

snd_dlsym()

void * snd_dlsym	(	void *	handle,
		const char *	name,
		const char *	version
	)

Resolves a symbol from a dynamic library - ALSA wrapper for dlsym.

Parameters

handle	Library handle, similar to dlsym.
name	Symbol name.
version	Version of the symbol.

This function can emulate dynamic linking for the static build of the alsa-lib library.

This special version of the dlsym function checks also the version of the symbol. A versioned symbol should be defined using the SND_DLSYM_BUILD_VERSION macro.

snd_user_file()

int snd_user_file	(	const char *	file,
		char **	result
	)

Get the full file name.

Parameters

file	The file name string to parse
result	The pointer to store the resultant file name

Returns

0 if successful, or a negative error code

Parses the given file name with POSIX-Shell-like expansion and stores the first matchine one. The returned string is strdup'ed.