Global defines and functions

Overview

Global defines and functions. More…

// typedefs

typedef struct _snd_async_handler snd_async_handler_t;
typedef void (*snd_async_callback_t)(snd_async_handler_t *handler);
typedef struct timeval snd_timestamp_t;
typedef struct timespec snd_htimestamp_t;

// global functions

const char*
snd_asoundlib_version(void);

void*
snd_dlopen(
    const char* file,
    int mode
);

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

int
snd_dlclose(void* handle);

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

int
snd_async_del_handler(snd_async_handler_t* handler);

int
snd_async_handler_get_fd(snd_async_handler_t* handler);

int
snd_async_handler_get_signo(snd_async_handler_t* handler);

void*
snd_async_handler_get_callback_private(snd_async_handler_t* handler);

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
);

// macros

#define SND_DLSYM_BUILD_VERSION( \
    name, \
    version \
)

#define SND_DLSYM_VERSION(version)

#define __SND_DLSYM_VERSION( \
    name, \
    version \
)

#define __STRING(x)

#define __snd_alloca( \
    ptr, \
    type \
)

Detailed Documentation

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

Typedefs

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.

typedef void (*snd_async_callback_t)(snd_async_handler_t *handler)

Async notification callback.

See the snd_async_add_handler function for details.

typedef struct timeval snd_timestamp_t

Timestamp

typedef struct timespec snd_htimestamp_t

Hi-res timestamp

Global Functions

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.

void*
snd_dlopen(
    const char* file,
    int mode
)

Opens a dynamic library - ALSA wrapper for dlopen.

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

Parameters:

name	name of the library, similar to `dlopen`.
mode	mode flags, similar to `dlopen`.

Returns:

Library handle if successful, otherwise NULL.

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

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

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.

Parameters:

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

int
snd_dlclose(void* handle)

Closes a dynamic library - ALSA wrapper for dlclose.

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

Parameters:

handle

Library handle, similar to dlclose.

Returns:

Zero if successful, otherwise an error code.

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

Registers an async handler.

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.

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.

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.

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.

int
snd_async_handler_get_signo(snd_async_handler_t* handler)

Returns the signal number assigned to an async handler.

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

Parameters:

handler

Handle to an async handler.

Returns:

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

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.

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

Get the full file name.

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

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

Macros

#define SND_DLSYM_BUILD_VERSION( \
    name, \
    version \
)

Appends the build version to the name of a versioned dynamic symbol.

#define SND_DLSYM_VERSION(version)

Returns the version of a dynamic symbol as a string.

#define __SND_DLSYM_VERSION( \
    name, \
    version \
)

Helper macro for SND_DLSYM_BUILD_VERSION.

#define __STRING(x)

Return ‘x’ argument as string.

#define __snd_alloca( \
    ptr, \
    type \
)

alloca helper macro.