Collaboration diagram for MIDI Sequencer:

Modules
	Sequencer Client Interface

	Sequencer Port Interface

	Sequencer Port Subscription

	Sequencer Queue Interface

	Sequencer Event API

	Sequencer Miscellaneous

	Sequencer Event Type Checks

	Sequencer Event Definitions

	Sequencer Middle Level Interface

	Sequencer event <-> MIDI byte stream coder

Macros
#define	SND_SEQ_DLSYM_VERSION _dlsym_seq_001

#define	SND_SEQ_OPEN_OUTPUT 1

#define	SND_SEQ_OPEN_INPUT 2

#define	SND_SEQ_OPEN_DUPLEX (SND_SEQ_OPEN_OUTPUT\|SND_SEQ_OPEN_INPUT)

#define	SND_SEQ_NONBLOCK 0x0001

#define	SND_SEQ_ADDRESS_UNKNOWN 253

#define	SND_SEQ_ADDRESS_SUBSCRIBERS 254

#define	SND_SEQ_ADDRESS_BROADCAST 255

#define	SND_SEQ_CLIENT_SYSTEM 0

#define	snd_seq_system_info_alloca(ptr) __snd_alloca(ptr, snd_seq_system_info)

Typedefs
typedef struct _snd_seq	snd_seq_t

typedef struct _snd_seq_system_info	snd_seq_system_info_t

Enumerations
enum	snd_seq_type_t { SND_SEQ_TYPE_HW , SND_SEQ_TYPE_SHM , SND_SEQ_TYPE_INET }

Functions
int	snd_seq_open (snd_seq_t *handle, const char name, int streams, int mode)
	Open the ALSA sequencer. More...

int	snd_seq_open_lconf (snd_seq_t *handle, const char name, int streams, int mode, snd_config_t *lconf)
	Open the ALSA sequencer using local configuration. More...

const char *	snd_seq_name (snd_seq_t *seq)
	get identifier of sequencer handle More...

snd_seq_type_t	snd_seq_type (snd_seq_t *seq)
	get type of sequencer handle More...

int	snd_seq_close (snd_seq_t *handle)
	Close the sequencer. More...

int	snd_seq_poll_descriptors_count (snd_seq_t *handle, short events)
	Returns the number of poll descriptors. More...

int	snd_seq_poll_descriptors (snd_seq_t handle, struct pollfd pfds, unsigned int space, short events)
	Get poll descriptors. More...

int	snd_seq_poll_descriptors_revents (snd_seq_t seq, struct pollfd pfds, unsigned int nfds, unsigned short *revents)
	get returned events from poll descriptors More...

int	snd_seq_nonblock (snd_seq_t *handle, int nonblock)
	Set nonblock mode. More...

int	snd_seq_client_id (snd_seq_t *handle)
	Get the client id. More...

size_t	snd_seq_get_output_buffer_size (snd_seq_t *handle)
	Return the size of output buffer. More...

size_t	snd_seq_get_input_buffer_size (snd_seq_t *handle)
	Return the size of input buffer. More...

int	snd_seq_set_output_buffer_size (snd_seq_t *handle, size_t size)
	Change the size of output buffer. More...

int	snd_seq_set_input_buffer_size (snd_seq_t *handle, size_t size)
	Resize the input buffer. More...

size_t	snd_seq_system_info_sizeof (void)
	Get size of snd_seq_system_info_t. More...

int	snd_seq_system_info_malloc (snd_seq_system_info_t **ptr)
	Allocate an empty snd_seq_system_info_t using standard malloc. More...

void	snd_seq_system_info_free (snd_seq_system_info_t *ptr)
	Frees a previously allocated snd_seq_system_info_t. More...

void	snd_seq_system_info_copy (snd_seq_system_info_t dst, const snd_seq_system_info_t src)
	Copy one snd_seq_system_info_t to another. More...

int	snd_seq_system_info_get_queues (const snd_seq_system_info_t *info)
	Get maximum number of queues. More...

int	snd_seq_system_info_get_clients (const snd_seq_system_info_t *info)
	Get maximum number of clients. More...

int	snd_seq_system_info_get_ports (const snd_seq_system_info_t *info)
	Get maximum number of ports. More...

int	snd_seq_system_info_get_channels (const snd_seq_system_info_t *info)
	Get maximum number of channels. More...

int	snd_seq_system_info_get_cur_clients (const snd_seq_system_info_t *info)
	Get the current number of clients. More...

int	snd_seq_system_info_get_cur_queues (const snd_seq_system_info_t *info)
	Get the current number of queues. More...

int	snd_seq_system_info (snd_seq_t handle, snd_seq_system_info_t info)
	obtain the sequencer system information More...

Detailed Description

MIDI Sequencer Interface. See Sequencer interface page for more details.

Macro Definition Documentation

◆ SND_SEQ_ADDRESS_BROADCAST

#define SND_SEQ_ADDRESS_BROADCAST 255

send event to all queues/clients/ports/channels

◆ SND_SEQ_ADDRESS_SUBSCRIBERS

#define SND_SEQ_ADDRESS_SUBSCRIBERS 254

send event to all subscribed ports

◆ SND_SEQ_ADDRESS_UNKNOWN

#define SND_SEQ_ADDRESS_UNKNOWN 253

special client (port) ids unknown source

◆ SND_SEQ_CLIENT_SYSTEM

#define SND_SEQ_CLIENT_SYSTEM 0

known client numbers system client

◆ SND_SEQ_DLSYM_VERSION

#define SND_SEQ_DLSYM_VERSION _dlsym_seq_001

dlsym version for interface entry callback

◆ SND_SEQ_NONBLOCK

#define SND_SEQ_NONBLOCK 0x0001

sequencer opening mode non-blocking mode (flag to open mode)

◆ SND_SEQ_OPEN_DUPLEX

#define SND_SEQ_OPEN_DUPLEX (SND_SEQ_OPEN_OUTPUT|SND_SEQ_OPEN_INPUT)

open for both input and output (read/write)

◆ SND_SEQ_OPEN_INPUT

#define SND_SEQ_OPEN_INPUT 2

open for input (read)

◆ SND_SEQ_OPEN_OUTPUT

#define SND_SEQ_OPEN_OUTPUT 1

sequencer opening stream types open for output (write)

◆ snd_seq_system_info_alloca

#define snd_seq_system_info_alloca ( ptr ) __snd_alloca(ptr, snd_seq_system_info)

allocate a snd_seq_system_info_t container on stack

Typedef Documentation

◆ snd_seq_system_info_t

typedef struct _snd_seq_system_info snd_seq_system_info_t

system information container

◆ snd_seq_t

typedef struct _snd_seq snd_seq_t

Sequencer handle

Enumeration Type Documentation

◆ snd_seq_type_t

enum snd_seq_type_t

sequencer handle type

Enumerator
SND_SEQ_TYPE_HW	hardware
SND_SEQ_TYPE_SHM	shared memory (NYI)
SND_SEQ_TYPE_INET	network (NYI)

Function Documentation

◆ snd_seq_client_id()

int snd_seq_client_id ( snd_seq_t * seq )

Get the client id.

Parameters

seq	sequencer handle

Returns: the client id

Returns the id of the specified client. If an error occurs, function returns the negative error code. A client id is necessary to inquiry or to set the client information. A user client is assigned from 128 to 191.

See also: snd_seq_open()

◆ snd_seq_close()

int snd_seq_close ( snd_seq_t * seq )

Close the sequencer.

Parameters

seq	Handle returned from snd_seq_open()

Returns: 0 on success otherwise a negative error code

Closes the sequencer client and releases its resources. After a client is closed, an event with SND_SEQ_EVENT_CLIENT_EXIT is broadcast to announce port. The connection between other clients are disconnected. Call this just before exiting your program.

See also: snd_seq_close()

◆ snd_seq_get_input_buffer_size()

size_t snd_seq_get_input_buffer_size ( snd_seq_t * seq )

Return the size of input buffer.

Parameters

seq	sequencer handle

Returns: the size of input buffer in bytes

Obtains the size of input buffer. This buffer is used to read byte-stream of input events from sequencer.

See also: snd_seq_set_input_buffer_size()

◆ snd_seq_get_output_buffer_size()

size_t snd_seq_get_output_buffer_size ( snd_seq_t * seq )

Return the size of output buffer.

Parameters

seq	sequencer handle

Returns: the size of output buffer in bytes

Obtains the size of output buffer. This buffer is used to store decoded byte-stream of output events before transferring to sequencer.

See also: snd_seq_set_output_buffer_size()

◆ snd_seq_name()

const char * snd_seq_name ( snd_seq_t * seq )

get identifier of sequencer handle

Parameters

seq	sequencer handle

Returns: ASCII identifier of sequencer handle

Returns the ASCII identifier of the given sequencer handle. It's the same identifier specified in snd_seq_open().

See also: snd_seq_open()

◆ snd_seq_nonblock()

int snd_seq_nonblock	(	snd_seq_t *	seq,
		int	nonblock
	)

Set nonblock mode.

Parameters

seq	sequencer handle
nonblock	0 = block, 1 = nonblock mode

Returns: 0 on success otherwise a negative error code

Change the blocking mode of the given client. In block mode, the client falls into sleep when it fills the output memory pool with full events. The client will be woken up after a certain amount of free space becomes available.

See also: snd_seq_open()

◆ snd_seq_open()

int snd_seq_open	(	snd_seq_t **	seqp,
		const char *	name,
		int	streams,
		int	mode
	)

Open the ALSA sequencer.

Parameters

seqp	Pointer to a snd_seq_t pointer. This pointer must be kept and passed to most of the other sequencer functions.
name	The sequencer's "name". This is not a name you make up for your own purposes; it has special significance to the ALSA library. Usually you need to pass `"default"` here.
streams	The read/write mode of the sequencer. Can be one of three values: SND_SEQ_OPEN_OUTPUT - open the sequencer for output only SND_SEQ_OPEN_INPUT - open the sequencer for input only SND_SEQ_OPEN_DUPLEX - open the sequencer for output and input

Note: Internally, these are translated to O_WRONLY, O_RDONLY and O_RDWR respectively and used as the second argument to the C library open() call.

Parameters

mode	Optional modifier. Can be either 0, or SND_SEQ_NONBLOCK, which will make read/write operations non-blocking. This can also be set later using snd_seq_nonblock().

Returns: 0 on success otherwise a negative error code

Creates a new handle and opens a connection to the kernel sequencer interface. After a client is created successfully, an event with SND_SEQ_EVENT_CLIENT_START is broadcast to announce port.

See also: snd_seq_open_lconf(), snd_seq_close(), snd_seq_type(), snd_seq_name(), snd_seq_nonblock(), snd_seq_client_id()

◆ snd_seq_open_lconf()

int snd_seq_open_lconf	(	snd_seq_t **	seqp,
		const char *	name,
		int	streams,
		int	mode,
		snd_config_t *	lconf
	)

Open the ALSA sequencer using local configuration.

Parameters

seqp	Pointer to a snd_seq_t pointer.
name	The name to open
streams	The read/write mode of the sequencer.
mode	Optional modifier
lconf	Local configuration

Returns: 0 on success otherwise a negative error code

See the snd_seq_open() function for further details. The extension is that the given configuration is used to resolve abstract name.

See also: snd_seq_open()

◆ snd_seq_poll_descriptors()

int snd_seq_poll_descriptors	(	snd_seq_t *	seq,
		struct pollfd *	pfds,
		unsigned int	space,
		short	events
	)

Get poll descriptors.

Parameters

seq	sequencer handle
pfds	array of poll descriptors
space	space in the poll descriptor array
events	polling events to be checked (`POLLIN` and `POLLOUT`)

Returns: count of filled descriptors

Get poll descriptors assigned to the sequencer handle. Since a sequencer handle can duplex streams, you need to set which direction(s) is/are polled in events argument. When POLLIN bit is specified, the incoming events to the ports are checked.

To check the returned poll-events, call snd_seq_poll_descriptors_revents() instead of reading the pollfd structs directly.

See also: snd_seq_poll_descriptors_count(), snd_seq_poll_descriptors_revents()

◆ snd_seq_poll_descriptors_count()

int snd_seq_poll_descriptors_count	(	snd_seq_t *	seq,
		short	events
	)

Returns the number of poll descriptors.

Parameters

seq	sequencer handle
events	the poll events to be checked (`POLLIN` and `POLLOUT`)

Returns: the number of poll descriptors.

Get the number of poll descriptors. The polling events to be checked can be specified by the second argument. When both input and output are checked, pass POLLIN|POLLOUT

See also: snd_seq_poll_descriptors()

◆ snd_seq_poll_descriptors_revents()

int snd_seq_poll_descriptors_revents	(	snd_seq_t *	seq,
		struct pollfd *	pfds,
		unsigned int	nfds,
		unsigned short *	revents
	)

get returned events from poll descriptors

Parameters

seq	sequencer handle
pfds	array of poll descriptors
nfds	count of poll descriptors
revents	returned events

Returns: zero if success, otherwise a negative error code

See also: snd_seq_poll_descriptors()

◆ snd_seq_set_input_buffer_size()

int snd_seq_set_input_buffer_size	(	snd_seq_t *	seq,
		size_t	size
	)

Resize the input buffer.

Parameters

seq	sequencer handle
size	the size of input buffer to be changed in bytes

Returns: 0 on success otherwise a negative error code

Changes the size of input buffer.

See also: snd_seq_get_input_buffer_size()

◆ snd_seq_set_output_buffer_size()

int snd_seq_set_output_buffer_size	(	snd_seq_t *	seq,
		size_t	size
	)

Change the size of output buffer.

Parameters

seq	sequencer handle
size	the size of output buffer to be changed in bytes

Returns: 0 on success otherwise a negative error code

Changes the size of output buffer.

See also: snd_seq_get_output_buffer_size()

◆ snd_seq_system_info()

int snd_seq_system_info	(	snd_seq_t *	seq,
		snd_seq_system_info_t *	info
	)

obtain the sequencer system information

Parameters

seq	sequencer handle
info	the pointer to be stored

Returns: 0 on success otherwise a negative error code

Stores the global system information of ALSA sequencer system. The returned data contains the maximum available numbers of queues, clients, ports and channels.

◆ snd_seq_system_info_copy()

void snd_seq_system_info_copy	(	snd_seq_system_info_t *	dst,
		const snd_seq_system_info_t *	src
	)

Copy one snd_seq_system_info_t to another.

Parameters

dst	pointer to destination
src	pointer to source

◆ snd_seq_system_info_free()

void snd_seq_system_info_free ( snd_seq_system_info_t * obj )

Frees a previously allocated snd_seq_system_info_t.

Parameters

obj	pointer to object to free

◆ snd_seq_system_info_get_channels()

int snd_seq_system_info_get_channels ( const snd_seq_system_info_t * info )

Get maximum number of channels.

Parameters

info	snd_seq_system_info_t container

Returns: maximum number of channels

See also: snd_seq_system_info()

◆ snd_seq_system_info_get_clients()

int snd_seq_system_info_get_clients ( const snd_seq_system_info_t * info )

Get maximum number of clients.

Parameters

info	snd_seq_system_info_t container

Returns: maximum number of clients

See also: snd_seq_system_info()

◆ snd_seq_system_info_get_cur_clients()

int snd_seq_system_info_get_cur_clients ( const snd_seq_system_info_t * info )

Get the current number of clients.

Parameters

info	snd_seq_system_info_t container

Returns: current number of clients

See also: snd_seq_system_info()

◆ snd_seq_system_info_get_cur_queues()

int snd_seq_system_info_get_cur_queues ( const snd_seq_system_info_t * info )

Get the current number of queues.

Parameters

info	snd_seq_system_info_t container

Returns: current number of queues

See also: snd_seq_system_info()

◆ snd_seq_system_info_get_ports()

int snd_seq_system_info_get_ports ( const snd_seq_system_info_t * info )

Get maximum number of ports.

Parameters

info	snd_seq_system_info_t container

Returns: maximum number of ports

See also: snd_seq_system_info()

◆ snd_seq_system_info_get_queues()

int snd_seq_system_info_get_queues ( const snd_seq_system_info_t * info )

Get maximum number of queues.

Parameters

info	snd_seq_system_info_t container

Returns: maximum number of queues

See also: snd_seq_system_info()

◆ snd_seq_system_info_malloc()

int snd_seq_system_info_malloc ( snd_seq_system_info_t ** ptr )

Allocate an empty snd_seq_system_info_t using standard malloc.

Parameters

ptr	returned pointer

Returns: 0 on success otherwise negative error code

◆ snd_seq_system_info_sizeof()

size_t snd_seq_system_info_sizeof ( void )

Get size of snd_seq_system_info_t.

Returns: size in bytes

◆ snd_seq_type()

snd_seq_type_t snd_seq_type ( snd_seq_t * seq )

get type of sequencer handle

Parameters

seq	sequencer handle

Returns: type of sequencer handle

Returns the type snd_seq_type_t of the given sequencer handle.

See also: snd_seq_open()

Modules

Macros

Typedefs

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ SND_SEQ_ADDRESS_BROADCAST

◆ SND_SEQ_ADDRESS_SUBSCRIBERS

◆ SND_SEQ_ADDRESS_UNKNOWN

◆ SND_SEQ_CLIENT_SYSTEM

◆ SND_SEQ_DLSYM_VERSION

◆ SND_SEQ_NONBLOCK

◆ SND_SEQ_OPEN_DUPLEX

◆ SND_SEQ_OPEN_INPUT

◆ SND_SEQ_OPEN_OUTPUT

◆ snd_seq_system_info_alloca

Typedef Documentation

◆ snd_seq_system_info_t

◆ snd_seq_t

Enumeration Type Documentation

◆ snd_seq_type_t

Function Documentation

◆ snd_seq_client_id()

◆ snd_seq_close()

◆ snd_seq_get_input_buffer_size()

◆ snd_seq_get_output_buffer_size()

◆ snd_seq_name()

◆ snd_seq_nonblock()

◆ snd_seq_open()

◆ snd_seq_open_lconf()

◆ snd_seq_poll_descriptors()

◆ snd_seq_poll_descriptors_count()

◆ snd_seq_poll_descriptors_revents()

◆ snd_seq_set_input_buffer_size()

◆ snd_seq_set_output_buffer_size()

◆ snd_seq_system_info()

◆ snd_seq_system_info_copy()

◆ snd_seq_system_info_free()

◆ snd_seq_system_info_get_channels()

◆ snd_seq_system_info_get_clients()

◆ snd_seq_system_info_get_cur_clients()

◆ snd_seq_system_info_get_cur_queues()

◆ snd_seq_system_info_get_ports()

◆ snd_seq_system_info_get_queues()

◆ snd_seq_system_info_malloc()

◆ snd_seq_system_info_sizeof()

◆ snd_seq_type()