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Sequencer Event API
[MIDI Sequencer]


Defines

#define SND_SEQ_REMOVE_INPUT   (1<<0)
#define SND_SEQ_REMOVE_OUTPUT   (1<<1)
#define SND_SEQ_REMOVE_DEST   (1<<2)
#define SND_SEQ_REMOVE_DEST_CHANNEL   (1<<3)
#define SND_SEQ_REMOVE_TIME_BEFORE   (1<<4)
#define SND_SEQ_REMOVE_TIME_AFTER   (1<<5)
#define SND_SEQ_REMOVE_TIME_TICK   (1<<6)
#define SND_SEQ_REMOVE_EVENT_TYPE   (1<<7)
#define SND_SEQ_REMOVE_IGNORE_OFF   (1<<8)
#define SND_SEQ_REMOVE_TAG_MATCH   (1<<9)
#define snd_seq_remove_events_alloca(ptr)   SND_ALLOCA(snd_seq_remove_events, ptr)

Typedefs

typedef _snd_seq_remove_events snd_seq_remove_events_t

Functions

int snd_seq_free_event (snd_seq_event_t *ev)
 (DEPRECATED) free an event

ssize_t snd_seq_event_length (snd_seq_event_t *ev)
 calculates the (encoded) byte-stream size of the event

int snd_seq_event_output (snd_seq_t *handle, snd_seq_event_t *ev)
 output an event

int snd_seq_event_output_buffer (snd_seq_t *handle, snd_seq_event_t *ev)
 output an event onto the lib buffer without draining buffer

int snd_seq_event_output_direct (snd_seq_t *handle, snd_seq_event_t *ev)
 output an event directly to the sequencer NOT through output buffer

int snd_seq_event_input (snd_seq_t *handle, snd_seq_event_t **ev)
 retrieve an event from sequencer

int snd_seq_event_input_pending (snd_seq_t *seq, int fetch_sequencer)
 check events in input buffer

int snd_seq_drain_output (snd_seq_t *handle)
 drain output buffer to sequencer

int snd_seq_event_output_pending (snd_seq_t *seq)
 return the size of pending events on output buffer

int snd_seq_extract_output (snd_seq_t *handle, snd_seq_event_t **ev)
 extract the first event in output buffer

int snd_seq_drop_output (snd_seq_t *handle)
 remove all events on output buffer

int snd_seq_drop_output_buffer (snd_seq_t *handle)
 remove all events on user-space output buffer

int snd_seq_drop_input (snd_seq_t *handle)
 clear input buffer and and remove events in sequencer queue

int snd_seq_drop_input_buffer (snd_seq_t *handle)
 remove all events on user-space input FIFO

size_t snd_seq_remove_events_sizeof (void)
 get size of snd_seq_remove_events_t

int snd_seq_remove_events_malloc (snd_seq_remove_events_t **ptr)
 allocate an empty snd_seq_remove_events_t using standard malloc

void snd_seq_remove_events_free (snd_seq_remove_events_t *ptr)
 frees a previously allocated snd_seq_remove_events_t

void snd_seq_remove_events_copy (snd_seq_remove_events_t *dst, const snd_seq_remove_events_t *src)
 copy one snd_seq_remove_events_t to another

unsigned int snd_seq_remove_events_get_condition (const snd_seq_remove_events_t *info)
 Get the removal condition bits.

int snd_seq_remove_events_get_queue (const snd_seq_remove_events_t *info)
 Get the queue as removal condition.

const snd_seq_timestamp_t * snd_seq_remove_events_get_time (const snd_seq_remove_events_t *info)
 Get the event timestamp as removal condition.

const snd_seq_addr_t * snd_seq_remove_events_get_dest (const snd_seq_remove_events_t *info)
 Get the event destination address as removal condition.

int snd_seq_remove_events_get_channel (const snd_seq_remove_events_t *info)
 Get the event channel as removal condition.

int snd_seq_remove_events_get_event_type (const snd_seq_remove_events_t *info)
 Get the event type as removal condition.

int snd_seq_remove_events_get_tag (const snd_seq_remove_events_t *info)
 Get the event tag id as removal condition.

void snd_seq_remove_events_set_condition (snd_seq_remove_events_t *info, unsigned int flags)
 Set the removal condition bits.

void snd_seq_remove_events_set_queue (snd_seq_remove_events_t *info, int queue)
 Set the queue as removal condition.

void snd_seq_remove_events_set_time (snd_seq_remove_events_t *info, const snd_seq_timestamp_t *time)
 Set the timestamp as removal condition.

void snd_seq_remove_events_set_dest (snd_seq_remove_events_t *info, const snd_seq_addr_t *addr)
 Set the destination address as removal condition.

void snd_seq_remove_events_set_channel (snd_seq_remove_events_t *info, int channel)
 Set the channel as removal condition.

void snd_seq_remove_events_set_event_type (snd_seq_remove_events_t *info, int type)
 Set the event type as removal condition.

void snd_seq_remove_events_set_tag (snd_seq_remove_events_t *info, int tag)
 Set the event tag as removal condition.

int snd_seq_remove_events (snd_seq_t *handle, snd_seq_remove_events_t *info)
 remove events on input/output buffers

Detailed Description

Sequencer Event API

Define Documentation

#define SND_SEQ_REMOVE_DEST   (1<<2)
 

Restrict by destination q:client:port

#define SND_SEQ_REMOVE_DEST_CHANNEL   (1<<3)
 

Restrict by channel

#define SND_SEQ_REMOVE_EVENT_TYPE   (1<<7)
 

Restrict to event type

#define snd_seq_remove_events_alloca (  ptr    )     SND_ALLOCA(snd_seq_remove_events, ptr)
 

allocate a snd_seq_remove_events_t container on stack

#define SND_SEQ_REMOVE_IGNORE_OFF   (1<<8)
 

Do not flush off events

#define SND_SEQ_REMOVE_INPUT   (1<<0)
 

Flush input queues

#define SND_SEQ_REMOVE_OUTPUT   (1<<1)
 

Flush output queues

#define SND_SEQ_REMOVE_TAG_MATCH   (1<<9)
 

Restrict to events with given tag

#define SND_SEQ_REMOVE_TIME_AFTER   (1<<5)
 

Restrict to time or after

#define SND_SEQ_REMOVE_TIME_BEFORE   (1<<4)
 

Restrict to before time

#define SND_SEQ_REMOVE_TIME_TICK   (1<<6)
 

Time is in ticks

Typedef Documentation

typedef struct _snd_seq_remove_events snd_seq_remove_events_t
 

event removal conditionals

Function Documentation

int snd_seq_drain_output (  snd_seq_t *    seq ) 
 

drain output buffer to sequencer

Parameters:
seq  sequencer handle
Returns:
0 when all events are drained and sent to sequencer. When events still remain on the buffer, the byte size of remaining events are returned. On error a negative error code is returned.

int snd_seq_drop_input (  snd_seq_t *    seq ) 
 

clear input buffer and and remove events in sequencer queue

Parameters:
seq  sequencer handle

int snd_seq_drop_input_buffer (  snd_seq_t *    seq ) 
 

remove all events on user-space input FIFO

Parameters:
seq  sequencer handle

int snd_seq_drop_output (  snd_seq_t *    seq ) 
 

remove all events on output buffer

Parameters:
seq  sequencer handle
Removes all events on both user-space output buffer and output memory pool on kernel.

int snd_seq_drop_output_buffer (  snd_seq_t *    seq ) 
 

remove all events on user-space output buffer

Parameters:
seq  sequencer handle
Removes all events on user-space output buffer. Unlike snd_seq_drain_output(), this function doesn't remove events on output memory pool of sequencer.

int snd_seq_event_input (  snd_seq_t *    seq,
snd_seq_event_t **    ev
) 
 

retrieve an event from sequencer

Parameters:
seq  sequencer handle
ev  event pointer to be stored
Returns:
Obtains an input event from sequencer. The event is created via snd_seq_create_event(), and its pointer is stored on ev argument.
This function firstly receives the event byte-stream data from sequencer as much as possible at once. Then it retrieves the first event record and store the pointer on ev. By calling this function sequentially, events are extracted from the input buffer.

If there is no input from sequencer, function falls into sleep in blocking mode until an event is received, or returns -EAGAIN error in non-blocking mode. Occasionally, this function may return -ENOSPC error. This means that the input FIFO of sequencer overran, and some events are lost. Once this error is returned, the input FIFO is cleared automatically.

Function returns the byte size of remaining events on the input buffer if an event is successfully received. Application can determine from the returned value whether to call input once more or not.

int snd_seq_event_input_pending (  snd_seq_t *    seq,
int    fetch_sequencer
) 
 

check events in input buffer

Returns:
the byte size of remaining input events on input buffer.
If events remain on the input buffer of user-space, function returns the total byte size of events on it. If fetch_sequencer argument is non-zero, this function checks the presence of events on sequencer FIFO When events exist, they are transferred to the input buffer, and the number of received events are returned. If fetch_sequencer argument is zero and no events remain on the input buffer, function simply returns zero.

ssize_t snd_seq_event_length (  snd_seq_event_t *    ev ) 
 

calculates the (encoded) byte-stream size of the event

Parameters:
ev  the event
Returns:
the size of decoded bytes

int snd_seq_event_output (  snd_seq_t *    seq,
snd_seq_event_t *    ev
) 
 

output an event

Parameters:
seq  sequencer handle
ev  event to be output
Returns:
the number of remaining events or a negative error code
An event is once expanded on the output buffer. The output buffer will be drained automatically if it becomes full.

If events remain unprocessed on output buffer before drained, the size of total byte data on output buffer is returned. If the output buffer is empty, this returns zero.

int snd_seq_event_output_buffer (  snd_seq_t *    seq,
snd_seq_event_t *    ev
) 
 

output an event onto the lib buffer without draining buffer

Parameters:
seq  sequencer handle
ev  event to be output
Returns:
the byte size of remaining events. -EAGAIN if the buffer becomes full.
This function doesn't drain buffer unlike snd_seq_event_output().

int snd_seq_event_output_direct (  snd_seq_t *    seq,
snd_seq_event_t *    ev
) 
 

output an event directly to the sequencer NOT through output buffer

Parameters:
seq  sequencer handle
ev  event to be output
Returns:
the byte size sent to sequencer or a negative error code
This function sends an event to the sequencer directly not through the output buffer. When the event is a variable length event, a temporary buffer is allocated inside alsa-lib and the data is copied there before actually sent.

int snd_seq_event_output_pending (  snd_seq_t *    seq ) 
 

return the size of pending events on output buffer

Parameters:
seq  sequencer handle
Returns:
the byte size of total of pending events

int snd_seq_extract_output (  snd_seq_t *    seq,
snd_seq_event_t **    ev_res
) 
 

extract the first event in output buffer

Parameters:
seq  sequencer handle
ev_res  event pointer to be extracted
Returns:
0 on success otherwise a negative error code
Extracts the first event in output buffer. If ev_res is NULL, just remove the event.

int snd_seq_free_event (  snd_seq_event_t *    ev ) 
 

(DEPRECATED) free an event

releases the event pointer which was allocated by snd_seq_event_input(). this function is obsolete and does nothing inside actually. used only for compatibility with the older version.

int snd_seq_remove_events (  snd_seq_t *    seq,
snd_seq_remove_events_t *    rmp
) 
 

remove events on input/output buffers

Parameters:
seq  sequencer handle
rmp  remove event container
Removes matching events with the given condition from input/output buffers. The removal condition is specified in rmp argument.

void snd_seq_remove_events_copy (  snd_seq_remove_events_t *    dst,
const snd_seq_remove_events_t *    src
) 
 

copy one snd_seq_remove_events_t to another

Parameters:
dst  pointer to destination
src  pointer to source

void snd_seq_remove_events_free (  snd_seq_remove_events_t *    obj ) 
 

frees a previously allocated snd_seq_remove_events_t

Parameters:
pointer  to object to free

int snd_seq_remove_events_get_channel (  const snd_seq_remove_events_t *    info ) 
 

Get the event channel as removal condition.

Parameters:
info  remove_events container
Returns:
channel number

unsigned int snd_seq_remove_events_get_condition (  const snd_seq_remove_events_t *    info ) 
 

Get the removal condition bits.

Parameters:
info  remove_events container
Returns:
removal condition bits

const snd_seq_addr_t* snd_seq_remove_events_get_dest (  const snd_seq_remove_events_t *    info ) 
 

Get the event destination address as removal condition.

Parameters:
info  remove_events container
Returns:
destination address

int snd_seq_remove_events_get_event_type (  const snd_seq_remove_events_t *    info ) 
 

Get the event type as removal condition.

Parameters:
info  remove_events container
Returns:
event type

int snd_seq_remove_events_get_queue (  const snd_seq_remove_events_t *    info ) 
 

Get the queue as removal condition.

Parameters:
info  remove_events container
Returns:
queue id

int snd_seq_remove_events_get_tag (  const snd_seq_remove_events_t *    info ) 
 

Get the event tag id as removal condition.

Parameters:
info  remove_events container
Returns:
tag id

const snd_seq_timestamp_t* snd_seq_remove_events_get_time (  const snd_seq_remove_events_t *    info ) 
 

Get the event timestamp as removal condition.

Parameters:
info  remove_events container
Returns:
time stamp

int snd_seq_remove_events_malloc (  snd_seq_remove_events_t **    ptr ) 
 

allocate an empty snd_seq_remove_events_t using standard malloc

Parameters:
ptr  returned pointer
Returns:
0 on success otherwise negative error code

void snd_seq_remove_events_set_channel (  snd_seq_remove_events_t *    info,
int    channel
) 
 

Set the channel as removal condition.

Parameters:
info  remove_events container
channel  channel number

void snd_seq_remove_events_set_condition (  snd_seq_remove_events_t *    info,
unsigned int    flags
) 
 

Set the removal condition bits.

Parameters:
info  remove_events container
flags  removal condition bits

void snd_seq_remove_events_set_dest (  snd_seq_remove_events_t *    info,
const snd_seq_addr_t *    addr
) 
 

Set the destination address as removal condition.

Parameters:
info  remove_events container
addr  destination address

void snd_seq_remove_events_set_event_type (  snd_seq_remove_events_t *    info,
int    type
) 
 

Set the event type as removal condition.

Parameters:
info  remove_events container
type  event type

void snd_seq_remove_events_set_queue (  snd_seq_remove_events_t *    info,
int    queue
) 
 

Set the queue as removal condition.

Parameters:
info  remove_events container
queue  queue id

void snd_seq_remove_events_set_tag (  snd_seq_remove_events_t *    info,
int    tag
) 
 

Set the event tag as removal condition.

Parameters:
info  remove_events container
tag  tag id

void snd_seq_remove_events_set_time (  snd_seq_remove_events_t *    info,
const snd_seq_timestamp_t *    time
) 
 

Set the timestamp as removal condition.

Parameters:
info  remove_events container
time  timestamp pointer

size_t snd_seq_remove_events_sizeof (  void    ) 
 

get size of snd_seq_remove_events_t

Returns:
size in bytes

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