libevent: event.h File Reference

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Data Structures
struct	bufferevent
struct	evbuffer
struct	event
struct	event_watermark
struct	eventop
struct	evkeyval
Defines
#define	_EVENT_LOG_DEBUG 0
#define	_EVENT_LOG_ERR 3
#define	_EVENT_LOG_MSG 1
#define	_EVENT_LOG_WARN 2
#define	EV_PERSIST 0x10
#define	EV_READ 0x02
#define	EV_SIGNAL 0x08
#define	EV_TIMEOUT 0x01
#define	EV_WRITE 0x04
#define	EVBUFFER_DATA(x) (x)->buffer
#define	EVBUFFER_EOF 0x10
#define	EVBUFFER_ERROR 0x20
#define	EVBUFFER_INPUT(x) (x)->input
#define	EVBUFFER_LENGTH(x) (x)->off
#define	EVBUFFER_OUTPUT(x) (x)->output
#define	EVBUFFER_READ 0x01
#define	EVBUFFER_TIMEOUT 0x40
#define	EVBUFFER_WRITE 0x02
#define	EVENT_FD(ev) (int)(ev)->ev_fd
#define	event_initialized(ev) ((ev)->ev_flags & EVLIST_INIT)
	Test if an event structure has been initialized.
#define	EVENT_SIGNAL(ev) (int)(ev)->ev_fd
#define	EVLIST_ACTIVE 0x08
#define	EVLIST_ALL (0xf000 \| 0x9f)
#define	EVLIST_INIT 0x80
#define	EVLIST_INSERTED 0x02
#define	EVLIST_INTERNAL 0x10
#define	EVLIST_SIGNAL 0x04
#define	EVLIST_TIMEOUT 0x01
#define	EVLOOP_NONBLOCK 0x02
	A flag for event_loop() to indicate .
#define	EVLOOP_ONCE 0x01
	A flag for event_loop() to indicate .
#define	evtimer_add(ev, tv) event_add(ev, tv)
	Add a timer event.
#define	evtimer_del(ev) event_del(ev)
	Delete a timer event.
#define	evtimer_initialized(ev) ((ev)->ev_flags & EVLIST_INIT)
#define	evtimer_pending(ev, tv) event_pending(ev, EV_TIMEOUT, tv)
#define	evtimer_set(ev, cb, arg) event_set(ev, -1, 0, cb, arg)
	Define a timer event.
#define	signal_add(ev, tv) event_add(ev, tv)
#define	signal_del(ev) event_del(ev)
#define	signal_initialized(ev) ((ev)->ev_flags & EVLIST_INIT)
#define	signal_pending(ev, tv) event_pending(ev, EV_SIGNAL, tv)
#define	signal_set(ev, x, cb, arg) event_set(ev, x, EV_SIGNAL\|EV_PERSIST, cb, arg)
#define	timeout_add(ev, tv) event_add(ev, tv)
	Add a timeout event.
#define	TIMEOUT_DEFAULT {5, 0}
#define	timeout_del(ev) event_del(ev)
	Disable a timeout event.
#define	timeout_initialized(ev) ((ev)->ev_flags & EVLIST_INIT)
#define	timeout_pending(ev, tv) event_pending(ev, EV_TIMEOUT, tv)
#define	timeout_set(ev, cb, arg) event_set(ev, -1, 0, cb, arg)
	Define a timeout event.
Typedefs
typedef void(*)	evbuffercb (struct bufferevent , void )
typedef void(*)	event_log_cb (int severity, const char *msg)
typedef void(*)	everrorcb (struct bufferevent , short what, void )
Functions
int	bufferevent_base_set (struct event_base base, struct bufferevent bufev)
	Assign a bufferevent to a specific event_base.
int	bufferevent_disable (struct bufferevent *bufev, short event)
	Disable a bufferevent.
int	bufferevent_enable (struct bufferevent *bufev, short event)
	Enable a bufferevent.
void	bufferevent_free (struct bufferevent *bufev)
	Deallocate the storage associated with a bufferevent structure.
bufferevent *	bufferevent_new (int fd, evbuffercb readcb, evbuffercb writecb, everrorcb errorcb, void *cbarg)
	Create a new bufferevent.
int	bufferevent_priority_set (struct bufferevent *bufev, int pri)
	Assign a priority to a bufferevent.
size_t	bufferevent_read (struct bufferevent bufev, void data, size_t size)
	Read data from a bufferevent buffer.
void	bufferevent_settimeout (struct bufferevent *bufev, int timeout_read, int timeout_write)
	Set the read and write timeout for a buffered event.
int	bufferevent_write (struct bufferevent bufev, void data, size_t size)
	Write data to a bufferevent buffer.
int	bufferevent_write_buffer (struct bufferevent bufev, struct evbuffer buf)
	Write data from an evbuffer to a bufferevent buffer.
void	encode_int (struct evbuffer *evbuf, u_int32_t number)
	Encode an integer and store it in an evbuffer.
int	evbuffer_add (struct evbuffer buf, const void data, size_t datlen)
	Append data to the end of an evbuffer.
int	evbuffer_add_buffer (struct evbuffer outbuf, struct evbuffer inbuf)
	Move data from one evbuffer into another evbuffer.
int	evbuffer_add_printf (struct evbuffer buf, const char fmt,...)
	Append a formatted string to the end of an evbuffer.
int	evbuffer_add_vprintf (struct evbuffer , const char fmt, va_list ap)
	Append a va_list formatted string to the end of an evbuffer.
void	evbuffer_drain (struct evbuffer *buf, size_t len)
	Remove a specified number of bytes data from the beginning of an evbuffer.
int	evbuffer_expand (struct evbuffer *buf, size_t datlen)
	Expands the available space in an event buffer.
u_char *	evbuffer_find (struct evbuffer buffer, const u_char what, size_t len)
	Find a string within an evbuffer.
void	evbuffer_free (struct evbuffer *buffer)
	Deallocate storage for an evbuffer.
evbuffer *	evbuffer_new (void)
	Allocate storage for a new evbuffer.
int	evbuffer_read (struct evbuffer *buf, int fd, int howmuch)
	Read from a file descriptor and store the result in an evbuffer.
char *	evbuffer_readline (struct evbuffer *)
	Read a single line from an event buffer.
int	evbuffer_remove (struct evbuffer buf, void data, size_t datlen)
	Read data from an event buffer and drain the bytes read.
void	evbuffer_setcb (struct evbuffer buffer, void(cb)(struct evbuffer , size_t, size_t, void ), void *cbarg)
	Set a callback to invoke when the evbuffer is modified.
int	evbuffer_write (struct evbuffer *buffer, int fd)
	Write the contents of an evbuffer to a file descriptor.
void	event_active (struct event *, int, short)
int	event_add (struct event ev, struct timeval tv)
	Add an event to the set of monitored events.
int	event_base_dispatch (struct event_base *)
	Threadsafe event dispatching loop.
void	event_base_free (struct event_base *eb)
	Deallocate all memory associated with an event_base.
int	event_base_loop (struct event_base *eb, int flags)
	Execute a single event (threadsafe variant).
int	event_base_loopexit (struct event_base eb, struct timeval tv)
	Execute a single event, with a timeout (threadsafe variant).
int	event_base_once (struct event_base base, int fd, short events, void(callback)(int, short, void ), void arg, struct timeval *tv)
	Schedule a one-time event (threadsafe variant).
int	event_base_priority_init (struct event_base *eb, int npriorities)
	Set the number of different event priorities (threadsafe variant).
int	event_base_set (struct event_base eb, struct event ev)
	Associate a different event base with an event.
int	event_del (struct event *ev)
	Remove an event from the set of monitored events.
int	event_dispatch (void)
	Loop to process events.
const char *	event_get_method (void)
	Get the kernel event notification mechanism used by libevent.
const char *	event_get_version (void)
	Get the libevent version number.
void *	event_init (void)
	Initialize the event API.
int	event_loop (int flags)
	Execute a single event.
int	event_loopexit (struct timeval *tv)
	Execute a single event, with a timeout.
int	event_once (int fd, short events, void(callback)(int, short, void ), void arg, struct timeval tv)
	Schedule a one-time event to occur.
int	event_pending (struct event ev, short event, struct timeval tv)
	Checks if a specific event is pending or scheduled.
int	event_priority_init (int npriorities)
	Set the number of different event priorities.
int	event_priority_set (struct event *ev, int priority)
	Assign a priority to an event.
void	event_set (struct event , int, short, void()(int, short, void ), void )
	Prepare an event structure to be added.
void	event_set_log_callback (event_log_cb cb)
int	evtag_consume (struct evbuffer *evbuf)
void	evtag_init (void)
void	evtag_marshal (struct evbuffer evbuf, u_int8_t tag, const void data, u_int32_t len)
void	evtag_marshal_int (struct evbuffer *evbuf, u_int8_t tag, u_int32_t integer)
void	evtag_marshal_string (struct evbuffer buf, u_int8_t tag, const char string)
void	evtag_marshal_timeval (struct evbuffer evbuf, u_int8_t tag, struct timeval tv)
int	evtag_payload_length (struct evbuffer evbuf, u_int32_t plength)
int	evtag_peek (struct evbuffer evbuf, u_int8_t ptag)
int	evtag_peek_length (struct evbuffer evbuf, u_int32_t plength)
void	evtag_test (void)
int	evtag_unmarshal (struct evbuffer src, u_int8_t ptag, struct evbuffer *dst)
int	evtag_unmarshal_fixed (struct evbuffer src, u_int8_t need_tag, void data, size_t len)
int	evtag_unmarshal_int (struct evbuffer evbuf, u_int8_t need_tag, u_int32_t pinteger)
int	evtag_unmarshal_string (struct evbuffer evbuf, u_int8_t need_tag, char *pstring)
int	evtag_unmarshal_timeval (struct evbuffer evbuf, u_int8_t need_tag, struct timeval ptv)

Define Documentation

#define event_initialized ( ev ) ((ev)->ev_flags & EVLIST_INIT)

Test if an event structure has been initialized.

The event_initialized() macro can be used to check if an event has been initialized.

Parameters:

an event structure to be tested

Returns:: 1 if the structure has been initialized, or 0 if it has not been initialized

#define EVLOOP_NONBLOCK 0x02

A flag for event_loop() to indicate .

.. (FIXME)

#define EVLOOP_ONCE 0x01

A flag for event_loop() to indicate .

.. (FIXME)

#define evtimer_add	(	ev,
		tv		)	event_add(ev, tv)

Add a timer event.

Parameters:

	ev	the event struct
	tv	timeval struct

#define evtimer_del ( ev ) event_del(ev)

Delete a timer event.

Parameters:

the event struct to be disabled

#define evtimer_set	(	ev,
		cb,
		arg	)	event_set(ev, -1, 0, cb, arg)

Define a timer event.

Parameters:

	ev	event struct to be modified
	cb	callback function
	arg	argument that will be passed to the callback function

#define timeout_add	(	ev,
		tv		)	event_add(ev, tv)

Add a timeout event.

Parameters:

	ev	the event struct to be disabled
	tv	the timeout value, in seconds

#define timeout_del ( ev ) event_del(ev)

Disable a timeout event.

Parameters:

the timeout event to be disabled

#define timeout_set	(	ev,
		cb,
		arg	)	event_set(ev, -1, 0, cb, arg)

Define a timeout event.

Parameters:

	ev	the event struct to be defined
	cb	the callback to be invoked when the timeout expires
	arg	the argument to be passed to the callback

Function Documentation

int bufferevent_base_set	(	struct event_base *	base,
		struct bufferevent *	bufev
	)

Assign a bufferevent to a specific event_base.

Parameters:

	base	an event_base returned by event_init()
	bufev	a bufferevent struct returned by bufferevent_new()

Returns:: 0 if successful, or -1 if an error occurred

See also:: bufferevent_new()

int bufferevent_disable	(	struct bufferevent *	bufev,
		short	event
	)

Disable a bufferevent.

Parameters:

	bufev	the bufferevent to be disabled
	event	any combination of EV_READ \| EV_WRITE.

Returns:: 0 if successful, or -1 if an error occurred

See also:: bufferevent_enable()

int bufferevent_enable	(	struct bufferevent *	bufev,
		short	event
	)

Enable a bufferevent.

Parameters:

	bufev	the bufferevent to be enabled
	event	any combination of EV_READ \| EV_WRITE.

Returns:: 0 if successful, or -1 if an error occurred

See also:: bufferevent_disable()

void bufferevent_free ( struct bufferevent * bufev )

Deallocate the storage associated with a bufferevent structure.

Parameters:

bufev

the bufferevent structure to be freed.

struct bufferevent* bufferevent_new	(	int	fd,
		evbuffercb	readcb,
		evbuffercb	writecb,
		everrorcb	errorcb,
		void *	cbarg
	)

Create a new bufferevent.

libevent provides an abstraction on top of the regular event callbacks. This abstraction is called a buffered event. A buffered event provides input and output buffers that get filled and drained automatically. The user of a buffered event no longer deals directly with the I/O, but instead is reading from input and writing to output buffers.

Once initialized, the bufferevent structure can be used repeatedly with bufferevent_enable() and bufferevent_disable().

When read enabled the bufferevent will try to read from the file descriptor and call the read callback. The write callback is executed whenever the output buffer is drained below the write low watermark, which is 0 by default.

If multiple bases are in use, bufferevent_base_set() must be called before enabling the bufferevent for the first time.

Parameters:

	fd	the file descriptor from which data is read and written to. This file descriptor is not allowed to be a pipe(2).
	readcb	callback to invoke when there is data to be read, or NULL if no callback is desired
	writecb	callback to invoke when the file descriptor is ready for writing, or NULL if no callback is desired
	errorcb	callback to invoke when there is an error on the file descriptor
	cbarg	an argument that will be supplied to each of the callbacks (readcb, writecb, and errorcb)

Returns:: a pointer to a newly allocated bufferevent struct, or NULL if an error occurred

See also:: bufferevent_base_set(), bufferevent_free()

int bufferevent_priority_set	(	struct bufferevent *	bufev,
		int	pri
	)

Assign a priority to a bufferevent.

Parameters:

	bufev	a bufferevent struct
	pri	the priority to be assigned

Returns:: 0 if successful, or -1 if an error occurred

size_t bufferevent_read	(	struct bufferevent *	bufev,
		void *	data,
		size_t	size
	)

Read data from a bufferevent buffer.

The bufferevent_read() function is used to read data from the input buffer.

Parameters:

	bufev	the bufferevent to be read from
	data	pointer to a buffer that will store the data
	size	the size of the data buffer, in bytes

Returns:: the amount of data read, in bytes.

void bufferevent_settimeout	(	struct bufferevent *	bufev,
		int	timeout_read,
		int	timeout_write
	)

Set the read and write timeout for a buffered event.

Parameters:

	bufev	the bufferevent to be modified
	timeout_read	the read timeout
	timeout_write	the write timeout

int bufferevent_write	(	struct bufferevent *	bufev,
		void *	data,
		size_t	size
	)

Write data to a bufferevent buffer.

The bufferevent_write() function can be used to write data to the file descriptor. The data is appended to the output buffer and written to the descriptor automatically as it becomes available for writing.

Parameters:

	bufev	the bufferevent to be written to
	data	a pointer to the data to be written
	size	the length of the data, in bytes

Returns:: 0 if successful, or -1 if an error occurred

See also:: bufferevent_write_buffer()

int bufferevent_write_buffer	(	struct bufferevent *	bufev,
		struct evbuffer *	buf
	)

Write data from an evbuffer to a bufferevent buffer.

Parameters:

	bufev	the bufferevent to be written to
	buf	the evbuffer to be written

Returns:: 0 if successful, or -1 if an error occurred

See also:: bufferevent_write()

void encode_int	(	struct evbuffer *	evbuf,
		u_int32_t	number
	)

Encode an integer and store it in an evbuffer.

We encode integer's by nibbles; the first nibble contains the number of significant nibbles - 1; this allows us to encode up to 64-bit integers. This function is byte-order independent.

Parameters:

	evbuf	evbuffer to store the encoded number
	number	a 32-bit integer

int evbuffer_add	(	struct evbuffer *	buf,
		const void *	data,
		size_t	datlen
	)

Append data to the end of an evbuffer.

Parameters:

	buf	the event buffer to be appended to
	data	pointer to the beginning of the data buffer
	datlen	the number of bytes to be copied from the data buffer

int evbuffer_add_buffer	(	struct evbuffer *	outbuf,
		struct evbuffer *	inbuf
	)

Move data from one evbuffer into another evbuffer.

This is a destructive add. The data from one buffer moves into the other buffer. The destination buffer is expanded as needed.

Parameters:

	outbuf	the output buffer
	inbuf	the input buffer

Returns:: 0 if successful, or -1 if an error occurred

int evbuffer_add_printf	(	struct evbuffer *	buf,
		const char *	fmt,
			...
	)

Append a formatted string to the end of an evbuffer.

Parameters:

	buf	the evbuffer that will be appended to
	fmt	a format string
	...	arguments that will be passed to printf(3)

Returns:: 0 if successful, or -1 if an error occurred

int evbuffer_add_vprintf	(	struct evbuffer *	,
		const char *	fmt,
		va_list	ap
	)

Append a va_list formatted string to the end of an evbuffer.

Parameters:

	buf	the evbuffer that will be appended to
	fmt	a format string
	ap	a varargs va_list argument array that will be passed to vprintf(3)

Returns:: 0 if successful, or -1 if an error occurred

void evbuffer_drain	(	struct evbuffer *	buf,
		size_t	len
	)

Remove a specified number of bytes data from the beginning of an evbuffer.

Parameters:

	buf	the evbuffer to be drained
	len	the number of bytes to drain from the beginning of the buffer

Returns:: 0 if successful, or -1 if an error occurred

int evbuffer_expand	(	struct evbuffer *	buf,
		size_t	datlen
	)

Expands the available space in an event buffer.

Expands the available space in the event buffer to at least datlen

Parameters:

	buf	the event buffer to be expanded
	datlen	the new minimum length requirement

Returns:: 0 if successful, or -1 if an error occurred

u_char* evbuffer_find	(	struct evbuffer *	buffer,
		const u_char *	what,
		size_t	len
	)

Find a string within an evbuffer.

Parameters:

	buffer	the evbuffer to be searched
	what	the string to be searched for
	len	the length of the search string

Returns:: a pointer to the beginning of the search string, or NULL if the search failed.

void evbuffer_free ( struct evbuffer * buffer )

Deallocate storage for an evbuffer.

Parameters:

pointer

to the evbuffer to be freed

struct evbuffer* evbuffer_new ( void )

Allocate storage for a new evbuffer.

Returns:: a pointer to a newly allocated evbuffer struct, or NULL if an error occurred

int evbuffer_read	(	struct evbuffer *	buf,
		int	fd,
		int	howmuch
	)

Read from a file descriptor and store the result in an evbuffer.

Parameters:

	buf	the evbuffer to store the result
	fd	the file descriptor to read from
	howmuch	the number of bytes to be read

Returns:: the number of bytes read, or -1 if an error occurred

See also:: evbuffer_write()

char* evbuffer_readline ( struct evbuffer * )

Read a single line from an event buffer.

Reads a line terminated by either '
', '
' or '' or '
'. The returned buffer needs to be freed by the caller.

Parameters:

buffer

the evbuffer to read from

Returns:: pointer to a single line, or NULL if an error occurred

int evbuffer_remove	(	struct evbuffer *	buf,
		void *	data,
		size_t	datlen
	)

Read data from an event buffer and drain the bytes read.

Parameters:

	buf	the event buffer to be read from
	data	the destination buffer to store the result
	datlen	the maximum size of the destination buffer

Returns:: the number of bytes read

void evbuffer_setcb	(	struct evbuffer *	buffer,
		void()(struct evbuffer , size_t, size_t, void *)	cb,
		void *	cbarg
	)

Set a callback to invoke when the evbuffer is modified.

Parameters:

	buffer	the evbuffer to be monitored
	cb	the callback function to invoke when the evbuffer is modified
	cbarg	an argument to be provided to the callback function

int evbuffer_write	(	struct evbuffer *	buffer,
		int	fd
	)

Write the contents of an evbuffer to a file descriptor.

The evbuffer will be drained after the bytes have been successfully written.

Parameters:

	buffer	the evbuffer to be written and drained
	fd	the file descriptor to be written to

Returns:: the number of bytes written, or -1 if an error occurred

See also:: evbuffer_read()

int event_add	(	struct event *	ev,
		struct timeval *	tv
	)

Add an event to the set of monitored events.

The function event_add() schedules the execution of the ev event when the event specified in event_set() occurs or in at least the time specified in the tv. If tv is NULL, no timeout occurs and the function will only be called if a matching event occurs on the file descriptor. The event in the ev argument must be already initialized by event_set() and may not be used in calls to event_set() until it has timed out or been removed with event_del(). If the event in the ev argument already has a scheduled timeout, the old timeout will be replaced by the new one.

Parameters:

	ev	an event struct initialized via event_set()
	timeout	the maximum amount of time to wait for the event, or NULL to wait forever

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_del(), event_set()

int event_base_dispatch ( struct event_base * )

Threadsafe event dispatching loop.

Parameters:

the event_base structure returned by event_init()

See also:: event_init(), event_dispatch()

void event_base_free ( struct event_base * eb )

Deallocate all memory associated with an event_base.

Parameters:

an event_base to be freed

int event_base_loop	(	struct event_base *	eb,
		int	flags
	)

Execute a single event (threadsafe variant).

The event_base_loop() function provides an interface for single pass execution of pending events.

Parameters:

	eb	the event_base structure returned by event_init()
	flags	any combination of EVLOOP_ONCE \| EVLOOP_NONBLOCK

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_loopexit(), event_base_loop()

int event_base_loopexit	(	struct event_base *	eb,
		struct timeval *	tv
	)

Execute a single event, with a timeout (threadsafe variant).

Parameters:

	eb	the event_base structure returned by event_init()
	tv	the amount of time after which the loop should terminate.

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_loopexit()

int event_base_once	(	struct event_base *	base,
		int	fd,
		short	events,
		void()(int, short, void )	callback,
		void *	arg,
		struct timeval *	tv
	)

Schedule a one-time event (threadsafe variant).

The function event_base_once() is similar to event_set(). However, it schedules a callback to be called exactly once and does not require the caller to prepare an event structure.

Parameters:

	base	an event_base returned by event_init()
	fd	a file descriptor to monitor
	events	event(s) to monitor; can be any of EV_TIMEOUT \| EV_READ \| EV_WRITE
	callback	callback function to be invoked when the event occurs
	arg	an argument to be passed to the callback function
	timeout	the maximum amount of time to wait for the event, or NULL to wait forever

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_once()

int event_base_priority_init	(	struct event_base *	eb,
		int	npriorities
	)

Set the number of different event priorities (threadsafe variant).

See the description of event_priority_init() for more information.

Parameters:

	eb	the event_base structure returned by event_init()
	npriorities	the maximum number of priorities

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_priority_init(), event_priority_set()

int event_base_set	(	struct event_base *	eb,
		struct event *	ev
	)

Associate a different event base with an event.

Parameters:

	eb	the event base
	ev	the event

int event_del ( struct event * ev )

Remove an event from the set of monitored events.

The function event_del() will cancel the event in the argument ev. If the event has already executed or has never been added the call will have no effect.

Parameters:

an event struct to be removed from the working set

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_add()

int event_dispatch ( void )

Loop to process events.

In order to process events, an application needs to call event_dispatch(). This function only returns on error, and should replace the event core of the application program.

See also:: event_base_dispatch()

const char* event_get_method ( void )

Get the kernel event notification mechanism used by libevent.

Returns:: a string identifying the kernel event mechanism (kqueue, epoll, etc.)

const char* event_get_version ( void )

Get the libevent version number.

Returns:: a string containing the version number of libevent

void* event_init ( void )

Initialize the event API.

The event API needs to be initialized with event_init() before it can be used.

int event_loop ( int flags )

Execute a single event.

The event_loop() function provides an interface for single pass execution of pending events.

Parameters:

flags

any combination of EVLOOP_ONCE | EVLOOP_NONBLOCK

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_loopexit(), event_base_loop()

int event_loopexit ( struct timeval * tv )

Execute a single event, with a timeout.

The event_loopexit() function is similar to event_loop(), but allows the loop to be terminated after some amount of time has passed.

Parameters:

the amount of time after which the loop should terminate.

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_loop(), event_base_loop(), event_base_loopexit()

int event_once	(	int	fd,
		short	events,
		void()(int, short, void )	callback,
		void *	arg,
		struct timeval *	tv
	)

Schedule a one-time event to occur.

The function event_once() is similar to event_set(). However, it schedules a callback to be called exactly once and does not require the caller to prepare an event structure.

Parameters:

	fd	a file descriptor to monitor
	events	event(s) to monitor; can be any of EV_TIMEOUT \| EV_READ \| EV_WRITE
	callback	callback function to be invoked when the event occurs
	arg	an argument to be passed to the callback function
	timeout	the maximum amount of time to wait for the event, or NULL to wait forever

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_set()

int event_pending	(	struct event *	ev,
		short	event,
		struct timeval *	tv
	)

Checks if a specific event is pending or scheduled.

Parameters:

	ev	an event struct previously passed to event_add()
	event	the requested event type; any of EV_TIMEOUT\|EV_READ\|EV_WRITE\|EV_SIGNAL
	tv	an alternate timeout (FIXME - is this true?)

Returns:: 1 if the event is pending, or 0 if the event has not occurred

int event_priority_init ( int npriorities )

Set the number of different event priorities.

By default libevent schedules all active events with the same priority. However, some time it is desirable to process some events with a higher priority than others. For that reason, libevent supports strict priority queues. Active events with a lower priority are always processed before events with a higher priority.

The number of different priorities can be set initially with the event_priority_init() function. This function should be called before the first call to event_dispatch(). The event_priority_set() function can be used to assign a priority to an event. By default, libevent assigns the middle priority to all events unless their priority is explicitly set.

Parameters:

npriorities

the maximum number of priorities

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_base_priority_init(), event_priority_set()

int event_priority_set	(	struct event *	ev,
		int	priority
	)

Assign a priority to an event.

Parameters:

	ev	an event struct
	priority	the new priority to be assigned

Returns:: 0 if successful, or -1 if an error occurred

See also:: event_priority_init()

void event_set	(	struct event *	,
		int	,
		short	,
		void()(int, short, void )	,
		void *
	)

Prepare an event structure to be added.

The function event_set() prepares the event structure ev to be used in future calls to event_add() and event_del(). The event will be prepared to call the function specified by the fn argument with an int argument indicating the file descriptor, a short argument indicating the type of event, and a void * argument given in the arg argument. The fd indicates the file descriptor that should be monitored for events. The events can be either EV_READ, EV_WRITE, or both. Indicating that an application can read or write from the file descriptor respectively without blocking.

The function fn will be called with the file descriptor that triggered the event and the type of event which will be either EV_TIMEOUT, EV_SIGNAL, EV_READ, or EV_WRITE. The additional flag EV_PERSIST makes an event_add() persistent until event_del() has been called.

Parameters:

	ev	an event struct to be modified
	fd	the file descriptor to be monitored
	event	desired events to monitor; can be

event.h File Reference

Detailed Description

Data Structures

Defines

Typedefs

Functions

Define Documentation

Function Documentation