event.h File Reference

A library for writing event-driven network servers. More...

#include <event-config.h>
#include <sys/types.h>
#include <sys/time.h>
#include <stdint.h>
#include <stdarg.h>
#include <evutil.h>

Go to the source code of this file.

Data Structures
struct	bufferevent
struct	evbuffer
struct	event
struct	event_watermark
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	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_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.
#define	EVLOOP_NONBLOCK   0x02
	Do not block.
#define	EVLOOP_ONCE   0x01
	event_loop() flags
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.
struct 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_setcb (struct bufferevent *bufev, evbuffercb readcb, evbuffercb writecb, everrorcb errorcb, void *cbarg)
	Changes the callbacks for a bufferevent.
void	bufferevent_setfd (struct bufferevent *bufev, int fd)
	Changes the file descriptor on which the bufferevent operates.
void	bufferevent_settimeout (struct bufferevent *bufev, int timeout_read, int timeout_write)
	Set the read and write timeout for a buffered event.
void	bufferevent_setwatermark (struct bufferevent *bufev, short events, size_t lowmark, size_t highmark)
	Sets the watermarks for read and write events.
int	bufferevent_write (struct bufferevent *bufev, const 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, ev_uint32_t number)
	Encode an integer and store it in an evbuffer.
int	evbuffer_add (struct evbuffer *, const void *, size_t)
	Append data to the end of an evbuffer.
int	evbuffer_add_buffer (struct evbuffer *, struct evbuffer *)
	Move data from one evbuffer into another evbuffer.
int	evbuffer_add_printf (struct evbuffer *, 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 *, size_t)
	Remove a specified number of bytes data from the beginning of an evbuffer.
int	evbuffer_expand (struct evbuffer *, size_t)
	Expands the available space in an event buffer.
u_char *	evbuffer_find (struct evbuffer *, const u_char *, size_t)
	Find a string within an evbuffer.
void	evbuffer_free (struct evbuffer *)
	Deallocate storage for an evbuffer.
struct evbuffer *	evbuffer_new (void)
	Allocate storage for a new evbuffer.
int	evbuffer_read (struct evbuffer *, int, int)
	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 *, void *, size_t)
	Read data from an event buffer and drain the bytes read.
void	evbuffer_setcb (struct evbuffer *, void(*)(struct evbuffer *, size_t, size_t, void *), void *)
	Set a callback to invoke when the evbuffer is modified.
int	evbuffer_write (struct evbuffer *, int)
	Write the contents of an evbuffer to a file descriptor.
void	event_active (struct event *, int, short)
int	event_add (struct event *ev, const struct timeval *timeout)
	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 *)
	Deallocate all memory associated with an event_base, and free the base.
const char *	event_base_get_method (struct event_base *)
	Get the kernel event notification mechanism used by libevent.
int	event_base_loop (struct event_base *, int)
	Handle events (threadsafe version).
int	event_base_loopbreak (struct event_base *)
	Abort the active event_base_loop() immediately.
int	event_base_loopexit (struct event_base *, const struct timeval *)
	Exit the event loop after the specified time (threadsafe variant).
struct event_base *	event_base_new (void)
	Initialize the event API.
int	event_base_once (struct event_base *base, int fd, short events, void(*callback)(int, short, void *), void *arg, const struct timeval *timeout)
	Schedule a one-time event (threadsafe variant).
int	event_base_priority_init (struct event_base *, int)
	Set the number of different event priorities (threadsafe variant).
int	event_base_set (struct event_base *, struct event *)
	Associate a different event base with an event.
int	event_del (struct event *)
	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.
struct event_base *	event_init (void)
	Initialize the event API.
int	event_loop (int)
	Handle events.
int	event_loopbreak (void)
	Abort the active event_loop() immediately.
int	event_loopexit (const struct timeval *)
	Exit the event loop after the specified time.
int	event_once (int, short, void(*)(int, short, void *), void *, const struct timeval *)
	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)
	Set the number of different event priorities.
int	event_priority_set (struct event *, int)
	Assign a priority to an event.
int	event_reinit (struct event_base *base)
	Reinitialized the event base after a fork.
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)
	Redirect libevent's log messages.
int	evtag_consume (struct evbuffer *evbuf)
void	evtag_init (void)
void	evtag_marshal (struct evbuffer *evbuf, ev_uint32_t tag, const void *data, ev_uint32_t len)
void	evtag_marshal_int (struct evbuffer *evbuf, ev_uint32_t tag, ev_uint32_t integer)
void	evtag_marshal_string (struct evbuffer *buf, ev_uint32_t tag, const char *string)
void	evtag_marshal_timeval (struct evbuffer *evbuf, ev_uint32_t tag, struct timeval *tv)
int	evtag_payload_length (struct evbuffer *evbuf, ev_uint32_t *plength)
int	evtag_peek (struct evbuffer *evbuf, ev_uint32_t *ptag)
int	evtag_peek_length (struct evbuffer *evbuf, ev_uint32_t *plength)
int	evtag_unmarshal (struct evbuffer *src, ev_uint32_t *ptag, struct evbuffer *dst)
int	evtag_unmarshal_fixed (struct evbuffer *src, ev_uint32_t need_tag, void *data, size_t len)
int	evtag_unmarshal_int (struct evbuffer *evbuf, ev_uint32_t need_tag, ev_uint32_t *pinteger)
int	evtag_unmarshal_string (struct evbuffer *evbuf, ev_uint32_t need_tag, char **pstring)
int	evtag_unmarshal_timeval (struct evbuffer *evbuf, ev_uint32_t need_tag, struct timeval *ptv)

---

Detailed Description

A library for writing event-driven network servers.

---

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:

ev

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

Do not block.

#define EVLOOP_ONCE   0x01

event_loop() flags

Block at most once.

#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:

ev

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:

ev

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
	)			[read]

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_setcb	(	struct bufferevent *	bufev,
		evbuffercb	readcb,
		evbuffercb	writecb,
		everrorcb	errorcb,
		void *	cbarg
	)

Changes the callbacks for a bufferevent.

Parameters:

	bufev	the bufferevent object for which to change callbacks
	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)

See also:

bufferevent_new()

void bufferevent_setfd	(	struct bufferevent *	bufev,
		int	fd
	)

Changes the file descriptor on which the bufferevent operates.

Parameters:

	bufev	the bufferevent object for which to change the file descriptor
	fd	the file descriptor to operate on

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

void bufferevent_setwatermark	(	struct bufferevent *	bufev,
		short	events,
		size_t	lowmark,
		size_t	highmark
	)

Sets the watermarks for read and write events.

On input, a bufferevent does not invoke the user read callback unless there is at least low watermark data in the buffer. If the read buffer is beyond the high watermark, the buffevent stops reading from the network.

On output, the user write callback is invoked whenever the buffered data falls below the low watermark.

Parameters:

	bufev	the bufferevent to be modified
	events	EV_READ, EV_WRITE or both
	lowmark	the lower watermark to set
	highmark	the high watermark to set

int bufferevent_write	(	struct bufferevent *	bufev,
		const 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.

The evbuffer is being drained as a result.

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,
		ev_uint32_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 *	,
		const void *	,
		size_t
	)

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 *	,
		struct evbuffer *
	)

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 *	,
		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:

The number of bytes added 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:

The number of bytes added if successful, or -1 if an error occurred.

void evbuffer_drain	(	struct evbuffer *	,
		size_t
	)

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

int evbuffer_expand	(	struct evbuffer *	,
		size_t
	)

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 *	,
		const u_char *	,
		size_t
	)

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 *

)

Deallocate storage for an evbuffer.

Parameters:

pointer

to the evbuffer to be freed

struct evbuffer* evbuffer_new

(

void

)

[read]

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 *	,
		int	,
		int
	)

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 *	,
		void *	,
		size_t
	)

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 *	,
		void(*)(struct evbuffer *, size_t, size_t, void *)	,
		void *
	)

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 *	,
		int
	)

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,
		const struct timeval *	timeout
	)

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:

eb

the event_base structure returned by event_init()

See also:

event_init(), event_dispatch()

void event_base_free

(

struct event_base *

)

Deallocate all memory associated with an event_base, and free the base.

Note that this function will not close any fds or free any memory passed to event_set as the argument to callback.

Parameters:

eb

an event_base to be freed

const char* event_base_get_method

(

struct event_base *

)

Get the kernel event notification mechanism used by libevent.

Parameters:

eb

the event_base structure returned by event_base_new()

Returns:

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

int event_base_loop	(	struct event_base *	,
		int
	)

Handle events (threadsafe version).

This is a more flexible version of event_base_dispatch().

Parameters:

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

Returns:

0 if successful, -1 if an error occurred, or 1 if no events were registered.

See also:

event_loopexit(), event_base_loop()

int event_base_loopbreak

(

struct event_base *

)

Abort the active event_base_loop() immediately.

event_base_loop() will abort the loop after the next event is completed; event_base_loopbreak() is typically invoked from this event's callback. This behavior is analogous to the "break;" statement.

Subsequent invocations of event_loop() will proceed normally.

Parameters:

eb

the event_base structure returned by event_init()

Returns:

0 if successful, or -1 if an error occurred

See also:

event_base_loopexit

int event_base_loopexit	(	struct event_base *	,
		const struct timeval *
	)

Exit the event loop after the specified time (threadsafe variant).

The next event_base_loop() iteration after the given timer expires will complete normally (handling all queued events) then exit without blocking for events again.

Subsequent invocations of event_base_loop() will proceed normally.

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()

struct event_base* event_base_new

(

void

)

[read]

Initialize the event API.

Use event_base_new() to initialize a new event base, but does not set the current_base global. If using only event_base_new(), each event added must have an event base set with event_base_set()

See also:

event_base_set(), event_base_free(), event_init()

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

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 *	,
		int
	)

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 *	,
		struct event *
	)

Associate a different event base with an event.

Parameters:

	eb	the event base
	ev	the event

int event_del

(

struct event *

)

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:

ev

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

struct event_base* event_init

(

void

)

[read]

Initialize the event API.

The event API needs to be initialized with event_init() before it can be used. Sets the current_base global representing the default base for events that have no base associated with them.

See also:

event_base_set(), event_base_new()

int event_loop

(

int

)

Handle events.

This is a more flexible version of event_dispatch().

Parameters:

flags

any combination of EVLOOP_ONCE | EVLOOP_NONBLOCK

Returns:

0 if successful, -1 if an error occurred, or 1 if no events were registered.

See also:

event_loopexit(), event_base_loop()

int event_loopbreak

(

void

)

Abort the active event_loop() immediately.

event_loop() will abort the loop after the next event is completed; event_loopbreak() is typically invoked from this event's callback. This behavior is analogous to the "break;" statement.

Subsequent invocations of event_loop() will proceed normally.

Returns:

0 if successful, or -1 if an error occurred

See also:

event_base_loopbreak(), event_loopexit()

int event_loopexit

(

const struct timeval *

)

Exit the event loop after the specified time.

The next event_loop() iteration after the given timer expires will complete normally (handling all queued events) then exit without blocking for events again.

Subsequent invocations of event_loop() will proceed normally.

Parameters:

tv

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	,
		short	,
		void(*)(int, short, void *)	,
		void *	,
		const struct timeval *
	)

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

)

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 *	,
		int
	)

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()

int event_reinit

(

struct event_base *

base

)

Reinitialized the event base after a fork.

Some event mechanisms do not survive across fork. The event base needs to be reinitialized with the event_reinit() function.

Parameters:

base

the event base that needs to be re-initialized

Returns:

0 if successful, or -1 if some events could not be re-added.

See also:

event_base_new(), event_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 EV_READ and/or EV_WRITE
	fn	callback function to be invoked when the event occurs
	arg	an argument to be passed to the callback function

See also:

event_add(), event_del(), event_once()

void event_set_log_callback

(

event_log_cb

cb

)

Redirect libevent's log messages.

Parameters:

cb

a function taking two arguments: an integer severity between _EVENT_LOG_DEBUG and _EVENT_LOG_ERR, and a string. If cb is NULL, then the default log is used.