2 * Copyright (c) 2000-2007 Niels Provos <provos@citi.umich.edu>
3 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 #ifndef EVENT2_EVENT_H_INCLUDED_
28 #define EVENT2_EVENT_H_INCLUDED_
33 @section intro Introduction
35 Libevent is an event notification library for developing scalable network
36 servers. The Libevent API provides a mechanism to execute a callback
37 function when a specific event occurs on a file descriptor or after a
38 timeout has been reached. Furthermore, Libevent also support callbacks due
39 to signals or regular timeouts.
41 Libevent is meant to replace the event loop found in event driven network
42 servers. An application just needs to call event_base_dispatch() and then add or
43 remove events dynamically without having to change the event loop.
46 Currently, Libevent supports /dev/poll, kqueue(2), select(2), poll(2),
47 epoll(4), and evports. The internal event mechanism is completely
48 independent of the exposed event API, and a simple update of Libevent can
49 provide new functionality without having to redesign the applications. As a
50 result, Libevent allows for portable application development and provides
51 the most scalable event notification mechanism available on an operating
52 system. Libevent can also be used for multithreaded programs. Libevent
53 should compile on Linux, *BSD, Mac OS X, Solaris and, Windows.
55 @section usage Standard usage
57 Every program that uses Libevent must include the <event2/event.h>
58 header, and pass the -levent flag to the linker. (You can instead link
59 -levent_core if you only want the main event and buffered IO-based code,
60 and don't want to link any protocol code.)
62 @section setup Library setup
64 Before you call any other Libevent functions, you need to set up the
65 library. If you're going to use Libevent from multiple threads in a
66 multithreaded application, you need to initialize thread support --
67 typically by using evthread_use_pthreads() or
68 evthread_use_windows_threads(). See <event2/thread.h> for more
71 This is also the point where you can replace Libevent's memory
72 management functions with event_set_mem_functions, and enable debug mode
73 with event_enable_debug_mode().
75 @section base Creating an event base
77 Next, you need to create an event_base structure, using event_base_new()
78 or event_base_new_with_config(). The event_base is responsible for
79 keeping track of which events are "pending" (that is to say, being
80 watched to see if they become active) and which events are "active".
81 Every event is associated with a single event_base.
83 @section event Event notification
85 For each file descriptor that you wish to monitor, you must create an
86 event structure with event_new(). (You may also declare an event
87 structure and call event_assign() to initialize the members of the
88 structure.) To enable notification, you add the structure to the list
89 of monitored events by calling event_add(). The event structure must
90 remain allocated as long as it is active, so it should generally be
91 allocated on the heap.
93 @section loop Dispatching events.
95 Finally, you call event_base_dispatch() to loop and dispatch events.
96 You can also use event_base_loop() for more fine-grained control.
98 Currently, only one thread can be dispatching a given event_base at a
99 time. If you want to run events in multiple threads at once, you can
100 either have a single event_base whose events add work to a work queue,
101 or you can create multiple event_base objects.
103 @section bufferevent I/O Buffers
105 Libevent provides a buffered I/O abstraction on top of the regular event
106 callbacks. This abstraction is called a bufferevent. A bufferevent
107 provides input and output buffers that get filled and drained
108 automatically. The user of a buffered event no longer deals directly
109 with the I/O, but instead is reading from input and writing to output
112 Once initialized via bufferevent_socket_new(), the bufferevent structure
113 can be used repeatedly with bufferevent_enable() and
114 bufferevent_disable(). Instead of reading and writing directly to a
115 socket, you would call bufferevent_read() and bufferevent_write().
117 When read enabled the bufferevent will try to read from the file descriptor
118 and call the read callback. The write callback is executed whenever the
119 output buffer is drained below the write low watermark, which is 0 by
122 See <event2/bufferevent*.h> for more information.
124 @section timers Timers
126 Libevent can also be used to create timers that invoke a callback after a
127 certain amount of time has expired. The evtimer_new() macro returns
128 an event struct to use as a timer. To activate the timer, call
129 evtimer_add(). Timers can be deactivated by calling evtimer_del().
130 (These macros are thin wrappers around event_new(), event_add(),
131 and event_del(); you can also use those instead.)
133 @section evdns Asynchronous DNS resolution
135 Libevent provides an asynchronous DNS resolver that should be used instead
136 of the standard DNS resolver functions. See the <event2/dns.h>
137 functions for more detail.
139 @section evhttp Event-driven HTTP servers
141 Libevent provides a very simple event-driven HTTP server that can be
142 embedded in your program and used to service HTTP requests.
144 To use this capability, you need to include the <event2/http.h> header in your
145 program. See that header for more information.
147 @section evrpc A framework for RPC servers and clients
149 Libevent provides a framework for creating RPC servers and clients. It
150 takes care of marshaling and unmarshaling all data structures.
152 @section api API Reference
154 To browse the complete documentation of the libevent API, click on any of
158 The primary libevent header
161 Functions for use by multithreaded programs
163 event2/buffer.h and event2/bufferevent.h
164 Buffer management for network reading and writing
167 Utility functions for portable nonblocking network code
170 Asynchronous DNS resolution
173 An embedded libevent-based HTTP server
176 A framework for creating RPC servers and clients
180 /** @file event2/event.h
182 Core functions for waiting for and receiving events, and using event bases.
185 #include <event2/visibility.h>
191 #include <event2/event-config.h>
192 #ifdef EVENT__HAVE_SYS_TYPES_H
193 #include <sys/types.h>
195 #ifdef EVENT__HAVE_SYS_TIME_H
196 #include <sys/time.h>
202 #include <event2/util.h>
205 * Structure to hold information and state for a Libevent dispatch loop.
207 * The event_base lies at the center of Libevent; every application will
208 * have one. It keeps track of all pending and active events, and
209 * notifies your application of the active ones.
211 * This is an opaque structure; you can allocate one using
212 * event_base_new() or event_base_new_with_config().
214 * @see event_base_new(), event_base_free(), event_base_loop(),
215 * event_base_new_with_config()
218 #ifdef EVENT_IN_DOXYGEN_
219 {/*Empty body so that doxygen will generate documentation here.*/}
226 * Structure to represent a single event.
228 * An event can have some underlying condition it represents: a socket
229 * becoming readable or writeable (or both), or a signal becoming raised.
230 * (An event that represents no underlying condition is still useful: you
231 * can use one to implement a timer, or to communicate between threads.)
233 * Generally, you can create events with event_new(), then make them
234 * pending with event_add(). As your event_base runs, it will run the
235 * callbacks of an events whose conditions are triggered. When you
236 * longer want the event, free it with event_free().
240 * An event may be "pending" (one whose condition we are watching),
241 * "active" (one whose condition has triggered and whose callback is about
242 * to run), neither, or both. Events come into existence via
243 * event_assign() or event_new(), and are then neither active nor pending.
245 * To make an event pending, pass it to event_add(). When doing so, you
246 * can also set a timeout for the event.
248 * Events become active during an event_base_loop() call when either their
249 * condition has triggered, or when their timeout has elapsed. You can
250 * also activate an event manually using event_active(). The even_base
251 * loop will run the callbacks of active events; after it has done so, it
252 * marks them as no longer active.
254 * You can make an event non-pending by passing it to event_del(). This
255 * also makes the event non-active.
257 * Events can be "persistent" or "non-persistent". A non-persistent event
258 * becomes non-pending as soon as it is triggered: thus, it only runs at
259 * most once per call to event_add(). A persistent event remains pending
260 * even when it becomes active: you'll need to event_del() it manually in
261 * order to make it non-pending. When a persistent event with a timeout
262 * becomes active, its timeout is reset: this means you can use persistent
263 * events to implement periodic timeouts.
265 * This should be treated as an opaque structure; you should never read or
266 * write any of its fields directly. For backward compatibility with old
267 * code, it is defined in the event2/event_struct.h header; including this
268 * header may make your code incompatible with other versions of Libevent.
270 * @see event_new(), event_free(), event_assign(), event_get_assignment(),
271 * event_add(), event_del(), event_active(), event_pending(),
272 * event_get_fd(), event_get_base(), event_get_events(),
273 * event_get_callback(), event_get_callback_arg(),
274 * event_priority_set()
277 #ifdef EVENT_IN_DOXYGEN_
278 {/*Empty body so that doxygen will generate documentation here.*/}
283 * Configuration for an event_base.
285 * There are many options that can be used to alter the behavior and
286 * implementation of an event_base. To avoid having to pass them all in a
287 * complex many-argument constructor, we provide an abstract data type
288 * wrhere you set up configation information before passing it to
289 * event_base_new_with_config().
291 * @see event_config_new(), event_config_free(), event_base_new_with_config(),
292 * event_config_avoid_method(), event_config_require_features(),
293 * event_config_set_flag(), event_config_set_num_cpus_hint()
296 #ifdef EVENT_IN_DOXYGEN_
297 {/*Empty body so that doxygen will generate documentation here.*/}
302 * Enable some relatively expensive debugging checks in Libevent that
303 * would normally be turned off. Generally, these checks cause code that
304 * would otherwise crash mysteriously to fail earlier with an assertion
305 * failure. Note that this method MUST be called before any events or
306 * event_bases have been created.
308 * Debug mode can currently catch the following errors:
309 * An event is re-assigned while it is added
310 * Any function is called on a non-assigned event
312 * Note that debugging mode uses memory to track every event that has been
313 * initialized (via event_assign, event_set, or event_new) but not yet
314 * released (via event_free or event_debug_unassign). If you want to use
315 * debug mode, and you find yourself running out of memory, you will need
316 * to use event_debug_unassign to explicitly stop tracking events that
317 * are no longer considered set-up.
319 * @see event_debug_unassign()
322 void event_enable_debug_mode(void);
325 * When debugging mode is enabled, informs Libevent that an event should no
326 * longer be considered as assigned. When debugging mode is not enabled, does
329 * This function must only be called on a non-added event.
331 * @see event_enable_debug_mode()
334 void event_debug_unassign(struct event *);
337 * Create and return a new event_base to use with the rest of Libevent.
339 * @return a new event_base on success, or NULL on failure.
341 * @see event_base_free(), event_base_new_with_config()
344 struct event_base *event_base_new(void);
347 Reinitialize the event base after a fork
349 Some event mechanisms do not survive across fork. The event base needs
350 to be reinitialized with the event_reinit() function.
352 @param base the event base that needs to be re-initialized
353 @return 0 if successful, or -1 if some events could not be re-added.
354 @see event_base_new()
357 int event_reinit(struct event_base *base);
360 Event dispatching loop
362 This loop will run the event base until either there are no more pending or
363 active, or until something calls event_base_loopbreak() or
364 event_base_loopexit().
366 @param base the event_base structure returned by event_base_new() or
367 event_base_new_with_config()
368 @return 0 if successful, -1 if an error occurred, or 1 if we exited because
369 no events were pending or active.
370 @see event_base_loop()
373 int event_base_dispatch(struct event_base *);
376 Get the kernel event notification mechanism used by Libevent.
378 @param eb the event_base structure returned by event_base_new()
379 @return a string identifying the kernel event mechanism (kqueue, epoll, etc.)
382 const char *event_base_get_method(const struct event_base *);
385 Gets all event notification mechanisms supported by Libevent.
387 This functions returns the event mechanism in order preferred by
388 Libevent. Note that this list will include all backends that
389 Libevent has compiled-in support for, and will not necessarily check
390 your OS to see whether it has the required resources.
392 @return an array with pointers to the names of support methods.
393 The end of the array is indicated by a NULL pointer. If an
394 error is encountered NULL is returned.
397 const char **event_get_supported_methods(void);
399 /** Query the current monotonic time from a the timer for a struct
403 int event_gettime_monotonic(struct event_base *base, struct timeval *tp);
406 @name event type flag
408 Flags to pass to event_base_get_num_events() to specify the kinds of events
409 we want to aggregate counts for
412 /** count the number of active events, which have been triggered.*/
413 #define EVENT_BASE_COUNT_ACTIVE 1U
414 /** count the number of virtual events, which is used to represent an internal
415 * condition, other than a pending event, that keeps the loop from exiting. */
416 #define EVENT_BASE_COUNT_VIRTUAL 2U
417 /** count the number of events which have been added to event base, including
418 * internal events. */
419 #define EVENT_BASE_COUNT_ADDED 4U
423 Gets the number of events in event_base, as specified in the flags.
425 Since event base has some internal events added to make some of its
426 functionalities work, EVENT_BASE_COUNT_ADDED may return more than the
427 number of events you added using event_add().
429 If you pass EVENT_BASE_COUNT_ACTIVE and EVENT_BASE_COUNT_ADDED together, an
430 active event will be counted twice. However, this might not be the case in
431 future libevent versions. The return value is an indication of the work
432 load, but the user shouldn't rely on the exact value as this may change in
435 @param eb the event_base structure returned by event_base_new()
436 @param flags a bitwise combination of the kinds of events to aggregate
438 @return the number of events specified in the flags
441 int event_base_get_num_events(struct event_base *, unsigned int);
444 Get the maximum number of events in a given event_base as specified in the
447 @param eb the event_base structure returned by event_base_new()
448 @param flags a bitwise combination of the kinds of events to aggregate
450 @param clear option used to reset the maximum count.
451 @return the number of events specified in the flags
454 int event_base_get_max_events(struct event_base *, unsigned int, int);
457 Allocates a new event configuration object.
459 The event configuration object can be used to change the behavior of
462 @return an event_config object that can be used to store configuration, or
463 NULL if an error is encountered.
464 @see event_base_new_with_config(), event_config_free(), event_config
467 struct event_config *event_config_new(void);
470 Deallocates all memory associated with an event configuration object
472 @param cfg the event configuration object to be freed.
475 void event_config_free(struct event_config *cfg);
478 Enters an event method that should be avoided into the configuration.
480 This can be used to avoid event mechanisms that do not support certain
481 file descriptor types, or for debugging to avoid certain event
482 mechanisms. An application can make use of multiple event bases to
483 accommodate incompatible file descriptor types.
485 @param cfg the event configuration object
486 @param method the name of the event method to avoid
487 @return 0 on success, -1 on failure.
490 int event_config_avoid_method(struct event_config *cfg, const char *method);
493 A flag used to describe which features an event_base (must) provide.
495 Because of OS limitations, not every Libevent backend supports every
496 possible feature. You can use this type with
497 event_config_require_features() to tell Libevent to only proceed if your
498 event_base implements a given feature, and you can receive this type from
499 event_base_get_features() to see which features are available.
501 enum event_method_feature {
502 /** Require an event method that allows edge-triggered events with EV_ET. */
503 EV_FEATURE_ET = 0x01,
504 /** Require an event method where having one event triggered among
505 * many is [approximately] an O(1) operation. This excludes (for
506 * example) select and poll, which are approximately O(N) for N
507 * equal to the total number of possible events. */
508 EV_FEATURE_O1 = 0x02,
509 /** Require an event method that allows file descriptors as well as
511 EV_FEATURE_FDS = 0x04,
512 /** Require an event method that allows you to use EV_CLOSED to detect
513 * connection close without the necessity of reading all the pending data.
515 * Methods that do support EV_CLOSED may not be able to provide support on
516 * all kernel versions.
518 EV_FEATURE_EARLY_CLOSE = 0x08
522 A flag passed to event_config_set_flag().
524 These flags change the behavior of an allocated event_base.
526 @see event_config_set_flag(), event_base_new_with_config(),
529 enum event_base_config_flag {
530 /** Do not allocate a lock for the event base, even if we have
533 Setting this option will make it unsafe and nonfunctional to call
534 functions on the base concurrently from multiple threads.
536 EVENT_BASE_FLAG_NOLOCK = 0x01,
537 /** Do not check the EVENT_* environment variables when configuring
539 EVENT_BASE_FLAG_IGNORE_ENV = 0x02,
540 /** Windows only: enable the IOCP dispatcher at startup
542 If this flag is set then bufferevent_socket_new() and
543 evconn_listener_new() will use IOCP-backed implementations
544 instead of the usual select-based one on Windows.
546 EVENT_BASE_FLAG_STARTUP_IOCP = 0x04,
547 /** Instead of checking the current time every time the event loop is
548 ready to run timeout callbacks, check after each timeout callback.
550 EVENT_BASE_FLAG_NO_CACHE_TIME = 0x08,
552 /** If we are using the epoll backend, this flag says that it is
553 safe to use Libevent's internal change-list code to batch up
554 adds and deletes in order to try to do as few syscalls as
555 possible. Setting this flag can make your code run faster, but
556 it may trigger a Linux bug: it is not safe to use this flag
557 if you have any fds cloned by dup() or its variants. Doing so
558 will produce strange and hard-to-diagnose bugs.
560 This flag can also be activated by setting the
561 EVENT_EPOLL_USE_CHANGELIST environment variable.
563 This flag has no effect if you wind up using a backend other than
566 EVENT_BASE_FLAG_EPOLL_USE_CHANGELIST = 0x10,
568 /** Ordinarily, Libevent implements its time and timeout code using
569 the fastest monotonic timer that we have. If this flag is set,
570 however, we use less efficient more precise timer, assuming one is
573 EVENT_BASE_FLAG_PRECISE_TIMER = 0x20
577 Return a bitmask of the features implemented by an event base. This
578 will be a bitwise OR of one or more of the values of
581 @see event_method_feature
584 int event_base_get_features(const struct event_base *base);
587 Enters a required event method feature that the application demands.
589 Note that not every feature or combination of features is supported
590 on every platform. Code that requests features should be prepared
591 to handle the case where event_base_new_with_config() returns NULL, as in:
593 event_config_require_features(cfg, EV_FEATURE_ET);
594 base = event_base_new_with_config(cfg);
596 // We can't get edge-triggered behavior here.
597 event_config_require_features(cfg, 0);
598 base = event_base_new_with_config(cfg);
602 @param cfg the event configuration object
603 @param feature a bitfield of one or more event_method_feature values.
604 Replaces values from previous calls to this function.
605 @return 0 on success, -1 on failure.
606 @see event_method_feature, event_base_new_with_config()
609 int event_config_require_features(struct event_config *cfg, int feature);
612 * Sets one or more flags to configure what parts of the eventual event_base
613 * will be initialized, and how they'll work.
615 * @see event_base_config_flags, event_base_new_with_config()
618 int event_config_set_flag(struct event_config *cfg, int flag);
621 * Records a hint for the number of CPUs in the system. This is used for
622 * tuning thread pools, etc, for optimal performance. In Libevent 2.0,
623 * it is only on Windows, and only when IOCP is in use.
625 * @param cfg the event configuration object
626 * @param cpus the number of cpus
627 * @return 0 on success, -1 on failure.
630 int event_config_set_num_cpus_hint(struct event_config *cfg, int cpus);
633 * Record an interval and/or a number of callbacks after which the event base
634 * should check for new events. By default, the event base will run as many
635 * events are as activated at the higest activated priority before checking
636 * for new events. If you configure it by setting max_interval, it will check
637 * the time after each callback, and not allow more than max_interval to
638 * elapse before checking for new events. If you configure it by setting
639 * max_callbacks to a value >= 0, it will run no more than max_callbacks
640 * callbacks before checking for new events.
642 * This option can decrease the latency of high-priority events, and
643 * avoid priority inversions where multiple low-priority events keep us from
644 * polling for high-priority events, but at the expense of slightly decreasing
645 * the throughput. Use it with caution!
647 * @param cfg The event_base configuration object.
648 * @param max_interval An interval after which Libevent should stop running
649 * callbacks and check for more events, or NULL if there should be
651 * @param max_callbacks A number of callbacks after which Libevent should
652 * stop running callbacks and check for more events, or -1 if there
653 * should be no such limit.
654 * @param min_priority A priority below which max_interval and max_callbacks
655 * should not be enforced. If this is set to 0, they are enforced
656 * for events of every priority; if it's set to 1, they're enforced
657 * for events of priority 1 and above, and so on.
658 * @return 0 on success, -1 on failure.
661 int event_config_set_max_dispatch_interval(struct event_config *cfg,
662 const struct timeval *max_interval, int max_callbacks,
666 Initialize the event API.
668 Use event_base_new_with_config() to initialize a new event base, taking
669 the specified configuration under consideration. The configuration object
670 can currently be used to avoid certain event notification mechanisms.
672 @param cfg the event configuration object
673 @return an initialized event_base that can be used to registering events,
674 or NULL if no event base can be created with the requested event_config.
675 @see event_base_new(), event_base_free(), event_init(), event_assign()
678 struct event_base *event_base_new_with_config(const struct event_config *);
681 Deallocate all memory associated with an event_base, and free the base.
683 Note that this function will not close any fds or free any memory passed
684 to event_new as the argument to callback.
686 If there are any pending finalizer callbacks, this function will invoke
689 @param eb an event_base to be freed
692 void event_base_free(struct event_base *);
695 As event_free, but do not run finalizers.
697 THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
701 void event_base_free_nofinalize(struct event_base *);
703 /** @name Log severities
706 #define EVENT_LOG_DEBUG 0
707 #define EVENT_LOG_MSG 1
708 #define EVENT_LOG_WARN 2
709 #define EVENT_LOG_ERR 3
712 /* Obsolete names: these are deprecated, but older programs might use them.
713 * They violate the reserved-identifier namespace. */
714 #define _EVENT_LOG_DEBUG EVENT_LOG_DEBUG
715 #define _EVENT_LOG_MSG EVENT_LOG_MSG
716 #define _EVENT_LOG_WARN EVENT_LOG_WARN
717 #define _EVENT_LOG_ERR EVENT_LOG_ERR
720 A callback function used to intercept Libevent's log messages.
722 @see event_set_log_callback
724 typedef void (*event_log_cb)(int severity, const char *msg);
726 Redirect Libevent's log messages.
728 @param cb a function taking two arguments: an integer severity between
729 EVENT_LOG_DEBUG and EVENT_LOG_ERR, and a string. If cb is NULL,
730 then the default log is used.
732 NOTE: The function you provide *must not* call any other libevent
733 functionality. Doing so can produce undefined behavior.
736 void event_set_log_callback(event_log_cb cb);
739 A function to be called if Libevent encounters a fatal internal error.
741 @see event_set_fatal_callback
743 typedef void (*event_fatal_cb)(int err);
746 Override Libevent's behavior in the event of a fatal internal error.
748 By default, Libevent will call exit(1) if a programming error makes it
749 impossible to continue correct operation. This function allows you to supply
750 another callback instead. Note that if the function is ever invoked,
751 something is wrong with your program, or with Libevent: any subsequent calls
752 to Libevent may result in undefined behavior.
754 Libevent will (almost) always log an EVENT_LOG_ERR message before calling
755 this function; look at the last log message to see why Libevent has died.
758 void event_set_fatal_callback(event_fatal_cb cb);
760 #define EVENT_DBG_ALL 0xffffffffu
761 #define EVENT_DBG_NONE 0
764 Turn on debugging logs and have them sent to the default log handler.
766 This is a global setting; if you are going to call it, you must call this
767 before any calls that create an event-base. You must call it before any
768 multithreaded use of Libevent.
770 Debug logs are verbose.
772 @param which Controls which debug messages are turned on. This option is
773 unused for now; for forward compatibility, you must pass in the constant
774 "EVENT_DBG_ALL" to turn debugging logs on, or "EVENT_DBG_NONE" to turn
778 void event_enable_debug_logging(ev_uint32_t which);
782 event_disable_debug_mode(void);
785 Associate a different event base with an event.
787 The event to be associated must not be currently active or pending.
789 @param eb the event base
791 @return 0 on success, -1 on failure.
794 int event_base_set(struct event_base *, struct event *);
798 These flags control the behavior of event_base_loop().
801 /** Block until we have an active event, then exit once all active events
802 * have had their callbacks run. */
803 #define EVLOOP_ONCE 0x01
804 /** Do not block: see which events are ready now, run the callbacks
805 * of the highest-priority ones, then exit. */
806 #define EVLOOP_NONBLOCK 0x02
807 /** Do not exit the loop because we have no pending events. Instead, keep
808 * running until event_base_loopexit() or event_base_loopbreak() makes us
811 #define EVLOOP_NO_EXIT_ON_EMPTY 0x04
815 Wait for events to become active, and run their callbacks.
817 This is a more flexible version of event_base_dispatch().
819 By default, this loop will run the event base until either there are no more
820 pending or active events, or until something calls event_base_loopbreak() or
821 event_base_loopexit(). You can override this behavior with the 'flags'
824 @param eb the event_base structure returned by event_base_new() or
825 event_base_new_with_config()
826 @param flags any combination of EVLOOP_ONCE | EVLOOP_NONBLOCK
827 @return 0 if successful, -1 if an error occurred, or 1 if we exited because
828 no events were pending or active.
829 @see event_base_loopexit(), event_base_dispatch(), EVLOOP_ONCE,
833 int event_base_loop(struct event_base *, int);
836 Exit the event loop after the specified time
838 The next event_base_loop() iteration after the given timer expires will
839 complete normally (handling all queued events) then exit without
840 blocking for events again.
842 Subsequent invocations of event_base_loop() will proceed normally.
844 @param eb the event_base structure returned by event_init()
845 @param tv the amount of time after which the loop should terminate,
846 or NULL to exit after running all currently active events.
847 @return 0 if successful, or -1 if an error occurred
848 @see event_base_loopbreak()
851 int event_base_loopexit(struct event_base *, const struct timeval *);
854 Abort the active event_base_loop() immediately.
856 event_base_loop() will abort the loop after the next event is completed;
857 event_base_loopbreak() is typically invoked from this event's callback.
858 This behavior is analogous to the "break;" statement.
860 Subsequent invocations of event_base_loop() will proceed normally.
862 @param eb the event_base structure returned by event_init()
863 @return 0 if successful, or -1 if an error occurred
864 @see event_base_loopexit()
867 int event_base_loopbreak(struct event_base *);
870 Tell the active event_base_loop() to scan for new events immediately.
872 Calling this function makes the currently active event_base_loop()
873 start the loop over again (scanning for new events) after the current
874 event callback finishes. If the event loop is not running, this
875 function has no effect.
877 event_base_loopbreak() is typically invoked from this event's callback.
878 This behavior is analogous to the "continue;" statement.
880 Subsequent invocations of event loop will proceed normally.
882 @param eb the event_base structure returned by event_init()
883 @return 0 if successful, or -1 if an error occurred
884 @see event_base_loopbreak()
887 int event_base_loopcontinue(struct event_base *);
890 Checks if the event loop was told to exit by event_base_loopexit().
892 This function will return true for an event_base at every point after
893 event_loopexit() is called, until the event loop is next entered.
895 @param eb the event_base structure returned by event_init()
896 @return true if event_base_loopexit() was called on this event base,
898 @see event_base_loopexit()
899 @see event_base_got_break()
902 int event_base_got_exit(struct event_base *);
905 Checks if the event loop was told to abort immediately by event_base_loopbreak().
907 This function will return true for an event_base at every point after
908 event_base_loopbreak() is called, until the event loop is next entered.
910 @param eb the event_base structure returned by event_init()
911 @return true if event_base_loopbreak() was called on this event base,
913 @see event_base_loopbreak()
914 @see event_base_got_exit()
917 int event_base_got_break(struct event_base *);
922 * Flags to pass to event_new(), event_assign(), event_pending(), and
923 * anything else with an argument of the form "short events"
926 /** Indicates that a timeout has occurred. It's not necessary to pass
927 * this flag to event_for new()/event_assign() to get a timeout. */
928 #define EV_TIMEOUT 0x01
929 /** Wait for a socket or FD to become readable */
931 /** Wait for a socket or FD to become writeable */
932 #define EV_WRITE 0x04
933 /** Wait for a POSIX signal to be raised*/
934 #define EV_SIGNAL 0x08
936 * Persistent event: won't get removed automatically when activated.
938 * When a persistent event with a timeout becomes activated, its timeout
941 #define EV_PERSIST 0x10
942 /** Select edge-triggered behavior, if supported by the backend. */
945 * If this option is provided, then event_del() will not block in one thread
946 * while waiting for the event callback to complete in another thread.
948 * To use this option safely, you may need to use event_finalize() or
949 * event_free_finalize() in order to safely tear down an event in a
950 * multithreaded application. See those functions for more information.
952 * THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
955 #define EV_FINALIZE 0x40
957 * Detects connection close events. You can use this to detect when a
958 * connection has been closed, without having to read all the pending data
961 * Not all backends support EV_CLOSED. To detect or require it, use the
962 * feature flag EV_FEATURE_EARLY_CLOSE.
964 #define EV_CLOSED 0x80
968 @name evtimer_* macros
970 Aliases for working with one-shot timer events */
972 #define evtimer_assign(ev, b, cb, arg) \
973 event_assign((ev), (b), -1, 0, (cb), (arg))
974 #define evtimer_new(b, cb, arg) event_new((b), -1, 0, (cb), (arg))
975 #define evtimer_add(ev, tv) event_add((ev), (tv))
976 #define evtimer_del(ev) event_del(ev)
977 #define evtimer_pending(ev, tv) event_pending((ev), EV_TIMEOUT, (tv))
978 #define evtimer_initialized(ev) event_initialized(ev)
982 @name evsignal_* macros
984 Aliases for working with signal events
987 #define evsignal_add(ev, tv) event_add((ev), (tv))
988 #define evsignal_assign(ev, b, x, cb, arg) \
989 event_assign((ev), (b), (x), EV_SIGNAL|EV_PERSIST, cb, (arg))
990 #define evsignal_new(b, x, cb, arg) \
991 event_new((b), (x), EV_SIGNAL|EV_PERSIST, (cb), (arg))
992 #define evsignal_del(ev) event_del(ev)
993 #define evsignal_pending(ev, tv) event_pending((ev), EV_SIGNAL, (tv))
994 #define evsignal_initialized(ev) event_initialized(ev)
998 A callback function for an event.
1000 It receives three arguments:
1002 @param fd An fd or signal
1003 @param events One or more EV_* flags
1004 @param arg A user-supplied argument.
1008 typedef void (*event_callback_fn)(evutil_socket_t, short, void *);
1011 Return a value used to specify that the event itself must be used as the callback argument.
1013 The function event_new() takes a callback argument which is passed
1014 to the event's callback function. To specify that the argument to be
1015 passed to the callback function is the event that event_new() returns,
1016 pass in the return value of event_self_cbarg() as the callback argument
1021 struct event *ev = event_new(base, sock, events, callback, %event_self_cbarg());
1024 For consistency with event_new(), it is possible to pass the return value
1025 of this function as the callback argument for event_assign() – this
1026 achieves the same result as passing the event in directly.
1028 @return a value to be passed as the callback argument to event_new() or
1030 @see event_new(), event_assign()
1032 EVENT2_EXPORT_SYMBOL
1033 void *event_self_cbarg(void);
1036 Allocate and asssign a new event structure, ready to be added.
1038 The function event_new() returns a new event that can be used in
1039 future calls to event_add() and event_del(). The fd and events
1040 arguments determine which conditions will trigger the event; the
1041 callback and callback_arg arguments tell Libevent what to do when the
1042 event becomes active.
1044 If events contains one of EV_READ, EV_WRITE, or EV_READ|EV_WRITE, then
1045 fd is a file descriptor or socket that should get monitored for
1046 readiness to read, readiness to write, or readiness for either operation
1047 (respectively). If events contains EV_SIGNAL, then fd is a signal
1048 number to wait for. If events contains none of those flags, then the
1049 event can be triggered only by a timeout or by manual activation with
1050 event_active(): In this case, fd must be -1.
1052 The EV_PERSIST flag can also be passed in the events argument: it makes
1053 event_add() persistent until event_del() is called.
1055 The EV_ET flag is compatible with EV_READ and EV_WRITE, and supported
1056 only by certain backends. It tells Libevent to use edge-triggered
1059 The EV_TIMEOUT flag has no effect here.
1061 It is okay to have multiple events all listening on the same fds; but
1062 they must either all be edge-triggered, or all not be edge triggerd.
1064 When the event becomes active, the event loop will run the provided
1065 callbuck function, with three arguments. The first will be the provided
1066 fd value. The second will be a bitfield of the events that triggered:
1067 EV_READ, EV_WRITE, or EV_SIGNAL. Here the EV_TIMEOUT flag indicates
1068 that a timeout occurred, and EV_ET indicates that an edge-triggered
1069 event occurred. The third event will be the callback_arg pointer that
1072 @param base the event base to which the event should be attached.
1073 @param fd the file descriptor or signal to be monitored, or -1.
1074 @param events desired events to monitor: bitfield of EV_READ, EV_WRITE,
1075 EV_SIGNAL, EV_PERSIST, EV_ET.
1076 @param callback callback function to be invoked when the event occurs
1077 @param callback_arg an argument to be passed to the callback function
1079 @return a newly allocated struct event that must later be freed with
1081 @see event_free(), event_add(), event_del(), event_assign()
1083 EVENT2_EXPORT_SYMBOL
1084 struct event *event_new(struct event_base *, evutil_socket_t, short, event_callback_fn, void *);
1088 Prepare a new, already-allocated event structure to be added.
1090 The function event_assign() prepares the event structure ev to be used
1091 in future calls to event_add() and event_del(). Unlike event_new(), it
1092 doesn't allocate memory itself: it requires that you have already
1093 allocated a struct event, probably on the heap. Doing this will
1094 typically make your code depend on the size of the event structure, and
1095 thereby create incompatibility with future versions of Libevent.
1097 The easiest way to avoid this problem is just to use event_new() and
1098 event_free() instead.
1100 A slightly harder way to future-proof your code is to use
1101 event_get_struct_event_size() to determine the required size of an event
1104 Note that it is NOT safe to call this function on an event that is
1105 active or pending. Doing so WILL corrupt internal data structures in
1106 Libevent, and lead to strange, hard-to-diagnose bugs. You _can_ use
1107 event_assign to change an existing event, but only if it is not active
1110 The arguments for this function, and the behavior of the events that it
1111 makes, are as for event_new().
1113 @param ev an event struct to be modified
1114 @param base the event base to which ev should be attached.
1115 @param fd the file descriptor to be monitored
1116 @param events desired events to monitor; can be EV_READ and/or EV_WRITE
1117 @param callback callback function to be invoked when the event occurs
1118 @param callback_arg an argument to be passed to the callback function
1120 @return 0 if success, or -1 on invalid arguments.
1122 @see event_new(), event_add(), event_del(), event_base_once(),
1123 event_get_struct_event_size()
1125 EVENT2_EXPORT_SYMBOL
1126 int event_assign(struct event *, struct event_base *, evutil_socket_t, short, event_callback_fn, void *);
1129 Deallocate a struct event * returned by event_new().
1131 If the event is pending or active, first make it non-pending and
1134 EVENT2_EXPORT_SYMBOL
1135 void event_free(struct event *);
1138 * Callback type for event_finalize and event_free_finalize().
1140 * THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
1144 typedef void (*event_finalize_callback_fn)(struct event *, void *);
1146 @name Finalization functions
1148 These functions are used to safely tear down an event in a multithreaded
1149 application. If you construct your events with EV_FINALIZE to avoid
1150 deadlocks, you will need a way to remove an event in the certainty that
1151 it will definitely not be running its callback when you deallocate it
1152 and its callback argument.
1154 To do this, call one of event_finalize() or event_free_finalize with
1155 0 for its first argument, the event to tear down as its second argument,
1156 and a callback function as its third argument. The callback will be
1157 invoked as part of the event loop, with the event's priority.
1159 After you call a finalizer function, event_add() and event_active() will
1160 no longer work on the event, and event_del() will produce a no-op. You
1161 must not try to change the event's fields with event_assign() or
1162 event_set() while the finalize callback is in progress. Once the
1163 callback has been invoked, you should treat the event structure as
1164 containing uninitialized memory.
1166 The event_free_finalize() function frees the event after it's finalized;
1167 event_finalize() does not.
1169 A finalizer callback must not make events pending or active. It must not
1170 add events, activate events, or attempt to "resucitate" the event being
1171 finalized in any way.
1173 THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
1176 @return 0 on succes, -1 on failure.
1179 EVENT2_EXPORT_SYMBOL
1180 int event_finalize(unsigned, struct event *, event_finalize_callback_fn);
1181 EVENT2_EXPORT_SYMBOL
1182 int event_free_finalize(unsigned, struct event *, event_finalize_callback_fn);
1186 Schedule a one-time event
1188 The function event_base_once() is similar to event_new(). However, it
1189 schedules a callback to be called exactly once, and does not require the
1190 caller to prepare an event structure.
1192 Note that in Libevent 2.0 and earlier, if the event is never triggered, the
1193 internal memory used to hold it will never be freed. In Libevent 2.1,
1194 the internal memory will get freed by event_base_free() if the event
1195 is never triggered. The 'arg' value, however, will not get freed in either
1196 case--you'll need to free that on your own if you want it to go away.
1198 @param base an event_base
1199 @param fd a file descriptor to monitor, or -1 for no fd.
1200 @param events event(s) to monitor; can be any of EV_READ |
1201 EV_WRITE, or EV_TIMEOUT
1202 @param callback callback function to be invoked when the event occurs
1203 @param arg an argument to be passed to the callback function
1204 @param timeout the maximum amount of time to wait for the event. NULL
1205 makes an EV_READ/EV_WRITE event make forever; NULL makes an
1206 EV_TIMEOUT event succees immediately.
1207 @return 0 if successful, or -1 if an error occurred
1209 EVENT2_EXPORT_SYMBOL
1210 int event_base_once(struct event_base *, evutil_socket_t, short, event_callback_fn, void *, const struct timeval *);
1213 Add an event to the set of pending events.
1215 The function event_add() schedules the execution of the event 'ev' when the
1216 condition specified by event_assign() or event_new() occurs, or when the time
1217 specified in timeout has elapesed. If atimeout is NULL, no timeout
1218 occurs and the function will only be
1219 called if a matching event occurs. The event in the
1220 ev argument must be already initialized by event_assign() or event_new()
1222 in calls to event_assign() until it is no longer pending.
1224 If the event in the ev argument already has a scheduled timeout, calling
1225 event_add() replaces the old timeout with the new one if tv is non-NULL.
1227 @param ev an event struct initialized via event_assign() or event_new()
1228 @param timeout the maximum amount of time to wait for the event, or NULL
1230 @return 0 if successful, or -1 if an error occurred
1231 @see event_del(), event_assign(), event_new()
1233 EVENT2_EXPORT_SYMBOL
1234 int event_add(struct event *ev, const struct timeval *timeout);
1237 Remove a timer from a pending event without removing the event itself.
1239 If the event has a scheduled timeout, this function unschedules it but
1240 leaves the event otherwise pending.
1242 @param ev an event struct initialized via event_assign() or event_new()
1243 @return 0 on success, or -1 if an error occurrect.
1245 EVENT2_EXPORT_SYMBOL
1246 int event_remove_timer(struct event *ev);
1249 Remove an event from the set of monitored events.
1251 The function event_del() will cancel the event in the argument ev. If the
1252 event has already executed or has never been added the call will have no
1255 @param ev an event struct to be removed from the working set
1256 @return 0 if successful, or -1 if an error occurred
1259 EVENT2_EXPORT_SYMBOL
1260 int event_del(struct event *);
1263 As event_del(), but never blocks while the event's callback is running
1264 in another thread, even if the event was constructed without the
1267 THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
1270 EVENT2_EXPORT_SYMBOL
1271 int event_del_noblock(struct event *ev);
1273 As event_del(), but always blocks while the event's callback is running
1274 in another thread, even if the event was constructed with the
1277 THIS IS AN EXPERIMENTAL API. IT MIGHT CHANGE BEFORE THE LIBEVENT 2.1 SERIES
1280 EVENT2_EXPORT_SYMBOL
1281 int event_del_block(struct event *ev);
1284 Make an event active.
1286 You can use this function on a pending or a non-pending event to make it
1287 active, so that its callback will be run by event_base_dispatch() or
1290 One common use in multithreaded programs is to wake the thread running
1291 event_base_loop() from another thread.
1293 @param ev an event to make active.
1294 @param res a set of flags to pass to the event's callback.
1295 @param ncalls an obsolete argument: this is ignored.
1297 EVENT2_EXPORT_SYMBOL
1298 void event_active(struct event *ev, int res, short ncalls);
1301 Checks if a specific event is pending or scheduled.
1303 @param ev an event struct previously passed to event_add()
1304 @param events the requested event type; any of EV_TIMEOUT|EV_READ|
1306 @param tv if this field is not NULL, and the event has a timeout,
1307 this field is set to hold the time at which the timeout will
1310 @return true if the event is pending on any of the events in 'what', (that
1311 is to say, it has been added), or 0 if the event is not added.
1313 EVENT2_EXPORT_SYMBOL
1314 int event_pending(const struct event *ev, short events, struct timeval *tv);
1317 If called from within the callback for an event, returns that event.
1319 The behavior of this function is not defined when called from outside the
1320 callback function for an event.
1322 EVENT2_EXPORT_SYMBOL
1323 struct event *event_base_get_running_event(struct event_base *base);
1326 Test if an event structure might be initialized.
1328 The event_initialized() function can be used to check if an event has been
1331 Warning: This function is only useful for distinguishing a a zeroed-out
1332 piece of memory from an initialized event, it can easily be confused by
1333 uninitialized memory. Thus, it should ONLY be used to distinguish an
1334 initialized event from zero.
1336 @param ev an event structure to be tested
1337 @return 1 if the structure might be initialized, or 0 if it has not been
1340 EVENT2_EXPORT_SYMBOL
1341 int event_initialized(const struct event *ev);
1344 Get the signal number assigned to a signal event
1346 #define event_get_signal(ev) ((int)event_get_fd(ev))
1349 Get the socket or signal assigned to an event, or -1 if the event has
1352 EVENT2_EXPORT_SYMBOL
1353 evutil_socket_t event_get_fd(const struct event *ev);
1356 Get the event_base associated with an event.
1358 EVENT2_EXPORT_SYMBOL
1359 struct event_base *event_get_base(const struct event *ev);
1362 Return the events (EV_READ, EV_WRITE, etc) assigned to an event.
1364 EVENT2_EXPORT_SYMBOL
1365 short event_get_events(const struct event *ev);
1368 Return the callback assigned to an event.
1370 EVENT2_EXPORT_SYMBOL
1371 event_callback_fn event_get_callback(const struct event *ev);
1374 Return the callback argument assigned to an event.
1376 EVENT2_EXPORT_SYMBOL
1377 void *event_get_callback_arg(const struct event *ev);
1380 Return the priority of an event.
1381 @see event_priority_init(), event_get_priority()
1383 EVENT2_EXPORT_SYMBOL
1384 int event_get_priority(const struct event *ev);
1387 Extract _all_ of arguments given to construct a given event. The
1388 event_base is copied into *base_out, the fd is copied into *fd_out, and so
1391 If any of the "_out" arguments is NULL, it will be ignored.
1393 EVENT2_EXPORT_SYMBOL
1394 void event_get_assignment(const struct event *event,
1395 struct event_base **base_out, evutil_socket_t *fd_out, short *events_out,
1396 event_callback_fn *callback_out, void **arg_out);
1399 Return the size of struct event that the Libevent library was compiled
1402 This will be NO GREATER than sizeof(struct event) if you're running with
1403 the same version of Libevent that your application was built with, but
1404 otherwise might not.
1406 Note that it might be SMALLER than sizeof(struct event) if some future
1407 version of Libevent adds extra padding to the end of struct event.
1408 We might do this to help ensure ABI-compatibility between different
1409 versions of Libevent.
1411 EVENT2_EXPORT_SYMBOL
1412 size_t event_get_struct_event_size(void);
1415 Get the Libevent version.
1417 Note that this will give you the version of the library that you're
1418 currently linked against, not the version of the headers that you've
1421 @return a string containing the version number of Libevent
1423 EVENT2_EXPORT_SYMBOL
1424 const char *event_get_version(void);
1427 Return a numeric representation of Libevent's version.
1429 Note that this will give you the version of the library that you're
1430 currently linked against, not the version of the headers you've used to
1433 The format uses one byte each for the major, minor, and patchlevel parts of
1434 the version number. The low-order byte is unused. For example, version
1435 2.0.1-alpha has a numeric representation of 0x02000100
1437 EVENT2_EXPORT_SYMBOL
1438 ev_uint32_t event_get_version_number(void);
1440 /** As event_get_version, but gives the version of Libevent's headers. */
1441 #define LIBEVENT_VERSION EVENT__VERSION
1442 /** As event_get_version_number, but gives the version number of Libevent's
1444 #define LIBEVENT_VERSION_NUMBER EVENT__NUMERIC_VERSION
1446 /** Largest number of priorities that Libevent can support. */
1447 #define EVENT_MAX_PRIORITIES 256
1449 Set the number of different event priorities
1451 By default Libevent schedules all active events with the same priority.
1452 However, some time it is desirable to process some events with a higher
1453 priority than others. For that reason, Libevent supports strict priority
1454 queues. Active events with a lower priority are always processed before
1455 events with a higher priority.
1457 The number of different priorities can be set initially with the
1458 event_base_priority_init() function. This function should be called
1459 before the first call to event_base_dispatch(). The
1460 event_priority_set() function can be used to assign a priority to an
1461 event. By default, Libevent assigns the middle priority to all events
1462 unless their priority is explicitly set.
1464 Note that urgent-priority events can starve less-urgent events: after
1465 running all urgent-priority callbacks, Libevent checks for more urgent
1466 events again, before running less-urgent events. Less-urgent events
1467 will not have their callbacks run until there are no events more urgent
1468 than them that want to be active.
1470 @param eb the event_base structure returned by event_base_new()
1471 @param npriorities the maximum number of priorities
1472 @return 0 if successful, or -1 if an error occurred
1473 @see event_priority_set()
1475 EVENT2_EXPORT_SYMBOL
1476 int event_base_priority_init(struct event_base *, int);
1479 Get the number of different event priorities.
1481 @param eb the event_base structure returned by event_base_new()
1482 @return Number of different event priorities
1483 @see event_base_priority_init()
1485 EVENT2_EXPORT_SYMBOL
1486 int event_base_get_npriorities(struct event_base *eb);
1489 Assign a priority to an event.
1491 @param ev an event struct
1492 @param priority the new priority to be assigned
1493 @return 0 if successful, or -1 if an error occurred
1494 @see event_priority_init(), event_get_priority()
1496 EVENT2_EXPORT_SYMBOL
1497 int event_priority_set(struct event *, int);
1500 Prepare an event_base to use a large number of timeouts with the same
1503 Libevent's default scheduling algorithm is optimized for having a large
1504 number of timeouts with their durations more or less randomly
1505 distributed. But if you have a large number of timeouts that all have
1506 the same duration (for example, if you have a large number of
1507 connections that all have a 10-second timeout), then you can improve
1508 Libevent's performance by telling Libevent about it.
1510 To do this, call this function with the common duration. It will return a
1511 pointer to a different, opaque timeout value. (Don't depend on its actual
1512 contents!) When you use this timeout value in event_add(), Libevent will
1513 schedule the event more efficiently.
1515 (This optimization probably will not be worthwhile until you have thousands
1516 or tens of thousands of events with the same timeout.)
1518 EVENT2_EXPORT_SYMBOL
1519 const struct timeval *event_base_init_common_timeout(struct event_base *base,
1520 const struct timeval *duration);
1522 #if !defined(EVENT__DISABLE_MM_REPLACEMENT) || defined(EVENT_IN_DOXYGEN_)
1524 Override the functions that Libevent uses for memory management.
1526 Usually, Libevent uses the standard libc functions malloc, realloc, and
1527 free to allocate memory. Passing replacements for those functions to
1528 event_set_mem_functions() overrides this behavior.
1530 Note that all memory returned from Libevent will be allocated by the
1531 replacement functions rather than by malloc() and realloc(). Thus, if you
1532 have replaced those functions, it will not be appropriate to free() memory
1533 that you get from Libevent. Instead, you must use the free_fn replacement
1536 Note also that if you are going to call this function, you should do so
1537 before any call to any Libevent function that does allocation.
1538 Otherwise, those funtions will allocate their memory using malloc(), but
1539 then later free it using your provided free_fn.
1541 @param malloc_fn A replacement for malloc.
1542 @param realloc_fn A replacement for realloc
1543 @param free_fn A replacement for free.
1545 EVENT2_EXPORT_SYMBOL
1546 void event_set_mem_functions(
1547 void *(*malloc_fn)(size_t sz),
1548 void *(*realloc_fn)(void *ptr, size_t sz),
1549 void (*free_fn)(void *ptr));
1550 /** This definition is present if Libevent was built with support for
1551 event_set_mem_functions() */
1552 #define EVENT_SET_MEM_FUNCTIONS_IMPLEMENTED
1556 Writes a human-readable description of all inserted and/or active
1557 events to a provided stdio stream.
1559 This is intended for debugging; its format is not guaranteed to be the same
1560 between libevent versions.
1562 @param base An event_base on which to scan the events.
1563 @param output A stdio file to write on.
1565 EVENT2_EXPORT_SYMBOL
1566 void event_base_dump_events(struct event_base *, FILE *);
1570 Activates all pending events for the given fd and event mask.
1572 This function activates pending events only. Events which have not been
1573 added will not become active.
1575 @param base the event_base on which to activate the events.
1576 @param fd An fd to active events on.
1577 @param events One or more of EV_{READ,WRITE}.
1579 EVENT2_EXPORT_SYMBOL
1580 void event_base_active_by_fd(struct event_base *base, evutil_socket_t fd, short events);
1583 Activates all pending signals with a given signal number
1585 This function activates pending events only. Events which have not been
1586 added will not become active.
1588 @param base the event_base on which to activate the events.
1589 @param fd The signal to active events on.
1591 EVENT2_EXPORT_SYMBOL
1592 void event_base_active_by_signal(struct event_base *base, int sig);
1595 * Callback for iterating events in an event base via event_base_foreach_event
1597 typedef int (*event_base_foreach_event_cb)(const struct event_base *, const struct event *, void *);
1600 Iterate over all added or active events events in an event loop, and invoke
1601 a given callback on each one.
1603 The callback must not call any function that modifies the event base, that
1604 modifies any event in the event base, or that adds or removes any event to
1605 the event base. Doing so is unsupported and will lead to undefined
1606 behavior -- likely, to crashes.
1608 event_base_foreach_event() holds a lock on the event_base() for the whole
1609 time it's running: slow callbacks are not advisable.
1611 Note that Libevent adds some events of its own to make pieces of its
1612 functionality work. You must not assume that the only events you'll
1613 encounter will be the ones you added yourself.
1615 The callback function must return 0 to continue iteration, or some other
1616 integer to stop iterating.
1618 @param base An event_base on which to scan the events.
1619 @param fn A callback function to receive the events.
1620 @param arg An argument passed to the callback function.
1621 @return 0 if we iterated over every event, or the value returned by the
1622 callback function if the loop exited early.
1624 EVENT2_EXPORT_SYMBOL
1625 int event_base_foreach_event(struct event_base *base, event_base_foreach_event_cb fn, void *arg);
1628 /** Sets 'tv' to the current time (as returned by gettimeofday()),
1629 looking at the cached value in 'base' if possible, and calling
1630 gettimeofday() or clock_gettime() as appropriate if there is no
1633 Generally, this value will only be cached while actually
1634 processing event callbacks, and may be very inaccuate if your
1635 callbacks take a long time to execute.
1637 Returns 0 on success, negative on failure.
1639 EVENT2_EXPORT_SYMBOL
1640 int event_base_gettimeofday_cached(struct event_base *base,
1641 struct timeval *tv);
1643 /** Update cached_tv in the 'base' to the current time
1645 * You can use this function is useful for selectively increasing
1646 * the accuracy of the cached time value in 'base' during callbacks
1647 * that take a long time to execute.
1649 * This function has no effect if the base is currently not in its
1650 * event loop, or if timeval caching is disabled via
1651 * EVENT_BASE_FLAG_NO_CACHE_TIME.
1653 * @return 0 on success, -1 on failure
1655 EVENT2_EXPORT_SYMBOL
1656 int event_base_update_cache_time(struct event_base *base);
1658 /** Release up all globally-allocated resources allocated by Libevent.
1660 This function does not free developer-controlled resources like
1661 event_bases, events, bufferevents, listeners, and so on. It only releases
1662 resources like global locks that there is no other way to free.
1664 It is not actually necessary to call this function before exit: every
1665 resource that it frees would be released anyway on exit. It mainly exists
1666 so that resource-leak debugging tools don't see Libevent as holding
1669 You should only call this function when no other Libevent functions will
1670 be invoked -- e.g., when cleanly exiting a program.
1672 EVENT2_EXPORT_SYMBOL
1673 void libevent_global_shutdown(void);
1679 #endif /* EVENT2_EVENT_H_INCLUDED_ */