ev_signal - signal me when a signal gets signalledev_child - wait for pid status changesev_idle - when you've got nothing better to doev_prepare and ev_check - your hooks into the event loopev_prepare and ev_check - customise your event looploop (which is always of type struct ev_loop
will not have this argument.
-TIME AND OTHER GLOBAL FUNCTIONS
-
+TIME REPRESENTATION
+
Libev represents time as a single floating point number, representing the
(fractional) number of seconds since the (POSIX) epoch (somewhere near
the beginning of 1970, details are complicated, don't ask). This type is
called ev_tstamp, which is what you should use too. It usually aliases
to the double type in C.
+
+
+GLOBAL FUNCTIONS
+
+These functions can be called anytime, even before initialising the
+library in any way.
- ev_tstamp ev_time ()
-
@@ -144,7 +153,7 @@ requested operation, or, if the condition doesn't go away, do bad stuff
types of such loops, the default loop, which supports signals and child
events, and dynamically created loops which do not.
If you use threads, a common model is to run the default event loop
-in your main thread (or in a separate thrad) and for each thread you
+in your main thread (or in a separate thread) and for each thread you
create, you also create another event loop. Libev itself does no locking
whatsoever, so if you mix calls to the same event loop in different
threads, make sure you lock (this is usually a bad idea, though, even if
@@ -435,14 +444,15 @@ in each iteration of the event loop (This behaviour is called
level-triggering because you keep receiving events as long as the
condition persists. Remember you can stop the watcher if you don't want to
act on the event and neither want to receive future events).
-In general you can register as many read and/or write event watchers oer
+
In general you can register as many read and/or write event watchers per
fd as you want (as long as you don't confuse yourself). Setting all file
descriptors to non-blocking mode is also usually a good idea (but not
required if you know what you are doing).
You have to be careful with dup'ed file descriptors, though. Some backends
(the linux epoll backend is a notable example) cannot handle dup'ed file
descriptors correctly if you register interest in two or more fds pointing
-to the same file/socket etc. description.
+to the same underlying file/socket etc. description (that is, they share
+the same underlying "file open").
If you must do this, then force the use of a known-to-be-good backend
(at the time of this writing, this includes only EVMETHOD_SELECT and
EVMETHOD_POLL).
@@ -462,7 +472,7 @@ EV_WRITE to receive the given events.
Timer watchers are simple relative timers that generate an event after a
given time, and optionally repeating in regular intervals after that.
The timers are based on real time, that is, if you register an event that
-times out after an hour and youreset your system clock to last years
+times out after an hour and you reset your system clock to last years
time, it will still time out after (roughly) and hour. "Roughly" because
detecting time jumps is hard, and soem inaccuracies are unavoidable (the
monotonic clock option helps a lot here).
@@ -470,7 +480,7 @@ monotonic clock option helps a lot here).
time. This is usually the right thing as this timestamp refers to the time
of the event triggering whatever timeout you are modifying/starting. If
you suspect event processing to be delayed and you *need* to base the timeout
-ion the current time, use something like this to adjust for this:
+on the current time, use something like this to adjust for this:
ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
@@ -485,7 +495,7 @@ later, again, and again, until stopped manually.
The timer itself will do a best-effort at avoiding drift, that is, if you
configure a timer to trigger every 10 seconds, then it will trigger at
exactly 10 second intervals. If, however, your program cannot keep up with
-the timer (ecause it takes longer than those 10 seconds to do stuff) the
+the timer (because it takes longer than those 10 seconds to do stuff) the
timer will not fire more than once per event loop iteration.
- ev_timer_again (loop)
@@ -564,11 +574,10 @@ time where time = at (mod interval), regardless of any time jumps.<
ignored. Instead, each time the periodic watcher gets scheduled, the
reschedule callback will be called with the watcher as first, and the
current time as second argument.
- NOTE: This callback MUST NOT stop or destroy the periodic or any other
-periodic watcher, ever, or make any event loop modifications. If you need
-to stop it, return now + 1e30 (or so, fudge fudge) and stop it afterwards.
- Also, this callback must always return a time that is later than the
-passed now value. Not even now itself will be ok.
+ NOTE: This callback MUST NOT stop or destroy any periodic watcher,
+ever, or make any event loop modifications. If you need to stop it,
+return now + 1e30 (or so, fudge fudge) and stop it afterwards (e.g. by
+starting a prepare watcher).
Its prototype is ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
ev_tstamp now), e.g.:
static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
@@ -581,10 +590,13 @@ ev_tstamp now), e.g.:
(that is, the lowest time value larger than to the second argument). It
will usually be called just before the callback will be triggered, but
might be called at other times, too.
+ NOTE: This callback must always return a time that is later than the
+passed now value. Not even now itself will do, it must be larger.
This can be used to create very complex timers, such as a timer that
triggers on each midnight, local time. To do this, you would calculate the
-next midnight after now and return the timestamp value for this. How you do this
-is, again, up to you (but it is not trivial).
+next midnight after now and return the timestamp value for this. How
+you do this is, again, up to you (but it is not trivial, which is the main
+reason I omitted it as an example).
@@ -664,10 +676,10 @@ believe me.
-ev_prepare and ev_check - your hooks into the event loop
+ev_prepare and ev_check - customise your event loop
Prepare and check watchers are usually (but not always) used in tandem:
-Prepare watchers get invoked before the process blocks and check watchers
+prepare watchers get invoked before the process blocks and check watchers
afterwards.
Their main purpose is to integrate other event mechanisms into libev. This
could be used, for example, to track variable changes, implement your own
@@ -678,16 +690,16 @@ them and starting an ev_timer watcher for any timeouts (many librar
provide just this functionality). Then, in the check watcher you check for
any events that occured (by checking the pending status of all watchers
and stopping them) and call back into the library. The I/O and timer
-callbacks will never actually be called (but must be valid neverthelles,
+callbacks will never actually be called (but must be valid nevertheless,
because you never know, you know?).
As another example, the Perl Coro module uses these hooks to integrate
coroutines into libev programs, by yielding to other active coroutines
during each prepare and only letting the process block if no coroutines
-are ready to run (its actually more complicated, it only runs coroutines
-with priority higher than the event loop and one lower priority once,
-using idle watchers to keep the event loop from blocking if lower-priority
-coroutines exist, thus mapping low-priority coroutines to idle/background
-tasks).
+are ready to run (it's actually more complicated: it only runs coroutines
+with priority higher than or equal to the event loop and one coroutine
+of lower priority, but only once, using idle watchers to keep the event
+loop from blocking if lower-priority coroutines are active, thus mapping
+low-priority coroutines to idle/background tasks).
- ev_prepare_init (ev_prepare *, callback)
- ev_check_init (ev_check *, callback)
@@ -708,7 +720,7 @@ macros, but using them is utterly, utterly and completely pointless.
This function combines a simple timer and an I/O watcher, calls your
callback on whichever event happens first and automatically stop both
watchers. This is useful if you want to wait for a single event on an fd
-or timeout without havign to allocate/configure/start/stop/free one or
+or timeout without having to allocate/configure/start/stop/free one or
more watchers yourself.
If fd is less than 0, then no I/O watcher will be started and events
is being ignored. Otherwise, an ev_io watcher for the given fd and
@@ -718,7 +730,7 @@ started. Otherwise an ev_timer watcher with after = timeout0 is a valid timeout, it is of
dubious value.
The callback has the type void (*cb)(int revents, void *arg) and gets
-passed an events set like normal event callbacks (with a combination of
+passed an revents set like normal event callbacks (a combination of
EV_ERROR, EV_READ, EV_WRITE or EV_TIMEOUT) and the arg
value passed to ev_once:
static void stdin_ready (int revents, void *arg)
@@ -750,6 +762,31 @@ the given events it.
+
+LIBEVENT EMULATION
+
+Libev offers a compatibility emulation layer for libevent. It cannot
+emulate the internals of libevent, so here are some usage hints:
+
+ - * Use it by including <event.h>, as usual.
+ - * The following members are fully supported: ev_base, ev_callback,
+ev_arg, ev_fd, ev_res, ev_events.
+ - * Avoid using ev_flags and the EVLIST_*-macros, while it is
+maintained by libev, it does not work exactly the same way as in libevent (consider
+it a private API).
+ - * Priorities are not currently supported. Initialising priorities
+will fail and all watchers will have the same priority, even though there
+is an ev_pri field.
+ - * Other members are not supported.
+ - * The libev emulation is not ABI compatible to libevent, you need
+to use the libev header file and library.
+
+
+
+C++ SUPPORT
+
+TBD.
+
AUTHOR