These functions can be called anytime, even before initialising the +library in any way.
Can be used to make a call to ev_loop return early (but only after it
has processed all outstanding events). The how argument must be either
-EVUNLOOP_ONCE, which will make the innermost ev_loop call return, or
+EVUNLOOP_ONE, which will make the innermost ev_loop call return, or
EVUNLOOP_ALL, which will make all nested ev_loop calls return.
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).
@@ -467,7 +472,7 @@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).
@@ -475,7 +480,7 @@ 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.);@@ -490,7 +495,7 @@
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.
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) @@ -586,10 +590,13 @@ (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
nowvalue. Not evennowitself 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
+next midnight afternowand return the timestamp value for this. How you do this -is, again, up to you (but it is not trivial).nowand 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).
ev_prepare and ev_check - customise your event loopPrepare 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 @@ -683,16 +690,16 @@ 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).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
@@ -723,7 +730,7 @@
repeat = 0) will be started. While 0 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) @@ -756,6 +763,31 @@
Libev offers a compatibility emulation layer for libevent. It cannot +emulate the internals of libevent, so here are some usage hints:
+TBD.
+ +Marc Lehmann <libev@schmorp.de>.