X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/d89bdc728203c12cec56cf6e5284882842f19ca4..c9877299894353b8aa7442192b15991de9d4767d:/ev.pod?ds=sidebyside diff --git a/ev.pod b/ev.pod index 81da7ea..f26f84b 100644 --- a/ev.pod +++ b/ev.pod @@ -41,7 +41,7 @@ support for multiple event loops, then all functions taking an initial argument of name C (which is always of type C) will not have this argument. -=head1 TIME AND OTHER GLOBAL FUNCTIONS +=head1 TIME REPRESENTATION Libev represents time as a single floating point number, representing the (fractional) number of seconds since the (POSIX) epoch (somewhere near @@ -49,11 +49,18 @@ the beginning of 1970, details are complicated, don't ask). This type is called C, which is what you should use too. It usually aliases to the double type in C. +=head1 GLOBAL FUNCTIONS + +These functions can be called anytime, even before initialising the +library in any way. + =over 4 =item ev_tstamp ev_time () -Returns the current time as libev would use it. +Returns the current time as libev would use it. Please note that the +C function is usually faster and also often returns the timestamp +you actually want to know. =item int ev_version_major () @@ -101,7 +108,7 @@ types of such loops, the I 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 @@ -126,12 +133,12 @@ It supports the following flags: =over 4 -=item EVFLAG_AUTO +=item C The default flags value. Use this if you have no clue (it's the right thing, believe me). -=item EVFLAG_NOENV +=item C If this flag bit is ored into the flag value (or the program runs setuid or setgid) then libev will I look at the environment variable @@ -140,17 +147,17 @@ override the flags completely if it is found in the environment. This is useful to try out specific backends to test their performance, or to work around bugs. -=item EVMETHOD_SELECT (portable select backend) +=item C (portable select backend) -=item EVMETHOD_POLL (poll backend, available everywhere except on windows) +=item C (poll backend, available everywhere except on windows) -=item EVMETHOD_EPOLL (linux only) +=item C (linux only) -=item EVMETHOD_KQUEUE (some bsds only) +=item C (some bsds only) -=item EVMETHOD_DEVPOLL (solaris 8 only) +=item C (solaris 8 only) -=item EVMETHOD_PORT (solaris 10 only) +=item C (solaris 10 only) If one or more of these are ored into the flags value, then only these backends will be tried (in the reverse order as given here). If one are @@ -238,7 +245,7 @@ more generic mechanism. Can be used to make a call to C return early (but only after it has processed all outstanding events). The C argument must be either -C, which will make the innermost C call return, or +C, which will make the innermost C call return, or C, which will make all nested C calls return. =item ev_ref (loop) @@ -262,7 +269,7 @@ libraries. Just remember to I and I. A watcher is a structure that you create and register to record your interest in some event. For instance, if you want to wait for STDIN to -become readable, you would create an ev_io watcher for that: +become readable, you would create an C watcher for that: static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) { @@ -301,61 +308,61 @@ As long as your watcher is active (has been started but not stopped) you must not touch the values stored in it. Most specifically you must never reinitialise it or call its set method. -You cna check whether an event is active by calling the C macro. To see whether an event is outstanding (but the -callback for it has not been called yet) you cna use the C macro. Each and every callback receives the event loop pointer as first, the registered watcher structure as second, and a bitset of received events as third argument. -The rceeived events usually include a single bit per event type received +The received events usually include a single bit per event type received (you can receive multiple events at the same time). The possible bit masks are: =over 4 -=item EV_READ +=item C -=item EV_WRITE +=item C -The file descriptor in the ev_io watcher has become readable and/or +The file descriptor in the C watcher has become readable and/or writable. -=item EV_TIMEOUT +=item C -The ev_timer watcher has timed out. +The C watcher has timed out. -=item EV_PERIODIC +=item C -The ev_periodic watcher has timed out. +The C watcher has timed out. -=item EV_SIGNAL +=item C -The signal specified in the ev_signal watcher has been received by a thread. +The signal specified in the C watcher has been received by a thread. -=item EV_CHILD +=item C -The pid specified in the ev_child watcher has received a status change. +The pid specified in the C watcher has received a status change. -=item EV_IDLE +=item C -The ev_idle watcher has determined that you have nothing better to do. +The C watcher has determined that you have nothing better to do. -=item EV_PREPARE +=item C -=item EV_CHECK +=item C -All ev_prepare watchers are invoked just I C starts -to gather new events, and all ev_check watchers are invoked just after +All C watchers are invoked just I C starts +to gather new events, and all C watchers are invoked just after C has gathered them, but before it invokes any callbacks for any received events. Callbacks of both watcher types can start and stop as many watchers as they want, and all of them will be taken into account -(for example, a ev_prepare watcher might start an idle watcher to keep +(for example, a C watcher might start an idle watcher to keep C from blocking). -=item EV_ERROR +=item C An unspecified error has occured, the watcher has been stopped. This might happen because the watcher could not be properly started because libev @@ -374,7 +381,7 @@ programs, though, so beware. =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER Each watcher has, by default, a member C that you can change -and read at any time, libev will completely ignore it. This cna be used +and read at any time, libev will completely ignore it. This can be used to associate arbitrary data with your watcher. If you need more data and don't want to allocate memory and store a pointer to it in that data member, you can also "subclass" the watcher type and provide your own @@ -406,15 +413,15 @@ have been omitted.... This section describes each watcher in detail, but will not repeat information given in the last section. -=head2 struct ev_io - is my file descriptor readable or writable +=head2 C - is this file descriptor readable or writable I/O watchers check whether a file descriptor is readable or writable 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 cna stop the watcher if you don't want to +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). @@ -422,7 +429,8 @@ 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 @@ -434,19 +442,19 @@ EVMETHOD_POLL). =item ev_io_set (ev_io *, int fd, int events) -Configures an ev_io watcher. The fd is the file descriptor to rceeive +Configures an C watcher. The fd is the file descriptor to rceeive events for and events is either C, C or C to receive the given events. =back -=head2 struct ev_timer - relative and optionally recurring timeouts +=head2 C - relative and optionally recurring timeouts 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). @@ -455,7 +463,7 @@ The relative timeouts are calculated relative to the C 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.); @@ -473,7 +481,7 @@ 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. =item ev_timer_again (loop) @@ -490,24 +498,24 @@ This sounds a bit complicated, but here is a useful and typical example: Imagine you have a tcp connection and you want a so-called idle timeout, that is, you want to be called when there have been, say, 60 seconds of inactivity on the socket. The easiest way to do this is to -configure an ev_timer with after=repeat=60 and calling ev_timer_again each +configure an C with after=repeat=60 and calling ev_timer_again each time you successfully read or write some data. If you go into an idle state where you do not expect data to travel on the socket, you can stop the timer, and again will automatically restart it if need be. =back -=head2 ev_periodic - to cron or not to cron it +=head2 C - to cron or not to cron Periodic watchers are also timers of a kind, but they are very versatile (and unfortunately a bit complex). -Unlike ev_timer's, they are not based on real time (or relative time) +Unlike C's, they are not based on real time (or relative time) but on wallclock time (absolute time). You can tell a periodic watcher to trigger "at" some specific point in time. For example, if you tell a periodic watcher to trigger in 10 seconds (by specifiying e.g. c) and then reset your system clock to the last year, then it will -take a year to trigger the event (unlike an ev_timer, which would trigger +take a year to trigger the event (unlike an C, which would trigger roughly 10 seconds later and of course not if you reset your system time again). @@ -546,11 +554,11 @@ time: This doesn't mean there will always be 3600 seconds in between triggers, but only that the the callback will be called when the system time shows a -full hour (UTC), or more correct, when the system time is evenly divisible +full hour (UTC), or more correctly, when the system time is evenly divisible by 3600. Another way to think about it (for the mathematically inclined) is that -ev_periodic will try to run the callback in this mode at the next possible +C will try to run the callback in this mode at the next possible time where C