--- EV/README 2007/12/18 01:37:46 1.19 +++ EV/README 2007/12/22 12:05:42 1.20 @@ -61,6 +61,39 @@ backends, or how to force a specific backend with "LIBEV_FLAGS", or just about in any case because it has much more detailed information. +EVENT LOOPS + EV supports multiple event loops: There is a single "default event loop" + that can handle everything including signals and child watchers, and any + number of "dynamic event loops" that can use different backends (with + various limitations), but no child and signal watchers. + + You do not have to do anything to create the default event loop: When + the module is loaded a suitable backend is selected on the premise of + selecting a working backend (which for example rules out kqueue on most + BSDs). Modules should, unless they have "special needs" always use the + default loop as this is fastest (perl-wise), best supported by other + modules (e.g. AnyEvent or Coro) and most portable event loop. + + For specific programs you cna create additional event loops dynamically. + + $loop = new EV::loop [$flags] + Create a new event loop as per the specified flags. Please refer to + the "ev_loop_new ()" function description in the libev documentation + () for more info. + + The loop will automatically be destroyed when it is no longer + referenced by any watcher and the loop object goes out of scope. + + Using "EV::FLAG_FORKCHECK" is recommended, as only the default event + loop is protected by this module. + + $loop->loop_fork + Must be called after a fork in the child, before entering or + continuing the event loop. An alternative is to use + "EV::FLAG_FORKCHECK" which calls this fucntion automatically, at + some performance loss (refer to the libev documentation). + BASIC INTERFACE $EV::DIED Must contain a reference to a function that is called when a @@ -73,15 +106,18 @@ Returns the current time in (fractional) seconds since the epoch. $time = EV::now + $time = $loop->now Returns the time the last event loop iteration has been started. This is the time that (relative) timers are based on, and refering to it is usually faster then calling EV::time. - $method = EV::method + $backend = EV::backend + $backend = $loop->backend Returns an integer describing the backend used by libev (EV::METHOD_SELECT or EV::METHOD_EPOLL). EV::loop [$flags] + $loop->loop ([$flags]) Begin checking for events and calling callbacks. It returns when a callback calls EV::unloop. @@ -92,6 +128,7 @@ EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) EV::unloop [$how] + $loop->unloop ([$how]) When called with no arguments or an argument of EV::UNLOOP_ONE, makes the innermost call to EV::loop return. @@ -99,10 +136,12 @@ EV::loop will return as fast as possible. $count = EV::loop_count + $count = $loop->loop_count Return the number of times the event loop has polled for new events. Sometiems useful as a generation counter. EV::once $fh_or_undef, $events, $timeout, $cb->($revents) + $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents)) This function rolls together an I/O and a timer watcher for a single one-shot event without the need for managing a watcher object. @@ -117,7 +156,7 @@ When an error occurs or either the timeout or I/O watcher triggers, then the callback will be called with the received event set (in - general you can expect it to be a combination of "EV:ERROR", + general you can expect it to be a combination of "EV::ERROR", "EV::READ", "EV::WRITE" and "EV::TIMEOUT"). EV::once doesn't return anything: the watchers stay active till @@ -125,6 +164,7 @@ the callback invoked. EV::feed_fd_event ($fd, $revents) + $loop->feed_fd_event ($fd, $revents) Feed an event on a file descriptor into EV. EV will react to this call as if the readyness notifications specified by $revents (a combination of "EV::READ" and "EV::WRITE") happened on the file @@ -134,14 +174,14 @@ Feed a signal event into EV. EV will react to this call as if the signal specified by $signal had occured. - WATCHER OBJECTS +WATCHER OBJECTS A watcher is an object that gets created 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: my $watcher = EV::io *STDIN, EV::READ, sub { my ($watcher, $revents) = @_; - warn "yeah, STDIN should not be readable without blocking!\n" + warn "yeah, STDIN should now be readable without blocking!\n" }; All watchers can be active (waiting for events) or inactive (paused). @@ -222,10 +262,9 @@ as if the watcher had received the given $revents mask. $revents = $w->clear_pending - If the watcher is pending, this function returns clears its pending - status and returns its $revents bitset (as if its callback was - invoked). If the watcher isn't pending it does nothing and returns - 0. + If the watcher is pending, this function clears its pending status + and returns its $revents bitset (as if its callback was invoked). If + the watcher isn't pending it does nothing and returns 0. $previous_state = $w->keepalive ($bool) Normally, "EV::loop" will return when there are no active watchers @@ -235,7 +274,7 @@ all your jobs are finished (or they forgot to register some watchers for their task :). - Sometimes, however, this gets in your way, for example when you the + Sometimes, however, this gets in your way, for example when the module that calls "EV::loop" (usually the main program) is not the same module as a long-living watcher (for example a DNS client module written by somebody else even). Then you might want any @@ -255,14 +294,19 @@ my $udp_socket = ... my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... }; - $udp_watcher->keepalive (0); + $1000udp_watcher->keepalive (0); + + $loop = $w->loop + Return the loop that this watcher is attached to. - WATCHER TYPES +WATCHER TYPES Each of the following subsections describes a single watcher type. I/O WATCHERS - is this file descriptor readable or writable? $w = EV::io $fileno_or_fh, $eventmask, $callback $w = EV::io_ns $fileno_or_fh, $eventmask, $callback + $w = $loop->io ($fileno_or_fh, $eventmask, $callback) + $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback) As long as the returned watcher object is alive, call the $callback when at least one of events specified in $eventmask occurs. @@ -289,6 +333,8 @@ TIMER WATCHERS - relative and optionally repeating timeouts $w = EV::timer $after, $repeat, $callback $w = EV::timer_ns $after, $repeat, $callback + $w = $loop->timer ($after, $repeat, $callback) + $w = $loop->timer_ns ($after, $repeat, $callback) Calls the callback after $after seconds (which may be fractional). If $repeat is non-zero, the timer will be restarted (with the $repeat value as $after) after the callback returns. @@ -334,6 +380,8 @@ PERIODIC WATCHERS - to cron or not to cron? $w = EV::periodic $at, $interval, $reschedule_cb, $callback $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback + $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback) + $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback) Similar to EV::timer, but is not based on relative timeouts but on absolute times. Apart from creating "simple" timers that trigger "at" the specified time, it can also be used for non-drifting @@ -442,6 +490,8 @@ CHILD WATCHERS - watch out for process status changes $w = EV::child $pid, $callback $w = EV::child_ns $pid, $callback + $w = $loop->child ($pid, $callback) + $w = $loop->child_ns ($pid, $callback) Call the callback when a status change for pid $pid (or any pid if $pid is 0) has been received. More precisely: when the process receives a "SIGCHLD", EV will fetch the outstanding exit/wait status @@ -481,6 +531,8 @@ STAT WATCHERS - did the file attributes just change? $w = EV::stat $path, $interval, $callback $w = EV::stat_ns $path, $interval, $callback + $w = $loop->stat ($path, $interval, $callback) + $w = $loop->stat_ns ($path, $interval, $callback) Call the callback when a file status change has been detected on $path. The $path does not need to exist, changing from "path exists" to "path does not exist" is a status change like any other. @@ -550,6 +602,8 @@ IDLE WATCHERS - when you've got nothing better to do... $w = EV::idle $callback $w = EV::idle_ns $callback + $w = $loop->idle ($callback) + $w = $loop->idle_ns ($callback) Call the callback when there are no other pending watchers of the same or higher priority (excluding check, prepare and other idle watchers of the same or lower priority, of course). They are called @@ -575,6 +629,8 @@ PREPARE WATCHERS - customise your event loop! $w = EV::prepare $callback $w = EV::prepare_ns $callback + $w = $loop->prepare ($callback) + $w = $loop->prepare_ns ($callback) Call the callback just before the process would block. You can still create/modify any watchers at this point. @@ -586,6 +642,8 @@ CHECK WATCHERS - customise your event loop even more! $w = EV::check $callback $w = EV::check_ns $callback + $w = $loop->check ($callback) + $w = $loop->check_ns ($callback) Call the callback just after the process wakes up again (after it has gathered events), but before any other callbacks have been invoked. @@ -644,6 +702,8 @@ $w = EV::fork $callback $w = EV::fork_ns $callback + $w = $loop->fork ($callback) + $w = $loop->fork_ns ($callback) Call the callback before the event loop is resumed in the child process after a fork. @@ -665,8 +725,8 @@ my $async_check = EV::check sub { }; - This ensures that perl shortly gets into control for a short time, and - also ensures slower overall operation. + This ensures that perl gets into control for a short time to handle any + pending signals, and also ensures (slightly) slower overall operation. THREADS Threads are not supported by this module in any way. Perl pseudo-threads @@ -691,8 +751,9 @@ course. SEE ALSO - EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event - loop), Coro::EV (efficient coroutines with EV). + EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event + loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines + with EV), Net::SNMP::EV (asynchronous SNMP). AUTHOR Marc Lehmann