| 1 |
NAME |
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EV - perl interface to libev, a high performance full-featured event |
| 3 |
loop |
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|
| 5 |
SYNOPSIS |
| 6 |
use EV; |
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|
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# TIMERS |
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|
| 10 |
my $w = EV::timer 2, 0, sub { |
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warn "is called after 2s"; |
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}; |
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|
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my $w = EV::timer 2, 1, sub { |
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warn "is called roughly every 2s (repeat = 1)"; |
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}; |
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|
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undef $w; # destroy event watcher again |
| 19 |
|
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my $w = EV::periodic 0, 60, 0, sub { |
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warn "is called every minute, on the minute, exactly"; |
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}; |
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|
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# IO |
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|
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my $w = EV::io *STDIN, EV::READ, sub { |
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my ($w, $revents) = @_; # all callbacks get the watcher object and event mask |
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warn "stdin is readable, you entered: ", <STDIN>; |
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}; |
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|
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# SIGNALS |
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|
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my $w = EV::signal 'QUIT', sub { |
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warn "sigquit received\n"; |
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}; |
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|
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my $w = EV::signal 3, sub { |
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warn "sigquit received (this is GNU/Linux, right?)\n"; |
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}; |
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|
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# CHILD/PID STATUS CHANGES |
| 42 |
|
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my $w = EV::child 666, sub { |
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my ($w, $revents) = @_; |
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# my $pid = $w->rpid; |
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my $status = $w->rstatus; |
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}; |
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|
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# MAINLOOP |
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EV::loop; # loop until EV::loop_done is called |
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EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled |
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EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block |
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|
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DESCRIPTION |
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This module provides an interface to libev |
| 56 |
(<http://software.schmorp.de/pkg/libev.html>). |
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|
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BASIC INTERFACE |
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$EV::DIED |
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Must contain a reference to a function that is called when a |
| 61 |
callback throws an exception (with $@ containing thr error). The |
| 62 |
default prints an informative message and continues. |
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|
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If this callback throws an exception it will be silently ignored. |
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|
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$time = EV::time |
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Returns the current time in (fractional) seconds since the epoch. |
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|
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$time = EV::now |
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Returns the time the last event loop iteration has been started. |
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This is the time that (relative) timers are based on, and refering |
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to it is usually faster then calling EV::time. |
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|
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$method = EV::ev_method |
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Returns an integer describing the backend used by libev |
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(EV::METHOD_SELECT or EV::METHOD_EPOLL). |
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|
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EV::loop [$flags] |
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Begin checking for events and calling callbacks. It returns when a |
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callback calls EV::loop_done. |
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|
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The $flags argument can be one of the following: |
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|
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0 as above |
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EV::LOOP_ONESHOT block at most once (wait, but do not loop) |
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EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) |
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|
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EV::loop_done [$how] |
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When called with no arguments or an argument of 1, makes the |
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innermost call to EV::loop return. |
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|
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When called with an agrument of 2, all calls to EV::loop will return |
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as fast as possible. |
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|
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WATCHER |
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A watcher is an object that gets created to record your interest in some |
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event. For instance, if you want to wait for STDIN to become readable, |
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you would create an EV::io watcher for that: |
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|
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my $watcher = EV::io *STDIN, EV::READ, sub { |
| 101 |
my ($watcher, $revents) = @_; |
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warn "yeah, STDIN should not be readable without blocking!\n" |
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}; |
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|
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All watchers can be active (waiting for events) or inactive (paused). |
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Only active watchers will have their callbacks invoked. All callbacks |
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will be called with at least two arguments: the watcher and a bitmask of |
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received events. |
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|
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Each watcher type has its associated bit in revents, so you can use the |
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same callback for multiple watchers. The event mask is named after the |
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type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, |
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EV::periodic sets EV::PERIODIC and so on, with the exception of IO |
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events (which can set both EV::READ and EV::WRITE bits), and EV::timer |
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(which uses EV::TIMEOUT). |
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|
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In the rare case where one wants to create a watcher but not start it at |
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the same time, each constructor has a variant with a trailing "_ns" in |
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its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. |
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|
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Please note that a watcher will automatically be stopped when the |
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watcher object is destroyed, so you *need* to keep the watcher objects |
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returned by the constructors. |
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|
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Also, all methods changing some aspect of a watcher (->set, ->priority, |
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->fh and so on) automatically stop and start it again if it is active, |
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which means pending events get lost. |
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|
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WATCHER TYPES |
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Now lets move to the existing watcher types and asociated methods. |
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|
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The following methods are available for all watchers. Then followes a |
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description of each watcher constructor (EV::io, EV::timer, |
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EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and |
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EV::check), followed by any type-specific methods (if any). |
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|
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$w->start |
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Starts a watcher if it isn't active already. Does nothing to an |
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already active watcher. By default, all watchers start out in the |
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active state (see the description of the "_ns" variants if you need |
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stopped watchers). |
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|
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$w->stop |
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Stop a watcher if it is active. Also clear any pending events |
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(events that have been received but that didn't yet result in a |
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callback invocation), regardless of wether the watcher was active or |
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not. |
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|
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$bool = $w->is_active |
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Returns true if the watcher is active, false otherwise. |
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|
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$current_data = $w->data |
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$old_data = $w->data ($new_data) |
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Queries a freely usable data scalar on the watcher and optionally |
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changes it. This is a way to associate custom data with a watcher: |
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|
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my $w = EV::timer 60, 0, sub { |
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warn $_[0]->data; |
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}; |
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$w->data ("print me!"); |
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|
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$current_cb = $w->cb |
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$old_cb = $w->cb ($new_cb) |
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Queries the callback on the watcher and optionally changes it. You |
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can do this at any time without the watcher restarting. |
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|
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$current_priority = $w->priority |
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$old_priority = $w->priority ($new_priority) |
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Queries the priority on the watcher and optionally changes it. |
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Pending watchers with higher priority will be invoked first. The |
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valid range of priorities lies between EV::MAXPRI (default 2) and |
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EV::MINPRI (default -2). If the priority is outside this range it |
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will automatically be normalised to the nearest valid priority. |
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|
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The default priority of any newly-created weatcher is 0. |
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|
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$w->trigger ($revents) |
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Call the callback *now* with the given event mask. |
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|
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$w = EV::io $fileno_or_fh, $eventmask, $callback |
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$w = EV::io_ns $fileno_or_fh, $eventmask, $callback |
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As long as the returned watcher object is alive, call the $callback |
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when the events specified in $eventmask. |
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|
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The $eventmask can be one or more of these constants ORed together: |
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|
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EV::READ wait until read() wouldn't block anymore |
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EV::WRITE wait until write() wouldn't block anymore |
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|
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The "io_ns" variant doesn't start (activate) the newly created |
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watcher. |
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|
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$w->set ($fileno_or_fh, $eventmask) |
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Reconfigures the watcher, see the constructor above for details. Can |
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be called at any time. |
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|
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$current_fh = $w->fh |
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$old_fh = $w->fh ($new_fh) |
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Returns the previously set filehandle and optionally set a new one. |
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|
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$current_eventmask = $w->events |
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$old_eventmask = $w->events ($new_eventmask) |
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Returns the previously set event mask and optionally set a new one. |
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|
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$w = EV::timer $after, $repeat, $callback |
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$w = EV::timer_ns $after, $repeat, $callback |
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Calls the callback after $after seconds. If $repeat is non-zero, the |
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timer will be restarted (with the $repeat value as $after) after the |
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callback returns. |
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|
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This means that the callback would be called roughly after $after |
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seconds, and then every $repeat seconds. "Roughly" because the time |
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of callback processing is not taken into account, so the timer will |
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slowly drift. If that isn't acceptable, look at EV::periodic. |
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|
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The timer is based on a monotonic clock, that is if somebody is |
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sitting in front of the machine while the timer is running and |
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changes the system clock, the timer will nevertheless run (roughly) |
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the same time. |
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|
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The "timer_ns" variant doesn't start (activate) the newly created |
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watcher. |
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|
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$w->set ($after, $repeat) |
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Reconfigures the watcher, see the constructor above for details. Can |
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be at any time. |
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|
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$w->again |
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Similar to the "start" method, but has special semantics for |
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repeating timers: |
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|
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If the timer is active and repeating, reset the timeout to occur |
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$repeat seconds after now. |
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|
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If the timer is active and non-repeating, it will be stopped. |
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|
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If the timer is in active and repeating, start it. |
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|
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Otherwise do nothing. |
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|
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This behaviour is useful when you have a timeout for some IO |
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operation. You create a timer object with the same value for $after |
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and $repeat, and then, in the read/write watcher, run the "again" |
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method on the timeout. |
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|
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$w = EV::periodic $at, $interval, $reschedule_cb, $callback |
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$w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback |
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Similar to EV::timer, but is not based on relative timeouts but on |
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absolute times. Apart from creating "simple" timers that trigger |
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"at" the specified time, it can also be used for non-drifting |
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absolute timers and more complex, cron-like, setups that are not |
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adversely affected by time jumps (i.e. when the system clock is |
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changed by explicit date -s or other means such as ntpd). It is also |
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the most complex watcher type in EV. |
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|
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It has three distinct "modes": |
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|
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* absolute timer ($interval = $reschedule_cb = 0) |
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This time simply fires at the wallclock time $at and doesn't |
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repeat. It will not adjust when a time jump occurs, that is, if |
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it is to be run at January 1st 2011 then it will run when the |
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system time reaches or surpasses this time. |
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|
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* non-repeating interval timer ($interval > 0, $reschedule_cb = 0) |
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In this mode the watcher will always be scheduled to time out at |
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the next "$at + N * $interval" time (for some integer N) and |
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then repeat, regardless of any time jumps. |
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|
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This can be used to create timers that do not drift with respect |
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to system time: |
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|
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my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" }; |
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|
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That doesn't mean there will always be 3600 seconds in between |
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triggers, but only that the the clalback will be called when the |
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system time shows a full hour (UTC). |
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|
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Another way to think about it (for the mathematically inclined) |
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is that EV::periodic will try to run the callback in this mode |
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at the next possible time where "$time = $at (mod $interval)", |
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regardless of any time jumps. |
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|
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* manual reschedule mode ($reschedule_cb = coderef) |
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In this mode $interval and $at are both being ignored. Instead, |
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each time the periodic watcher gets scheduled, the first |
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callback ($reschedule_cb) will be called with the watcher as |
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first, and the current time as second argument. |
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|
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*This callback MUST NOT stop or destroy this or any other |
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periodic watcher, ever*. If you need to stop it, return 1e30 and |
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stop it afterwards. |
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|
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It must return the next time to trigger, based on the passed |
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time value (that is, the lowest time value larger than to the |
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second argument). It will usually be called just before the |
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callback will be triggered, but might be called at other times, |
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too. |
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|
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This can be used to create very complex timers, such as a timer |
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that triggers on each midnight, local time (actually 24 hours |
| 301 |
after the last midnight, to keep the example simple. If you know |
| 302 |
a way to do it correctly in about the same space (without |
| 303 |
requiring elaborate modules), drop me a note :): |
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|
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my $daily = EV::periodic 0, 0, sub { |
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my ($w, $now) = @_; |
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|
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use Time::Local (); |
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my (undef, undef, undef, $d, $m, $y) = localtime $now; |
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86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y |
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}, sub { |
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print "it's midnight or likely shortly after, now\n"; |
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}; |
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|
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The "periodic_ns" variant doesn't start (activate) the newly created |
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watcher. |
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|
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$w->set ($at, $interval, $reschedule_cb) |
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Reconfigures the watcher, see the constructor above for details. Can |
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be at any time. |
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|
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$w->again |
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Simply stops and starts the watcher again. |
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|
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$w = EV::signal $signal, $callback |
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$w = EV::signal_ns $signal, $callback |
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Call the callback when $signal is received (the signal can be |
| 328 |
specified by number or by name, just as with kill or %SIG). |
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|
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EV will grab the signal for the process (the kernel only allows one |
| 331 |
component to receive a signal at a time) when you start a signal |
| 332 |
watcher, and removes it again when you stop it. Perl does the same |
| 333 |
when you add/remove callbacks to %SIG, so watch out. |
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|
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You can have as many signal watchers per signal as you want. |
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|
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The "signal_ns" variant doesn't start (activate) the newly created |
| 338 |
watcher. |
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|
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$w->set ($signal) |
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Reconfigures the watcher, see the constructor above for details. Can |
| 342 |
be at any time. |
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|
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$current_signum = $w->signal |
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$old_signum = $w->signal ($new_signal) |
| 346 |
Returns the previously set signal (always as a number not name) and |
| 347 |
optionally set a new one. |
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|
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$w = EV::child $pid, $callback |
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$w = EV::child_ns $pid, $callback |
| 351 |
Call the callback when a status change for pid $pid (or any pid if |
| 352 |
$pid is 0) has been received. More precisely: when the process |
| 353 |
receives a SIGCHLD, EV will fetch the outstanding exit/wait status |
| 354 |
for all changed/zombie children and call the callback. |
| 355 |
|
| 356 |
You can access both status and pid by using the "rstatus" and "rpid" |
| 357 |
methods on the watcher object. |
| 358 |
|
| 359 |
You can have as many pid watchers per pid as you want. |
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|
| 361 |
The "child_ns" variant doesn't start (activate) the newly created |
| 362 |
watcher. |
| 363 |
|
| 364 |
$w->set ($pid) |
| 365 |
Reconfigures the watcher, see the constructor above for details. Can |
| 366 |
be at any time. |
| 367 |
|
| 368 |
$current_pid = $w->pid |
| 369 |
$old_pid = $w->pid ($new_pid) |
| 370 |
Returns the previously set process id and optionally set a new one. |
| 371 |
|
| 372 |
$exit_status = $w->rstatus |
| 373 |
Return the exit/wait status (as returned by waitpid, see the waitpid |
| 374 |
entry in perlfunc). |
| 375 |
|
| 376 |
$pid = $w->rpid |
| 377 |
Return the pid of the awaited child (useful when you have installed |
| 378 |
a watcher for all pids). |
| 379 |
|
| 380 |
$w = EV::idle $callback |
| 381 |
$w = EV::idle_ns $callback |
| 382 |
Call the callback when there are no pending io, timer/periodic, |
| 383 |
signal or child events, i.e. when the process is idle. |
| 384 |
|
| 385 |
The process will not block as long as any idle watchers are active, |
| 386 |
and they will be called repeatedly until stopped. |
| 387 |
|
| 388 |
The "idle_ns" variant doesn't start (activate) the newly created |
| 389 |
watcher. |
| 390 |
|
| 391 |
$w = EV::prepare $callback |
| 392 |
$w = EV::prepare_ns $callback |
| 393 |
Call the callback just before the process would block. You can still |
| 394 |
create/modify any watchers at this point. |
| 395 |
|
| 396 |
See the EV::check watcher, below, for explanations and an example. |
| 397 |
|
| 398 |
The "prepare_ns" variant doesn't start (activate) the newly created |
| 399 |
watcher. |
| 400 |
|
| 401 |
$w = EV::check $callback |
| 402 |
$w = EV::check_ns $callback |
| 403 |
Call the callback just after the process wakes up again (after it |
| 404 |
has gathered events), but before any other callbacks have been |
| 405 |
invoked. |
| 406 |
|
| 407 |
This is used to integrate other event-based software into the EV |
| 408 |
mainloop: You register a prepare callback and in there, you create |
| 409 |
io and timer watchers as required by the other software. Here is a |
| 410 |
real-world example of integrating Net::SNMP (with some details left |
| 411 |
out): |
| 412 |
|
| 413 |
our @snmp_watcher; |
| 414 |
|
| 415 |
our $snmp_prepare = EV::prepare sub { |
| 416 |
# do nothing unless active |
| 417 |
$dispatcher->{_event_queue_h} |
| 418 |
or return; |
| 419 |
|
| 420 |
# make the dispatcher handle any outstanding stuff |
| 421 |
|
| 422 |
# create an IO watcher for each and every socket |
| 423 |
@snmp_watcher = ( |
| 424 |
(map { EV::io $_, EV::READ, sub { } } |
| 425 |
keys %{ $dispatcher->{_descriptors} }), |
| 426 |
); |
| 427 |
|
| 428 |
# if there are any timeouts, also create a timer |
| 429 |
push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { } |
| 430 |
if $event->[Net::SNMP::Dispatcher::_ACTIVE]; |
| 431 |
}; |
| 432 |
|
| 433 |
The callbacks are irrelevant, the only purpose of those watchers is |
| 434 |
to wake up the process as soon as one of those events occurs (socket |
| 435 |
readable, or timer timed out). The corresponding EV::check watcher |
| 436 |
will then clean up: |
| 437 |
|
| 438 |
our $snmp_check = EV::check sub { |
| 439 |
# destroy all watchers |
| 440 |
@snmp_watcher = (); |
| 441 |
|
| 442 |
# make the dispatcher handle any new stuff |
| 443 |
}; |
| 444 |
|
| 445 |
The callbacks of the created watchers will not be called as the |
| 446 |
watchers are destroyed before this cna happen (remember EV::check |
| 447 |
gets called first). |
| 448 |
|
| 449 |
The "check_ns" variant doesn't start (activate) the newly created |
| 450 |
watcher. |
| 451 |
|
| 452 |
THREADS |
| 453 |
Threads are not supported by this in any way. Perl pseudo-threads is |
| 454 |
evil stuff and must die. |
| 455 |
|
| 456 |
SEE ALSO |
| 457 |
L<EV::DNS>, L<EV::AnyEvent>. |
| 458 |
|
| 459 |
AUTHOR |
| 460 |
Marc Lehmann <schmorp@schmorp.de> |
| 461 |
http://home.schmorp.de/ |
| 462 |
|
