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      ev.html
  2. 94
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96
ev.html

@ -6,7 +6,7 @@
<meta name="description" content="Pod documentation for libev" />
<meta name="inputfile" content="&lt;standard input&gt;" />
<meta name="outputfile" content="&lt;standard output&gt;" />
<meta name="created" content="Mon Nov 12 09:35:36 2007" />
<meta name="created" content="Mon Nov 12 09:45:48 2007" />
<meta name="generator" content="Pod::Xhtml 1.57" />
<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
<body>
@ -28,7 +28,7 @@
<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</a></li>
<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
@ -324,14 +324,14 @@ corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>
<p>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.</p>
<p>You cna check whether an event is active by calling the <code>ev_is_active
<p>You can check whether an event is active by calling the <code>ev_is_active
(watcher *)</code> macro. To see whether an event is outstanding (but the
callback for it has not been called yet) you cna use the <code>ev_is_pending
callback for it has not been called yet) you can use the <code>ev_is_pending
(watcher *)</code> macro.</p>
<p>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.</p>
<p>The rceeived events usually include a single bit per event type received
<p>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:</p>
<dl>
@ -391,7 +391,7 @@ programs, though, so beware.</p>
<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
<p>Each watcher has, by default, a member <code>void *data</code> 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 &quot;subclass&quot; the watcher type and provide your own
@ -433,7 +433,7 @@ information given in the last section.</p>
<p>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).</p>
<p>In general you can register as many read and/or write event watchers oer
fd as you want (as long as you don't confuse yourself). Setting all file
@ -507,7 +507,7 @@ the timer, and again will automatically restart it if need be.</p>
</dl>
</div>
<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</h2>
<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
<div id="code_ev_periodic_code_to_cron_or_not-2">
<p>Periodic watchers are also timers of a kind, but they are very versatile
(and unfortunately a bit complex).</p>
@ -605,7 +605,7 @@ program when the crontabs have changed).</p>
signal one or more times. Even though signals are very asynchronous, libev
will try it's best to deliver signals synchronously, i.e. as part of the
normal event processing, like any other event.</p>
<p>You cna configure as many watchers as you like per signal. Only when the
<p>You can configure as many watchers as you like per signal. Only when the
first watcher gets started will libev actually register a signal watcher
with the kernel (thus it coexists with your own signal handlers as long
as you don't register any with libev). Similarly, when the last signal
@ -632,19 +632,22 @@ some child status changes (most typically when a child of yours dies).</p>
<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member
contains the pid of the process causing the status change.</p>
the status word (use the macros from <code>sys/wait.h</code> and see your systems
<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
process causing the status change.</p>
</dd>
</dl>
</div>
<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
<div id="code_ev_idle_code_when_you_ve_got_no-2">
<p>Idle watchers trigger events when there are no other I/O or timer (or
periodic) events pending. That is, as long as your process is busy
handling sockets or timeouts it will not be called. But when your process
is idle all idle watchers are being called again and again - until
stopped, that is, or your process receives more events.</p>
<p>Idle watchers trigger events when there are no other events are pending
(prepare, check and other idle watchers do not count). That is, as long
as your process is busy handling sockets or timeouts (or even signals,
imagine) it will not be triggered. But when your process is idle all idle
watchers are being called again and again, once per event loop iteration -
until stopped, that is, or your process receives more events and becomes
busy.</p>
<p>The most noteworthy effect is that as long as any idle watchers are
active, the process will not block when waiting for new events.</p>
<p>Apart from keeping your process non-blocking (which is a useful
@ -663,36 +666,42 @@ believe me.</p>
</div>
<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>
<div id="prepare_and_check_your_hooks_into_th-2">
<p>Prepare and check watchers usually (but not always) are used in
tandom. Prepare watchers get invoked before the process blocks and check
watchers afterwards.</p>
<p>Prepare and check watchers are usually (but not always) used in tandem:
Prepare watchers get invoked before the process blocks and check watchers
afterwards.</p>
<p>Their main purpose is to integrate other event mechanisms into libev. This
could be used, for example, to track variable changes, implement your own
watchers, integrate net-snmp or a coroutine library and lots more.</p>
<p>This is done by examining in each prepare call which file descriptors need
to be watched by the other library, registering <code>ev_io</code> watchers for them
and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide
just this functionality). Then, in the check watcher you check for any
events that occured (by making your callbacks set soem flags for example)
and call back into the library.</p>
<p>As another example, the perl Coro module uses these hooks to integrate
to be watched by the other library, registering <code>ev_io</code> watchers for
them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
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,
because you never know, you know?).</p>
<p>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.</p>
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).</p>
<dl>
<dt>ev_prepare_init (ev_prepare *, callback)</dt>
<dt>ev_check_init (ev_check *, callback)</dt>
<dd>
<p>Initialises and configures the prepare or check watcher - they have no
parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
macros, but using them is utterly, utterly pointless.</p>
macros, but using them is utterly, utterly and completely pointless.</p>
</dd>
</dl>
</div>
<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
<div id="OTHER_FUNCTIONS_CONTENT">
<p>There are some other fucntions of possible interest. Described. Here. Now.</p>
<p>There are some other functions of possible interest. Described. Here. Now.</p>
<dl>
<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
<dd>
@ -701,36 +710,39 @@ 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
more watchers yourself.</p>
<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is
ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set
will be craeted and started.</p>
<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
<code>events</code> set will be craeted and started.</p>
<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat
= 0) will be started.</p>
<p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and
gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>,
<code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p>
started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
dubious value.</p>
<p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
passed an events set like normal event callbacks (with a combination of
<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
value passed to <code>ev_once</code>:</p>
<pre> static void stdin_ready (int revents, void *arg)
{
if (revents &amp; EV_TIMEOUT)
/* doh, nothing entered */
/* doh, nothing entered */;
else if (revents &amp; EV_READ)
/* stdin might have data for us, joy! */
/* stdin might have data for us, joy! */;
}
ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);
ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
</pre>
</dd>
<dt>ev_feed_event (loop, watcher, int events)</dt>
<dd>
<p>Feeds the given event set into the event loop, as if the specified event
has happened for the specified watcher (which must be a pointer to an
initialised but not necessarily active event watcher).</p>
had happened for the specified watcher (which must be a pointer to an
initialised but not necessarily started event watcher).</p>
</dd>
<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
<dd>
<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>
<p>Feed an event on the given fd, as if a file descriptor backend detected
the given events it.</p>
</dd>
<dt>ev_feed_signal_event (loop, int signum)</dt>
<dd>

94
ev.pod

@ -301,16 +301,16 @@ 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<ev_is_active
You can check whether an event is active by calling the C<ev_is_active
(watcher *)> macro. To see whether an event is outstanding (but the
callback for it has not been called yet) you cna use the C<ev_is_pending
callback for it has not been called yet) you can use the C<ev_is_pending
(watcher *)> 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:
@ -374,7 +374,7 @@ programs, though, so beware.
=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
Each watcher has, by default, a member C<void *data> 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
@ -411,7 +411,7 @@ information given in the last section.
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
@ -497,7 +497,7 @@ the timer, and again will automatically restart it if need be.
=back
=head2 C<ev_periodic> - to cron or not to cron it
=head2 C<ev_periodic> - to cron or not to cron
Periodic watchers are also timers of a kind, but they are very versatile
(and unfortunately a bit complex).
@ -603,7 +603,7 @@ signal one or more times. Even though signals are very asynchronous, libev
will try it's best to deliver signals synchronously, i.e. as part of the
normal event processing, like any other event.
You cna configure as many watchers as you like per signal. Only when the
You can configure as many watchers as you like per signal. Only when the
first watcher gets started will libev actually register a signal watcher
with the kernel (thus it coexists with your own signal handlers as long
as you don't register any with libev). Similarly, when the last signal
@ -635,18 +635,21 @@ some child status changes (most typically when a child of yours dies).
Configures the watcher to wait for status changes of process C<pid> (or
I<any> process if C<pid> is specified as C<0>). The callback can look
at the C<rstatus> member of the C<ev_child> watcher structure to see
the status word (use the macros from C<sys/wait.h>). The C<rpid> member
contains the pid of the process causing the status change.
the status word (use the macros from C<sys/wait.h> and see your systems
C<waitpid> documentation). The C<rpid> member contains the pid of the
process causing the status change.
=back
=head2 C<ev_idle> - when you've got nothing better to do
Idle watchers trigger events when there are no other I/O or timer (or
periodic) events pending. That is, as long as your process is busy
handling sockets or timeouts it will not be called. But when your process
is idle all idle watchers are being called again and again - until
stopped, that is, or your process receives more events.
Idle watchers trigger events when there are no other events are pending
(prepare, check and other idle watchers do not count). That is, as long
as your process is busy handling sockets or timeouts (or even signals,
imagine) it will not be triggered. But when your process is idle all idle
watchers are being called again and again, once per event loop iteration -
until stopped, that is, or your process receives more events and becomes
busy.
The most noteworthy effect is that as long as any idle watchers are
active, the process will not block when waiting for new events.
@ -668,25 +671,31 @@ believe me.
=head2 prepare and check - your hooks into the event loop
Prepare and check watchers usually (but not always) are used in
tandom. Prepare watchers get invoked before the process blocks and check
watchers afterwards.
Prepare and check watchers are usually (but not always) used in tandem:
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
watchers, integrate net-snmp or a coroutine library and lots more.
This is done by examining in each prepare call which file descriptors need
to be watched by the other library, registering C<ev_io> watchers for them
and starting an C<ev_timer> watcher for any timeouts (many libraries provide
just this functionality). Then, in the check watcher you check for any
events that occured (by making your callbacks set soem flags for example)
and call back into the library.
As another example, the perl Coro module uses these hooks to integrate
to be watched by the other library, registering C<ev_io> watchers for
them and starting an C<ev_timer> watcher for any timeouts (many libraries
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,
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.
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).
=over 4
@ -696,13 +705,13 @@ are ready to run.
Initialises and configures the prepare or check watcher - they have no
parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
macros, but using them is utterly, utterly pointless.
macros, but using them is utterly, utterly and completely pointless.
=back
=head1 OTHER FUNCTIONS
There are some other fucntions of possible interest. Described. Here. Now.
There are some other functions of possible interest. Described. Here. Now.
=over 4
@ -714,37 +723,40 @@ 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
more watchers yourself.
If C<fd> is less than 0, then no I/O watcher will be started and events is
ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set
will be craeted and started.
If C<fd> is less than 0, then no I/O watcher will be started and events
is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
C<events> set will be craeted and started.
If C<timeout> is less than 0, then no timeout watcher will be
started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and repeat
= 0) will be started.
started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
repeat = 0) will be started. While C<0> is a valid timeout, it is of
dubious value.
The callback has the type C<void (*cb)(int revents, void *arg)> and
gets passed an events set (normally a combination of C<EV_ERROR>, C<EV_READ>,
C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> value passed to C<ev_once>:
The callback has the type C<void (*cb)(int revents, void *arg)> and gets
passed an events set like normal event callbacks (with a combination of
C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
value passed to C<ev_once>:
static void stdin_ready (int revents, void *arg)
{
if (revents & EV_TIMEOUT)
/* doh, nothing entered */
/* doh, nothing entered */;
else if (revents & EV_READ)
/* stdin might have data for us, joy! */
/* stdin might have data for us, joy! */;
}
ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);
ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
=item ev_feed_event (loop, watcher, int events)
Feeds the given event set into the event loop, as if the specified event
has happened for the specified watcher (which must be a pointer to an
initialised but not necessarily active event watcher).
had happened for the specified watcher (which must be a pointer to an
initialised but not necessarily started event watcher).
=item ev_feed_fd_event (loop, int fd, int revents)
Feed an event on the given fd, as if a file descriptor backend detected it.
Feed an event on the given fd, as if a file descriptor backend detected
the given events it.
=item ev_feed_signal_event (loop, int signum)

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