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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@328897 c90b9560-bf6c-de11-be94-00142212c4b1
120 lines
4.1 KiB
XML
120 lines
4.1 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<chapter xml:id="ev.periodic-modes" xmlns:phpdoc="http://php.net/ns/phpdoc" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>Periodic watcher operation modes</title>
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<para>
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<classname>EvPeriodic</classname> watcher works in different modes depending
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on the <parameter>offset</parameter>, <parameter>interval</parameter> and
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<parameter>reschedule_cb</parameter> parameters.
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</para>
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<orderedlist>
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<listitem>
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<para><emphasis>Absolute timer</emphasis>.
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In this mode <parameter>interval</parameter> = <constant>0</constant>, <parameter>reschedule_cb</parameter> = &null;.
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This time simply fires at the wallclock time <parameter>offset</parameter> and doesn't repeat. It will
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not adjust when a time jump occurs, that is, if it is to be run at <emphasis>January
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1st 2014</emphasis> then it will run when the system time reaches or surpasses this
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time.
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</para>
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</listitem>
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<listitem>
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<para><emphasis>Repeating interval timer</emphasis>.
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In this mode <parameter>interval</parameter> > <constant>0</constant>, <parameter>reschedule_cb</parameter> = &null;;
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the watcher will always be scheduled to timeout at the next <parameter>offset</parameter> + <constant>N</constant> *
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<parameter>interval</parameter> time(for some integer <constant>N</constant>) and then repeat, regardless of any time
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jumps.
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</para>
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<para>
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This can be used to create timers that do not drift with respect to system time:
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<programlisting role="php">
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<![CDATA[
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<?php
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$hourly = EvPeriodic(0, 3600, NULL, function () {
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echo "once per hour\n";
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};
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?>
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]]>
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</programlisting>
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That doesn't mean there will always be <constant>3600</constant> seconds in
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between triggers, but only that the the callback will be called when the
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system time shows a full hour(<emphasis>UTC</emphasis>).
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</para>
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<para>
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<classname>EvPeriodic</classname> will try to run the callback in this mode
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at the next possible time where <varname>time</varname> =
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<parameter>offset</parameter> (<literal>mod</literal>
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<parameter>interval</parameter>), regardless of any time jumps.
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</para>
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</listitem>
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<listitem>
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<para><emphasis>Manual reschedule mode</emphasis>.
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In this mode <parameter>reschedule_cb</parameter> is a
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<type>callable</type>.
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</para>
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<para>
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<parameter>interval</parameter> and <parameter>offset</parameter> are both
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being ignored. Instead, each time the periodic watcher gets scheduled, the
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reschedule callback (<parameter>reschedule_cb</parameter>) will be called
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with the watcher as first, and the current time as second argument.
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</para>
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<para>
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This callback <emphasis>must not</emphasis> stop or destroy this or any other
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periodic watchers, ever, and <emphasis>must not</emphasis> call any event loop
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functions or methods. If you need to stop it, return <constant>1e30</constant>
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and stop it afterwards. You may create and start a
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<classname>EvPrepare</classname> watcher for this task.
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</para>
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<para>
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It must return the next time to trigger, based on the passed time value (that
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is, the lowest time value larger than or equal to to the second argument). It
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will usually be called just before the callback will be triggered, but might
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be called at other times, too.
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</para>
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<example>
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<title>Using reschedule callback</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// Tick each 10.5 seconds
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function reschedule_cb ($watcher, $now) {
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return $now + (10.5. - fmod($now, 10.5));
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}
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$w = new EvPeriodic(0., 0., "reschedule_cb", function ($w, $revents) {
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echo time(), PHP_EOL;
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});
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Ev::run();
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?>
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]]>
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</programlisting>
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</example>
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</listitem>
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</orderedlist>
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</chapter>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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