+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2015 Zbigniew Jędrzejewski-Szmek
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_event_wait" conditional="ENABLE_KDBUS">
+
+ <refentryinfo>
+ <title>sd_event_wait</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Tom</firstname>
+ <surname>Gundersen</surname>
+ <email>teg@jklm.no</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_wait</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_wait</refname>
+ <refname>sd_event_prepare</refname>
+ <refname>sd_event_dispatch</refname>
+
+ <refpurpose>Run parts of libsystemd event loop</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_prepare</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_wait</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>uint64_t <parameter>timeout</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_dispatch</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>Functions described here form parts of an event loop.</para>
+
+ <para><function>sd_event_prepare</function> checks for pending
+ events and arms necessary timers. If any events are ready to be
+ processed, it returns a positive value, and the events should be
+ processed with <function>sd_event_dispatch</function>.
+ <function>sd_event_dispatch</function> runs a handler for one of
+ the events from the sources with the highest priority. On success,
+ <function>sd_event_dispatch</function> returns either 0, which
+ means that the loop is finished, or a positive value, which means
+ that the loop is again in the initial state and
+ <function>sd_event_prepare</function> should be called again.
+ </para>
+
+ <para>In case <function>sd_event_prepare</function> returned 0,
+ <function>sd_event_wait</function> should be called to wait for
+ events or a timeout. If any events are ready to be processed, it
+ returns a positive value, and the events should be processed with
+ <function>sd_event_dispatch</function>. Otherwise, the loop is
+ back in the inital state and <function>sd_event_prepare</function>
+ should be called again.</para>
+
+ <programlisting>
+ ┌──────────┐
+ │ initial ├──←←←←←←←←←←←←←←←←←←←─┐
+ └───┬──────┘ ↑
+ │ ↑
+ sd_event_prepare ┌─────────┐ ↑
+ ├ 0 →→→→→→→──┤ armed │ ↑
+ 1 └───┬─────┘ ↑
+ ↓ │ ↑
+ ↓ sd_event_wait ↑
+ ├───←←←←←←←─── 1 ┴─ 0 →→→→→→→─┘
+ ┌───┴──────┐ ↑
+ │ pending │ ↑
+ └───┬──────┘ ↑
+ │ ↑
+ sd_event_dispatch ↑
+ ↓ ↑
+ ├ 1 ──────────→→→→→→→─────────┘
+ 0
+ ↓
+ ┌───┴──────┐
+ │ finished │
+ └──────────┘
+ </programlisting>
+
+ <para>All three functions as the first argument take the event
+ loop object <parameter>event</parameter> that is created with with
+ <function>sd_event_new</function>. The timeout for
+ <function>sd_event_wait</function> is specified with
+ <parameter>timeout</parameter> in milliseconds.
+ <constant>(uint64_t) -1</constant> may be used to specify an
+ infinite timeout.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, these functions return 0 or a positive integer.
+ On failure, they return a negative errno-style error code. In case
+ of <function>sd_event_prepare</function> and
+ <function>sd_event_wait</function> a positive value means that
+ events are ready to be processed and 0 means that no events are
+ ready. In case of <function>sd_event_dispatch</function> a
+ positive value means that the loop is again in the initial state
+ and 0 means the loop is finished. For any of those functions, a
+ negative return value means the loop must be aborted.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>Parameter <parameter>event</parameter> is
+ <constant>NULL</constant>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EBUSY</constant></term>
+
+ <listitem><para>The event loop object is not in the right
+ state.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ESTALE</constant></term>
+
+ <listitem><para>The event loop is already terminated.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+ </varlistentry>
+
+ </variablelist>
+
+ <para>Other errors are possible too.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>Functions described here are available
+ as a shared library, which can be compiled and linked to with the
+ <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / commitdiff