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+<?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 Lennart Poettering
+
+ 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_source_set_prepare" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_source_set_prepare</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_source_set_prepare</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_source_set_prepare</refname>
+
+ <refpurpose>Set a preparation callback for event sources</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_prepare</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>sd_event_handler_t <parameter>callback</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef>
+ <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_source_set_prepare()</function> may be
+ used to set a preparation callback for the event source object
+ specified as <parameter>source</parameter>. The callback function
+ specified as <parameter>callback</parameter> will be invoked
+ immediately before the event loop goes to sleep to wait for
+ incoming events. It is invoked with the user data pointer passed
+ when the event source was created. The callback function may be
+ used to reconfigure the precise events to wait for. If the
+ <parameter>callback</parameter> parameter is passed as NULL the
+ callback function is reset. </para>
+
+ <para>Event source objects have no preparation callback associated
+ when they are first created with calls such as
+ <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation
+ callback functions are supported for all event source types with
+ the exception of those created with
+ <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation
+ callback functions are dispatched in the order indicated by the
+ event source's priority field, as set with
+ <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation
+ callbacks of disabled event sources (see
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
+ are not invoked.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success,
+ <function>sd_event_source_set_prepare()</function> returns a
+ non-negative integer. On failure, it returns a negative
+ errno-style error code.</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>source</parameter> is not a valid
+ pointer to an <structname>sd_event_source</structname>
+ object.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ESTALE</constant></term>
+
+ <listitem><para>The event loop is already terminated.</para></listitem>
+
+ </varlistentry>
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Not enough memory.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EDOM</constant></term>
+
+ <listitem><para>The specified event source has been created
+ with
+ <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
+
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libsystemd-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>sd-event</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_child</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_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>