--- /dev/null
+<?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 2014 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_new" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_new</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_new</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_new</refname>
+ <refname>sd_event_default</refname>
+ <refname>sd_event_ref</refname>
+ <refname>sd_event_unref</refname>
+ <refname>sd_event_unrefp</refname>
+ <refname>sd_event_get_tid</refname>
+ <refname>sd_event</refname>
+
+ <refpurpose>Acquire and release an event loop object</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
+
+ <funcsynopsisinfo><token>typedef</token> struct sd_event sd_event;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_new</function></funcdef>
+ <paramdef>sd_event **<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_default</function></funcdef>
+ <paramdef>sd_event **<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>sd_event *<function>sd_event_ref</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>sd_event *<function>sd_event_unref</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>void <function>sd_event_unrefp</function></funcdef>
+ <paramdef>sd_event **<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_get_tid</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>pid_t *<parameter>tid</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_new()</function> allocates a new event
+ loop object. The event loop object is returned in the
+ <parameter>event</parameter> parameter. After use, drop
+ the returned reference with
+ <function>sd_event_unref()</function>. When the last reference is
+ dropped, the object is freed.</para>
+
+ <para><function>sd_event_default()</function> acquires a reference
+ to the default event loop object of the calling thread, possibly
+ allocating a new object if no default event loop object has been
+ allocated yet for the thread. After use, drop the returned
+ reference with <function>sd_event_unref()</function>. When the
+ last reference is dropped, the event loop is freed. If this
+ function is called while the object returned from a previous call
+ from the same thread is still referenced, the same object is
+ returned again, but the reference is increased by one. It is
+ recommended to use this call instead of
+ <function>sd_event_new()</function> in order to share event loop
+ objects between various components that are dispatched in the same
+ thread. All threads have exactly either zero or one default event loop
+ objects associated, but never more.</para>
+
+ <para>After allocating an event loop object, add event sources to
+ it with
+ <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_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ or
+ <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ and then execute the event loop using
+ <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para><function>sd_event_ref()</function> increases the reference
+ count of the specified event loop object by one.</para>
+
+ <para><function>sd_event_unref()</function> decreases the
+ reference count of the specified event loop object by one. If
+ the count hits zero, the object is freed. Note that it
+ is freed regardless of whether it is the default event loop object for a
+ thread or not. This means that allocating an event loop with
+ <function>sd_event_default()</function>, then releasing it, and
+ then acquiring a new one with
+ <function>sd_event_default()</function> will result in two
+ distinct objects. Note that, in order to free an event loop object,
+ all remaining event sources of the event loop also need to be
+ freed as each keeps a reference to it.</para>
+
+ <para><function>sd_event_unrefp()</function> is similar to
+ <function>sd_event_unref()</function> but takes a pointer to a
+ pointer to an <type>sd_event</type> object. This call is useful in
+ conjunction with GCC's and LLVM's <ulink
+ url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
+ Variable Attribute</ulink>. Note that this function is defined as
+ inline function. Use a declaration like the following,
+ in order to allocate an event loop object that is freed
+ automatically as the code block is left:</para>
+
+ <programlisting>{
+ __attribute__((cleanup(sd_event_unrefp)) sd_event *event = NULL;
+ int r;
+ …
+ r = sd_event_default(&event);
+ if (r < 0)
+ fprintf(stderr, "Failed to allocate event loop: %s\n", strerror(-r));
+ …
+}</programlisting>
+
+ <para><function>sd_event_ref()</function>,
+ <function>sd_event_unref()</function> and
+ <function>sd_event_unrefp()</function> execute no operation if the
+ passed in event loop object is <constant>NULL</constant>.</para>
+
+ <para><function>sd_event_get_tid()</function> retrieves the thread
+ identifier ("TID") of the thread the specified event loop object
+ is associated with. This call is only supported for event loops
+ allocated with <function>sd_event_default()</function>, and
+ returns the identifier for the thread the event loop is the
+ default event loop of. See <citerefentry
+ project='man-pages'><refentrytitle>gettid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for more information on thread identifiers.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, <function>sd_event_new()</function>,
+ <function>sd_event_default()</function> and
+ <function>sd_event_get_tid()</function> return 0 or a positive
+ integer. On failure, they return a negative errno-style error
+ code. <function>sd_event_ref()</function> always returns a pointer
+ to the event loop object passed
+ in. <function>sd_event_unref()</function> always returns
+ <constant>NULL</constant>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Not enough memory to allocate the object.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EMFILE</constant></term>
+
+ <listitem><para>The maximum number of event loops has been allocated.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENXIO</constant></term>
+
+ <listitem><para><function>sd_event_get_tid()</function> was
+ invoked on an event loop object that was not allocated with
+ <function>sd_event_default()</function>.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libelogind-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <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_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>gettid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / blobdiff