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Diffstat (limited to 'src/libsystemd/sd_event_new.xml')
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diff --git a/src/libsystemd/sd_event_new.xml b/src/libsystemd/sd_event_new.xml new file mode 100644 index 0000000000..c0a5e98177 --- /dev/null +++ b/src/libsystemd/sd_event_new.xml @@ -0,0 +1,246 @@ +<?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="libsystemd-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> |