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1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> | |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
6 | SPDX-License-Identifier: LGPL-2.1+ | |
7 | ||
8 | Copyright © 2014 Zbigniew Jędrzejewski-Szmek | |
9 | --> | |
10 | ||
11 | <refentry id="sd_event_add_defer" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
12 | ||
13 | <refentryinfo> | |
14 | <title>sd_event_add_defer</title> | |
15 | <productname>systemd</productname> | |
16 | ||
17 | <authorgroup> | |
18 | <author> | |
19 | <contrib>More text</contrib> | |
20 | <firstname>Zbigniew</firstname> | |
21 | <surname>Jędrzejewski-Szmek</surname> | |
22 | <email>zbyszek@in.waw.pl</email> | |
23 | </author> | |
24 | </authorgroup> | |
25 | </refentryinfo> | |
26 | ||
27 | <refmeta> | |
28 | <refentrytitle>sd_event_add_defer</refentrytitle> | |
29 | <manvolnum>3</manvolnum> | |
30 | </refmeta> | |
31 | ||
32 | <refnamediv> | |
33 | <refname>sd_event_add_defer</refname> | |
34 | <refname>sd_event_add_post</refname> | |
35 | <refname>sd_event_add_exit</refname> | |
36 | <refname>sd_event_handler_t</refname> | |
37 | ||
38 | <refpurpose>Add static event sources to an event loop</refpurpose> | |
39 | </refnamediv> | |
40 | ||
41 | <refsynopsisdiv> | |
42 | <funcsynopsis> | |
43 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
44 | ||
45 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
46 | ||
47 | <funcprototype> | |
48 | <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef> | |
49 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
50 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
51 | </funcprototype> | |
52 | ||
53 | <funcprototype> | |
54 | <funcdef>int <function>sd_event_add_defer</function></funcdef> | |
55 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
56 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
57 | <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef> | |
58 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
59 | </funcprototype> | |
60 | ||
61 | <funcprototype> | |
62 | <funcdef>int <function>sd_event_add_post</function></funcdef> | |
63 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
64 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
65 | <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef> | |
66 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
67 | </funcprototype> | |
68 | ||
69 | <funcprototype> | |
70 | <funcdef>int <function>sd_event_add_exit</function></funcdef> | |
71 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
72 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
73 | <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef> | |
74 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
75 | </funcprototype> | |
76 | ||
77 | </funcsynopsis> | |
78 | </refsynopsisdiv> | |
79 | ||
80 | <refsect1> | |
81 | <title>Description</title> | |
82 | ||
83 | <para>These three functions add new static event sources to an | |
84 | event loop. The event loop object is specified in the | |
85 | <parameter>event</parameter> parameter, the event source object is | |
86 | returned in the <parameter>source</parameter> parameter. The event | |
87 | sources are enabled statically and will "fire" when the event loop | |
88 | is run and the conditions described below are met. The handler | |
89 | function will be passed the <parameter>userdata</parameter> | |
90 | pointer, which may be chosen freely by the caller.</para> | |
91 | ||
92 | <para><function>sd_event_add_defer()</function> adds a new event | |
93 | source that will be dispatched instantly, before the event loop | |
94 | goes to sleep again and waits for new events. By default, the | |
95 | handler will be called once | |
96 | (<constant>SD_EVENT_ONESHOT</constant>). Note that if the event | |
97 | source is set to <constant>SD_EVENT_ON</constant> the event loop | |
98 | will never go to sleep again, but continuously call the handler, | |
99 | possibly interleaved with other event sources.</para> | |
100 | ||
101 | <para><function>sd_event_add_post()</function> adds a new event | |
102 | source that is run before the event loop will sleep and wait | |
103 | for new events, but only after at least one other non-post event | |
104 | source was dispatched. By default, the source is enabled | |
105 | permanently (<constant>SD_EVENT_ON</constant>). Note that this | |
106 | event source type will still allow the event loop to go to sleep | |
107 | again, even if set to <constant>SD_EVENT_ON</constant>, as long as | |
108 | no other event source is ever triggered.</para> | |
109 | ||
110 | <para><function>sd_event_add_exit()</function> adds a new event | |
111 | source that will be dispatched when the event loop is terminated | |
112 | with <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
113 | ||
114 | <para>The | |
115 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
116 | function may be used to enable the event source permanently | |
117 | (<constant>SD_EVENT_ON</constant>) or to make it fire just once | |
118 | (<constant>SD_EVENT_ONESHOT</constant>).</para> | |
119 | ||
120 | <para>If the handler function returns a negative error code, it | |
121 | will be disabled after the invocation, even if the | |
122 | <constant>SD_EVENT_ON</constant> mode was requested before.</para> | |
123 | ||
124 | <para>To destroy an event source object use | |
125 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
126 | but note that the event source is only removed from the event loop | |
127 | when all references to the event source are dropped. To make sure | |
128 | an event source does not fire anymore, even when there's still a | |
129 | reference to it kept, consider setting the event source to | |
130 | <constant>SD_EVENT_OFF</constant> with | |
131 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
132 | ||
133 | <para>If the second parameter of these functions is passed as | |
134 | NULL no reference to the event source object is returned. In this | |
135 | case the event source is considered "floating", and will be | |
136 | destroyed implicitly when the event loop itself is | |
137 | destroyed.</para> | |
138 | </refsect1> | |
139 | ||
140 | <refsect1> | |
141 | <title>Return Value</title> | |
142 | ||
143 | <para>On success, these functions return 0 or a positive | |
144 | integer. On failure, they return a negative errno-style error | |
145 | code.</para> | |
146 | </refsect1> | |
147 | ||
148 | <refsect1> | |
149 | <title>Errors</title> | |
150 | ||
151 | <para>Returned errors may indicate the following problems:</para> | |
152 | ||
153 | <variablelist> | |
154 | <varlistentry> | |
155 | <term><constant>-ENOMEM</constant></term> | |
156 | ||
157 | <listitem><para>Not enough memory to allocate an object.</para></listitem> | |
158 | </varlistentry> | |
159 | ||
160 | <varlistentry> | |
161 | <term><constant>-EINVAL</constant></term> | |
162 | ||
163 | <listitem><para>An invalid argument has been passed.</para></listitem> | |
164 | </varlistentry> | |
165 | ||
166 | <varlistentry> | |
167 | <term><constant>-ESTALE</constant></term> | |
168 | ||
169 | <listitem><para>The event loop is already terminated.</para></listitem> | |
170 | </varlistentry> | |
171 | ||
172 | <varlistentry> | |
173 | <term><constant>-ECHILD</constant></term> | |
174 | ||
175 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
176 | </varlistentry> | |
177 | ||
178 | </variablelist> | |
179 | </refsect1> | |
180 | ||
181 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
182 | ||
183 | <refsect1> | |
184 | <title>See Also</title> | |
185 | ||
186 | <para> | |
187 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
188 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
189 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
190 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
191 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
192 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
193 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
194 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
195 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
196 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
197 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
198 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
199 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
200 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
201 | </para> | |
202 | </refsect1> | |
203 | ||
204 | </refentry> |