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6e866b33 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
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4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
5 | ||
6 | <refentry id="sd_event_source_set_destroy_callback" | |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
8 | ||
9 | <refentryinfo> | |
10 | <title>sd_event_source_set_destroy_callback</title> | |
11 | <productname>systemd</productname> | |
12 | </refentryinfo> | |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_event_source_set_destroy_callback</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_event_source_set_destroy_callback</refname> | |
21 | <refname>sd_event_source_get_destroy_callback</refname> | |
22 | <refname>sd_event_destroy_t</refname> | |
23 | ||
24 | <refpurpose>Define the callback function for resource cleanup.</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
29 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
30 | ||
31 | <funcprototype> | |
32 | <funcdef>typedef int (*<function>sd_event_destroy_t</function>)</funcdef> | |
33 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
34 | </funcprototype> | |
35 | ||
36 | <funcprototype> | |
37 | <funcdef>int <function>sd_event_source_set_destroy_callback</function></funcdef> | |
38 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
39 | <paramdef>sd_event_destroy_t <parameter>callback</parameter></paramdef> | |
40 | </funcprototype> | |
41 | ||
42 | <funcprototype> | |
43 | <funcdef>int <function>sd_event_source_get_destroy_callback</function></funcdef> | |
44 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
45 | <paramdef>sd_event_destroy_t *<parameter>callback</parameter></paramdef> | |
46 | </funcprototype> | |
47 | ||
48 | </funcsynopsis> | |
49 | </refsynopsisdiv> | |
50 | ||
51 | <refsect1> | |
52 | <title>Description</title> | |
53 | ||
54 | <para><function>sd_event_source_set_destroy_callback()</function> sets <parameter>callback</parameter> as the | |
55 | callback function to be called right before the event source object <parameter>source</parameter> is | |
56 | deallocated. The <parameter>userdata</parameter> pointer from the event source object will be passed as the | |
57 | <parameter>userdata</parameter> parameter. This pointer can be set by an argument to the constructor functions, see | |
58 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly, | |
59 | see | |
60 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
61 | This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that | |
62 | this callback is invoked at a time where the event source object itself is already invalidated, and executing | |
63 | operations or taking new references to the event source object is not permissible.</para> | |
64 | ||
65 | <para><function>sd_event_source_get_destroy_callback()</function> returns the current callback | |
66 | for <parameter>source</parameter> in the <parameter>callback</parameter> parameter.</para> | |
67 | </refsect1> | |
68 | ||
69 | <refsect1> | |
70 | <title>Return Value</title> | |
71 | ||
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72 | <para>On success, <function>sd_event_source_set_destroy_callback()</function> returns 0 or a positive |
73 | integer. On failure, it returns a negative errno-style error code.</para> | |
b012e921 | 74 | |
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75 | <para><function>sd_event_source_get_destroy_callback()</function> returns positive if the destroy |
76 | callback function is set, 0 if not. On failure, returns a negative errno-style error code.</para> | |
b012e921 | 77 | |
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78 | <refsect2> |
79 | <title>Errors</title> | |
b012e921 | 80 | |
bb4f798a | 81 | <para>Returned errors may indicate the following problems:</para> |
b012e921 | 82 | |
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83 | <variablelist> |
84 | <varlistentry> | |
85 | <term><constant>-EINVAL</constant></term> | |
b012e921 | 86 | |
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87 | <listitem><para>The <parameter>source</parameter> parameter is <constant>NULL</constant>. |
88 | </para></listitem> | |
89 | </varlistentry> | |
90 | </variablelist> | |
91 | </refsect2> | |
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92 | </refsect1> |
93 | ||
94 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
95 | ||
96 | <refsect1> | |
97 | <title>See Also</title> | |
98 | ||
99 | <para> | |
100 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
101 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
102 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
103 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
104 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
105 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
106 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
107 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
108 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
109 | </para> | |
110 | </refsect1> | |
111 | ||
112 | </refentry> |