1<?xml version='1.0'?>
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
5
6<refentry id="sd_bus_slot_ref" xmlns:xi="http://www.w3.org/2001/XInclude">
7  <refentryinfo>
8    <title>sd_bus_slot_ref</title>
9    <productname>systemd</productname>
10  </refentryinfo>
11
12  <refmeta>
13    <refentrytitle>sd_bus_slot_ref</refentrytitle>
14    <manvolnum>3</manvolnum>
15  </refmeta>
16
17  <refnamediv>
18    <refname>sd_bus_slot_ref</refname>
19    <refname>sd_bus_slot_unref</refname>
20    <refname>sd_bus_slot_unrefp</refname>
21
22    <refpurpose>Create and destroy references to a bus slot object</refpurpose>
23  </refnamediv>
24
25  <refsynopsisdiv>
26    <funcsynopsis>
27      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
28
29      <funcprototype>
30        <funcdef>sd_bus_slot *<function>sd_bus_slot_ref</function></funcdef>
31        <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
32      </funcprototype>
33
34      <funcprototype>
35        <funcdef>sd_bus_slot *<function>sd_bus_slot_unref</function></funcdef>
36        <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
37      </funcprototype>
38
39      <funcprototype>
40        <funcdef>void <function>sd_bus_slot_unrefp</function></funcdef>
41        <paramdef>sd_bus_slot **<parameter>slotp</parameter></paramdef>
42      </funcprototype>
43    </funcsynopsis>
44  </refsynopsisdiv>
45
46  <refsect1>
47    <title>Description</title>
48
49    <para><function>sd_bus_slot_ref()</function> increases the internal reference counter of
50    <parameter>slot</parameter> by one.</para>
51
52    <para><function>sd_bus_slot_unref()</function> decreases the internal reference counter of
53    <parameter>slot</parameter> by one. Once the reference count has dropped to zero, slot object is
54    destroyed and cannot be used anymore, so further calls to <function>sd_bus_slot_ref()</function>
55    or <function>sd_bus_slot_unref()</function> are illegal.</para>
56
57    <para><function>sd_bus_slot_unrefp()</function> is similar to
58    <function>sd_bus_slot_unref()</function> but takes a pointer to a pointer to an
59    <type>sd_bus_slot</type> object. This call is useful in conjunction with GCC's and LLVM's <ulink
60    url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
61    Attribute</ulink>. See
62    <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
63    for an example how to use the cleanup attribute.</para>
64
65    <para><function>sd_bus_slot_ref()</function> and <function>sd_bus_slot_unref()</function>
66    execute no operation if the passed in bus object address is
67    <constant>NULL</constant>. <function>sd_bus_slot_unrefp()</function> will first dereference
68    its argument, which must not be <constant>NULL</constant>, and will execute no operation if
69    <emphasis>that</emphasis> is <constant>NULL</constant>.</para>
70  </refsect1>
71
72  <refsect1>
73    <title>Return Value</title>
74
75    <para><function>sd_bus_slot_ref()</function> always returns the argument.</para>
76
77    <para><function>sd_bus_slot_unref()</function> always returns <constant>NULL</constant>.</para>
78  </refsect1>
79
80  <xi:include href="libsystemd-pkgconfig.xml" />
81
82  <refsect1>
83    <title>See Also</title>
84
85    <para>
86      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
87      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
88      <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
89      <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
90      <citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
91    </para>
92  </refsect1>
93
94</refentry>
95