man/sd_bus_slot_ref.xml

   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+ -->
   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     <refname>sd_bus_slot_get_bus</refname>
  22
  23     <refpurpose>Create and destroy references to a bus slot object</refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <funcsynopsis>
  28       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  29
  30       <funcprototype>
  31         <funcdef>sd_bus_slot *<function>sd_bus_slot_ref</function></funcdef>
  32         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>sd_bus_slot *<function>sd_bus_slot_unref</function></funcdef>
  37         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  38       </funcprototype>
  39
  40       <funcprototype>
  41         <funcdef>void <function>sd_bus_slot_unrefp</function></funcdef>
  42         <paramdef>sd_bus_slot **<parameter>slotp</parameter></paramdef>
  43       </funcprototype>
  44
  45       <funcprototype>
  46         <funcdef>sd_bus *<function>sd_bus_slot_get_bus</function></funcdef>
  47         <paramdef>sd_bus_slot *<parameter>m</parameter></paramdef>
  48       </funcprototype>
  49     </funcsynopsis>
  50   </refsynopsisdiv>
  51
  52   <refsect1>
  53     <title>Description</title>
  54
  55     <para><function>sd_bus_slot_ref()</function> increases the reference counter of
  56     <parameter>slot</parameter> by one.</para>
  57
  58     <para><function>sd_bus_slot_unref()</function> decreases the reference counter of
  59     <parameter>slot</parameter> by one. Once the reference count has dropped to zero, slot object is
  60     destroyed and cannot be used anymore, so further calls to <function>sd_bus_slot_ref()</function>
  61     or <function>sd_bus_slot_unref()</function> are illegal.</para>
  62
  63     <para><function>sd_bus_slot_unrefp()</function> is similar to
  64     <function>sd_bus_slot_unref()</function> but takes a pointer to a pointer to an
  65     <type>sd_bus_slot</type> object. This call is useful in conjunction with GCC's and LLVM's <ulink
  66     url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
  67     Attribute</ulink>. See
  68     <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  69     for an example how to use the cleanup attribute.</para>
  70
  71     <para><function>sd_bus_slot_ref()</function> and <function>sd_bus_slot_unref()</function>
  72     execute no operation if the passed in bus object address is
  73     <constant>NULL</constant>. <function>sd_bus_slot_unrefp()</function> will first dereference
  74     its argument, which must not be <constant>NULL</constant>, and will execute no operation if
  75     <emphasis>that</emphasis> is <constant>NULL</constant>.
  76     </para>
  77
  78     <para><function>sd_bus_slot_get_bus()</function> returns the bus object that message
  79     <parameter>slot</parameter> is attached to.</para>
  80   </refsect1>
  81
  82   <refsect1>
  83     <title>Return Value</title>
  84
  85     <para><function>sd_bus_slot_ref()</function> always returns the argument.</para>
  86
  87     <para><function>sd_bus_slot_unref()</function> always returns <constant>NULL</constant>.</para>
  88
  89     <para><function>sd_bus_slot_get_bus()</function> always returns the bus object.</para>
  90   </refsect1>
  91
  92   <xi:include href="libsystemd-pkgconfig.xml" />
  93
  94   <refsect1>
  95     <title>See Also</title>
  96
  97     <para>
  98       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  99       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 100       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 101       <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 102       <citerefentry><refentrytitle>sd_bus_slot_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 103       <citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 104     </para>
 105   </refsect1>
 106
 107 </refentry>