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-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>History</title>
  84     <para><function>sd_bus_slot_ref()</function>,
  85     <function>sd_bus_slot_unref()</function>, and
  86     <function>sd_bus_slot_unrefp()</function> were added in version 240.</para>
  87   </refsect1>
  88
  89   <refsect1>
  90     <title>See Also</title>
  91
  92     <para>
  93       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  94       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  95       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  96       <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  97       <citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  98     </para>
  99   </refsect1>
 100
 101 </refentry>