man/sd_bus_slot_ref.xml


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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="sd_bus_slot_ref" xmlns:xi="http://www.w3.org/2001/XInclude">
  <refentryinfo>
    <title>sd_bus_slot_ref</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_slot_ref</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_slot_ref</refname>
    <refname>sd_bus_slot_unref</refname>
    <refname>sd_bus_slot_unrefp</refname>

    <refpurpose>Create and destroy references to a bus slot object</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>sd_bus_slot *<function>sd_bus_slot_ref</function></funcdef>
        <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>sd_bus_slot *<function>sd_bus_slot_unref</function></funcdef>
        <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>void <function>sd_bus_slot_unrefp</function></funcdef>
        <paramdef>sd_bus_slot **<parameter>slotp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_slot_ref()</function> increases the internal reference counter of
    <parameter>slot</parameter> by one.</para>

    <para><function>sd_bus_slot_unref()</function> decreases the internal reference counter of
    <parameter>slot</parameter> by one. Once the reference count has dropped to zero, slot object is
    destroyed and cannot be used anymore, so further calls to <function>sd_bus_slot_ref()</function>
    or <function>sd_bus_slot_unref()</function> are illegal.</para>

    <para><function>sd_bus_slot_unrefp()</function> is similar to
    <function>sd_bus_slot_unref()</function> but takes a pointer to a pointer to an
    <type>sd_bus_slot</type> object. This call is useful in conjunction with GCC's and LLVM's <ulink
    url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
    Attribute</ulink>. See
    <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    for an example how to use the cleanup attribute.</para>

    <para><function>sd_bus_slot_ref()</function> and <function>sd_bus_slot_unref()</function>
    execute no operation if the passed in bus object address is
    <constant>NULL</constant>. <function>sd_bus_slot_unrefp()</function> will first dereference
    its argument, which must not be <constant>NULL</constant>, and will execute no operation if
    <emphasis>that</emphasis> is <constant>NULL</constant>.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para><function>sd_bus_slot_ref()</function> always returns the argument.</para>

    <para><function>sd_bus_slot_unref()</function> always returns <constant>NULL</constant>.</para>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <refsect1>
    <title>History</title>
    <para><function>sd_bus_slot_ref()</function>,
    <function>sd_bus_slot_unref()</function>, and
    <function>sd_bus_slot_unrefp()</function> were added in version 240.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>