man/sd_bus_slot_set_destroy_callback.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   6
   7 <refentry id="sd_bus_slot_set_destroy_callback"
   8           xmlns:xi="http://www.w3.org/2001/XInclude">
   9
  10   <refentryinfo>
  11     <title>sd_bus_slot_set_destroy_callback</title>
  12     <productname>systemd</productname>
  13   </refentryinfo>
  14
  15   <refmeta>
  16     <refentrytitle>sd_bus_slot_set_destroy_callback</refentrytitle>
  17     <manvolnum>3</manvolnum>
  18   </refmeta>
  19
  20   <refnamediv>
  21     <refname>sd_bus_slot_set_destroy_callback</refname>
  22     <refname>sd_bus_slot_get_destroy_callback</refname>
  23
  24     <refpurpose>Define the callback function for resource cleanup.</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <funcsynopsis>
  29       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  30
  31       <funcprototype>
  32         <funcdef>typedef int (*<function>sd_bus_destroy_t</function>)</funcdef>
  33         <paramdef>void *<parameter>userdata</parameter></paramdef>
  34       </funcprototype>
  35
  36       <funcprototype>
  37         <funcdef>int <function>sd_bus_slot_set_destroy_callback</function></funcdef>
  38         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  39         <paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
  40       </funcprototype>
  41
  42       <funcprototype>
  43         <funcdef>int <function>sd_bus_slot_get_destroy_callback</function></funcdef>
  44         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  45         <paramdef>sd_bus_destroy_t *<parameter>callback</parameter></paramdef>
  46       </funcprototype>
  47     </funcsynopsis>
  48   </refsynopsisdiv>
  49
  50   <refsect1>
  51     <title>Description</title>
  52
  53     <para><function>sd_bus_slot_set_destroy_callback()</function> sets
  54     <parameter>callback</parameter> as the callback function to be called right before the bus slot
  55     object <parameter>slot</parameter> is deallocated. The <parameter>userdata</parameter> pointer
  56     from the slot object will be passed as the <parameter>userdata</parameter> parameter. This
  57     pointer can be set specified as an argument to the constuctor functions, see
  58     <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  59     or directly, see
  60     <citerefentry><refentrytitle>sd_bus_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  61     This callback function is called even if <parameter>userdata</parameter> is
  62     <constant>NULL</constant>.</para>
  63
  64     <para><function>sd_bus_slot_get_destroy_callback()</function> returns the current callback
  65     for <parameter>slot</parameter> in the <parameter>callback</parameter> parameter.</para>
  66   </refsect1>
  67
  68   <refsect1>
  69     <title>Return Value</title>
  70
  71     <para>On success, <function>sd_bus_slot_set_destroy_callback()</function> returns 0 or a
  72     positive integer. On failure, it returns a negative errno-style error code.</para>
  73
  74     <para><function>sd_bus_slot_get_destroy_callback()</function> returns 1 if the destroy callback
  75     function is set, 0 if not. On failure, it returns a negative errno-style error code.</para>
  76   </refsect1>
  77
  78   <refsect1>
  79     <title>Errors</title>
  80
  81     <para>Returned errors may indicate the following problems:</para>
  82
  83     <variablelist>
  84       <varlistentry>
  85         <term><constant>-EINVAL</constant></term>
  86
  87         <listitem><para>The <parameter>slot</parameter> parameter is <constant>NULL</constant>.
  88         </para></listitem>
  89       </varlistentry>
  90     </variablelist>
  91   </refsect1>
  92
  93   <xi:include href="libsystemd-pkgconfig.xml" />
  94
  95   <refsect1>
  96     <title>See Also</title>
  97
  98     <para>
  99       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 100       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 101       <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 102     </para>
 103   </refsect1>
 104
 105 </refentry>