man/sd_bus_slot_set_destroy_callback.xml

   1 <?xml version='1.0'?>
   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     <refname>sd_bus_track_set_destroy_callback</refname>
  24     <refname>sd_bus_track_get_destroy_callback</refname>
  25     <refname>sd_bus_destroy_t</refname>
  26
  27     <refpurpose>Define the callback function for resource cleanup.</refpurpose>
  28   </refnamediv>
  29
  30   <refsynopsisdiv>
  31     <funcsynopsis>
  32       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  33
  34       <funcprototype>
  35         <funcdef>typedef int (*<function>sd_bus_destroy_t</function>)</funcdef>
  36         <paramdef>void *<parameter>userdata</parameter></paramdef>
  37       </funcprototype>
  38
  39       <funcprototype>
  40         <funcdef>int <function>sd_bus_slot_set_destroy_callback</function></funcdef>
  41         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  42         <paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
  43       </funcprototype>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_slot_get_destroy_callback</function></funcdef>
  47         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  48         <paramdef>sd_bus_destroy_t *<parameter>callback</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_track_set_destroy_callback</function></funcdef>
  53         <paramdef>sd_bus_track *<parameter>track</parameter></paramdef>
  54         <paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
  55       </funcprototype>
  56
  57       <funcprototype>
  58         <funcdef>int <function>sd_bus_track_get_destroy_callback</function></funcdef>
  59         <paramdef>sd_bus_track *<parameter>track</parameter></paramdef>
  60         <paramdef>sd_bus_destroy_t *<parameter>callback</parameter></paramdef>
  61       </funcprototype>
  62     </funcsynopsis>
  63   </refsynopsisdiv>
  64
  65   <refsect1>
  66     <title>Description</title>
  67
  68     <para><function>sd_bus_slot_set_destroy_callback()</function> sets <parameter>callback</parameter> as the callback
  69     function to be called right before the bus slot object <parameter>slot</parameter> is deallocated. The
  70     <parameter>userdata</parameter> pointer from the slot object will be passed as the <parameter>userdata</parameter>
  71     parameter. This pointer can be set by an argument to the constructor functions, see
  72     <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly,
  73     see <citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  74     This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that
  75     this callback is invoked at a time where the bus slot object itself is already invalidated, and executing
  76     operations or taking new references to the bus slot object is not permissible.</para>
  77
  78     <para><function>sd_bus_slot_get_destroy_callback()</function> returns the current callback
  79     for <parameter>slot</parameter> in the <parameter>callback</parameter> parameter.</para>
  80
  81     <para><function>sd_bus_track_set_destroy_callback()</function> and
  82     <function>sd_bus_track_get_destroy_callback()</function> provide equivalent functionality for the
  83     <parameter>userdata</parameter> pointer associated with bus peer tracking objects. For details about bus peer
  84     tracking objects, see
  85     <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  86   </refsect1>
  87
  88   <refsect1>
  89     <title>Return Value</title>
  90
  91     <para>On success, <function>sd_bus_slot_set_destroy_callback()</function> and
  92     <function>sd_bus_track_set_destroy_callback()</function> return 0 or a positive integer. On failure, they return a
  93     negative errno-style error code.</para>
  94
  95     <para><function>sd_bus_slot_get_destroy_callback()</function> and
  96     <function>sd_bus_track_get_destroy_callback()</function> return positive if the destroy callback function is set, 0
  97     if not. On failure, they return a negative errno-style error code.</para>
  98   </refsect1>
  99
 100   <refsect1>
 101     <title>Errors</title>
 102
 103     <para>Returned errors may indicate the following problems:</para>
 104
 105     <variablelist>
 106       <varlistentry>
 107         <term><constant>-EINVAL</constant></term>
 108
 109         <listitem><para>The <parameter>slot</parameter> or <parameter>track</parameter> parameter is
 110         <constant>NULL</constant>.</para></listitem>
 111       </varlistentry>
 112     </variablelist>
 113   </refsect1>
 114
 115   <xi:include href="libsystemd-pkgconfig.xml" />
 116
 117   <refsect1>
 118     <title>See Also</title>
 119
 120     <para>
 121       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 122       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 123       <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 124       <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 127       <citerefentry><refentrytitle>sd_bus_track_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 128     </para>
 129   </refsect1>
 130
 131 </refentry>