man/sd_bus_slot_set_destroy_callback.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_set_destroy_callback"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_bus_slot_set_destroy_callback</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_bus_slot_set_destroy_callback</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_bus_slot_set_destroy_callback</refname>
  21     <refname>sd_bus_slot_get_destroy_callback</refname>
  22     <refname>sd_bus_track_set_destroy_callback</refname>
  23     <refname>sd_bus_track_get_destroy_callback</refname>
  24     <refname>sd_bus_destroy_t</refname>
  25
  26     <refpurpose>Define the callback function for resource cleanup</refpurpose>
  27   </refnamediv>
  28
  29   <refsynopsisdiv>
  30     <funcsynopsis>
  31       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  32
  33       <funcprototype>
  34         <funcdef>typedef int (*<function>sd_bus_destroy_t</function>)</funcdef>
  35         <paramdef>void *<parameter>userdata</parameter></paramdef>
  36       </funcprototype>
  37
  38       <funcprototype>
  39         <funcdef>int <function>sd_bus_slot_set_destroy_callback</function></funcdef>
  40         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  41         <paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
  42       </funcprototype>
  43
  44       <funcprototype>
  45         <funcdef>int <function>sd_bus_slot_get_destroy_callback</function></funcdef>
  46         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  47         <paramdef>sd_bus_destroy_t *<parameter>callback</parameter></paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>int <function>sd_bus_track_set_destroy_callback</function></funcdef>
  52         <paramdef>sd_bus_track *<parameter>track</parameter></paramdef>
  53         <paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
  54       </funcprototype>
  55
  56       <funcprototype>
  57         <funcdef>int <function>sd_bus_track_get_destroy_callback</function></funcdef>
  58         <paramdef>sd_bus_track *<parameter>track</parameter></paramdef>
  59         <paramdef>sd_bus_destroy_t *<parameter>callback</parameter></paramdef>
  60       </funcprototype>
  61     </funcsynopsis>
  62   </refsynopsisdiv>
  63
  64   <refsect1>
  65     <title>Description</title>
  66
  67     <para><function>sd_bus_slot_set_destroy_callback()</function> sets <parameter>callback</parameter> as the callback
  68     function to be called right before the bus slot object <parameter>slot</parameter> is deallocated. The
  69     <parameter>userdata</parameter> pointer from the slot object will be passed as the <parameter>userdata</parameter>
  70     parameter. This pointer can be set by an argument to the constructor functions, see
  71     <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly,
  72     see <citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  73     This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that
  74     this callback is invoked at a time where the bus slot object itself is already invalidated, and executing
  75     operations or taking new references to the bus slot object is not permissible.</para>
  76
  77     <para><function>sd_bus_slot_get_destroy_callback()</function> returns the current callback
  78     for <parameter>slot</parameter> in the <parameter>callback</parameter> parameter.</para>
  79
  80     <para><function>sd_bus_track_set_destroy_callback()</function> and
  81     <function>sd_bus_track_get_destroy_callback()</function> provide equivalent functionality for the
  82     <parameter>userdata</parameter> pointer associated with bus peer tracking objects. For details about bus peer
  83     tracking objects, see
  84     <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>Return Value</title>
  89
  90     <para>On success, <function>sd_bus_slot_set_destroy_callback()</function> and
  91     <function>sd_bus_track_set_destroy_callback()</function> return 0 or a positive integer. On failure, they
  92     return a negative errno-style error code.</para>
  93
  94     <para><function>sd_bus_slot_get_destroy_callback()</function> and
  95     <function>sd_bus_track_get_destroy_callback()</function> return positive if the destroy callback function
  96     is set, 0 if not. On failure, they return a negative errno-style error code.</para>
  97
  98     <refsect2>
  99       <title>Errors</title>
 100
 101       <para>Returned errors may indicate the following problems:</para>
 102
 103       <variablelist>
 104         <varlistentry>
 105           <term><constant>-EINVAL</constant></term>
 106
 107           <listitem><para>The <parameter>slot</parameter> or <parameter>track</parameter> parameter is
 108           <constant>NULL</constant>.</para></listitem>
 109         </varlistentry>
 110       </variablelist>
 111     </refsect2>
 112   </refsect1>
 113
 114   <xi:include href="libsystemd-pkgconfig.xml" />
 115
 116   <refsect1>
 117     <title>History</title>
 118     <para><function>sd_bus_destroy_t()</function>,
 119     <function>sd_bus_slot_set_destroy_callback()</function>,
 120     <function>sd_bus_slot_get_destroy_callback()</function>,
 121     <function>sd_bus_track_set_destroy_callback()</function>, and
 122     <function>sd_bus_track_get_destroy_callback()</function> were added in version 239.</para>
 123   </refsect1>
 124
 125   <refsect1>
 126     <title>See Also</title>
 127
 128     <para>
 129       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 130       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 131       <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132       <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 133       <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134       <citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_bus_track_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 136     </para>
 137   </refsect1>
 138
 139 </refentry>