man/sd_event_source_unref.xml

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  10   Copyright 2015 Lennart Poettering
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  25
  26 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
  27
  28   <refentryinfo>
  29     <title>sd_event_source_unref</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Lennart</firstname>
  36         <surname>Poettering</surname>
  37         <email>lennart@poettering.net</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>sd_event_source_unref</refentrytitle>
  44     <manvolnum>3</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>sd_event_source_unref</refname>
  49     <refname>sd_event_source_unrefp</refname>
  50     <refname>sd_event_source_ref</refname>
  51
  52     <refpurpose>Increase or decrease event source reference counters</refpurpose>
  53   </refnamediv>
  54
  55   <refsynopsisdiv>
  56     <funcsynopsis>
  57       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  58
  59       <funcprototype>
  60         <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
  61         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  62       </funcprototype>
  63
  64       <funcprototype>
  65         <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
  66         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  67       </funcprototype>
  68
  69       <funcprototype>
  70         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
  71         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  72       </funcprototype>
  73
  74     </funcsynopsis>
  75   </refsynopsisdiv>
  76
  77   <refsect1>
  78     <title>Description</title>
  79
  80     <para><function>sd_event_source_unref()</function> may be used to
  81     decrement by one the reference counter of the event source object
  82     specified as <parameter>source</parameter>. The reference counter
  83     is initially set to one, when the event source is created with calls
  84     such as
  85     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  86     or
  87     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
  88     the reference counter reaches zero it is removed from its event loop
  89     object and destroyed.</para>
  90
  91     <para><function>sd_event_source_unrefp()</function> is similar to
  92     <function>sd_event_source_unref()</function> but takes a pointer to a
  93     pointer to an <type>sd_event_source</type> object. This call is useful in
  94     conjunction with GCC's and LLVM's <ulink
  95     url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
  96     Variable Attribute</ulink>. Note that this function is defined as
  97     inline function.</para>
  98
  99     <para><function>sd_event_source_ref()</function> may be used
 100     to increase by one the reference counter of the event source object
 101     specified as <parameter>source</parameter>.</para>
 102
 103     <para><function>sd_event_source_unref()</function>,
 104     <function>sd_bus_creds_unrefp()</function> and
 105     <function>sd_bus_creds_ref()</function> execute no operation if
 106     the passed event source object is
 107     <constant>NULL</constant>.</para>
 108
 109     <para>Note that event source objects stay alive and may be
 110     dispatched as long as they have a reference counter greater than
 111     zero. In order to drop a reference of an event source and make
 112     sure the associated event source handler function is not called
 113     anymore it is recommended to combine a call of
 114     <function>sd_event_source_unref()</function> with a prior call to
 115     <function>sd_event_source_set_enabled()</function> with
 116     <constant>SD_EVENT_OFF</constant>.</para>
 117   </refsect1>
 118
 119   <refsect1>
 120     <title>Return Value</title>
 121
 122     <para><function>sd_event_source_unref()</function> always returns
 123     <constant>NULL</constant>.
 124     <function>sd_event_source_ref()</function> always returns the
 125     event source object passed in.</para>
 126   </refsect1>
 127
 128   <xi:include href="libsystemd-pkgconfig.xml" />
 129
 130   <refsect1>
 131     <title>See Also</title>
 132
 133     <para>
 134       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 136       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 137       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 138       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 139       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 140       <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 141     </para>
 142   </refsect1>
 143
 144 </refentry>