man/sd_bus_message_get_cookie.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
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   8   Copyright 2013 Lennart Poettering
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  23
  24 <refentry id="sd_bus_message_get_cookie" conditional="ENABLE_KDBUS">
  25
  26         <refentryinfo>
  27                 <title>sd_bus_message_get_cookie</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>sd_bus_message_get_cookie</refentrytitle>
  42                 <manvolnum>3</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>sd_bus_message_get_cookie</refname>
  47                 <refname>sd_bus_message_get_reply_cookie</refname>
  48                 <refpurpose>Returns the transaction cookie of a message</refpurpose>
  49         </refnamediv>
  50
  51         <refsynopsisdiv>
  52                 <funcsynopsis>
  53                         <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  54
  55                         <funcprototype>
  56                                 <funcdef>int <function>sd_bus_message_get_cookie</function></funcdef>
  57                                 <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
  58                                 <paramdef>uint64_t* <parameter>cookie</parameter></paramdef>
  59                         </funcprototype>
  60
  61                         <funcprototype>
  62                                 <funcdef>int <function>sd_bus_message_get_reply_cookie</function></funcdef>
  63                                 <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
  64                                 <paramdef>uint64_t* <parameter>cookie</parameter></paramdef>
  65                         </funcprototype>
  66                 </funcsynopsis>
  67         </refsynopsisdiv>
  68
  69         <refsect1>
  70                 <title>Description</title>
  71
  72                 <para><function>sd_bus_message_get_cookie()</function> returns
  73                 the transaction cookie of a message. The cookie
  74                 uniquely identifies a message within each bus peer,
  75                 but is not globally unique. It is assigned when a
  76                 message is sent.</para>
  77
  78                 <para><function>sd_bus_message_get_reply_cookie()</function>
  79                 returns the transaction cookie of the message the
  80                 specified message is a response to. When a reply
  81                 message is generated for a method call message, its
  82                 cookie is copied over into this field. Note that while
  83                 every message that is transferred is identified by a
  84                 cookie, only response messages carry a reply cookie
  85                 field.</para>
  86
  87                 <para>Both functions take a message object as first
  88                 parameter and a place to store the 64-bit cookie
  89                 in.</para>
  90         </refsect1>
  91
  92         <refsect1>
  93                 <title>Return Value</title>
  94
  95                 <para>On success, these calls return 0 or a positive
  96                 integer. On failure, these calls return a negative
  97                 errno-style error code.</para>
  98
  99                 <para>On success, the cookie/reply cookie is returned
 100                 in the specified 64-bit unsigned integer variable.</para>
 101         </refsect1>
 102
 103         <refsect1>
 104                 <title>Errors</title>
 105
 106                 <para>Returned errors may indicate the following problems:</para>
 107
 108                 <variablelist>
 109                         <varlistentry>
 110                                 <term><varname>-EINVAL</varname></term>
 111
 112                                 <listitem><para>A specified parameter
 113                                 is invalid.</para></listitem>
 114                         </varlistentry>
 115
 116                         <varlistentry>
 117                                 <term><varname>-ENODATA</varname></term>
 118
 119                                 <listitem><para>No cookie has been
 120                                 assigned to this message. This either
 121                                 indicates that the message has not
 122                                 been sent yet and hence has no cookie
 123                                 assigned, or that the message is not a
 124                                 method response message and hence
 125                                 carries a reply cookie
 126                                 field.</para></listitem>
 127                         </varlistentry>
 128                 </variablelist>
 129         </refsect1>
 130
 131         <refsect1>
 132                 <title>Notes</title>
 133
 134                 <para>The <function>sd_bus_message_get_cookie()</function>
 135                 and <function>sd_bus_message_get_reply_cookie()</function>
 136                 interfaces are available as a shared library, which can
 137                 be compiled and linked to with the
 138                 <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 139                 file.</para>
 140         </refsect1>
 141
 142         <refsect1>
 143                 <title>See Also</title>
 144
 145                 <para>
 146                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 147                         <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 148                         <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 149                 </para>
 150         </refsect1>
 151
 152 </refentry>