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
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_bus_message_get_cookie"
  10           xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>sd_bus_message_get_cookie</title>
  14     <productname>systemd</productname>
  15
  16     <authorgroup>
  17       <author>
  18         <contrib>Developer</contrib>
  19         <firstname>Lennart</firstname>
  20         <surname>Poettering</surname>
  21         <email>lennart@poettering.net</email>
  22       </author>
  23     </authorgroup>
  24   </refentryinfo>
  25
  26   <refmeta>
  27     <refentrytitle>sd_bus_message_get_cookie</refentrytitle>
  28     <manvolnum>3</manvolnum>
  29   </refmeta>
  30
  31   <refnamediv>
  32     <refname>sd_bus_message_get_cookie</refname>
  33     <refname>sd_bus_message_get_reply_cookie</refname>
  34     <refpurpose>Returns the transaction cookie of a message</refpurpose>
  35   </refnamediv>
  36
  37   <refsynopsisdiv>
  38     <funcsynopsis>
  39       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  40
  41       <funcprototype>
  42         <funcdef>int <function>sd_bus_message_get_cookie</function></funcdef>
  43         <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
  44         <paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
  45       </funcprototype>
  46
  47       <funcprototype>
  48         <funcdef>int <function>sd_bus_message_get_reply_cookie</function></funcdef>
  49         <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
  50         <paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
  51       </funcprototype>
  52     </funcsynopsis>
  53   </refsynopsisdiv>
  54
  55   <refsect1>
  56     <title>Description</title>
  57
  58     <para><function>sd_bus_message_get_cookie()</function> returns the
  59     transaction cookie of a message. The cookie uniquely identifies a
  60     message within each bus peer, but is not globally unique. It is
  61     assigned when a message is sent.</para>
  62
  63     <para><function>sd_bus_message_get_reply_cookie()</function>
  64     returns the transaction cookie of the message the specified
  65     message is a response to. When a reply message is generated for a
  66     method call message, its cookie is copied over into this field.
  67     Note that while every message that is transferred is identified by
  68     a cookie, only response messages carry a reply cookie
  69     field.</para>
  70
  71     <para>Both functions take a message object as first parameter and
  72     a place to store the 64-bit cookie in.</para>
  73   </refsect1>
  74
  75   <refsect1>
  76     <title>Return Value</title>
  77
  78     <para>On success, these calls return 0 or a positive integer. On
  79     failure, these calls return a negative errno-style error
  80     code.</para>
  81
  82     <para>On success, the cookie/reply cookie is returned in the
  83     specified 64-bit unsigned integer variable.</para>
  84   </refsect1>
  85
  86   <refsect1>
  87     <title>Errors</title>
  88
  89     <para>Returned errors may indicate the following problems:</para>
  90
  91     <variablelist>
  92       <varlistentry>
  93         <term><constant>-EINVAL</constant></term>
  94
  95         <listitem><para>A specified parameter
  96         is invalid.</para></listitem>
  97       </varlistentry>
  98
  99       <varlistentry>
 100         <term><constant>-ENODATA</constant></term>
 101
 102         <listitem><para>No cookie has been assigned to this message.
 103         This either indicates that the message has not been sent yet
 104         and hence has no cookie assigned, or that the message is not a
 105         method response message and hence carries a reply cookie
 106         field.</para></listitem>
 107       </varlistentry>
 108     </variablelist>
 109   </refsect1>
 110
 111   <xi:include href="libsystemd-pkgconfig.xml" />
 112
 113   <refsect1>
 114     <title>See Also</title>
 115
 116     <para>
 117       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 118       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 119       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 120     </para>
 121   </refsect1>
 122
 123 </refentry>