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   This file is part of systemd.
   9
  10   Copyright 2013 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_bus_message_get_cookie"
  14           xmlns:xi="http://www.w3.org/2001/XInclude">
  15
  16   <refentryinfo>
  17     <title>sd_bus_message_get_cookie</title>
  18     <productname>systemd</productname>
  19
  20     <authorgroup>
  21       <author>
  22         <contrib>Developer</contrib>
  23         <firstname>Lennart</firstname>
  24         <surname>Poettering</surname>
  25         <email>lennart@poettering.net</email>
  26       </author>
  27     </authorgroup>
  28   </refentryinfo>
  29
  30   <refmeta>
  31     <refentrytitle>sd_bus_message_get_cookie</refentrytitle>
  32     <manvolnum>3</manvolnum>
  33   </refmeta>
  34
  35   <refnamediv>
  36     <refname>sd_bus_message_get_cookie</refname>
  37     <refname>sd_bus_message_get_reply_cookie</refname>
  38     <refpurpose>Returns the transaction cookie of a message</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_message_get_cookie</function></funcdef>
  47         <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
  48         <paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_message_get_reply_cookie</function></funcdef>
  53         <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
  54         <paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
  55       </funcprototype>
  56     </funcsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><function>sd_bus_message_get_cookie()</function> returns the
  63     transaction cookie of a message. The cookie uniquely identifies a
  64     message within each bus peer, but is not globally unique. It is
  65     assigned when a message is sent.</para>
  66
  67     <para><function>sd_bus_message_get_reply_cookie()</function>
  68     returns the transaction cookie of the message the specified
  69     message is a response to. When a reply message is generated for a
  70     method call message, its cookie is copied over into this field.
  71     Note that while every message that is transferred is identified by
  72     a cookie, only response messages carry a reply cookie
  73     field.</para>
  74
  75     <para>Both functions take a message object as first parameter and
  76     a place to store the 64-bit cookie in.</para>
  77   </refsect1>
  78
  79   <refsect1>
  80     <title>Return Value</title>
  81
  82     <para>On success, these calls return 0 or a positive integer. On
  83     failure, these calls return a negative errno-style error
  84     code.</para>
  85
  86     <para>On success, the cookie/reply cookie is returned in the
  87     specified 64-bit unsigned integer variable.</para>
  88   </refsect1>
  89
  90   <refsect1>
  91     <title>Errors</title>
  92
  93     <para>Returned errors may indicate the following problems:</para>
  94
  95     <variablelist>
  96       <varlistentry>
  97         <term><constant>-EINVAL</constant></term>
  98
  99         <listitem><para>A specified parameter
 100         is invalid.</para></listitem>
 101       </varlistentry>
 102
 103       <varlistentry>
 104         <term><constant>-ENODATA</constant></term>
 105
 106         <listitem><para>No cookie has been assigned to this message.
 107         This either indicates that the message has not been sent yet
 108         and hence has no cookie assigned, or that the message is not a
 109         method response message and hence carries a reply cookie
 110         field.</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_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 124     </para>
 125   </refsect1>
 126
 127 </refentry>