man/sd_bus_message_get_cookie.xml

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