man/sd_bus_message_get_type.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_bus_message_get_type" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_bus_message_get_type</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_bus_message_get_type</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_bus_message_get_type</refname>
  20     <refname>sd_bus_message_get_error</refname>
  21     <refname>sd_bus_message_get_errno</refname>
  22     <refname>sd_bus_message_get_creds</refname>
  23     <refname>sd_bus_message_is_signal</refname>
  24     <refname>sd_bus_message_is_method_call</refname>
  25     <refname>sd_bus_message_is_method_error</refname>
  26
  27     <refpurpose>Query bus message addressing/credentials metadata</refpurpose>
  28   </refnamediv>
  29
  30   <refsynopsisdiv>
  31     <funcsynopsis>
  32       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  33
  34       <funcprototype>
  35         <funcdef>int <function>sd_bus_message_get_type</function></funcdef>
  36         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  37         <paramdef>uint8_t *<parameter>type</parameter></paramdef>
  38       </funcprototype>
  39
  40       <funcprototype>
  41         <funcdef>sd_bus_error* <function>sd_bus_message_get_error</function></funcdef>
  42         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  43       </funcprototype>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_message_get_errno</function></funcdef>
  47         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>sd_bus_creds* <function>sd_bus_message_get_creds</function></funcdef>
  52         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  53       </funcprototype>
  54
  55       <funcprototype>
  56         <funcdef>int <function>sd_bus_message_is_signal</function></funcdef>
  57         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  58         <paramdef>const char *<parameter>interface</parameter></paramdef>
  59         <paramdef>const char *<parameter>member</parameter></paramdef>
  60       </funcprototype>
  61
  62       <funcprototype>
  63         <funcdef>int <function>sd_bus_message_is_method_call</function></funcdef>
  64         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  65         <paramdef>const char *<parameter>interface</parameter></paramdef>
  66         <paramdef>const char *<parameter>member</parameter></paramdef>
  67       </funcprototype>
  68
  69       <funcprototype>
  70         <funcdef>int <function>sd_bus_message_is_method_error</function></funcdef>
  71         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  72         <paramdef>const char *<parameter>name</parameter></paramdef>
  73       </funcprototype>
  74     </funcsynopsis>
  75
  76   </refsynopsisdiv>
  77
  78   <refsect1>
  79     <title>Description</title>
  80
  81     <para><function>sd_bus_message_get_type()</function> returns the type of a message in the output
  82     parameter <parameter>type</parameter>, one of <constant>SD_BUS_MESSAGE_METHOD_CALL</constant>,
  83     <constant>SD_BUS_MESSAGE_METHOD_RETURN</constant>, <constant>SD_BUS_MESSAGE_METHOD_ERROR</constant>,
  84     <constant>SD_BUS_MESSAGE_SIGNAL</constant>. This type is either specified as a parameter when the message
  85     is created using
  86     <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  87     or is set automatically when the message is created using
  88     <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  89     <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  90     <citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  91     and similar functions.</para>
  92
  93     <para><function>sd_bus_message_get_error()</function> returns the error stored in the message
  94     <parameter>m</parameter>, if there is any. Otherwise, it returns <constant>NULL</constant>.
  95     <function>sd_bus_message_get_errno()</function> returns the error stored in the message
  96     <parameter>m</parameter> as a positive errno-style value, if there is any. Otherwise, it returns zero.
  97     Errors are mapped to errno values according to the default and any additional registered error mappings.
  98     See <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
  99     <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 100     </para>
 101
 102     <para><function>sd_bus_message_get_creds()</function> returns the message credentials attached to the
 103     message <parameter>m</parameter>. If no credentials are attached to the message, it returns
 104     <constant>NULL</constant>. Ownership of the credentials instance is not transferred to the caller and
 105     hence should not be freed.</para>
 106
 107     <para><function>sd_bus_message_is_signal()</function> checks if message <parameter>m</parameter> is a
 108     signal message. If <parameter>interface</parameter> is non-null, it also checks if the message has the
 109     same interface set. If <parameter>member</parameter> is non-null, it also checks if the message has the
 110     same member set. Also see
 111     <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 112     It returns true when all checks pass.</para>
 113
 114     <para><function>sd_bus_message_is_method_call()</function> checks if message <parameter>m</parameter>
 115     is a method call message. If <parameter>interface</parameter> is non-null, it also checks if the message
 116     has the same interface set. If <parameter>member</parameter> is non-null, it also checks if the message
 117     has the same member set. Also see
 118     <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 119     It returns true when all checks pass.</para>
 120
 121     <para><function>sd_bus_message_is_method_error()</function> checks if message <parameter>m</parameter>
 122     is an error reply message. If <parameter>name</parameter> is non-null, it also checks if the message has
 123     the same error identifier set. Also see
 124     <citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 125     It returns true when all checks pass.</para>
 126   </refsect1>
 127
 128   <refsect1>
 129     <title>Return Value</title>
 130
 131     <para>On success, these functions (except <function>sd_bus_message_get_error()</function> and
 132     <function>sd_bus_message_get_creds()</function>) return a non-negative integer. On failure, they return a
 133     negative errno-style error code. <function>sd_bus_message_get_errno()</function> always returns a
 134     non-negative integer, even on failure.</para>
 135
 136     <refsect2>
 137       <title>Errors</title>
 138
 139       <para>Returned errors may indicate the following problems:</para>
 140
 141       <variablelist>
 142         <varlistentry>
 143           <term><constant>-EINVAL</constant></term>
 144
 145           <listitem><para>The message parameter <parameter>m</parameter> or an output parameter is
 146           <constant>NULL</constant>.</para></listitem>
 147         </varlistentry>
 148       </variablelist>
 149     </refsect2>
 150   </refsect1>
 151
 152   <xi:include href="libsystemd-pkgconfig.xml" />
 153
 154   <refsect1>
 155     <title>See Also</title>
 156
 157     <para>
 158       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 159       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 160       <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 161       <citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 162       <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 163       <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 164     </para>
 165   </refsect1>
 166
 167 </refentry>