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_is_signal</refname>
  23     <refname>sd_bus_message_is_method_call</refname>
  24     <refname>sd_bus_message_is_method_error</refname>
  25
  26     <refpurpose>Query bus message addressing metadata</refpurpose>
  27   </refnamediv>
  28
  29   <refsynopsisdiv>
  30     <funcsynopsis>
  31       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  32
  33       <funcprototype>
  34         <funcdef>int <function>sd_bus_message_get_type</function></funcdef>
  35         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  36         <paramdef>uint8_t *<parameter>type</parameter></paramdef>
  37       </funcprototype>
  38
  39       <funcprototype>
  40         <funcdef>sd_bus_error* <function>sd_bus_message_get_error</function></funcdef>
  41         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  42       </funcprototype>
  43
  44       <funcprototype>
  45         <funcdef>int <function>sd_bus_message_get_errno</function></funcdef>
  46         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  47       </funcprototype>
  48
  49       <funcprototype>
  50         <funcdef>int <function>sd_bus_message_is_signal</function></funcdef>
  51         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  52         <paramdef>const char *<parameter>interface</parameter></paramdef>
  53         <paramdef>const char *<parameter>member</parameter></paramdef>
  54       </funcprototype>
  55
  56       <funcprototype>
  57         <funcdef>int <function>sd_bus_message_is_method_call</function></funcdef>
  58         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  59         <paramdef>const char *<parameter>interface</parameter></paramdef>
  60         <paramdef>const char *<parameter>member</parameter></paramdef>
  61       </funcprototype>
  62
  63       <funcprototype>
  64         <funcdef>int <function>sd_bus_message_is_method_error</function></funcdef>
  65         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  66         <paramdef>const char *<parameter>name</parameter></paramdef>
  67       </funcprototype>
  68     </funcsynopsis>
  69
  70   </refsynopsisdiv>
  71
  72   <refsect1>
  73     <title>Description</title>
  74
  75     <para><function>sd_bus_message_get_type()</function> returns the type of a message in the output
  76     parameter <parameter>type</parameter>, one of <constant>SD_BUS_MESSAGE_METHOD_CALL</constant>,
  77     <constant>SD_BUS_MESSAGE_METHOD_RETURN</constant>, <constant>SD_BUS_MESSAGE_METHOD_ERROR</constant>,
  78     <constant>SD_BUS_MESSAGE_SIGNAL</constant>. This type is either specified as a parameter when the message
  79     is created using
  80     <citerefentry><refentrytitle>sd_bus_set_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  81     or is set automatically when the message is created using
  82     <citerefentry><refentrytitle>sd_bus_set_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  83     <citerefentry><refentrytitle>sd_bus_set_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  84     <citerefentry><refentrytitle>sd_bus_set_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  85     and similar functions.</para>
  86
  87     <para><function>sd_bus_message_get_error()</function> returns the error stored in the message
  88     <parameter>m</parameter>, if there is any. Otherwise, it returns <constant>NULL</constant>.
  89     <function>sd_bus_message_get_errno()</function> returns the error stored in the message
  90     <parameter>m</parameter> as a positive errno-style value, if there is any. Otherwise, it returns zero.
  91     Errors are mapped to errno values according to the default and any additional registered error mappings.
  92     See <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
  93     <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  94     </para>
  95
  96     <para><function>sd_bus_message_is_signal()</function> checks if message <parameter>m</parameter> is a
  97     signal message. If <parameter>interface</parameter> is non-null, it also checks if the message has the
  98     same interface set. If <parameter>member</parameter> is non-null, it also checks if the message has the
  99     same member set. Also see
 100     <citerefentry><refentrytitle>sd_bus_set_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 101     It returns true when all checks pass.</para>
 102
 103     <para><function>sd_bus_message_is_method_call()</function> checks if message <parameter>m</parameter>
 104     is a method call message. If <parameter>interface</parameter> is non-null, it also checks if the message
 105     has the same interface set. If <parameter>member</parameter> is non-null, it also checks if the message
 106     has the same member set. Also see
 107     <citerefentry><refentrytitle>sd_bus_set_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 108     It returns true when all checks pass.</para>
 109
 110     <para><function>sd_bus_message_is_method_error()</function> checks if message <parameter>m</parameter>
 111     is an error reply message. If <parameter>name</parameter> is non-null, it also checks if the message has
 112     the same error identifier set. Also see
 113     <citerefentry><refentrytitle>sd_bus_set_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 114     It returns true when all checks pass.</para>
 115   </refsect1>
 116
 117   <refsect1>
 118     <title>Return Value</title>
 119
 120     <para>On success, these functions return a non-negative integer. On failure, they return a negative
 121     errno-style error code. <function>sd_bus_message_get_errno()</function> always returns a non-negative
 122     integer, even on failure.</para>
 123
 124     <refsect2>
 125       <title>Errors</title>
 126
 127       <para>Returned errors may indicate the following problems:</para>
 128
 129       <variablelist>
 130         <varlistentry>
 131           <term><constant>-EINVAL</constant></term>
 132
 133           <listitem><para>The message parameter <parameter>m</parameter> or an output parameter is
 134           <constant>NULL</constant>.</para></listitem>
 135         </varlistentry>
 136       </variablelist>
 137     </refsect2>
 138   </refsect1>
 139
 140   <xi:include href="libsystemd-pkgconfig.xml" />
 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_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 149       <citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 150       <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 151       <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 152     </para>
 153   </refsect1>
 154
 155 </refentry>