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[thirdparty/systemd.git] / man / sd_bus_message_read_basic.xml

<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  SPDX-License-Identifier: LGPL-2.1+

  This file is part of systemd.

  Copyright 2016 Julian Orth
-->

<refentry id="sd_bus_message_read_basic">

  <refentryinfo>
    <title>sd_bus_message_read_basic</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <firstname>Julian</firstname>
        <surname>Orth</surname>
        <email>ju.orth@gmail.com</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_message_read_basic</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_message_read_basic</refname>

    <refpurpose>Read a basic type from a message</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_bus_message_read_basic</function></funcdef>
        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
        <paramdef>char <parameter>type</parameter></paramdef>
        <paramdef>void *<parameter>p</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>
      <function>sd_bus_message_read_basic()</function> reads a basic type from a
      message and advances the read position in the message. The set of basic
      types and their ascii codes passed in <parameter>type</parameter> are
      described in the <ulink
        url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus
        Specification</ulink>.
    </para>

    <para>
      If <parameter>p</parameter> is not NULL, it should contain a pointer to an
      appropriate object. For example, if <parameter>type</parameter> is
      <constant>'y'</constant>, the object passed in <parameter>p</parameter>
      should have type <code>uint8_t *</code>. If <parameter>type</parameter>
      is <constant>'s'</constant>, the object passed in <parameter>p</parameter>
      should have type <code>const char **</code>. Note that, if the basic type
      is a pointer (e.g., <code>const char *</code> in the case of a string),
      the pointer is only borrowed and the contents must be copied if they are
      to be used after the end of the messages lifetime. Similarly, during the
      lifetime of such a pointer, the message must not be modified.
    </para>

    <para>
      If there is no object of the specified type at the current position in the
      message, an error is returned.
    </para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>
      On success, <function>sd_bus_message_read_basic()</function> returns 0 or
      a positive integer. On failure, it returns a negative errno-style error
      code.
    </para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    </para>
  </refsect1>

</refentry>