Merge pull request #288 from phomes/cgroup-util

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

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  Copyright 2014 Zbigniew Jędrzejewski-Szmek

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<refentry id="sd_bus_message_append_basic">

  <refentryinfo>
    <title>sd_bus_message_append_basic</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>A monkey with a typewriter</contrib>
        <firstname>Zbigniew</firstname>
        <surname>Jędrzejewski-Szmek</surname>
        <email>zbyszek@in.waw.pl</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_message_append_basic</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_message_append_basic</refname>

    <refpurpose>Attach a single part to a message</refpurpose>
  </refnamediv>

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

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

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_message_append_basic</function> appends a
    single item to the message <parameter>m</parameter>. Parameter
    <parameter>type</parameter> determines how pointer
    <parameter>p</parameter> is interpreted.
    <parameter>type</parameter> must be one of the basic types
    as defined by the

    <ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic Types</ulink>
    section of the D-Bus specification, and listed in the table below.
    </para>

    <table id='format-specifiers'>
      <title>Item format specifiers</title>

      <tgroup cols='4'>
        <colspec colname='specifier' />
        <colspec colname='constant' />
        <colspec colname='description' />
        <colspec colname='size' />
        <thead>
          <row>
            <entry>Specifier</entry>
            <entry>Constant</entry>
            <entry>Description</entry>
            <entry>Size</entry>
          </row>
        </thead>
        <tbody>
          <row>
            <entry><literal>y</literal></entry>
            <entry><constant>SD_BUS_TYPE_BYTE</constant></entry>
            <entry>unsigned integer</entry>
            <entry>1 byte</entry>
          </row>

          <row>
            <entry><literal>b</literal></entry>
            <entry><constant>SD_BUS_TYPE_BOOLEAN</constant></entry>
            <entry>boolean</entry>
            <entry>4 bytes</entry>
          </row>

          <row>
            <entry><literal>n</literal></entry>
            <entry><constant>SD_BUS_TYPE_INT16</constant></entry>
            <entry>signed integer</entry>
            <entry>2 bytes</entry>
          </row>

          <row>
            <entry><literal>q</literal></entry>
            <entry><constant>SD_BUS_TYPE_UINT16</constant></entry>
            <entry>unsigned integer</entry>
            <entry>2 bytes</entry>
          </row>

          <row>
            <entry><literal>i</literal></entry>
            <entry><constant>SD_BUS_TYPE_INT32</constant></entry>
            <entry>signed integer</entry>
            <entry>4 bytes</entry>
          </row>

          <row>
            <entry><literal>u</literal></entry>
            <entry><constant>SD_BUS_TYPE_UINT32</constant></entry>
            <entry>unsigned integer</entry>
            <entry>4 bytes</entry>
          </row>

          <row>
            <entry><literal>x</literal></entry>
            <entry><constant>SD_BUS_TYPE_INT64</constant></entry>
            <entry>signed integer</entry>
            <entry>8 bytes</entry>
          </row>

          <row>
            <entry><literal>t</literal></entry>
            <entry><constant>SD_BUS_TYPE_UINT64</constant></entry>
            <entry>unsigned integer</entry>
            <entry>8 bytes</entry>
          </row>

          <row>
            <entry><literal>d</literal></entry>
            <entry><constant>SD_BUS_TYPE_DOUBLE</constant></entry>
            <entry>floating-point</entry>
            <entry>8 bytes</entry>
          </row>

          <row>
            <entry><literal>s</literal></entry>
            <entry><constant>SD_BUS_TYPE_STRING</constant></entry>
            <entry>Unicode string</entry>
            <entry>variable</entry>
          </row>

          <row>
            <entry><literal>o</literal></entry>
            <entry><constant>SD_BUS_TYPE_OBJECT_PATH</constant></entry>
            <entry>object path</entry>
            <entry>variable</entry>
          </row>

          <row>
            <entry><literal>g</literal></entry>
            <entry><constant>SD_BUS_TYPE_SIGNATURE</constant></entry>
            <entry>signature</entry>
            <entry>variable</entry>
          </row>

          <row>
            <entry><literal>h</literal></entry>
            <entry><constant>SD_BUS_TYPE_UNIX_FD</constant></entry>
            <entry>UNIX file descriptor</entry>
            <entry>4 bytes</entry>
          </row>
       </tbody>
      </tgroup>
    </table>

    <para>The value of the parameter is copied into the memory area
    containing the message and may be changed after this call. If
    <parameter>type</parameter> is <literal>h</literal> (UNIX file
    descriptor), it is always "consumed" by this call, and either
    successfully appended to the message or closed.</para>

    <para>For types <literal>s</literal>, <literal>o</literal>, and
    <literal>g</literal>, the parameter <parameter>p</parameter> is
    interpreted as a pointer to a <constant>NUL</constant>-terminated
    character sequence. As a special case, a <constant>NULL</constant>
    pointer is interpreted as an empty string. The string should be
    valid Unicode string encoded as UTF-8. In case of the two latter
    types, the additional requirements for a D-Bus object path or
    type signature should be satisfied. Those requirements should be
    verified by the recipient of the message.
    </para>
  </refsect1>

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

    <para>On success, this call returns 0 or a positive integer. On
    failure, it returns a negative errno-style error code.</para>
  </refsect1>

  <refsect1 id='errors'>
    <title>Errors</title>

    <para>Returned errors may indicate the following problems:</para>

    <variablelist>

      <varlistentry>
        <term><constant>-EINVAL</constant></term>

        <listitem><para>Specified parameter is invalid.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-EPERM</constant></term>

        <listitem><para>Message has been sealed.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ESTALE</constant></term>

        <listitem><para>Message is in invalid state.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENXIO</constant></term>

        <listitem><para>Message cannot be appended to.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENOMEM</constant></term>

        <listitem><para>Memory allocation failed.</para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para>The <function>sd_bus_append_basic()</function> function
    described here is available as a shared library, which can be
    compiled and linked to with the
    <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    file.</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>,
      <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink>
    </para>
  </refsect1>

</refentry>