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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+  This file is part of elogind.
+
+  Copyright 2012 Lennart Poettering
+
+  elogind is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  elogind is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with elogind; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_id128_to_string">
+
+  <refentryinfo>
+    <title>sd_id128_to_string</title>
+    <productname>elogind</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Lennart</firstname>
+        <surname>Poettering</surname>
+        <email>lennart@poettering.net</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_id128_to_string</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_id128_to_string</refname>
+    <refname>sd_id128_from_string</refname>
+    <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;elogind/sd-id128.h&gt;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>char *<function>sd_id128_to_string</function></funcdef>
+        <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_id128_from_string</function></funcdef>
+        <paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_id128_to_string()</function> formats a 128-bit
+    ID as a character string. It expects the ID and a string array
+    capable of storing 33 characters. The ID will be formatted as 32
+    lowercase hexadecimal digits and be terminated by a
+    <constant>NUL</constant> byte.</para>
+
+    <para><function>sd_id128_from_string()</function> implements the
+    reverse operation: it takes a 33 character string with 32
+    hexadecimal digits (either lowercase or uppercase, terminated by
+    <constant>NUL</constant>) and parses them back into a 128-bit ID
+    returned in <parameter>ret</parameter>. Alternatively, this call
+    can also parse a 37-character string with a 128-bit ID formatted
+    as RFC UUID.</para>
+
+    <para>For more information about the <literal>sd_id128_t</literal>
+    type see
+    <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+    Note that these calls operate the same way on all architectures,
+    i.e. the results do not depend on endianness.</para>
+
+    <para>When formatting a 128-bit ID into a string, it is often
+    easier to use a format string for
+    <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+    This is easily done using the
+    <function>SD_ID128_FORMAT_STR</function> and
+    <function>SD_ID128_FORMAT_VAL()</function> macros. For more
+    information see
+    <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Return Value</title>
+
+    <para><function>sd_id128_to_string()</function> always succeeds
+    and returns a pointer to the string array passed in.
+    <function>sd_id128_from_string</function> returns 0 on success, in
+    which case <parameter>ret</parameter> is filled in, or a negative
+    errno-style error code.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Notes</title>
+
+    <para>The <function>sd_id128_to_string()</function> and
+    <function>sd_id128_from_string()</function> interfaces are
+    available as a shared library, which can be compiled and linked to
+    with the
+    <literal>libelogind</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    file.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>