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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">
+
+<!--
+ SPDX-License-Identifier: LGPL-2.1+
+-->
+
+<refentry id="sd_id128_to_string" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_id128_to_string</title>
+ <productname>systemd</productname>
+ </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;systemd/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. If <parameter>ret</parameter> is passed as NULL the
+ function will validate the passed ID string, but not actually return it in parsed form.</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>
+
+ <xi:include href="libsystemd-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</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>