1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 SPDX-License-Identifier: LGPL-2.1+
8 Copyright 2012 Lennart Poettering
11 <refentry id="sd_id128_to_string" xmlns:xi="http://www.w3.org/2001/XInclude">
14 <title>sd_id128_to_string</title>
15 <productname>elogind</productname>
19 <contrib>Developer</contrib>
20 <firstname>Lennart</firstname>
21 <surname>Poettering</surname>
22 <email>lennart@poettering.net</email>
28 <refentrytitle>sd_id128_to_string</refentrytitle>
29 <manvolnum>3</manvolnum>
33 <refname>sd_id128_to_string</refname>
34 <refname>sd_id128_from_string</refname>
35 <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
40 <funcsynopsisinfo>#include <elogind/sd-id128.h></funcsynopsisinfo>
43 <funcdef>char *<function>sd_id128_to_string</function></funcdef>
44 <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
48 <funcdef>int <function>sd_id128_from_string</function></funcdef>
49 <paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
56 <title>Description</title>
58 <para><function>sd_id128_to_string()</function> formats a 128-bit
59 ID as a character string. It expects the ID and a string array
60 capable of storing 33 characters. The ID will be formatted as 32
61 lowercase hexadecimal digits and be terminated by a
62 <constant>NUL</constant> byte.</para>
64 <para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 character string
65 with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
66 back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
67 37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
68 function will validate the passed ID string, but not actually return it in parsed form.</para>
70 <para>For more information about the <literal>sd_id128_t</literal>
72 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
73 Note that these calls operate the same way on all architectures,
74 i.e. the results do not depend on endianness.</para>
76 <para>When formatting a 128-bit ID into a string, it is often
77 easier to use a format string for
78 <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
79 This is easily done using the
80 <function>SD_ID128_FORMAT_STR</function> and
81 <function>SD_ID128_FORMAT_VAL()</function> macros. For more
83 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
87 <title>Return Value</title>
89 <para><function>sd_id128_to_string()</function> always succeeds
90 and returns a pointer to the string array passed in.
91 <function>sd_id128_from_string</function> returns 0 on success, in
92 which case <parameter>ret</parameter> is filled in, or a negative
93 errno-style error code.</para>
96 <xi:include href="libelogind-pkgconfig.xml" />
99 <title>See Also</title>
102 <!-- 0 /// elogind is in section 8
103 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
105 <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
107 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
108 <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>