1 <?xml version='
1.0'
?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
6 <refentry id=
"sd_id128_to_string" xmlns:
xi=
"http://www.w3.org/2001/XInclude">
9 <title>sd_id128_to_string
</title>
10 <productname>systemd
</productname>
14 <refentrytitle>sd_id128_to_string
</refentrytitle>
15 <manvolnum>3</manvolnum>
19 <refname>sd_id128_to_string
</refname>
20 <refname>sd_id128_from_string
</refname>
21 <refpurpose>Format or parse
128-bit IDs as strings
</refpurpose>
26 <funcsynopsisinfo>#include
<systemd/sd-id128.h
></funcsynopsisinfo>
29 <funcdef>char *
<function>sd_id128_to_string
</function></funcdef>
30 <paramdef>sd_id128_t
<parameter>id
</parameter>, char
<parameter>s
</parameter>[
33]
</paramdef>
34 <funcdef>int
<function>sd_id128_from_string
</function></funcdef>
35 <paramdef>const char *
<parameter>s
</parameter>, sd_id128_t *
<parameter>ret
</parameter></paramdef>
42 <title>Description
</title>
44 <para><function>sd_id128_to_string()
</function> formats a
128-bit
45 ID as a character string. It expects the ID and a string array
46 capable of storing
33 characters. The ID will be formatted as
32
47 lowercase hexadecimal digits and be terminated by a
48 <constant>NUL
</constant> byte.
</para>
50 <para><function>sd_id128_from_string()
</function> implements the reverse operation: it takes a
33 character string
51 with
32 hexadecimal digits (either lowercase or uppercase, terminated by
<constant>NUL
</constant>) and parses them
52 back into a
128-bit ID returned in
<parameter>ret
</parameter>. Alternatively, this call can also parse a
53 37-character string with a
128-bit ID formatted as RFC UUID. If
<parameter>ret
</parameter> is passed as NULL the
54 function will validate the passed ID string, but not actually return it in parsed form.
</para>
56 <para>For more information about the
<literal>sd_id128_t
</literal>
58 <citerefentry><refentrytitle>sd-id128
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
59 Note that these calls operate the same way on all architectures,
60 i.e. the results do not depend on endianness.
</para>
62 <para>When formatting a
128-bit ID into a string, it is often
63 easier to use a format string for
64 <citerefentry project='man-pages'
><refentrytitle>printf
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
65 This is easily done using the
66 <function>SD_ID128_FORMAT_STR
</function> and
67 <function>SD_ID128_FORMAT_VAL()
</function> macros. For more
69 <citerefentry><refentrytitle>sd-id128
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
73 <title>Return Value
</title>
75 <para><function>sd_id128_to_string()
</function> always succeeds
76 and returns a pointer to the string array passed in.
77 <function>sd_id128_from_string
</function> returns
0 on success, in
78 which case
<parameter>ret
</parameter> is filled in, or a negative
79 errno-style error code.
</para>
82 <xi:include href=
"libsystemd-pkgconfig.xml" />
85 <title>See Also
</title>
88 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
89 <citerefentry><refentrytitle>sd-id128
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
90 <citerefentry project='man-pages'
><refentrytitle>printf
</refentrytitle><manvolnum>3</manvolnum></citerefentry>