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+
9 <refentry id=
"sd_id128_to_string" xmlns:
xi=
"http://www.w3.org/2001/XInclude">
12 <title>sd_id128_to_string
</title>
13 <productname>systemd
</productname>
17 <refentrytitle>sd_id128_to_string
</refentrytitle>
18 <manvolnum>3</manvolnum>
22 <refname>sd_id128_to_string
</refname>
23 <refname>sd_id128_from_string
</refname>
24 <refpurpose>Format or parse
128-bit IDs as strings
</refpurpose>
29 <funcsynopsisinfo>#include
<systemd/sd-id128.h
></funcsynopsisinfo>
32 <funcdef>char *
<function>sd_id128_to_string
</function></funcdef>
33 <paramdef>sd_id128_t
<parameter>id
</parameter>, char
<parameter>s
</parameter>[
33]
</paramdef>
37 <funcdef>int
<function>sd_id128_from_string
</function></funcdef>
38 <paramdef>const char *
<parameter>s
</parameter>, sd_id128_t *
<parameter>ret
</parameter></paramdef>
45 <title>Description
</title>
47 <para><function>sd_id128_to_string()
</function> formats a
128-bit
48 ID as a character string. It expects the ID and a string array
49 capable of storing
33 characters. The ID will be formatted as
32
50 lowercase hexadecimal digits and be terminated by a
51 <constant>NUL
</constant> byte.
</para>
53 <para><function>sd_id128_from_string()
</function> implements the reverse operation: it takes a
33 character string
54 with
32 hexadecimal digits (either lowercase or uppercase, terminated by
<constant>NUL
</constant>) and parses them
55 back into a
128-bit ID returned in
<parameter>ret
</parameter>. Alternatively, this call can also parse a
56 37-character string with a
128-bit ID formatted as RFC UUID. If
<parameter>ret
</parameter> is passed as NULL the
57 function will validate the passed ID string, but not actually return it in parsed form.
</para>
59 <para>For more information about the
<literal>sd_id128_t
</literal>
61 <citerefentry><refentrytitle>sd-id128
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
62 Note that these calls operate the same way on all architectures,
63 i.e. the results do not depend on endianness.
</para>
65 <para>When formatting a
128-bit ID into a string, it is often
66 easier to use a format string for
67 <citerefentry project='man-pages'
><refentrytitle>printf
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
68 This is easily done using the
69 <function>SD_ID128_FORMAT_STR
</function> and
70 <function>SD_ID128_FORMAT_VAL()
</function> macros. For more
72 <citerefentry><refentrytitle>sd-id128
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
76 <title>Return Value
</title>
78 <para><function>sd_id128_to_string()
</function> always succeeds
79 and returns a pointer to the string array passed in.
80 <function>sd_id128_from_string
</function> returns
0 on success, in
81 which case
<parameter>ret
</parameter> is filled in, or a negative
82 errno-style error code.
</para>
85 <xi:include href=
"libsystemd-pkgconfig.xml" />
88 <title>See Also
</title>
91 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
92 <citerefentry><refentrytitle>sd-id128
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
93 <citerefentry project='man-pages'
><refentrytitle>printf
</refentrytitle><manvolnum>3</manvolnum></citerefentry>