man/sd_id128_to_string.xml

   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">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2012 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_id128_to_string" xmlns:xi="http://www.w3.org/2001/XInclude">
  14
  15   <refentryinfo>
  16     <title>sd_id128_to_string</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_id128_to_string</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_id128_to_string</refname>
  36     <refname>sd_id128_from_string</refname>
  37     <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
  38   </refnamediv>
  39
  40   <refsynopsisdiv>
  41     <funcsynopsis>
  42       <funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
  43
  44       <funcprototype>
  45         <funcdef>char *<function>sd_id128_to_string</function></funcdef>
  46         <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
  47       </funcprototype>
  48
  49       <funcprototype>
  50         <funcdef>int <function>sd_id128_from_string</function></funcdef>
  51         <paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
  52       </funcprototype>
  53
  54     </funcsynopsis>
  55   </refsynopsisdiv>
  56
  57   <refsect1>
  58     <title>Description</title>
  59
  60     <para><function>sd_id128_to_string()</function> formats a 128-bit
  61     ID as a character string. It expects the ID and a string array
  62     capable of storing 33 characters. The ID will be formatted as 32
  63     lowercase hexadecimal digits and be terminated by a
  64     <constant>NUL</constant> byte.</para>
  65
  66     <para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 character string
  67     with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
  68     back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
  69     37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
  70     function will validate the passed ID string, but not actually return it in parsed form.</para>
  71
  72     <para>For more information about the <literal>sd_id128_t</literal>
  73     type see
  74     <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  75     Note that these calls operate the same way on all architectures,
  76     i.e. the results do not depend on endianness.</para>
  77
  78     <para>When formatting a 128-bit ID into a string, it is often
  79     easier to use a format string for
  80     <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  81     This is easily done using the
  82     <function>SD_ID128_FORMAT_STR</function> and
  83     <function>SD_ID128_FORMAT_VAL()</function> macros. For more
  84     information see
  85     <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  86   </refsect1>
  87
  88   <refsect1>
  89     <title>Return Value</title>
  90
  91     <para><function>sd_id128_to_string()</function> always succeeds
  92     and returns a pointer to the string array passed in.
  93     <function>sd_id128_from_string</function> returns 0 on success, in
  94     which case <parameter>ret</parameter> is filled in, or a negative
  95     errno-style error code.</para>
  96   </refsect1>
  97
  98   <xi:include href="libsystemd-pkgconfig.xml" />
  99
 100   <refsect1>
 101     <title>See Also</title>
 102
 103     <para>
 104       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 105       <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 106       <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 107     </para>
 108   </refsect1>
 109
 110 </refentry>