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">
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   8   Copyright 2012 Lennart Poettering
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  23
  24 <refentry id="sd_id128_to_string">
  25
  26         <refentryinfo>
  27                 <title>sd_id128_to_string</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>sd_id128_to_string</refentrytitle>
  42                 <manvolnum>3</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>sd_id128_to_string</refname>
  47                 <refname>sd_id128_from_string</refname>
  48                 <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
  49         </refnamediv>
  50
  51         <refsynopsisdiv>
  52                 <funcsynopsis>
  53                         <funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
  54
  55                         <funcprototype>
  56                                 <funcdef>char* <function>sd_id128_to_string</function></funcdef>
  57                                 <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
  58                         </funcprototype>
  59
  60                         <funcprototype>
  61                                 <funcdef>int <function>sd_id128_from_string</function></funcdef>
  62                                 <paramdef>const char* <parameter>s</parameter>, sd_id128_t* <parameter>ret</parameter></paramdef>
  63                         </funcprototype>
  64
  65                 </funcsynopsis>
  66         </refsynopsisdiv>
  67
  68         <refsect1>
  69                 <title>Description</title>
  70
  71                 <para><function>sd_id128_to_string()</function>
  72                 formats a 128-bit ID as a character string. It expects
  73                 the ID and a string array capable of storing 33
  74                 characters. The ID will be formatted as 32 lowercase
  75                 hexadecimal digits and be terminated by a
  76                 <constant>NUL</constant> byte.</para>
  77
  78                 <para><function>sd_id128_from_string()</function>
  79                 implements the reverse operation: it takes a 33
  80                 character string with 32 hexadecimal digits (either
  81                 lowercase or uppercase, terminated by
  82                 <constant>NUL</constant>) and parses them back into a
  83                 128-bit ID returned in
  84                 <parameter>ret</parameter>. Alternatively, this call
  85                 can also parse a 37-character string with a 128-bit ID
  86                 formatted as RFC UUID.</para>
  87
  88                 <para>For more information about the
  89                 <literal>sd_id128_t</literal> type see
  90                 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Note
  91                 that these calls operate the same way on all
  92                 architectures, i.e. the results do not depend on
  93                 endianness.</para>
  94
  95                 <para>When formatting a 128-bit ID into a string, it is
  96                 often easier to use a format string for
  97                 <citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This
  98                 is easily done using the
  99                 <function>SD_ID128_FORMAT_STR</function> and
 100                 <function>SD_ID128_FORMAT_VAL()</function> macros. For
 101                 more information see
 102                 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 103         </refsect1>
 104
 105         <refsect1>
 106                 <title>Return Value</title>
 107
 108                 <para><function>sd_id128_to_string()</function> always
 109                 succeeds and returns a pointer to the string array
 110                 passed in. <function>sd_id128_from_string</function>
 111                 returns 0 on success, in which case
 112                 <parameter>ret</parameter> is filled in, or a negative
 113                 errno-style error code.</para>
 114         </refsect1>
 115
 116         <refsect1>
 117                 <title>Notes</title>
 118
 119                 <para>The <function>sd_id128_to_string()</function>
 120                 and <function>sd_id128_from_string()</function> interfaces are
 121                 available as shared library, which can be compiled and
 122                 linked to with the <literal>libsystemd-id128</literal> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 123                 file.</para>
 124         </refsect1>
 125
 126         <refsect1>
 127                 <title>See Also</title>
 128
 129                 <para>
 130                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 131                         <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132                         <citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 133                 </para>
 134         </refsect1>
 135
 136 </refentry>