man/sd_id128_to_string.xml

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