| <?xml version='1.0'?> <!--*-nxml-*--> |
| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
| "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
| <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
| |
| <refentry id="sd_id128_to_string" xmlns:xi="http://www.w3.org/2001/XInclude"> |
| |
| <refentryinfo> |
| <title>sd_id128_to_string</title> |
| <productname>systemd</productname> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>sd_id128_to_string</refentrytitle> |
| <manvolnum>3</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>sd_id128_to_string</refname> |
| <refname>SD_ID128_TO_STRING</refname> |
| <refname>SD_ID128_STRING_MAX</refname> |
| <refname>sd_id128_to_uuid_string</refname> |
| <refname>SD_ID128_TO_UUID_STRING</refname> |
| <refname>SD_ID128_UUID_STRING_MAX</refname> |
| <refname>sd_id128_from_string</refname> |
| <refpurpose>Format or parse 128-bit IDs as strings</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <funcsynopsis> |
| <funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo> |
| |
| <funcsynopsisinfo>#define SD_ID128_STRING_MAX 33U</funcsynopsisinfo> |
| |
| <funcsynopsisinfo>#define SD_ID128_UUID_STRING_MAX 37U</funcsynopsisinfo> |
| |
| <funcsynopsisinfo>#define SD_ID128_TO_STRING(id) …</funcsynopsisinfo> |
| |
| <funcsynopsisinfo>#define SD_ID128_TO_UUID_STRING(id) …</funcsynopsisinfo> |
| |
| <funcprototype> |
| <funcdef>char *<function>sd_id128_to_string</function></funcdef> |
| <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[static SD_ID128_STRING_MAX]</paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>char *<function>sd_id128_uuid_string</function></funcdef> |
| <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[static SD_ID128_UUID_STRING_MAX]</paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_id128_from_string</function></funcdef> |
| <paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef> |
| </funcprototype> |
| |
| </funcsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para><function>sd_id128_to_string()</function> formats a 128-bit ID as a character string. It expects |
| the ID and a string array capable of storing 33 characters |
| (<constant>SD_ID128_STRING_MAX</constant>). The ID will be formatted as 32 lowercase hexadecimal digits |
| and be terminated by a <constant>NUL</constant> byte.</para> |
| |
| <para><function>SD_ID128_TO_STRING()</function> is a macro that wraps |
| <function>sd_id128_to_string()</function> and passes an appropriately sized buffer as second argument, |
| allocated as C99 compound literal. Each use will thus implicitly acquire a suitable buffer on the stack |
| which remains valid until the end of the current code block. This is usually the simplest way to acquire |
| a string representation of a 128-bit ID in a buffer that is valid in the current code block.</para> |
| |
| <para><function>sd_id128_to_uuid_string()</function> and <function>SD_ID128_TO_UUID_STRING()</function> |
| are similar to these two functions/macros, but format the 128bit values as RFC4122 UUIDs, i.e. a series |
| of 36 lowercase hexadeciaml digits and dashes, terminated by a <constant>NUL</constant> byte.</para> |
| |
| <para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 |
| character string with 32 hexadecimal digits (either lowercase or uppercase, terminated by |
| <constant>NUL</constant>) and parses them back into a 128-bit ID returned in |
| <parameter>ret</parameter>. Alternatively, this call can also parse a 37-character string with a 128-bit |
| ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as <constant>NULL</constant> the |
| function will validate the passed ID string, but not actually return it in parsed form.</para> |
| |
| <para>Note that when formatting and parsing 36 character UUIDs this is done strictly in Big Endian byte order, |
| i.e. according to <ulink url="https://tools.ietf.org/html/rfc4122">RFC4122</ulink> Variant 1 rules, even |
| if the UUID encodes a different variant. This matches behaviour in various other Linux userspace |
| tools. It's probably wise to avoid UUIDs of other variant types.</para> |
| |
| <para>For more information about the <literal>sd_id128_t</literal> type see |
| <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Note that |
| these calls operate the same way on all architectures, i.e. the results do not depend on |
| endianness.</para> |
| |
| <para>When formatting a 128-bit ID into a string, it is often easier to use a format string for |
| <citerefentry |
| project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This |
| is easily done using the <constant>SD_ID128_FORMAT_STR</constant> and |
| <function>SD_ID128_FORMAT_VAL()</function> macros. For more information see |
| <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Return Value</title> |
| |
| <para><function>sd_id128_to_string()</function> always succeeds and returns a pointer to the string array |
| passed in. <function>sd_id128_from_string()</function> returns 0 on success, in which case |
| <parameter>ret</parameter> is filled in, or a negative errno-style error code.</para> |
| </refsect1> |
| |
| <xi:include href="libsystemd-pkgconfig.xml" /> |
| |
| <refsect1> |
| <title>See Also</title> |
| |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |