133 lines
5.0 KiB
XML
133 lines
5.0 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_id128_to_string">
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<refentryinfo>
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<title>sd_id128_to_string</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_id128_to_string</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_id128_to_string</refname>
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<refname>sd_id128_from_string</refname>
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<refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>char *<function>sd_id128_to_string</function></funcdef>
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<paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_id128_from_string</function></funcdef>
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<paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_id128_to_string()</function> formats a 128-bit
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ID as a character string. It expects the ID and a string array
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capable of storing 33 characters. The ID will be formatted as 32
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lowercase hexadecimal digits and be terminated by a
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<constant>NUL</constant> byte.</para>
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<para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 character string
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with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
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back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
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37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
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function will validate the passed ID string, but not actually return it in parsed form.</para>
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<para>For more information about the <literal>sd_id128_t</literal>
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type see
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<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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Note that these calls operate the same way on all architectures,
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i.e. the results do not depend on endianness.</para>
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<para>When formatting a 128-bit ID into a string, it is often
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easier to use a format string for
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<citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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This is easily done using the
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<function>SD_ID128_FORMAT_STR</function> and
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<function>SD_ID128_FORMAT_VAL()</function> macros. For more
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information see
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<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_id128_to_string()</function> always succeeds
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and returns a pointer to the string array passed in.
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<function>sd_id128_from_string</function> returns 0 on success, in
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which case <parameter>ret</parameter> is filled in, or a negative
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errno-style error code.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_id128_to_string()</function> and
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<function>sd_id128_from_string()</function> interfaces are
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available as a shared library, which can be compiled and linked to
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with the
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<literal>libsystemd</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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