+++ /dev/null
-<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2012 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
-
-<refentry id="sd-id128"
- xmlns:xi="http://www.w3.org/2001/XInclude">
-
- <refentryinfo>
- <title>sd-id128</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>sd-id128</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd-id128</refname>
- <refname>sd_id128_t</refname>
- <refname>SD_ID128_MAKE</refname>
- <refname>SD_ID128_CONST_STR</refname>
- <refname>SD_ID128_FORMAT_STR</refname>
- <refname>SD_ID128_FORMAT_VAL</refname>
- <refname>sd_id128_equal</refname>
- <refpurpose>APIs for processing 128-bit IDs</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo>
- </funcsynopsis>
-
- <cmdsynopsis>
- <command>pkg-config --cflags --libs libsystemd</command>
- </cmdsynopsis>
-
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><filename>sd-id128.h</filename> provides APIs to process and
- generate 128-bit ID values. The 128-bit ID values processed and
- generated by these APIs are a generalization of OSF UUIDs as
- defined by <ulink url="https://tools.ietf.org/html/rfc4122">RFC
- 4122</ulink> but use a simpler string format. These functions
- impose no structure on the used IDs, much unlike OSF UUIDs or
- Microsoft GUIDs, but are fully compatible with those types of IDs.
- </para>
-
- <para>See
- <citerefentry><refentrytitle>sd_id128_to_string</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- and
- <citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- for more information about the implemented functions.</para>
-
- <para>A 128-bit ID is implemented as the following
- union type:</para>
-
- <programlisting>typedef union sd_id128 {
- uint8_t bytes[16];
- uint64_t qwords[2];
-} sd_id128_t;</programlisting>
-
- <para>This union type allows accessing the 128-bit ID as 16
- separate bytes or two 64-bit words. It is generally safer to
- access the ID components by their 8-bit array to avoid endianness
- issues. This union is intended to be passed call-by-value (as
- opposed to call-by-reference) and may be directly manipulated by
- clients.</para>
-
- <para>A couple of macros are defined to denote and decode 128-bit
- IDs:</para>
-
- <para><function>SD_ID128_MAKE()</function> may be used to denote a
- constant 128-bit ID in source code. A commonly used idiom is to
- assign a name to a 128-bit ID using this macro:</para>
-
- <programlisting>#define SD_MESSAGE_COREDUMP SD_ID128_MAKE(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)</programlisting>
-
- <para><function>SD_ID128_CONST_STR()</function> may be used to
- convert constant 128-bit IDs into constant strings for output. The
- following example code will output the string
- "fc2e22bc6ee647b6b90729ab34a250b1":</para>
- <programlisting>int main(int argc, char *argv[]) {
- puts(SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
-}</programlisting>
-
- <para><function>SD_ID128_FORMAT_STR</function> and
- <function>SD_ID128_FORMAT_VAL()</function> may be used to format a
- 128-bit ID in a
- <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- format string, as shown in the following example:</para>
-
- <programlisting>int main(int argc, char *argv[]) {
- sd_id128_t id;
- id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
- printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id));
- return 0;
-}</programlisting>
-
- <para>Use <function>sd_id128_equal()</function> to compare two 128-bit IDs:</para>
-
- <programlisting>int main(int argc, char *argv[]) {
- sd_id128_t a, b, c;
- a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
- b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e);
- c = a;
- assert(sd_id128_equal(a, c));
- assert(!sd_id128_equal(a, b));
- return 0;
-}</programlisting>
-
- <para>Note that new, randomized IDs may be generated with
- <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
- <option>--new-id</option> option.</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_to_string</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- </para>
- </refsect1>
-
-</refentry>
~ianmdlvl / elogind.git / blobdiff