]>
Commit | Line | Data |
---|---|---|
12355095 LP |
1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
12355095 LP |
4 | |
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
12355095 LP |
8 | This file is part of systemd. |
9 | ||
10 | Copyright 2012 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
6a70f3aa | 26 | <refentry id="sd-id128" |
798d3a52 ZJS |
27 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
28 | ||
29 | <refentryinfo> | |
30 | <title>sd-id128</title> | |
31 | <productname>systemd</productname> | |
32 | ||
33 | <authorgroup> | |
34 | <author> | |
35 | <contrib>Developer</contrib> | |
36 | <firstname>Lennart</firstname> | |
37 | <surname>Poettering</surname> | |
38 | <email>lennart@poettering.net</email> | |
39 | </author> | |
40 | </authorgroup> | |
41 | </refentryinfo> | |
42 | ||
43 | <refmeta> | |
44 | <refentrytitle>sd-id128</refentrytitle> | |
45 | <manvolnum>3</manvolnum> | |
46 | </refmeta> | |
47 | ||
48 | <refnamediv> | |
49 | <refname>sd-id128</refname> | |
50 | <refname>sd_id128_t</refname> | |
51 | <refname>SD_ID128_MAKE</refname> | |
2b044526 | 52 | <refname>SD_ID128_MAKE_STR</refname> |
3dbea941 | 53 | <refname>SD_ID128_NULL</refname> |
798d3a52 ZJS |
54 | <refname>SD_ID128_CONST_STR</refname> |
55 | <refname>SD_ID128_FORMAT_STR</refname> | |
56 | <refname>SD_ID128_FORMAT_VAL</refname> | |
57 | <refname>sd_id128_equal</refname> | |
3dbea941 | 58 | <refname>sd_id128_is_null</refname> |
798d3a52 ZJS |
59 | <refpurpose>APIs for processing 128-bit IDs</refpurpose> |
60 | </refnamediv> | |
61 | ||
62 | <refsynopsisdiv> | |
63 | <funcsynopsis> | |
64 | <funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo> | |
65 | </funcsynopsis> | |
66 | ||
67 | <cmdsynopsis> | |
68 | <command>pkg-config --cflags --libs libsystemd</command> | |
69 | </cmdsynopsis> | |
70 | ||
71 | </refsynopsisdiv> | |
72 | ||
73 | <refsect1> | |
74 | <title>Description</title> | |
75 | ||
76 | <para><filename>sd-id128.h</filename> provides APIs to process and | |
77 | generate 128-bit ID values. The 128-bit ID values processed and | |
78 | generated by these APIs are a generalization of OSF UUIDs as | |
79 | defined by <ulink url="https://tools.ietf.org/html/rfc4122">RFC | |
80 | 4122</ulink> but use a simpler string format. These functions | |
81 | impose no structure on the used IDs, much unlike OSF UUIDs or | |
82 | Microsoft GUIDs, but are fully compatible with those types of IDs. | |
83 | </para> | |
84 | ||
85 | <para>See | |
86 | <citerefentry><refentrytitle>sd_id128_to_string</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
87 | <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
88 | and | |
89 | <citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
90 | for more information about the implemented functions.</para> | |
91 | ||
92 | <para>A 128-bit ID is implemented as the following | |
93 | union type:</para> | |
94 | ||
95 | <programlisting>typedef union sd_id128 { | |
3dbea941 LP |
96 | uint8_t bytes[16]; |
97 | uint64_t qwords[2]; | |
12355095 LP |
98 | } sd_id128_t;</programlisting> |
99 | ||
798d3a52 ZJS |
100 | <para>This union type allows accessing the 128-bit ID as 16 |
101 | separate bytes or two 64-bit words. It is generally safer to | |
102 | access the ID components by their 8-bit array to avoid endianness | |
103 | issues. This union is intended to be passed call-by-value (as | |
104 | opposed to call-by-reference) and may be directly manipulated by | |
105 | clients.</para> | |
106 | ||
107 | <para>A couple of macros are defined to denote and decode 128-bit | |
108 | IDs:</para> | |
109 | ||
110 | <para><function>SD_ID128_MAKE()</function> may be used to denote a | |
111 | constant 128-bit ID in source code. A commonly used idiom is to | |
112 | assign a name to a 128-bit ID using this macro:</para> | |
113 | ||
114 | <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> | |
115 | ||
3dbea941 LP |
116 | <para><function>SD_ID128_NULL</function> may be used to refer to the 128bit ID consisting of only NUL |
117 | bytes.</para> | |
118 | ||
2b044526 ZJS |
119 | <para><function>SD_ID128_MAKE_STR()</function> is similar to <function>SD_ID128_MAKE()</function>, but creates a |
120 | <type>const char*</type> expression that can be conveniently used in message formats and such:</para> | |
121 | ||
122 | <programlisting>#include <stdio.h> | |
123 | #define SD_MESSAGE_COREDUMP_STR SD_ID128_MAKE_STR(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1) | |
124 | ||
125 | int main(int argc, char **argv) { | |
126 | puts("Match for coredumps: MESSAGE_ID=" SD_MESSAGE_COREDUMP_STR); | |
127 | } | |
128 | </programlisting> | |
129 | ||
130 | ||
798d3a52 ZJS |
131 | <para><function>SD_ID128_CONST_STR()</function> may be used to |
132 | convert constant 128-bit IDs into constant strings for output. The | |
133 | following example code will output the string | |
134 | "fc2e22bc6ee647b6b90729ab34a250b1":</para> | |
135 | <programlisting>int main(int argc, char *argv[]) { | |
2b044526 | 136 | puts("Match for coredumps: %s", SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP)); |
183de6d7 LP |
137 | }</programlisting> |
138 | ||
3dbea941 | 139 | <para><function>SD_ID128_FORMAT_STR()</function> and |
798d3a52 ZJS |
140 | <function>SD_ID128_FORMAT_VAL()</function> may be used to format a |
141 | 128-bit ID in a | |
142 | <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
143 | format string, as shown in the following example:</para> | |
144 | ||
145 | <programlisting>int main(int argc, char *argv[]) { | |
3dbea941 LP |
146 | sd_id128_t id; |
147 | id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07); | |
148 | printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id)); | |
149 | return 0; | |
12355095 LP |
150 | }</programlisting> |
151 | ||
798d3a52 | 152 | <para>Use <function>sd_id128_equal()</function> to compare two 128-bit IDs:</para> |
12355095 | 153 | |
798d3a52 | 154 | <programlisting>int main(int argc, char *argv[]) { |
3dbea941 LP |
155 | sd_id128_t a, b, c; |
156 | a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07); | |
157 | b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e); | |
158 | c = a; | |
159 | assert(sd_id128_equal(a, c)); | |
160 | assert(!sd_id128_equal(a, b)); | |
161 | return 0; | |
162 | }</programlisting> | |
163 | ||
164 | <para>Use <function>sd_id128_is_null()</function> to check if an 128bit ID consists of only NUL bytes:</para> | |
165 | ||
166 | <programlisting>int main(int argc, char *argv[]) { | |
167 | assert(sd_id128_is_null(SD_ID128_NULL)); | |
12355095 LP |
168 | }</programlisting> |
169 | ||
798d3a52 ZJS |
170 | <para>Note that new, randomized IDs may be generated with |
171 | <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
b22319ea | 172 | <option>--new-id128</option> option.</para> |
798d3a52 ZJS |
173 | </refsect1> |
174 | ||
175 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
176 | ||
177 | <refsect1> | |
178 | <title>See Also</title> | |
179 | <para> | |
180 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
181 | <citerefentry><refentrytitle>sd_id128_to_string</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
182 | <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
183 | <citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
184 | <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
185 | <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
186 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
187 | <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
188 | <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
189 | </para> | |
190 | </refsect1> | |
12355095 LP |
191 | |
192 | </refentry> |