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diff --git a/man/sd-id128.xml b/man/sd-id128.xml new file mode 100644 index 0000000000..ac2000e275 --- /dev/null +++ b/man/sd-id128.xml @@ -0,0 +1,181 @@ +<?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"> + + <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-id128</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="http://tools.ietf.org/html/rfc4122">RFC + 4122</ulink>, though use a simpler string + formatting. 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 128bit 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><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 + <literal>--new-id</literal> option.</para> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para>These APIs are implemented as a shared library, + which can be compiled and linked to with the + <literal>libsystemd-id128</literal> + <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> + file.</para> + + </refsect1> + + <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><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><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |