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diff --git a/man/sd-id128.xml b/man/sd-id128.xml new file mode 100644 index 0000000..4425c45 --- /dev/null +++ b/man/sd-id128.xml @@ -0,0 +1,165 @@ +<?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"> + +<!-- + SPDX-License-Identifier: LGPL-2.1+ +--> + +<refentry id="sd-id128" + xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd-id128</title> + <productname>systemd</productname> + </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_MAKE_STR</refname> + <refname>SD_ID128_NULL</refname> + <refname>SD_ID128_CONST_STR</refname> + <refname>SD_ID128_FORMAT_STR</refname> + <refname>SD_ID128_FORMAT_VAL</refname> + <refname>sd_id128_equal</refname> + <refname>sd_id128_is_null</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_NULL</function> may be used to refer to the 128bit ID consisting of only NUL + bytes.</para> + + <para><function>SD_ID128_MAKE_STR()</function> is similar to <function>SD_ID128_MAKE()</function>, but creates a + <type>const char*</type> expression that can be conveniently used in message formats and such:</para> + + <programlisting>#include <stdio.h> +#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) + +int main(int argc, char **argv) { + puts("Match for coredumps: MESSAGE_ID=" SD_MESSAGE_COREDUMP_STR); +} + </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("Match for coredumps: %s", 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>Use <function>sd_id128_is_null()</function> to check if an 128bit ID consists of only NUL bytes:</para> + + <programlisting>int main(int argc, char *argv[]) { + assert(sd_id128_is_null(SD_ID128_NULL)); +}</programlisting> + + <para>Note that new, randomized IDs may be generated with + <citerefentry><refentrytitle>systemd-id128</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s + <command>new</command> command.</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> |