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diff --git a/man/sd-id128.xml b/man/sd-id128.xml new file mode 100644 index 0000000..c869943 --- /dev/null +++ b/man/sd-id128.xml @@ -0,0 +1,283 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<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_ALLF</refname> + <refname>SD_ID128_CONST_STR</refname> + <refname>SD_ID128_FORMAT_STR</refname> + <refname>SD_ID128_FORMAT_VAL</refname> + <refname>SD_ID128_MAKE</refname> + <refname>SD_ID128_MAKE_STR</refname> + <refname>SD_ID128_MAKE_UUID_STR</refname> + <refname>SD_ID128_NULL</refname> + <refname>SD_ID128_UUID_FORMAT_STR</refname> + <refname>sd_id128_equal</refname> + <refname>sd_id128_string_equal</refname> + <refname>sd_id128_in_set</refname> + <refname>sd_id128_in_set_sentinel</refname> + <refname>sd_id128_in_setv</refname> + <refname>sd_id128_is_allf</refname> + <refname>sd_id128_is_null</refname> + <refname>sd_id128_t</refname> + <refpurpose>APIs for processing 128-bit IDs</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo> + + <para> + <constant>SD_ID128_ALLF</constant> + </para> + <para> + <constant>SD_ID128_NULL</constant> + </para> + <para> + <constant>SD_ID128_CONST_STR(<replaceable>id</replaceable>)</constant> + </para> + <para> + <constant>SD_ID128_FORMAT_STR</constant> + </para> + <para> + <constant>SD_ID128_FORMAT_VAL(<replaceable>id</replaceable>)</constant> + </para> + <para> + <constant>SD_ID128_MAKE(<replaceable>v0</replaceable>, <replaceable>v1</replaceable>, <replaceable>v2</replaceable>, <replaceable>v3</replaceable>, <replaceable>v4</replaceable>, <replaceable>v5</replaceable>, <replaceable>v6</replaceable>, <replaceable>v7</replaceable>, <replaceable>v8</replaceable>, <replaceable>v9</replaceable>, <replaceable>vA</replaceable>, <replaceable>vB</replaceable>, <replaceable>vC</replaceable>, <replaceable>vD</replaceable>, <replaceable>vE</replaceable>, <replaceable>vF</replaceable>)</constant> + </para> + <para> + <constant>SD_ID128_MAKE_STR(<replaceable>v0</replaceable>, <replaceable>v1</replaceable>, <replaceable>v2</replaceable>, <replaceable>v3</replaceable>, <replaceable>v4</replaceable>, <replaceable>v5</replaceable>, <replaceable>v6</replaceable>, <replaceable>v7</replaceable>, <replaceable>v8</replaceable>, <replaceable>v9</replaceable>, <replaceable>vA</replaceable>, <replaceable>vB</replaceable>, <replaceable>vC</replaceable>, <replaceable>vD</replaceable>, <replaceable>vE</replaceable>, <replaceable>vF</replaceable>)</constant> + </para> + <para> + <constant>SD_ID128_MAKE_UUID_STR(<replaceable>v0</replaceable>, <replaceable>v1</replaceable>, <replaceable>v2</replaceable>, <replaceable>v3</replaceable>, <replaceable>v4</replaceable>, <replaceable>v5</replaceable>, <replaceable>v6</replaceable>, <replaceable>v7</replaceable>, <replaceable>v8</replaceable>, <replaceable>v9</replaceable>, <replaceable>vA</replaceable>, <replaceable>vB</replaceable>, <replaceable>vC</replaceable>, <replaceable>vD</replaceable>, <replaceable>vE</replaceable>, <replaceable>vF</replaceable>)</constant> + </para> + <para> + <constant>SD_ID128_UUID_FORMAT_STR</constant> + </para> + + <funcprototype> + <funcdef>int <function>sd_id128_equal</function></funcdef> + <paramdef>sd_id128_t <parameter>a</parameter></paramdef> + <paramdef>sd_id128_t <parameter>b</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_id128_string_equal</function></funcdef> + <paramdef>const char *<parameter>a</parameter></paramdef> + <paramdef>sd_id128_t <parameter>b</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_id128_is_null</function></funcdef> + <paramdef>sd_id128_t <parameter>id</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_id128_is_allf</function></funcdef> + <paramdef>sd_id128_t <parameter>id</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_id128_in_setv</function></funcdef> + <paramdef>sd_id128_t <parameter>id</parameter></paramdef> + <paramdef>va_list <parameter>ap</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_id128_in_set_sentinel</function></funcdef> + <paramdef>sd_id128_t <parameter>id</parameter></paramdef> + <paramdef>…</paramdef> + <paramdef><constant>SD_ID128_NULL</constant></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_id128_in_set</function></funcdef> + <paramdef>sd_id128_t <parameter>id</parameter></paramdef> + <paramdef>…</paramdef> + </funcprototype> + </funcsynopsis> + + <cmdsynopsis> + <command>pkg-config --cflags --libs libsystemd</command> + </cmdsynopsis> + + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><filename>sd-id128.h</filename> provides APIs to generate, convert, and compare 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 + mostly compatible with those types of IDs. + </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 by value (as opposed to pass-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> is used to write a constant ID in source code. A commonly used + idiom is to assign a name to an 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><constant>SD_ID128_NULL</constant> defines an ID consisting of only <constant>NUL</constant> bytes + (i.e. all bits off).</para> + + <para><constant>SD_ID128_ALLF</constant> defines an ID consisting of only <constant>0xFF</constant> bytes + (i.e. all bits on).</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> converts constant 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><constant>SD_ID128_FORMAT_STR</constant> and <function>SD_ID128_FORMAT_VAL()</function> is used to + format an 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><constant>SD_ID128_UUID_FORMAT_STR</constant> and <function>SD_ID128_MAKE_UUID_STR()</function> + are similar to + <constant>SD_ID128_FORMAT_STR</constant> and <function>SD_ID128_MAKE_STR()</function>, + but include separating hyphens to conform to the + "<ulink url="https://en.wikipedia.org/wiki/Universally_unique_identifier#Format">canonical representation</ulink>". + They format the string based on <ulink + url="https://tools.ietf.org/html/rfc4122">RFC4122</ulink> Variant 1 rules, i.e. converting from Big + Endian byte order. This matches behaviour of most other Linux userspace infrastructure. It's probably + best to avoid UUIDs of other variants, in order to avoid unnecessary ambiguities. All 128-bit IDs + generated by the sd-id128 APIs strictly conform to Variant 1 Version 4 UUIDs, as per RFC 4122.</para> + + <para><function>sd_id128_equal()</function> compares 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><function>sd_id128_string_equal()</function> is similar to <function>sd_id128_equal()</function>, + but the first ID is formatted as <type>const char*</type>. The same restrictions apply as to the first + argument of <function>sd_id128_from_string()</function>.</para> + + <para><function>sd_id128_is_null()</function> checks if an ID consists of only <constant>NUL</constant> + bytes:</para> + + <programlisting>assert(sd_id128_is_null(SD_ID128_NULL));</programlisting> + + <para>Similarly, <function>sd_id128_is_allf()</function> checks if an ID consists of only + <constant>0xFF</constant> bytes (all bits on):</para> + + <programlisting>assert(sd_id128_is_allf(SD_ID128_ALLF));</programlisting> + + <para><function>sd_id128_in_set_sentinel()</function> takes a list of IDs and returns true if the first + argument is equal to any of the subsequent arguments. The argument list is terminated by an + <constant>SD_ID128_NULL</constant> sentinel, which must be present.</para> + + <para><function>sd_id128_in_set()</function> is a convenience function that takes a list of IDs and + returns true if the first argument is equal to any of the subsequent arguments:</para> + + <programlisting>int main(int argc, char *argv[]) { + sd_id12_t a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07); + assert(sd_id128_in_set(a, a)); + assert(sd_id128_in_set(a, a, a)); + assert(!sd_id128_in_set(a)); + assert(!sd_id128_in_set(a, + SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e) + SD_ID128_MAKE(2f,88,28,5f,9c,44,09,9d,d7,15,77,04,bc,85,7e,e3) + SD_ID128_ALLF)); + return 0; +} +</programlisting> + + <para><function>sd_id128_in_set()</function> is defined as a macro over + <function>sd_id128_in_set_sentinel()</function>, adding the <constant>SD_ID128_NULL</constant> sentinel + automatically. Since <function>sd_id128_in_set_sentinel()</function> uses + <constant>SD_ID128_NULL</constant> as the sentinel, <constant>SD_ID128_NULL</constant> cannot be + otherwise placed in the argument list.</para> + + <para><function>sd_id128_in_setv()</function> is similar to + <function>sd_id128_in_set_sentinel()</function>, but takes a <structname>struct varargs</structname> + argument.</para> + + <para>New randomized IDs may be generated with + <citerefentry><refentrytitle>systemd-id128</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s + <command>new</command> command.</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 information about other implemented functions.</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> |