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man: rework the text in sd-id128

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In places the text was overly formal, e.g. "an 128-bit ID" was repeated, even
though it is clear from the context that we're talking about this type of ID.
OTOH, in other places the text was informal, e.g. "You can use …".
Also, "you may use f() to frob" → "f() frobs". The text without all the
flourishes is easier to read.

sd_id128_in_set_sentinel() was described only in passing when taking about
sd_id128_in_set(), now it gets is own brief paragraph.

The synopsis was missing.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2022-06-13 10:38:14 +02:00
parent e16144844b
commit d13f105165
1 changed files with 108 additions and 45 deletions
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153
man/sd-id128.xml
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@ -40,6 +40,69 @@
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</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_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>
@ -51,20 +114,13 @@
<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 mostly
compatible with those types of IDs.
<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>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>
@ -73,30 +129,28 @@
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
<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> 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>
<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> may be used to refer to the 128-bit ID consisting of only
<constant>NUL</constant> bytes (i.e. all bits off).</para>
<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> may be used to refer to the 128-bit ID consisting of only
<constant>0xFF</constant> bytes (i.e. all bits on).</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>
<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 &lt;stdio.h&gt;
#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)
@ -105,18 +159,16 @@ 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>
<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> 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>
<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;
@ -136,7 +188,7 @@ int main(int argc, char **argv) {
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>Use <function>sd_id128_equal()</function> to compare two 128-bit IDs:</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;
@ -148,18 +200,22 @@ int main(int argc, char **argv) {
return 0;
}</programlisting>
<para>Use <function>sd_id128_is_null()</function> to check if an 128-bit ID consists of only
<constant>NUL</constant> bytes:</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, use <function>sd_id128_is_allf()</function> to check if an 128-bit ID consists of only
<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>For convenience, <function>sd_id128_in_set()</function> takes a list of IDs and
returns true if any are equal to the first argument:</para>
<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);
@ -175,18 +231,25 @@ int main(int argc, char **argv) {
</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. 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>
<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>Note that new, randomized IDs may be generated with
<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" />