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man: add brief intro page to new sd-json APIs

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This commit is contained in:
Lennart Poettering 2024-05-02 14:44:37 +02:00
parent 309a747fa6
commit 86d754050b
3 changed files with 94 additions and 2 deletions
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4
man/libsystemd.xml
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@ -24,8 +24,6 @@
<refsynopsisdiv>
<programlisting>
#include &lt;systemd/sd-bus.h&gt;
#include &lt;systemd/sd-bus-vtable.h&gt;
#include &lt;systemd/sd-bus-protocol.h&gt;
#include &lt;systemd/sd-daemon.h&gt;
#include &lt;systemd/sd-device.h&gt;
#include &lt;systemd/sd-event.h&gt;
@ -33,6 +31,7 @@
#include &lt;systemd/sd-hwdb.h&gt;
#include &lt;systemd/sd-id128.h&gt;
#include &lt;systemd/sd-journal.h&gt;
#include &lt;systemd/sd-json.h&gt;
#include &lt;systemd/sd-login.h&gt;
#include &lt;systemd/sd-messages.h&gt;
#include &lt;systemd/sd-path.h&gt;
@ -61,6 +60,7 @@
<citerefentry><refentrytitle>sd-hwdb</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-json</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
and
<citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for information about different parts of the library interface.</para>

1
man/rules/meson.build
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@ -151,6 +151,7 @@ manpages = [
'sd_id128_t'],
''],
['sd-journal', '3', [], ''],
['sd-json', '3', [], ''],
['sd-login', '3', [], 'HAVE_PAM'],
['sd_booted', '3', [], ''],
['sd_bus_add_match',

91
man/sd-json.xml Normal file
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@ -0,0 +1,91 @@
<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd-json"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd-json</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd-json</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd-json</refname>
<refpurpose>APIs for Dealing with JSON Objects</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-json.h&gt;</funcsynopsisinfo>
</funcsynopsis>
<cmdsynopsis>
<command>pkg-config --cflags --libs libsystemd</command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><filename>sd-json.h</filename> is part of
<citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
provides APIs to parse, generate, format and otherwise operate with JSON objects.</para>
<para>The API's central data structure is <type>JsonVariant</type> which encapsulates a JSON object,
array, string, boolean, number or null value. These data structures are mostly considered immutable after
construction (i.e. their contents won't change, but some meta-data might, such as reference counters).</para>
<para>The APIs broadly fall into five categories:</para>
<itemizedlist>
<listitem><para>APIs to directly operate with <type>JsonVariant</type> objects, in the
<function>sd_json_variant*</function> namespace.</para></listitem>
<listitem><para>APIs to construct complex JSON objects, in the <function>sd_json_build*</function>
namespace.</para></listitem>
<listitem><para>APIs to map <type>JsonVariant</type> objects and their fields to matching fields in C
structures, in the <function>sd_json_dispatch*</function> namespace.</para></listitem>
<listitem><para>APIs to convert a string representation of a JSON object into a
<type>JsonVariant</type> object, in the <function>sd_json_parse*</function>
namespace.</para></listitem>
<listitem><para>APIs to convert an <type>JsonVariant</type> object into its string representation, in
the <function>sd_json_format*</function> namespace.</para></listitem>
</itemizedlist>
<para>This JSON library will internally encode JSON integer numbers in the range
<constant>INT64_MIN</constant>…<constant>UINT64_MAX</constant> into native 64bit signed or unsigned
integers, and will reproduce them without loss of precision. Non-integer numbers are stored in 64bit IEEE
floating point numbers.</para>
<para>If the functions return string arrays, these are generally
<constant>NULL</constant> terminated and need to be freed by the
caller with the libc
<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
call after use, including the strings referenced therein.
Similarly, individual strings returned need to be freed, as
well.</para>
<para>As a special exception, instead of an empty string array <constant>NULL</constant> may be returned,
which should be treated equivalent to an empty string array.</para>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>,
<member><citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>