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<?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 <systemd/sd-json.h></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><refentrytitle>sd-varlink</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
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