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