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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE chapter
[
<!ENTITY libagsthreadso "libags_thread.so">
<!ENTITY libagsaudioso "libags_audio.so">
<!ENTITY libagsso "libags.so">
<!ENTITY chap2 "chapter 2">
<!ENTITY % agsdocentities SYSTEM "xml/agsdocentities.ent">
%agsdocentities;
]>
<!-- Copyright (C) 2005-2018 Jo\u00EBl Kr\u00E4hemann -->
<!-- Permission is granted to copy, distribute and/or modify this document -->
<!-- under the terms of the GNU Free Documentation License, Version 1.3 -->
<!-- or any later version published by the Free Software Foundation; -->
<!-- with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. -->
<!-- A copy of the license is included in the section entitled "GNU -->
<!-- Free Documentation License". -->
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0">
<title>XML Input/Output</title>
<para>
Saving and restoring your files is done by using XML supporting XPath. The complete
persistence layer is described by ags_file.dtd installed on your system. There various
classes involved by doing XML IO. It does it in stages as following for reading:
</para>
<orderedlist numeration="lowerroman">
<listitem>
Parsing the XML tree and map nodes and objects.
</listitem>
<listitem>
Resolving XPath expressions retrieve objects by their nodes.
</listitem>
<listitem>
Do as needed callbacks of AgsFileLaunch to setup up the application.
</listitem>
</orderedlist>
<para>
Writing files does ommit the last step. The current AgsConfig is going to be embedded
in your file. So you can have per project configuration. Certain objects implement
AgsPlugin interface to do an abstraction of reading and writing xmlNode.
</para>
<sect1>
<title>Writing XML files</title>
<para>
Writing files is pretty easy. You just have to instantiate AgsFile, set the application
context, open it in read-write mode, call ags_file_write() and finally ags_file_close().
</para>
<example>
<title>Writing XML</title>
<programlisting language="C">
<xi:include href="../listings/file_write.c" parse="text" />
</programlisting>
</example>
</sect1>
<sect1>
<title>Reading XML files</title>
<para>
Normally you instantiate a new application context to be used to load objects into. Create
a file object by passing the application context and filename. Then open it and read the
content. At the end you close the file descriptor. To use your application start the
main loop.
</para>
<example>
<title>Reading XML</title>
<programlisting language="C">
<xi:include href="../listings/file_read.c" parse="text" />
</programlisting>
</example>
</sect1>
</chapter>
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