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Libxml2 Overview

This section describes the libxml2 component which is a wrapper for the standard libxml2 C library.

Purpose

The libxml2 component provides XML processing, parsing and validation APIs. You can call its C functions directly or use the C++ wrapper.

Required background

The libxml2 component is based on the standard libxml2 library.

Architecture

The libxml2 component is the core of the XML collection. Two other components rely on it: the XML Framework and the XML DOM Engine.

Figure 1. Package diagram for the libxml2 component

The libxml2 sub-component provides direct access to the C API of the standard libxml2 library.

The Utilities sub-component provides object-oriented access to the C functions: it also implements the resource management and error handling capabilities of the Symbian Platform.

If your Symbian Platform build does not include the libxml2 component, the XML DOM Engine and the libxml2 SAX parser plug-in are automatically excluded.

APIs

The XMLEngPushL() function opens and initializes the libxml2 library parser. The XMLEngPopAndClose() function closes the library parser and frees its resources. You must call the XMLEngPushL() function before any parsing and serialisation operations, and call the XMLEngPopAndClose() function when these operations are completed.

The following table lists the most relevant wrapper classes of the libxml2 library. High-level classes are in the XML DOM Engine component.

API	Description
xmlGlobalState	Global data providing access to most of the libxml2 library: settings, function pointers, and so on. Available through TLS
TXmlEngString	General-purpose string: pointer-sized object containing a zero-terminated UTF-8 string.
TXmlEngConstString	Read-only version of `TXmlEngString`.

The following table lists the most relevant C structures of the libxml2 library.

API	Description
_xmlDoc	Document. Provides access to the tree of nodes.
_xmlNode	Node. Provides access to its children and chain of attributes.
_xmlAttribute	Attribute.
_xmlElement	Element.
xmlAttributeType::_xmlElementContent	Container for the contents of an element.
_xmlSchema and _xmlDtd	Validation trees. These structures have no C++ wrappers.
_xmlXPathParserContext	XPath evaluation context.

Typical uses

When porting existing software, use the C functions of the standard libxml2 library and refer to the libxml2 Reference Manual for more information.

To take advantage of the standard types and exception handling provided by the Symbian Platform, use the C++ APIs.

Parent topic: Libxml2 Libraries Component

Related concepts

XML DOM Engine error handling