= LibXML Ruby

== Overview
The libxml gem provides Ruby language bindings for GNOME's Libxml2
XML toolkit. It is free software, released under the MIT License.

libxml-ruby provides several advantages over REXML:

* Speed - libxml is many times faster than REXML
* Features - libxml provides a number of additional features over REXML, including XML Schema Validation, RelaxNg validation, xslt (see libxslt-ruby)
* Conformance - libxml passes all 1800+ tests from the OASIS XML Tests Suite 


== Requirements
libxml-ruby requires Ruby 1.8.4 or higher.  It is dependent on 
the following libraries to function properly:

* libm      (math routines: very standard)
* libz      (zlib)
* libiconv
* libxml2

If you are running Linux or Unix you'll need a C compiler so the
extension can be compiled when it is installed.  If you are running
Windows, then install the Windows specific RubyGem which
includes an already built extension.

== INSTALLATION
The easiest way to install libxml-ruby is via Ruby Gems.  To install:

<tt>gem install libxml-ruby</tt>

If you are running Windows, make sure to install the Win32 RubyGem
which includes an already built binary file.  The binary is built
against libxml2 version 2.6.32 and iconv version 1.11.  Both of these
are also included as pre-built binaries, and should be put either in
the libxml/lib directory or on the Windows path.

The Windows binaries are built with MingW and include libxml-ruby, 
libxml2 and iconv.  The gem also includes a Microsoft VC++ 2008
solution.  If you wish to run a debug version of libxml-ruby on
Windows, then it is highly recommended you use VC++.

== Functionality
LibXML is a highly conformant XML parser, passing all 1800+ tests 
from the OASIS XML Tests Suite.  It includes rich functionality such as:

* DOM (LibXML::XML::Parser)
* SAX (LibXML::XML::SaxParser)
* HTML Parsing (LibXML::XML::HTMLParser)
* Reader (LibXML::XML::Reader)
* XPath (LibXML::XML::XPath)
* XPointer (LibXML::XML::XPointer)
* DTDs (LibXML::XML::Dtd)
* RelaxNG Schemas (LibXML::XML::RelaxNG)
* XML Schema (LibXML::XML::Schema)
* XSLT (http://rubyforge.org/projects/libxsl/)

libxml-ruby provides impressive coverage of libxml's functionality 
through an easy-to-use C api.  

== Performance
In addition to being feature rich and conformation, the main reason
people use libxml-ruby is for performance.  Here are the results 
of a couple simple benchmarks recently blogged about on the
Web (you can find them in the benchmark directory of the 
libxml distribution).

From http://depixelate.com/2008/4/23/ruby-xml-parsing-benchmarks

               user     system      total        real
 libxml    0.032000   0.000000   0.032000 (  0.031000)
 Hpricot   0.640000   0.031000   0.671000 (  0.890000)
 REXML     1.813000   0.047000   1.860000 (  2.031000)

From https://svn.concord.org/svn/projects/trunk/common/ruby/xml_benchmarks/

               user     system      total        real
 libxml    0.641000   0.031000   0.672000 (  0.672000)
 hpricot   5.359000   0.062000   5.421000 (  5.516000)
 rexml    22.859000   0.047000  22.906000 ( 23.203000) 

== USAGE
For in-depth information about using libxml-ruby please refer
to its online Rdoc documentation.  

All libxml classes are in the LibXML::XML module. The most
expedient way to use libxml is to require 'xml'.  This will mixin
the LibXML module into the global namespace, allowing you to 
write code like this: 

  require 'xml'
  document = XML::Document.new

However, when creating an application or library you plan to 
redistribute, it is best to not add the LibXML module to the global
namespace, in which case you can either write your code like this:

  require 'libxml'
  document = LibXML::XML::Document.new

or, more conveniently, utilize a proper namespace for you own work
and include LibXML into it. For example:

  require 'libxml'

  mdoule MyApplication
    include LibXML

    class MyClass
      def some_method
        document = XML::Document.new
      end
    end
  end

For simplicity's sake we will use require 'xml in the basic examples
shown below.

=== READING
There are several ways to read xml documents.

  require 'xml'
  doc = XML::Document.file('output.xml')
  root = doc.root
  
  puts "Root element name: #{root.name}"
  
  elem3 = root.find('elem3').to_a.first
  puts "Elem3: #{elem3['attr']}"
  
  doc.find('//root_node/foo/bar').each do |node|
    puts "Node path: #{node.path} \t Contents: #{node.content}"
  end

And your terminal should look like this:

  Root element name: root_node
  Elem3: baz
  Node path: /root_node/foo/bar[1]         Contents: 1
  Node path: /root_node/foo/bar[2]         Contents: 2
  Node path: /root_node/foo/bar[3]         Contents: 3
  Node path: /root_node/foo/bar[4]         Contents: 4
  Node path: /root_node/foo/bar[5]         Contents: 5
  Node path: /root_node/foo/bar[6]         Contents: 6
  Node path: /root_node/foo/bar[7]         Contents: 7
  Node path: /root_node/foo/bar[8]         Contents: 8
  Node path: /root_node/foo/bar[9]         Contents: 9
  Node path: /root_node/foo/bar[10]        Contents: 10

=== WRITING
To write a simple document:

  require 'xml'
  
  doc = XML::Document.new()
  doc.root = XML::Node.new('root_node')
  root = doc.root
  
  root << elem1 = XML::Node.new('elem1')
  elem1['attr1'] = 'val1'
  elem1['attr2'] = 'val2'
  
  root << elem2 = XML::Node.new('elem2')
  elem2['attr1'] = 'val1'
  elem2['attr2'] = 'val2'
  
  root << elem3 = XML::Node.new('elem3')
  elem3 << elem4 = XML::Node.new('elem4')
  elem3 << elem5 = XML::Node.new('elem5')
  
  elem5 << elem6 = XML::Node.new('elem6')
  elem6 << 'Content for element 6'
  
  elem3['attr'] = 'baz'
  
  format = true
  doc.save('output.xml', format)

The file output.xml contains:

  <?xml version="1.0"?>
  <root_node>
    <elem1 attr1="val1" attr2="val2"/>
    <elem2 attr1="val1" attr2="val2"/>
    <elem3 attr="baz">
      <elem4/>
      <elem5>
        <elem6>Content for element 6</elem6>
      </elem5>
    </elem3>
    <foo>
      <bar>1</bar>
      <bar>2</bar>
      <bar>3</bar>
      <bar>4</bar>
      <bar>5</bar>
      <bar>6</bar>
      <bar>7</bar>
      <bar>8</bar>
      <bar>9</bar>
      <bar>10</bar>
    </foo>
  </root_node>

== DOCUMENTATION
RDoc comments are included - run 'rake doc' to generate documentation.
You can find the latest documentation at:

* http://libxml.rubyforge.org/rdoc/

== License
See LICENSE for license information.

== MORE INFORMATION
For more information please refer to the documentation.  If you have any
questions, please send email to libxml-devel@rubyforge.org.