About

SXRB aims to provide nice DSL for ruby developers to cope with XML files that are too big to be loaded at once with Nokogiri or other parser. It is based on external SAX implementation.

DSL instructing SXRB how to treat encountered entities is very similar to one that would be usually used to build parsed document, which makes it very easy to represent business logic behind the code.

With SXRB one can write readable code that handles XML data, which later runs fast and has low memory usage. DSL combines SAX robustness with DOM simplicity.

For quick start install SXRB with:

gem install sxrb

Few examples

Parsing html

Given html variable containing string with any webpage code this piece of code builds links Hash that contains arrays of anchor texts related to each link.

require 'sxrb'

html = <<-HTML
<html>
  <body>
    <a href="https://github.com/samuil/sxrb">SXRB</a>
  </body>
</html>
HTML

links = Hash.new {|h,k| h[k] = []}

SXRB::Parser.new(html) do |html|
  html.descendant 'body' do |body|
    body.descendant 'a' do |a|
      a.on_element do |element|
        links[element.attributes['href']] << element.content
      end
    end
  end
end

Typical `SAX` application

If you have ever used SAX before you should be familiar with idea of event that it provides. SXRB wraps those events, so usually you won't need them, but they are still available. Elements in DSL provide on_start and on_end methods, that call provided block whenever matching element is encountered (at beginning and end of the tag respectively).

counter = 0
SXRB::Parser.new(file, :mode => :file) do |xml|
  xml.descendant 'test_element' do |el|
    el.on_start {counter += 1}
  end
end

Few details

As you could see in above examples DSL provides on_element method which is easy-to-use wrapper of internal SAX events. This method changes the way parser treats incoming data when matching element is encountered. All events within this element are used to build small DOM-like structure, which is more comfortable than typical series of events. Please note that without additional memory usage you can define nested on_element blocks.

Resources

Latest SXRB gem build at rubygems.org
SXRB documentation at yard
Browse SXRB code at github

Future plans

Right now SXRB is using LibXML implementation of SAX. Next important step (and probably last before 1.0.0) is integration with other backends (REXML, Nokogiri). It would also be nice to test current code against xml using namespaces.

Disclaimer

SXRB is in early development stage (currently released version is 0.3.0). It is not yet production-ready, because of a bit unstable API (versioning convention is maintained though -- minor upgrades don't break compatibility). I'm planning to end wild development, stabilize API and have full test suite with version 1.0.0.

License

SXRB is distributed under MIT license (see LICENSE for details).

sxrb

Runtime