Erbal: Very small, very fast Ragel/C based ERB parser

Intro

Erbal is a lightweight ERB parser based on the Ragel State Machine Compiler (www.complang.org/ragel/) and written in C. It’s very fast.

Please note that Erbal isn’t intended as a full replacement for the ERB implementation that ships with Ruby. Erbal only implements parsing of the following tags:

<%, <%=, <%#, -%>, %>

This is to keep Erbal very simple and very fast. If there’s a good case for implementing more features from ERB and it doesn’t impact performance or add much complexity then I’ll consider it. Personally I’ve never needed anything more.

Using Erbal

require 'erbal'
e = Erbal.new("<% a=1 -%> a is: <%= a -%>", "@output_buffer")
src = e.parse
eval(src)

Rails

In your after_initialize block in config/environment.rb add:

require 'erbal/rails'
ActionView::Template.register_template_handler :erb, ErbalTemplateHandler

Benchmarks

This benchmark was performed on a MacBook Pro with a 2.4Ghz Intel Core 2 Duo and 4GB 667Mhz DDR2 SDRAM. Running Mac OS X 10.6 (Snow Leopard). The code to run it is located in benchmark/bench.rb

Summary:

Erbal is 14.6x faster than Ruby’s ERB and 7.5x faster than Erubis.

Details:

Ruby: 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin10] Erubis: 2.6.5 using Erubis::FastEruby. Erbal: 0.0.2

=> Warming up.... done
=> 10000 runs repeated 6 times

=> Erb:
 1) 13.01
 2) 13.00
 3) 13.01
 4) 13.04
 5) 13.13
 6) 13.23
=> Average: 13.07

=> Erbal:
 1) 0.90
 2) 0.89
 3) 0.89
 4) 0.90
 5) 0.89
 6) 0.89
=> Average: 0.89

=> Erubis:
 1) 6.63
 2) 6.67
 3) 6.69
 4) 6.71
 5) 6.72
 6) 6.75
=> Average: 6.70

Credits

Many thanks to Adrian Thurston for writing the Ragel State Machine Compiler (www.complang.org/ragel/)!