Adds optional msgpack serialization format to Rabl.

README.md

@@ -87,7 +87,9 @@ RABL is intended to require little to no configuration to get working. This is t
 Rabl.configure do |config|
   # Commented as these are the defaults
   # config.json_engine = nil # Any multi\_json engines
+  # config.msgpack_engine = nil # Defaults to ::MessagePack
   # config.include_json_root = true
+  # config.include_msgpack_root = true
   # config.include_xml_root  = false
   # config.enable_json_callbacks = false
   # config.xml_options = { :dasherize  => true, :skip_types => false }
@@ -105,6 +107,32 @@ gem 'yajl-ruby', :require => "yajl"
 
 and RABL will automatically start using that engine for encoding your JSON responses!
 
+### Message Pack ###
+
+Rabl also includes optional support for [Message Pack](http://www.msgpack.org/) serialization format using the [msgpack gem](https://rubygems.org/gems/msgpack).
+To enable, include the msgpack gem in your project's Gemfile. Then use Rabl as normal with the `msgpack` format (akin to json and xml formats).
+
+```ruby
+# Gemfile
+gem 'msgpack', '~> 0.4.5'
+```
+
+One can additionally use a custom Message Pack implementation by setting the Rabl `msgpack_engine` configuration attribute. This custom message pack engine must conform to the MessagePack#pack method signature.
+
+```ruby
+class CustomEncodeEngine
+  def self.pack string
+    # Custom Encoding by your own engine.
+  end
+end
+
+Rabl.configure do |config|
+  config.msgpack_engine = CustomEncodeEngine
+end
+```
+
+*NOTE*: Attempting to render the msgpack format without either including the msgpack gem or setting a `msgpack_engine` will cause an exception to be raised.
+
 ## Usage ##
 
 ### Object Assignment ###
@@ -359,4 +387,4 @@ See the [examples](https://github.com/nesquena/rabl/tree/master/examples) direct
 
 ## Copyright
 
-Copyright © 2011 Nathan Esquenazi. See [MIT-LICENSE](https://github.com/nesquena/rabl/blob/master/MIT-LICENSE) for details.
+Copyright © 2011 Nathan Esquenazi. See [MIT-LICENSE](https://github.com/nesquena/rabl/blob/master/MIT-LICENSE) for details.

lib/rabl/configuration.rb

@@ -1,19 +1,29 @@
+# We load the msgpack library if it is available.
+begin
+  require 'msgpack'
+rescue LoadError
+end
+
 module Rabl
   # Rabl.host
   class Configuration
     attr_accessor :include_json_root
+    attr_accessor :include_msgpack_root
     attr_accessor :include_xml_root
     attr_accessor :enable_json_callbacks
     attr_writer   :json_engine
+    attr_writer   :msgpack_engine
     attr_writer   :xml_options
 
     DEFAULT_XML_OPTIONS = { :dasherize  => true, :skip_types => false }
 
     def initialize
       @include_json_root     = true
+      @include_msgpack_root  = true
       @include_xml_root      = false
       @enable_json_callbacks = false
       @json_engine           = nil
+      @msgpack_engine        = nil
       @xml_options           = {}
     end
 
@@ -22,6 +32,12 @@ def json_engine
       @json_engine || MultiJson.engine
     end
 
+    ##
+    # @return the MessagePack encoder/engine to use.
+    def msgpack_engine
+      @msgpack_engine || ::MessagePack
+    end
+
     # Allows config options to be read like a hash
     #
     # @param [Symbol] option Key for a given attribute

lib/rabl/engine.rb

@@ -46,6 +46,15 @@ def to_json(options={})
       format_json result
     end
 
+    # Returns a msgpack representation of the data object
+    # to_msgpack(:root => true)
+    def to_msgpack(options={})
+      include_root = Rabl.configuration.include_msgpack_root
+      options = options.reverse_merge(:root => include_root, :child_root => include_root)
+      result = @_collection_name ? { @_collection_name => to_hash(options) } : to_hash(options)
+      Rabl.configuration.msgpack_engine.pack result
+    end
+
     # Returns an xml representation of the data object
     # to_xml(:root => true)
     def to_xml(options={})

rabl.gemspec

@@ -27,4 +27,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'tilt'
   s.add_development_dependency 'bson_ext'
   s.add_development_dependency 'yajl-ruby'
+  s.add_development_dependency 'msgpack', '~> 0.4.5'
 end