use :em_client_class in Rainbows!

This allows us to avoid modifying the builtin
Rainbows::EventMachine::Client class.

This is intended for Rainbows! with the following commits:
7223b868624d19f3421045c2bc5b075bacd83694
ab175517f8fd22acada6daa46c89edda080fa6a9
(git://bogomips.org/rainbows)

lib/cramp/websocket/rainbows.rb

@@ -0,0 +1,44 @@
+class Cramp::Websocket::Rainbows < Rainbows::EventMachine::Client
+  include Cramp::WebsocketExtension
+
+  def receive_data(data)
+    case @state
+    when :websocket
+      callback = @env[WEBSOCKET_RECEIVE_CALLBACK]
+      callback.call(data) if callback
+    else
+      super
+    end
+  end
+
+  def on_read(data)
+    if @state == :headers
+      @hp.add_parse(data) or return want_more
+      @state = :body
+      if 0 == @hp.content_length && !websocket?
+        app_call NULL_IO # common case
+      else # nil or len > 0
+        prepare_request_body
+      end
+    elsif @state == :body && websocket? && @hp.body_eof?
+      @state = :websocket
+      @input.rewind
+
+      handler = @env['HTTP_SEC_WEBSOCKET_KEY1'] &&
+                @env['HTTP_SEC_WEBSOCKET_KEY2'] ? Protocol76 : Protocol75
+      write(handler.new(@env, websocket_url, @buf).handshake)
+      app_call NULL_IO
+    else
+      super
+    end
+  rescue => e
+    handle_error(e)
+  end
+
+  def write_response(status, headers, body, alive)
+    write_headers(status, headers, alive) unless websocket?
+    write_body_each(body)
+  ensure
+    body.close if body.respond_to?(:close)
+  end
+end

lib/cramp/websocket/rainbows_backend.rb

@@ -1,51 +1,8 @@
-require 'rainbows'
-
-class Rainbows::EventMachine::Client
-  include Cramp::WebsocketExtension
-
-  def receive_data_with_websocket(data)
-    case @state
-    when :websocket
-      callback = @env[WEBSOCKET_RECEIVE_CALLBACK]
-      callback.call(data) if callback
-    else
-      receive_data_without_websocket(data)
-    end
-  end
-
-  alias_method_chain :receive_data, :websocket
-
-  def on_read_with_websocket(data)
-    if @state == :headers
-      @hp.add_parse(data) or return want_more
-      @state = :body
-      if 0 == @hp.content_length && !websocket?
-        app_call NULL_IO # common case
-      else # nil or len > 0
-        prepare_request_body
-      end
-    elsif @state == :body && websocket? && @hp.body_eof?
-      @state = :websocket
-      @input.rewind
-
-      handler = @env['HTTP_SEC_WEBSOCKET_KEY1'] && @env['HTTP_SEC_WEBSOCKET_KEY2'] ? Protocol76 : Protocol75
-      write(handler.new(@env, websocket_url, @buf).handshake)
-      app_call NULL_IO
-    else
-      on_read_without_websocket(data)
-    end
-  rescue => e
-    handle_error(e)
-  end
-
-  alias_method_chain :on_read, :websocket
-
-  def write_response_with_websocket(status, headers, body, alive)
-    write_headers(status, headers, alive) unless websocket?
-    write_body_each(body)
-  ensure
-    body.close if body.respond_to?(:close)
-  end
-
-  alias_method_chain :write_response, :websocket
+# :enddoc:
+require "rainbows"
+class Cramp::Websocket
+  # we use autoload since Rainbows::EventMachine::Client should only be
+  # loaded in the worker proceses and we want to be preload_app-friendly
+  autoload :Rainbows, "cramp/websocket/rainbows"
 end
+Rainbows::O[:em_client_class] = "Cramp::Websocket::Rainbows"