add initial EM Deferrable API

examples/eventmachine.rb

@@ -0,0 +1,21 @@
+# encoding: utf-8
+
+$LOAD_PATH.unshift 'lib'
+
+require 'rubygems'
+require 'eventmachine'
+require 'mysql2/em'
+
+EM.run do
+  client1 = Mysql2::EM::Client.new
+  defer1 = client1.query "SELECT sleep(3) as first_query"
+  defer1.callback do |result|
+    puts "Result: #{result.to_a.inspect}"
+  end
+
+  client2 = Mysql2::EM::Client.new
+  defer2 = client2.query "SELECT sleep(1) second_query"
+  defer2.callback do |result|
+    puts "Result: #{result.to_a.inspect}"
+  end
+end

lib/mysql2/em.rb

@@ -0,0 +1,33 @@
+# encoding: utf-8
+
+require 'eventmachine' unless defined? EventMachine
+require 'mysql2' unless defined? Mysql2
+
+module Mysql2
+  module EM
+    class Client < ::Mysql2::Client
+      module Watcher
+        def initialize(client, deferable)
+          @client = client
+          @deferable = deferable
+        end
+
+        def notify_readable
+          begin
+            @deferable.succeed(@client.async_result)
+          rescue Exception => e
+            @deferable.fail(e)
+          end
+          detach
+        end
+      end
+
+      def query(sql, opts={})
+        super(sql, opts.merge(:async => true))
+        deferable = ::EM::DefaultDeferrable.new
+        ::EM.watch(self.socket, Watcher, self, deferable).notify_readable = true
+        deferable
+      end
+    end
+  end
+end

spec/em/em_spec.rb

@@ -0,0 +1,26 @@
+# encoding: UTF-8
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper.rb')
+require 'mysql2/em'
+
+describe Mysql2::EM::Client do
+  it "should support async queries" do
+    results = []
+    EM.run do
+      client1 = Mysql2::EM::Client.new
+      defer1 = client1.query "SELECT sleep(0.05) as first_query"
+      defer1.callback do |result|
+        results << result.first
+        EM.stop_event_loop
+      end
+
+      client2 = Mysql2::EM::Client.new
+      defer2 = client2.query "SELECT sleep(0.025) second_query"
+      defer2.callback do |result|
+        results << result.first
+      end
+    end
+    
+    results[0].keys.should include("second_query")
+    results[1].keys.should include("first_query")
+  end
+end