create a context with a Ruby object as its scope

lib/v8.rb

@@ -19,4 +19,5 @@ require 'v8/access/indices'
 require 'v8/access'
 require 'v8/context'
 require 'v8/object'
-require 'v8/array'
+require 'v8/array'
+require 'v8/util/weakcell'

lib/v8/context.rb

@@ -2,10 +2,24 @@ module V8
   class Context
     attr_reader :native, :conversion, :access
 
-    def initialize
-      @native = V8::C::Context::New()
+    def initialize(options = {})
       @conversion = Conversion.new
       @access = Access.new
+      if global = options[:with]
+        V8::C::Locker() do
+          V8::C::HandleScope() do
+            tmp = V8::C::Context::New()
+            tmp.Enter()
+            global_template = global.to_v8_template
+            tmp.Exit()
+            @native = V8::C::Context::New(nil, global_template)
+            enter { link global, @native.Global() }
+          end
+        end
+      else
+        @native = V8::C::Context::New()
+      end
+      yield self if block_given?
     end
 
     def to_ruby(v8_object)

lib/v8/conversion/object.rb

@@ -1,11 +1,15 @@
 class V8::Conversion
   module Object
     def to_v8
-      template = V8::C::ObjectTemplate::New()
-      template.SetNamedPropertyHandler(Get, Set, nil, nil, nil, V8::C::External::New(self))
-      instance = template.NewInstance()
-      V8::Context.link self, instance
-      return instance
+      object = to_v8_template.NewInstance()
+      V8::Context.link self, object
+      return object
+    end
+
+    def to_v8_template
+      V8::C::ObjectTemplate::New().tap do |template|
+        template.SetNamedPropertyHandler(Get, Set, nil, nil, nil, V8::C::External::New(self))
+      end
     end
 
     def to_ruby

lib/v8/util/weakcell.rb

@@ -0,0 +1,32 @@
+require 'weakref'
+module V8
+  module Util
+    module Weakcell
+      def weakcell(name, &block)
+        unless storage = instance_variable_get("@#{name}")
+          storage = instance_variable_set("@#{name}", Storage.new)
+        end
+        storage.access(&block)
+      end
+      class Storage
+        def access(&block)
+          if @ref
+            @ref.__getobj__
+          else
+            populate(block)
+          end
+        rescue RefError
+          populate(block)
+        end
+
+        private
+
+        def populate(block)
+          occupant = block.call()
+          @ref = WeakRef.new(occupant)
+          return occupant
+        end
+      end
+    end
+  end
+end