removing those ugly slot index constants

The constants were bad enough,
but they were also at the wrong level

Now register level is defining mappings from
symbol names to indexes, by using the layout

lib/register/register_reference.rb

@@ -48,33 +48,66 @@ module Register
       RegisterReference.new( sym )
     end
 
-    MESSAGE_REGISTER = :r0
-    SELF_REGISTER = :r1
-    FRAME_REGISTER = :r2
-    NEW_MESSAGE_REGISTER = :r3
-
-    TMP_REGISTER = :r4
-
-    def self.self_reg
-      new SELF_REGISTER
-    end
-    def self.message_reg
-      new MESSAGE_REGISTER
-    end
-    def self.frame_reg
-      new FRAME_REGISTER
-    end
-    def self.new_message_reg
-      new NEW_MESSAGE_REGISTER
-    end
-    def self.tmp_reg
-      new TMP_REGISTER
-    end
-
     def sof_reference_name
       @symbol
     end
 
   end
 
+  MESSAGE_REGISTER = :r0
+  SELF_REGISTER = :r1
+  FRAME_REGISTER = :r2
+  NEW_MESSAGE_REGISTER = :r3
+
+  TMP_REGISTER = :r4
+
+  def self.self_reg
+    RegisterReference.new SELF_REGISTER
+  end
+  def self.message_reg
+    RegisterReference.new MESSAGE_REGISTER
+  end
+  def self.frame_reg
+    RegisterReference.new FRAME_REGISTER
+  end
+  def self.new_message_reg
+    RegisterReference.new NEW_MESSAGE_REGISTER
+  end
+  def self.tmp_reg
+    RegisterReference.new TMP_REGISTER
+  end
+
+  def self.get_slot from , index , to
+    index = resolve_index( from , index)
+    from = resolve_to_register from
+    to = resolve_to_register to
+    GetSlot.new( from , index , to)
+  end
+
+  def self.resolve_index( clazz_name , instance_name )
+    return instance_name unless instance_name.is_a? Symbol
+    real_name = "#{clazz_name}".capitalize.to_sym
+    clazz = Parfait::Space.object_space.get_class_by_name(real_name)
+    raise "Class name not given #{real_name}" unless clazz
+    index = clazz.object_layout.index_of( instance_name )
+    raise "Instance name=#{instance_name} not found on #{real_name}" unless index
+    return index
+  end
+
+  def self.resolve_to_register reference
+    register = reference
+    if reference.is_a? Symbol
+      case reference
+      when :message
+        register = message_reg
+      when :self
+        register = self_reg
+      when :frame
+        register = frame_reg
+      else
+        raise "not recognized register reference #{reference}"
+      end
+    end
+    return register
+  end
 end