Work in progres, please take a look and give early feedback if this is the way we want to structure…

lib/io/system.dart

 // Copyright (c) 2014, the Fletch project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 library system;
 
 import 'dart:ffi';
 import 'dart:io';
 import 'dart:typed_data';
 
@@ skipping 70 matching lines @@
   int setBlocking(int fd, bool blocking);
   int setReuseaddr(int fd);
 
   static int eventHandler = _getEventHandler();
   @fletch.native external static int _getEventHandler();
   @fletch.native external static int _incrementPortRef(Port port);
 }
 
 final int hostWordSize = Foreign.bitsPerMachineWord ~/ 8;
 
-class Struct extends Foreign {
+class Struct extends ForeignMemory {
   final wordSize;
 
   Struct(int fields)
       : this.wordSize = hostWordSize,
         super.allocated(fields * hostWordSize);
 
   Struct.finalize(int fields)
       : this.wordSize = hostWordSize,
         super.allocatedFinalize(fields * hostWordSize);
 
@@ skipping 38 matching lines @@
 
 class Struct64 extends Struct {
   Struct64(int fields) : super.withWordSize(fields, 8);
   Struct64.finalize(int fields) : super.withWordSizeFinalize(fields, 8);
 }
 
 class _InternetAddress extends InternetAddress {
   final List<int> _bytes;
   _InternetAddress(this._bytes);
 }