message: added rewind()
diff: @@ -142,6 +142,13 @@ class Buffer {
  initWithNone();
  }
  + void rewind(ValueLength position) {
  + if (position >= _alloc) {
  + throw Exception(Exception::IndexOutOfBounds);
  + }
  + _pos = position;
  + }
  +
  void clear() {
  reset();
  if (_buffer != _local) {
  