------------------------------------------------------------------------------
--                                                                          --
--                            Matreshka Project                             --
--                                                                          --
--         Localization, Internationalization, Globalization for Ada        --
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--                        Runtime Library Component                         --
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------------------------------------------------------------------------------
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-- Copyright © 2011, Vadim Godunko <vgodunko@gmail.com>                     --
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------------------------------------------------------------------------------
--  $Revision: 1811 $ $Date: 2011-06-20 00:30:28 +0400 (Mon, 20 Jun 2011) $
------------------------------------------------------------------------------

package body League.Holders.Generic_Holders is

   -----------------
   -- Constructor --
   -----------------

   overriding function Constructor
    (Is_Empty : not null access Boolean) return Element_Container
   is
      pragma Assert (Is_Empty.all);

   begin
      return
       (Counter  => <>,
        Is_Empty => Is_Empty.all,
        Value    => <>);
   end Constructor;

   -------------
   -- Element --
   -------------

   function Element (Self : Holder) return Element_Type is
   begin
      if Self.Data.all not in Element_Container then
         raise Constraint_Error with "invalid type of value";
      end if;

      if Self.Data.Is_Empty then
         raise Constraint_Error with "value is empty";
      end if;

      return Element_Container'Class (Self.Data.all).Value;
   end Element;

   ---------------------
   -- Replace_Element --
   ---------------------

   procedure Replace_Element (Self : in out Holder; To : Element_Type) is
   begin
      if Self.Data.all not in Element_Container then
         raise Constraint_Error with "invalid type of value";
      end if;

      --  XXX This subprogram can be improved to reuse shared segment when
      --  possible.

      Dereference (Self.Data);
      Self.Data :=
        new Element_Container'(Counter  => <>, Is_Empty => False, Value => To);
   end Replace_Element;

   ---------------
   -- To_Holder --
   ---------------

   function To_Holder (Item : Element_Type) return Holder is
   begin
      return
       (Ada.Finalization.Controlled with
          new Element_Container'
               (Counter  => <>, Is_Empty => False, Value => Item));
   end To_Holder;

end League.Holders.Generic_Holders;
