note
   description:
      "A wrapper factory that "
   copyright:
      "[
               Copyright (C) 2006-2017: , 2007 Paolo Redaelli
               This library is free software; you can redistribute it and/or
               modify it under the terms of the GNU Lesser General Public License
               as published by the Free Software Foundation; either version 2.1 of
               the License, or (at your option) any later version.

               This library is distributed in the hope that it will be useful, but
               WITHOUT ANY WARRANTY; without even the implied warranty of
               MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
               Lesser General Public License for more details.

               You should have received a copy of the GNU Lesser General Public
               License along with this library; if not, write to the Free Software
               Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
               02110-1301 USA
         ]"
deferred class CACHING_FACTORY[ITEM_ -> WRAPPER]
   -- A factory that retrieves wrappers from a cache, usually a
   -- dictionary; used to implement collection of wrapped objects

inherit
   WRAPPER_FACTORY[ITEM_]

feature {WRAPPER, WRAPPER_HANDLER}
   wrappers: HASHED_DICTIONARY[ITEM_, POINTER]
         -- Dictionary cache storing wrappers; usually used in
         -- WRAPPER_COLLECTIONs or WRAPPER_DICTIONARY
         -- Key is the address (pointer) to the wrapped C structure,
         -- value is the corresponding Eiffel wrapper. This way you
         -- can get back an already-created Eiffel wrapper. Heirs of
         -- SHARED_C_STRUCT, i.e. G_OBJECT could provide alternative
         -- implementation that will not rely on this dictionary.
      deferred
      end

   wrapper (a_pointer: POINTER): ITEM_
      deferred
      ensure then
         wrappers.has(a_pointer)
      end

invariant
   dictionary_not_void: wrappers /= Void

end -- class CACHING_FACTORY