121 lines
3.5 KiB
C++
121 lines
3.5 KiB
C++
/*
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HA-ID.hpp - generic hash based and hierarchically typed ID
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Copyright (C) Lumiera.org
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2009, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file ha-id.hpp
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** A template for generating hash based ID tags carrying compile-time type info.
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** While the actual storage is assumed to be based on a POD, the type info is crucial
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** to circumvent the problems with an "object" base class. Frequently, the need to
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** manage some objects in a central facility drives us to rely on a common base class,
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** irrespective of an actual common denominator in the semantics of the objects to
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** be managed within this collection. Typically this results in this common base class
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** being almost worthless as an API or interface, causing lots of type casts when using
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** such a common object management facility. Passing additional context or API information
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** on a metaprogramming level through the management interface helps avoiding these
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** shortcomings.
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**
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** Here we build an ID facility with the following properties:
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** - based on a configurable storage/implementation of the actual hash or index code.
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** - tied to a specific hierarchy of objects (template parameter "BA")
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** - providing an additional template parameter to pass the desired type info
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** - establishing an type hierarchy relation between ID template instances, such that
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** the IDs typed to the derived/specialised objects can stand-in for the generic
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** ID typed to the base class.
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** - providing a Mixin, which allows any hierarchy to use this facility without
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** much code duplication.
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**
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** @see HashIndexed_test
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** @see Placement usage example
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**
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*/
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#ifndef LIB_HA_ID_H
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#define LIB_HA_ID_H
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//#include "lib/util.hpp"
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//#include <tr1/memory>
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#include <cstdlib>
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namespace lib {
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// using std::tr1::shared_ptr;
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using std::rand;
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struct LuidH
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{
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long dummy_;
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LuidH() : dummy_(rand()) {}
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};
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template<class BA>
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struct HashIndexed
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{
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/**
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* Generic hash based and hierarchically typed ID
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* @todo WIP maybe also usable for assets?
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*/
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template<typename T>
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struct Id;
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struct ID : LuidH
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{
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ID () : LuidH () {}
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ID (BA const& ref) : LuidH (ref.getID()) {}
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};
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template<typename T>
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struct Id : ID
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{
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Id () : ID () {}
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Id (T const& ref) : ID (ref) {}
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};
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ID const& getID() const
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{
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return id_;
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}
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void resetID(HashIndexed const& ref)
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{
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this->id_ = ref.getID();
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}
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void resetID(ID const& ref) ///< @todo this mutator should be removed in the final version to keep the actual hash opaque
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{
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this->id_.dummy_ = ref.dummy_;
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}
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private:
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ID id_;
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};
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} // namespace lib
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#endif
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