handle.hpp

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/*
  HANDLE.hpp  -  opaque handle to an implementation entity, automatically managing lifecycle

   Copyright (C)
     2009,            Hermann Vosseler <Ichthyostega@web.de>

  **Lumiera** is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version. See the file COPYING for further details.

*/

#ifndef LIB_HANDLE_H
#define LIB_HANDLE_H

#include "lib/nobug-init.hpp"

#include <memory>
#include <utility>


namespace lib {
  
  using std::shared_ptr;
  using std::unique_ptr;
  using std::weak_ptr;
  using std::move;
  
  
  
  template<class IMP>
  class Handle
    {
    protected:
      typedef std::shared_ptr<IMP> SmPtr;
      
      SmPtr smPtr_;
      
    public:
      
      Handle()  = default;
      
      explicit
      Handle (IMP* imp)
        : smPtr_{imp}
        { }
      
                                 Handle (Handle const& r)          = default;
                                 Handle (Handle && rr)             = default;
      template<class Y> explicit Handle (shared_ptr<Y> const& r)   : smPtr_{r}         { }
      template<class Y> explicit Handle (shared_ptr<Y> && srr)     : smPtr_{move(srr)} { }
      template<class Y> explicit Handle (weak_ptr<Y> const& wr)    : smPtr_{wr}        { }
      template<class Y> explicit Handle (unique_ptr<Y> && urr)     : smPtr_{move(urr)} { }
      
                        Handle& operator=(Handle const& r)         = default;
                        Handle& operator=(Handle && rr)            = default;
      template<class Y> Handle& operator=(shared_ptr<Y> const& sr) { smPtr_ = sr;        return *this; }
      template<class Y> Handle& operator=(shared_ptr<Y> && srr)    { smPtr_ = move(srr); return *this; }
      template<class Y> Handle& operator=(unique_ptr<Y> && urr)    { smPtr_ = move(urr); return *this; }
      
      
      explicit operator bool()  const { return bool(smPtr_); }
      bool isValid()            const { return bool(smPtr_); }
      
      
      
      template<typename DEL>
      Handle&
      activate (IMP* impl, DEL whenDead)
        {
          smPtr_.reset (impl, whenDead);
          return *this;
        }
      
      Handle&
      activate(shared_ptr<IMP> const& impl)
        {
          smPtr_ = impl;
          return *this;
        }
      
      Handle&
      activate(shared_ptr<IMP> && impl)
        {
          smPtr_ = move (impl);
          return *this;
        }
      
      void close ()
        {
          smPtr_.reset();
        }
      
      
      
    protected:
      IMP&
      impl()  const
        {
          REQUIRE (smPtr_.get(), "Lifecycle-Error");
          return *(smPtr_.get());
        }
    };
  
  
} // namespace lib
#endif