allocator-handle.hpp

Go to the documentation of this file.

/*
  ALLOCATOR-HANDLE.hpp  -  front-end handle for custom allocation schemes

  Copyright (C)         Lumiera.org
    2023,               Hermann Vosseler <Ichthyostega@web.de>

  This program 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.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#ifndef LIB_ALLOCATOR_HANDLE_H
#define LIB_ALLOCATOR_HANDLE_H

#include "lib/error.hpp"

#include <cstddef>
#include <utility>
#include <list>



namespace lib {
  
  
  template<typename TY>
  class AllocatorHandle
    {
      struct Allocation
        {
          alignas(TY)
            std::byte buf_[sizeof(TY)];
          
          template<typename...ARGS>
          TY&
          create (ARGS&& ...args)
            {
              return *new(&buf_) TY {std::forward<ARGS> (args)...};
            }
          
          TY&
          access()
            {
              return * std::launder (reinterpret_cast<TY*> (&buf_));
            }
          void
          discard() 
            {
              access().~TY();
            }
        };
      
      std::list<Allocation> storage_;
      
    public:
      template<typename...ARGS>
      TY&
      operator() (ARGS&& ...args)
        {                  // EX_STRONG
          auto pos = storage_.emplace (storage_.end());  
          try {
              return pos->create (std::forward<ARGS> (args)...);
            }
          catch(...)
            {
              storage_.erase (pos); // EX_FREE
              
              const char* errID = lumiera_error();
              ERROR (memory, "Allocation failed with unknown exception. "
                             "Lumiera errorID=%s", errID?errID:"??");
              throw;
            }
        }
      
     ~AllocatorHandle()
        try {
            for (auto& alloc : storage_)
              alloc.discard();
          }
        ERROR_LOG_AND_IGNORE (memory, "clean-up of custom AllocatorHandle")
    };
  
  
  
} // namespace lib
#endif /*LIB_ALLOCATOR_HANDLE_H*/