diagnostic-context.hpp

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/*
  DIAGNOSTIC-CONTEXT.hpp  -  thread local stack for explicitly collecting diagnostic context info

  Copyright (C)         Lumiera.org
    2010,               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_DIAGNOSTIC_CONTEXT_H
#define LIB_DIAGNOSTIC_CONTEXT_H


#include "lib/error.hpp"
#include "lib/nocopy.hpp"



namespace lib {
  
  
  
  
  template<typename VAL>
  class DiagnosticContext
    : util::NonCopyable
    {
      using ValSequence = std::vector<VAL>;
      
      const VAL value_;
      DiagnosticContext * const prev_;
      
      static DiagnosticContext* &
      current()
        {
          thread_local DiagnosticContext* accessPoint;
          return accessPoint;
        }
      
      
    public:
      DiagnosticContext(VAL const& value_to_log = VAL())
        : value_{value_to_log}
        , prev_{current()}
        {
          current() = this;
        }
      
     ~DiagnosticContext()
        {
          ASSERT (this == current());
          current() = prev_;
        }
      
      
      operator VAL const&()  
        {
          return value_;
        }
      
      static DiagnosticContext&
      access ()
        {
          DiagnosticContext* innermost = current();
          if (!innermost)
            throw lumiera::error::Logic ("Accessing Diagnostic context out of order; "
                                         "an instance should have been created within "
                                         "an enclosing scope");
          return *innermost;
        }
      
      
      static ValSequence
      extractStack()
        {
          ValSequence loggedValues;
          DiagnosticContext* next = current();
          while (next)
            {
              loggedValues.push_back (*next);
              next = next->prev_;
            }
          return loggedValues;
        }
    };
  
  
  
  
  
} // namespace lib
#endif