LUMIERA.clone/src/lib/symbol-impl.cpp

/*
  Symbol(impl)  -  helpers for working with literal string IDs 
 
  Copyright (C)         Lumiera.org
    2009,               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.
 
* *****************************************************/

/** @file symbol-impl.hpp
 ** Collection of helpers for working with the lib::Symbol.
 ** 
 ** @todo currently as of 9/09 this is more of a placeholder.
 ** And maybe a location for collecting small bits of implementation,
 ** which could be usable later for real Symbol and Literal datatypes.
 ** 
 ** lib::Symbol
 ** control::CommandRegistry for usage example of the hash function.
 ** 
 */



#include "lib/symbol.hpp"
extern "C" {
#include "lib/safeclib.h"
}

#include <boost/functional/hash.hpp>
#include <cstddef>

using std::size_t;
using boost::hash_combine;




namespace lib {
  
  /** equality on Symbol values is defined
   *  based on the content, not the address. */
  bool
  operator== (Literal sy1, Literal sy2)
  {
    return lumiera_strncmp (sy1,sy2, STRING_MAX_RELEVANT); 
  }
  
  
  /** generating a hash value, e.g. for hashtables.
      This function is intended to be picked up by ADL,
      and should be usable both with  \c std::tr1 and 
      \c <boost/functional/hash.hpp> . It is implemented
      similar as the boost::hash specialisation for std::string */
  size_t hash_value (Literal sym)
  {
    size_t hash=0;
    const char *pos = sym;
    size_t maxpos = STRING_MAX_RELEVANT;
    for ( ; pos && --maxpos; ++pos)
      hash_combine(hash, *pos);
    
    return hash;
  }
  
  
  
} // namespace lib