tuple_hash.hh

// This file is a part of Aurelia.
// Copyright (C) 2010  Valentin David
// Copyright (C) 2010  University of Bergen
//
// 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 3 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, see <http://www.gnu.org/licenses/>.
#ifndef __TUPLE_HASH_HH
# define __TUPLE_HASH_HH

# include <tuple>
# include "mhash.hh"

namespace aurelia {
  template <typename T, size_t N = 0>
  struct get_hash {
  };

  template <typename... T, size_t N>
  struct get_hash<std::tuple<T...>, N> {
    static void make(size_t& hash, const std::tuple<T...>& t) {
      get_hash<std::tuple<T...>, N-1>::make(hash, t);
      hash = (hash << 11) | (hash >> 21);
      hash ^= mhash<typename std::tuple_element<N, std::tuple<T...> >::type>()
        (std::get<N>(t));
    }
  };

  template <typename... T>
  struct get_hash<std::tuple<T...>, 0u> {
    static void make(size_t& hash, const std::tuple<T...>& t) {
      hash = mhash<typename std::tuple_element<0, std::tuple<T...> >::type>()
        (std::get<0>(t));
    }
  };

}

namespace std {
  template <typename... T>
  struct hash<tuple<T...> >: public unary_function<tuple<T...>, size_t> {
    size_t operator()(const tuple<T...>& t) const {
      size_t hash = 0;
      aurelia::get_hash<tuple<T...>, tuple_size<tuple<T...> >::value-1>::make(hash, t);
      return hash;
    }
  };

  template <>
  struct hash<tuple<> >: public unary_function<tuple<>, size_t> {
    size_t operator()(const tuple<>& ) const {
      return 0;
    }
  };
}

#endif