text: // TR1 functional -*- C++ -*-
  
  // Copyright (C) 2007, 2008 Free Software Foundation, Inc.
  //
  // This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
  // any later version.
  
  // This library 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 library; see the file COPYING.  If not, write to the Free
  // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  // USA.
  
  // As a special exception, you may use this file as part of a free software
  // library without restriction.  Specifically, if other files instantiate
  // templates or use macros or inline functions from this file, or you compile
  // this file and link it with other files to produce an executable, this
  // file does not by itself cause the resulting executable to be covered by
  // the GNU General Public License.  This exception does not however
  // invalidate any other reasons why the executable file might be covered by
  // the GNU General Public License.
  
  /** @file tr1_impl/functional_hash.h
   *  This is an internal header file, included by other library headers.
   *  You should not attempt to use it directly.
   */
  
  namespace std
  {
  _GLIBCXX_BEGIN_NAMESPACE_TR1
  
    /// Class template hash.
    // Declaration of default hash functor std::tr1::hash.  The types for
    // which std::tr1::hash<T> is well-defined is in clause 6.3.3. of the PDTR.
    template<typename _Tp>
      struct hash : public std::unary_function<_Tp, size_t>
      {
        size_t
        operator()(_Tp __val) const;
      };
  
    /// Partial specializations for pointer types.
    template<typename _Tp>
      struct hash<_Tp*> : public std::unary_function<_Tp*, size_t>
      {
        size_t
        operator()(_Tp* __p) const
        { return reinterpret_cast<size_t>(__p); }
      };
  
    /// Explicit specializations for integer types.
  #define _TR1_hashtable_define_trivial_hash(_Tp) 	\
    template<>						\
      inline size_t					\
      hash<_Tp>::operator()(_Tp __val) const		\
      { return static_cast<size_t>(__val); }
  
    _TR1_hashtable_define_trivial_hash(bool);
    _TR1_hashtable_define_trivial_hash(char);
    _TR1_hashtable_define_trivial_hash(signed char);
    _TR1_hashtable_define_trivial_hash(unsigned char);
    _TR1_hashtable_define_trivial_hash(wchar_t);
    _TR1_hashtable_define_trivial_hash(short);
    _TR1_hashtable_define_trivial_hash(int);
    _TR1_hashtable_define_trivial_hash(long);
    _TR1_hashtable_define_trivial_hash(long long);
    _TR1_hashtable_define_trivial_hash(unsigned short);
    _TR1_hashtable_define_trivial_hash(unsigned int);
    _TR1_hashtable_define_trivial_hash(unsigned long);
    _TR1_hashtable_define_trivial_hash(unsigned long long);
  
  #undef _TR1_hashtable_define_trivial_hash
  
    // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
    // (Used by the next specializations of std::tr1::hash.)
  
    /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
    template<size_t = sizeof(size_t)>
      struct _Fnv_hash
      {
        static size_t
        hash(const char* __first, size_t __length)
        {
  	size_t __result = 0;
  	for (; __length > 0; --__length)
  	  __result = (__result * 131) + *__first++;
  	return __result;
        }
      };
  
    template<>
      struct _Fnv_hash<4>
      {
        static size_t
        hash(const char* __first, size_t __length)
        {
  	size_t __result = static_cast<size_t>(2166136261UL);
  	for (; __length > 0; --__length)
  	  {
  	    __result ^= static_cast<size_t>(*__first++);
  	    __result *= static_cast<size_t>(16777619UL);
  	  }
  	return __result;
        }
      };
    
    template<>
      struct _Fnv_hash<8>
      {
        static size_t
        hash(const char* __first, size_t __length)
        {
  	size_t __result =
  	  static_cast<size_t>(14695981039346656037ULL);
  	for (; __length > 0; --__length)
  	  {
  	    __result ^= static_cast<size_t>(*__first++);
  	    __result *= static_cast<size_t>(1099511628211ULL);
  	  }
  	return __result;
        }
      };
  
    /// Explicit specializations for float.
    template<>
      inline size_t
      hash<float>::operator()(float __val) const
      {
        size_t __result = 0;
        
        // 0 and -0 both hash to zero.
        if (__val != 0.0f)
  	__result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
  				     sizeof(__val));
        return __result;
      };
  
    /// Explicit specializations for double.
    template<>
      inline size_t
      hash<double>::operator()(double __val) const
      {
  	size_t __result = 0;
  
  	// 0 and -0 both hash to zero.
  	if (__val != 0.0)
  	  __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
  				       sizeof(__val));
  	return __result;
      };
  
    /// Explicit specializations for long double.
    template<>
      size_t
      hash<long double>::operator()(long double __val) const;
  
    /// Explicit specialization of member operator for non-builtin types.
    template<>
      size_t
      hash<string>::operator()(string) const;
  
    template<>
      size_t
      hash<const string&>::operator()(const string&) const;
  
  #ifdef _GLIBCXX_USE_WCHAR_T
    template<>
      size_t
      hash<wstring>::operator()(wstring) const;
  
    template<>
      size_t
      hash<const wstring&>::operator()(const wstring&) const;
  #endif
  
  _GLIBCXX_END_NAMESPACE_TR1
  }
  