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// functional_hash.h header -*- C++ -*-

// Copyright (C) 2007, 2008, 2009, 2010 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 3, 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.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

/** @file bits/functional_hash.h

 *  This is an internal header file, included by other library headers.

 *  You should not attempt to use it directly.

 */

#ifndef _FUNCTIONAL_HASH_H

#define _FUNCTIONAL_HASH_H 1

#pragma GCC system_header

#include <cstddef>

#include <bits/stl_function.h>

namespace std

{

  /** @defgroup hashes Hashes

   *  @ingroup functors

   *

   *   Hashing functors taking a variable type and returning a @c std::size_t.

   *

   *  @{

   */

  /// Primary class template hash.

  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 _Cxx_hashtable_define_trivial_hash(_Tp)         \

  template<>                                            \

    inline size_t                                       \

    hash<_Tp>::operator()(_Tp __val) const              \

    { return static_cast<size_t>(__val); }

  /// Explicit specialization for bool.

  _Cxx_hashtable_define_trivial_hash(bool);

  /// Explicit specialization for char.

  _Cxx_hashtable_define_trivial_hash(char);

  /// Explicit specialization for signed char.

  _Cxx_hashtable_define_trivial_hash(signed char);

  /// Explicit specialization for unsigned char.

  _Cxx_hashtable_define_trivial_hash(unsigned char);

  /// Explicit specialization for wchar_t.

  _Cxx_hashtable_define_trivial_hash(wchar_t);

  /// Explicit specialization for char16_t.

  _Cxx_hashtable_define_trivial_hash(char16_t);

  /// Explicit specialization for char32_t.

  _Cxx_hashtable_define_trivial_hash(char32_t);

  /// Explicit specialization for short.

  _Cxx_hashtable_define_trivial_hash(short);

  /// Explicit specialization for int.

  _Cxx_hashtable_define_trivial_hash(int);

  /// Explicit specialization for long.

  _Cxx_hashtable_define_trivial_hash(long);

  /// Explicit specialization for long long.

  _Cxx_hashtable_define_trivial_hash(long long);

  /// Explicit specialization for unsigned short.

  _Cxx_hashtable_define_trivial_hash(unsigned short);

  /// Explicit specialization for unsigned int.

  _Cxx_hashtable_define_trivial_hash(unsigned int);

  /// Explicit specialization for unsigned long.

  _Cxx_hashtable_define_trivial_hash(unsigned long);

  /// Explicit specialization for unsigned long long.

  _Cxx_hashtable_define_trivial_hash(unsigned long long);

#undef _Cxx_hashtable_define_trivial_hash

  // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)

  // Dummy generic implementation (for sizeof(size_t) != 4, 8).

  template<size_t>

    struct _Fnv_hash_base

    {

      template<typename _Tp>

        static size_t

        hash(const _Tp* __ptr, size_t __clength, size_t __hash = 0)

        {

          const char* __cptr = reinterpret_cast<const char*>(__ptr);

          for (; __clength; --__clength)

            __hash = (__hash * 131) + *__cptr++;

          return __hash;

        }

    };

  template<>

    struct _Fnv_hash_base<4>

    {

      template<typename _Tp>

        static size_t

        hash(const _Tp* __ptr, size_t __clength,

             size_t __hash = static_cast<size_t>(2166136261UL))

        {

          const char* __cptr = reinterpret_cast<const char*>(__ptr);

          for (; __clength; --__clength)

            {

              __hash ^= static_cast<size_t>(*__cptr++);

              __hash *= static_cast<size_t>(16777619UL);

            }

          return __hash;

        }

    };

  template<>

    struct _Fnv_hash_base<8>

    {

      template<typename _Tp>

        static size_t

        hash(const _Tp* __ptr, size_t __clength,

             size_t __hash = static_cast<size_t>(14695981039346656037ULL))

        {

          const char* __cptr = reinterpret_cast<const char*>(__ptr);

          for (; __clength; --__clength)

            {

              __hash ^= static_cast<size_t>(*__cptr++);

              __hash *= static_cast<size_t>(1099511628211ULL);

            }

          return __hash;

        }

    };

    struct _Fnv_hash

    : public _Fnv_hash_base<sizeof(size_t)>

    {

      using _Fnv_hash_base<sizeof(size_t)>::hash;

      template<typename _Tp>

        static size_t

        hash(const _Tp& __val)

        { return hash(&__val, sizeof(__val)); }

      template<typename _Tp>

        static size_t

        __hash_combine(const _Tp& __val, size_t __hash)

        { return hash(&__val, sizeof(__val), __hash); }

    };

  /// Specialization for float.

  template<>

    inline size_t

    hash<float>::operator()(float __val) const

    {

      // 0 and -0 both hash to zero.

      return __val != 0.0f ? std::_Fnv_hash::hash(__val) : 0;

    }

  /// Specialization for double.

  template<>

    inline size_t

    hash<double>::operator()(double __val) const

    {

      // 0 and -0 both hash to zero.

      return __val != 0.0 ? std::_Fnv_hash::hash(__val) : 0;

    }

  /// Specialization for long double.

  template<>

    _GLIBCXX_PURE size_t

    hash<long double>::operator()(long double __val) const;

  // @} group hashes

}

#endif // _FUNCTIONAL_HASH_H