/storage/packages/gcc/5.3.0/include/c++/5.3.0/bits/functional_hash.h

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

// Copyright (C) 2007-2015 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.

 *  Do not attempt to use it directly. @headername{functional}

 */

#ifndef _FUNCTIONAL_HASH_H

#define _FUNCTIONAL_HASH_H 1

#pragma GCC system_header

#include <bits/hash_bytes.h>

namespace std _GLIBCXX_VISIBILITY(default)

{

_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /** @defgroup hashes Hashes

   *  @ingroup functors

   *

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

   *

   *  @{

   */

  template<typename _Result, typename _Arg>

    struct __hash_base

    {

      typedef _Result     result_type;

      typedef _Arg      argument_type;

    };

  /// Primary class template hash.

  template<typename _Tp>

    struct hash;

  /// Partial specializations for pointer types.

  template<typename _Tp>

    struct hash<_Tp*> : public __hash_base<size_t, _Tp*>

    {

      size_t

      operator()(_Tp* __p) const noexcept

      { return reinterpret_cast<size_t>(__p); }

    };

  // Explicit specializations for integer types.

#define _Cxx_hashtable_define_trivial_hash(_Tp) 	\

  template<>						\

    struct hash<_Tp> : public __hash_base<size_t, _Tp>  \

    {                                                   \

      size_t                                            \

      operator()(_Tp __val) const noexcept              \

      { 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

  struct _Hash_impl

  {

    static size_t

    hash(const void* __ptr, size_t __clength,

	 size_t __seed = static_cast<size_t>(0xc70f6907UL))

    { return _Hash_bytes(__ptr, __clength, __seed); }

    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); }

  };

  struct _Fnv_hash_impl

  {

    static size_t

    hash(const void* __ptr, size_t __clength,

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

    { return _Fnv_hash_bytes(__ptr, __clength, __seed); }

    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<>

    struct hash<float> : public __hash_base<size_t, float>

    {

      size_t

      operator()(float __val) const noexcept

      {

	// 0 and -0 both hash to zero.

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

      }

    };

  /// Specialization for double.

  template<>

    struct hash<double> : public __hash_base<size_t, double>

    {

      size_t

      operator()(double __val) const noexcept

      {

	// 0 and -0 both hash to zero.

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

      }

    };

  /// Specialization for long double.

  template<>

    struct hash<long double>

    : public __hash_base<size_t, long double>

    {

      _GLIBCXX_PURE size_t

      operator()(long double __val) const noexcept;

    };

  // @} group hashes

  // Hint about performance of hash functor. If not fast the hash based

  // containers will cache the hash code.

  // Default behavior is to consider that hasher are fast unless specified

  // otherwise.

  template<typename _Hash>

    struct __is_fast_hash : public std::true_type

    { };

  template<>

    struct __is_fast_hash<hash<long double>> : public std::false_type

    { };

_GLIBCXX_END_NAMESPACE_VERSION

} // namespace

#endif // _FUNCTIONAL_HASH_H