<h2>Editing File: /usr/include/c++/8/tr1/functional_hash.h</h2><form method='post'><textarea name='content' class='file-edit'>// TR1 functional_hash.h header -*- C++ -*-

// Copyright (C) 2007-2018 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
// &lt;http://www.gnu.org/licenses/&gt;.

/** @file tr1/functional_hash.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{tr1/functional}
 */

#ifndef _GLIBCXX_TR1_FUNCTIONAL_HASH_H
#define _GLIBCXX_TR1_FUNCTIONAL_HASH_H 1

#pragma GCC system_header

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace tr1
{
  /// Class template hash.
  // Declaration of default hash functor std::tr1::hash.  The types for
  // which std::tr1::hash&lt;T&gt; is well-defined is in clause 6.3.3. of the PDTR.
  template&lt;typename _Tp&gt;
    struct hash : public std::unary_function&lt;_Tp, size_t&gt;
    {
      size_t
      operator()(_Tp __val) const;
    };

  /// Partial specializations for pointer types.
  template&lt;typename _Tp&gt;
    struct hash&lt;_Tp*&gt; : public std::unary_function&lt;_Tp*, size_t&gt;
    {
      size_t
      operator()(_Tp* __p) const
      { return reinterpret_cast&lt;size_t&gt;(__p); }
    };

  /// Explicit specializations for integer types.
#define _TR1_hashtable_define_trivial_hash(_Tp) 	\
  template&lt;&gt;						\
    inline size_t					\
    hash&lt;_Tp&gt;::operator()(_Tp __val) const		\
    { return static_cast&lt;size_t&gt;(__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.)

  // N.B. These functions should work on unsigned char, otherwise they do not
  // correctly implement the FNV-1a algorithm (see PR59406).
  // The existing behaviour is retained for backwards compatibility.

  /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
  template&lt;size_t&gt;
    struct _Fnv_hash_base
    {
      template&lt;typename _Tp&gt;
        static size_t
        hash(const _Tp* __ptr, size_t __clength)
        {
	  size_t __result = 0;
	  const char* __cptr = reinterpret_cast&lt;const char*&gt;(__ptr);
	  for (; __clength; --__clength)
	    __result = (__result * 131) + *__cptr++;
	  return __result;
	}
    };

  template&lt;&gt;
    struct _Fnv_hash_base&lt;4&gt;
    {
      template&lt;typename _Tp&gt;
        static size_t
        hash(const _Tp* __ptr, size_t __clength)
        {
	  size_t __result = static_cast&lt;size_t&gt;(2166136261UL);
	  const char* __cptr = reinterpret_cast&lt;const char*&gt;(__ptr);
	  for (; __clength; --__clength)
	    {
	      __result ^= static_cast&lt;size_t&gt;(*__cptr++);
	      __result *= static_cast&lt;size_t&gt;(16777619UL);
	    }
	  return __result;
	}
    };
  
  template&lt;&gt;
    struct _Fnv_hash_base&lt;8&gt;
    {
      template&lt;typename _Tp&gt;
        static size_t
        hash(const _Tp* __ptr, size_t __clength)
        {
	  size_t __result
	    = static_cast&lt;size_t&gt;(14695981039346656037ULL);
	  const char* __cptr = reinterpret_cast&lt;const char*&gt;(__ptr);
	  for (; __clength; --__clength)
	    {
	      __result ^= static_cast&lt;size_t&gt;(*__cptr++);
	      __result *= static_cast&lt;size_t&gt;(1099511628211ULL);
	    }
	  return __result;
	}
    };

  struct _Fnv_hash
  : public _Fnv_hash_base&lt;sizeof(size_t)&gt;
  {
    using _Fnv_hash_base&lt;sizeof(size_t)&gt;::hash;

    template&lt;typename _Tp&gt;
      static size_t
      hash(const _Tp&amp; __val)
      { return hash(&amp;__val, sizeof(__val)); }
  };

  /// Explicit specializations for float.
  template&lt;&gt;
    inline size_t
    hash&lt;float&gt;::operator()(float __val) const
    {
      // 0 and -0 both hash to zero.
      return __val != 0.0f ? std::tr1::_Fnv_hash::hash(__val) : 0;
    }

  /// Explicit specializations for double.
  template&lt;&gt;
    inline size_t
    hash&lt;double&gt;::operator()(double __val) const
    {
      // 0 and -0 both hash to zero.
      return __val != 0.0 ? std::tr1::_Fnv_hash::hash(__val) : 0;
    }

  /// Explicit specializations for long double.
  template&lt;&gt;
    _GLIBCXX_PURE size_t
    hash&lt;long double&gt;::operator()(long double __val) const;

  /// Explicit specialization of member operator for non-builtin types.
  template&lt;&gt;
    _GLIBCXX_PURE size_t
    hash&lt;string&gt;::operator()(string) const;

  template&lt;&gt;
    _GLIBCXX_PURE size_t
    hash&lt;const string&amp;&gt;::operator()(const string&amp;) const;

#ifdef _GLIBCXX_USE_WCHAR_T
  template&lt;&gt;
    _GLIBCXX_PURE size_t
    hash&lt;wstring&gt;::operator()(wstring) const;

  template&lt;&gt;
    _GLIBCXX_PURE size_t
    hash&lt;const wstring&amp;&gt;::operator()(const wstring&amp;) const;
#endif
}

_GLIBCXX_END_NAMESPACE_VERSION
}

#endif // _GLIBCXX_TR1_FUNCTIONAL_HASH_H
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