1  // Declarations for hash functions. -*- C++ -*-
       2  
       3  // Copyright (C) 2010-2023 Free Software Foundation, Inc.
       4  //
       5  // This file is part of the GNU ISO C++ Library.  This library is free
       6  // software; you can redistribute it and/or modify it under the
       7  // terms of the GNU General Public License as published by the
       8  // Free Software Foundation; either version 3, or (at your option)
       9  // any later version.
      10  
      11  // This library is distributed in the hope that it will be useful,
      12  // but WITHOUT ANY WARRANTY; without even the implied warranty of
      13  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14  // GNU General Public License for more details.
      15  
      16  // Under Section 7 of GPL version 3, you are granted additional
      17  // permissions described in the GCC Runtime Library Exception, version
      18  // 3.1, as published by the Free Software Foundation.
      19  
      20  // You should have received a copy of the GNU General Public License and
      21  // a copy of the GCC Runtime Library Exception along with this program;
      22  // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23  // <http://www.gnu.org/licenses/>.
      24  
      25  /** @file bits/hash_bytes.h
      26   *  This is an internal header file, included by other library headers.
      27   *  Do not attempt to use it directly. @headername{functional}
      28   */
      29  
      30  #ifndef _HASH_BYTES_H
      31  #define _HASH_BYTES_H 1
      32  
      33  #pragma GCC system_header
      34  
      35  #include <bits/c++config.h>
      36  
      37  namespace std
      38  {
      39  _GLIBCXX_BEGIN_NAMESPACE_VERSION
      40  
      41    // Hash function implementation for the nontrivial specialization.
      42    // All of them are based on a primitive that hashes a pointer to a
      43    // byte array. The actual hash algorithm is not guaranteed to stay
      44    // the same from release to release -- it may be updated or tuned to
      45    // improve hash quality or speed.
      46    size_t
      47    _Hash_bytes(const void* __ptr, size_t __len, size_t __seed);
      48  
      49    // A similar hash primitive, using the FNV hash algorithm. This
      50    // algorithm is guaranteed to stay the same from release to release.
      51    // (although it might not produce the same values on different
      52    // machines.)
      53    size_t
      54    _Fnv_hash_bytes(const void* __ptr, size_t __len, size_t __seed);
      55  
      56  _GLIBCXX_END_NAMESPACE_VERSION
      57  } // namespace
      58  
      59  #endif