libstdc++-v3/libsupc++/hash_bytes.h

   1 // Declarations for hash functions. -*- C++ -*-
   2
   3 // Copyright (C) 2010-2018 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