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

// Declarations for hash functions. -*- C++ -*-

// Copyright (C) 2010-2021 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/hash_bytes.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{functional}
 */

#ifndef _HASH_BYTES_H
#define _HASH_BYTES_H 1

#pragma GCC system_header

#include <bits/c++config.h>

namespace std
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Hash function implementation for the nontrivial specialization.
  // All of them are based on a primitive that hashes a pointer to a
  // byte array. The actual hash algorithm is not guaranteed to stay
  // the same from release to release -- it may be updated or tuned to
  // improve hash quality or speed.
  size_t
  _Hash_bytes(const void* __ptr, size_t __len, size_t __seed);

  // A similar hash primitive, using the FNV hash algorithm. This
  // algorithm is guaranteed to stay the same from release to release.
  // (although it might not produce the same values on different
  // machines.)
  size_t
  _Fnv_hash_bytes(const void* __ptr, size_t __len, size_t __seed);

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif