libstdc++: hash_bytes.h Source File

libstdc++

hash_bytes.h
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1// Declarations for hash functions. -*- C++ -*-
2
3// Copyright (C) 2010-2026 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#ifdef _GLIBCXX_SYSHDR
34#pragma GCC system_header
35#endif
36
37#include <bits/c++config.h>
38
39namespace std
40{
41_GLIBCXX_BEGIN_NAMESPACE_VERSION
42
43 // Hash function implementation for the nontrivial specialization.
44 // All of them are based on a primitive that hashes a pointer to a
45 // byte array. The actual hash algorithm is not guaranteed to stay
46 // the same from release to release -- it may be updated or tuned to
47 // improve hash quality or speed.
48 size_t
49 _Hash_bytes(const void* __ptr, size_t __len, size_t __seed);
50
51 // A similar hash primitive, using the FNV hash algorithm. This
52 // algorithm is guaranteed to stay the same from release to release.
53 // (although it might not produce the same values on different
54 // machines.)
55 size_t
56 _Fnv_hash_bytes(const void* __ptr, size_t __len, size_t __seed);
57
58_GLIBCXX_END_NAMESPACE_VERSION
59} // namespace
60
61#endif
c++config.h
std
ISO C++ entities toplevel namespace is std.