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The C and C++ Include Header Files

cat -n /usr/include/c++/15/bits/hash_bytes.h

     1	// Declarations for hash functions. -*- C++ -*-
     2	
     3	// Copyright (C) 2010-2025 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	
    39	namespace 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