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The C and C++ Include Header Files

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

     1	// Saturation arithmetic -*- C++ -*-
     2	
     3	// Copyright The GNU Toolchain Authors.
     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 include/bits/sat_arith.h
    26	 *  This is an internal header file, included by other library headers.
    27	 *  Do not attempt to use it directly. @headername{numeric}
    28	 */
    29	
    30	#ifndef _GLIBCXX_SAT_ARITH_H
    31	#define _GLIBCXX_SAT_ARITH_H 1
    32	
    33	#ifdef _GLIBCXX_SYSHDR
    34	#pragma GCC system_header
    35	#endif
    36	
    37	#include <bits/version.h>
    38	
    39	#ifdef __glibcxx_saturation_arithmetic // C++ >= 26
    40	
    41	#include <concepts>
    42	#include <ext/numeric_traits.h>
    43	
    44	namespace std _GLIBCXX_VISIBILITY(default)
    45	{
    46	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    47	
    48	  /// Add two integers, with saturation in case of overflow.
    49	  template<typename _Tp> requires __is_standard_integer<_Tp>::value
    50	    constexpr _Tp
    51	    add_sat(_Tp __x, _Tp __y) noexcept
    52	    {
    53	      _Tp __z;
    54	      if (!__builtin_add_overflow(__x, __y, &__z))
    55		return __z;
    56	      if constexpr (is_unsigned_v<_Tp>)
    57		return __gnu_cxx::__int_traits<_Tp>::__max;
    58	      else if (__x < 0)
    59		return __gnu_cxx::__int_traits<_Tp>::__min;
    60	      else
    61		return __gnu_cxx::__int_traits<_Tp>::__max;
    62	    }
    63	
    64	  /// Subtract one integer from another, with saturation in case of overflow.
    65	  template<typename _Tp> requires __is_standard_integer<_Tp>::value
    66	    constexpr _Tp
    67	    sub_sat(_Tp __x, _Tp __y) noexcept
    68	    {
    69	      _Tp __z;
    70	      if (!__builtin_sub_overflow(__x, __y, &__z))
    71		return __z;
    72	      if constexpr (is_unsigned_v<_Tp>)
    73		return __gnu_cxx::__int_traits<_Tp>::__min;
    74	      else if (__x < 0)
    75		return __gnu_cxx::__int_traits<_Tp>::__min;
    76	      else
    77		return __gnu_cxx::__int_traits<_Tp>::__max;
    78	    }
    79	
    80	  /// Multiply two integers, with saturation in case of overflow.
    81	  template<typename _Tp> requires __is_standard_integer<_Tp>::value
    82	    constexpr _Tp
    83	    mul_sat(_Tp __x, _Tp __y) noexcept
    84	    {
    85	      _Tp __z;
    86	      if (!__builtin_mul_overflow(__x, __y, &__z))
    87		return __z;
    88	      if constexpr (is_unsigned_v<_Tp>)
    89		return __gnu_cxx::__int_traits<_Tp>::__max;
    90	      else if (__x < 0 != __y < 0)
    91		return __gnu_cxx::__int_traits<_Tp>::__min;
    92	      else
    93		return __gnu_cxx::__int_traits<_Tp>::__max;
    94	    }
    95	
    96	  /// Divide one integer by another, with saturation in case of overflow.
    97	  template<typename _Tp> requires __is_standard_integer<_Tp>::value
    98	    constexpr _Tp
    99	    div_sat(_Tp __x, _Tp __y) noexcept
   100	    {
   101	      __glibcxx_assert(__y != 0);
   102	      if constexpr (is_signed_v<_Tp>)
   103		if (__x == __gnu_cxx::__int_traits<_Tp>::__min && __y == _Tp(-1))
   104		  return __gnu_cxx::__int_traits<_Tp>::__max;
   105	      return __x / __y;
   106	    }
   107	
   108	  /// Divide one integer by another, with saturation in case of overflow.
   109	  template<typename _Res, typename _Tp>
   110	    requires __is_standard_integer<_Res>::value
   111	      && __is_standard_integer<_Tp>::value
   112	    constexpr _Res
   113	    saturate_cast(_Tp __x) noexcept
   114	    {
   115	      constexpr int __digits_R = __gnu_cxx::__int_traits<_Res>::__digits;
   116	      constexpr int __digits_T = __gnu_cxx::__int_traits<_Tp>::__digits;
   117	      constexpr _Res __max_Res = __gnu_cxx::__int_traits<_Res>::__max;
   118	
   119	      if constexpr (is_signed_v<_Res> == is_signed_v<_Tp>)
   120		{
   121		  if constexpr (__digits_R < __digits_T)
   122		    {
   123		      constexpr _Res __min_Res = __gnu_cxx::__int_traits<_Res>::__min;
   124	
   125		      if (__x < static_cast<_Tp>(__min_Res))
   126			return __min_Res;
   127		      else if (__x > static_cast<_Tp>(__max_Res))
   128			return __max_Res;
   129		    }
   130		}
   131	      else if constexpr (is_signed_v<_Tp>) // Res is unsigned
   132		{
   133		  if (__x < 0)
   134		    return 0;
   135		  else if (make_unsigned_t<_Tp>(__x) > __max_Res)
   136		    return __gnu_cxx::__int_traits<_Res>::__max;
   137		}
   138	      else // Tp is unsigned, Res is signed
   139		{
   140		  if (__x > make_unsigned_t<_Res>(__max_Res))
   141		    return __max_Res;
   142		}
   143	      return static_cast<_Res>(__x);
   144	    }
   145	
   146	_GLIBCXX_END_NAMESPACE_VERSION
   147	} // namespace
   148	
   149	#endif // __glibcxx_saturation_arithmetic
   150	#endif /* _GLIBCXX_SAT_ARITH_H */