1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___RANDOM_CLAMP_TO_INTEGRAL_H
10 #define _LIBCPP___RANDOM_CLAMP_TO_INTEGRAL_H
11 
12 #include <__config>
13 #include <cmath>
14 #include <limits>
15 #include <type_traits>
16 
17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18 #  pragma GCC system_header
19 #endif
20 
21 _LIBCPP_PUSH_MACROS
22 #include <__undef_macros>
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 template <class _IntT, class _FloatT,
27     bool _FloatBigger = (numeric_limits<_FloatT>::digits > numeric_limits<_IntT>::digits),
28     int _Bits = (numeric_limits<_IntT>::digits - numeric_limits<_FloatT>::digits)>
29 _LIBCPP_INLINE_VISIBILITY
30 _LIBCPP_CONSTEXPR _IntT __max_representable_int_for_float() _NOEXCEPT {
31   static_assert(is_floating_point<_FloatT>::value, "must be a floating point type");
32   static_assert(is_integral<_IntT>::value, "must be an integral type");
33   static_assert(numeric_limits<_FloatT>::radix == 2, "FloatT has incorrect radix");
34   static_assert((_IsSame<_FloatT, float>::value || _IsSame<_FloatT, double>::value
35                  || _IsSame<_FloatT,long double>::value), "unsupported floating point type");
36   return _FloatBigger ? numeric_limits<_IntT>::max() :  (numeric_limits<_IntT>::max() >> _Bits << _Bits);
37 }
38 
39 // Convert a floating point number to the specified integral type after
40 // clamping to the integral type's representable range.
41 //
42 // The behavior is undefined if `__r` is NaN.
43 template <class _IntT, class _RealT>
44 _LIBCPP_INLINE_VISIBILITY
45 _IntT __clamp_to_integral(_RealT __r) _NOEXCEPT {
46   using _Lim = numeric_limits<_IntT>;
47   const _IntT _MaxVal = __max_representable_int_for_float<_IntT, _RealT>();
48   if (__r >= ::nextafter(static_cast<_RealT>(_MaxVal), INFINITY)) {
49     return _Lim::max();
50   } else if (__r <= _Lim::lowest()) {
51     return _Lim::min();
52   }
53   return static_cast<_IntT>(__r);
54 }
55 
56 _LIBCPP_END_NAMESPACE_STD
57 
58 _LIBCPP_POP_MACROS
59 
60 #endif // _LIBCPP___RANDOM_CLAMP_TO_INTEGRAL_H
61