libcxx/include/__cxx03/__bit/bit_ceil.h

   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___BIT_BIT_CEIL_H
  10 #define _LIBCPP___BIT_BIT_CEIL_H
  11
  12 #include <__cxx03/__assert>
  13 #include <__cxx03/__bit/countl.h>
  14 #include <__cxx03/__concepts/arithmetic.h>
  15 #include <__cxx03/__config>
  16 #include <__cxx03/limits>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 #if _LIBCPP_STD_VER >= 17
  25
  26 template <class _Tp>
  27 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp __bit_ceil(_Tp __t) noexcept {
  28   if (__t < 2)
  29     return 1;
  30   const unsigned __n = numeric_limits<_Tp>::digits - std::__countl_zero((_Tp)(__t - 1u));
  31   _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__n != numeric_limits<_Tp>::digits, "Bad input to bit_ceil");
  32
  33   if constexpr (sizeof(_Tp) >= sizeof(unsigned))
  34     return _Tp{1} << __n;
  35   else {
  36     const unsigned __extra   = numeric_limits<unsigned>::digits - numeric_limits<_Tp>::digits;
  37     const unsigned __ret_val = 1u << (__n + __extra);
  38     return (_Tp)(__ret_val >> __extra);
  39   }
  40 }
  41
  42 #  if _LIBCPP_STD_VER >= 20
  43
  44 template <__libcpp_unsigned_integer _Tp>
  45 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp bit_ceil(_Tp __t) noexcept {
  46   return std::__bit_ceil(__t);
  47 }
  48
  49 #  endif // _LIBCPP_STD_VER >= 20
  50 #endif   // _LIBCPP_STD_VER >= 17
  51
  52 _LIBCPP_END_NAMESPACE_STD
  53
  54 #endif // _LIBCPP___BIT_BIT_CEIL_H