libcxx/include/__bit/rotate.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_ROTATE_H
  10 #define _LIBCPP___BIT_ROTATE_H
  11
  12 #include <__concepts/arithmetic.h>
  13 #include <__config>
  14 #include <__type_traits/is_unsigned_integer.h>
  15 #include <limits>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 template <class _Tp>
  24 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __rotr(_Tp __t, int __cnt) _NOEXCEPT {
  25   static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotr requires an unsigned integer type");
  26   const unsigned int __dig = numeric_limits<_Tp>::digits;
  27   if ((__cnt % __dig) == 0)
  28     return __t;
  29
  30   if (__cnt < 0) {
  31     __cnt *= -1;
  32     return (__t << (__cnt % __dig)) | (__t >> (__dig - (__cnt % __dig))); // rotr with negative __cnt is similar to rotl
  33   }
  34
  35   return (__t >> (__cnt % __dig)) | (__t << (__dig - (__cnt % __dig)));
  36 }
  37
  38 template <class _Tp>
  39 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __rotl(_Tp __t, int __cnt) _NOEXCEPT {
  40   return std::__rotr(__t, -__cnt);
  41 }
  42
  43 #if _LIBCPP_STD_VER >= 20
  44
  45 template <__libcpp_unsigned_integer _Tp>
  46 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp rotl(_Tp __t, int __cnt) noexcept {
  47   return std::__rotl(__t, __cnt);
  48 }
  49
  50 template <__libcpp_unsigned_integer _Tp>
  51 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp rotr(_Tp __t, int __cnt) noexcept {
  52   return std::__rotr(__t, __cnt);
  53 }
  54
  55 #endif // _LIBCPP_STD_VER >= 20
  56
  57 _LIBCPP_END_NAMESPACE_STD
  58
  59 #endif // _LIBCPP___BIT_ROTATE_H