1*4824e7fdSDimitry Andric //===----------------------------------------------------------------------===// 2*4824e7fdSDimitry Andric // 3*4824e7fdSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*4824e7fdSDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 5*4824e7fdSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*4824e7fdSDimitry Andric // 7*4824e7fdSDimitry Andric //===----------------------------------------------------------------------===// 8*4824e7fdSDimitry Andric 9*4824e7fdSDimitry Andric #ifndef _LIBCPP___RANDOM_LOG2_H 10*4824e7fdSDimitry Andric #define _LIBCPP___RANDOM_LOG2_H 11*4824e7fdSDimitry Andric 12*4824e7fdSDimitry Andric #include <__config> 13*4824e7fdSDimitry Andric #include <cstddef> 14*4824e7fdSDimitry Andric #include <type_traits> 15*4824e7fdSDimitry Andric 16*4824e7fdSDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 17*4824e7fdSDimitry Andric #pragma GCC system_header 18*4824e7fdSDimitry Andric #endif 19*4824e7fdSDimitry Andric 20*4824e7fdSDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD 21*4824e7fdSDimitry Andric 22*4824e7fdSDimitry Andric template <class _UIntType, _UIntType _Xp, size_t _Rp> 23*4824e7fdSDimitry Andric struct __log2_imp; 24*4824e7fdSDimitry Andric 25*4824e7fdSDimitry Andric template <unsigned long long _Xp, size_t _Rp> 26*4824e7fdSDimitry Andric struct __log2_imp<unsigned long long, _Xp, _Rp> 27*4824e7fdSDimitry Andric { 28*4824e7fdSDimitry Andric static const size_t value = _Xp & ((unsigned long long)(1) << _Rp) ? _Rp 29*4824e7fdSDimitry Andric : __log2_imp<unsigned long long, _Xp, _Rp - 1>::value; 30*4824e7fdSDimitry Andric }; 31*4824e7fdSDimitry Andric 32*4824e7fdSDimitry Andric template <unsigned long long _Xp> 33*4824e7fdSDimitry Andric struct __log2_imp<unsigned long long, _Xp, 0> 34*4824e7fdSDimitry Andric { 35*4824e7fdSDimitry Andric static const size_t value = 0; 36*4824e7fdSDimitry Andric }; 37*4824e7fdSDimitry Andric 38*4824e7fdSDimitry Andric template <size_t _Rp> 39*4824e7fdSDimitry Andric struct __log2_imp<unsigned long long, 0, _Rp> 40*4824e7fdSDimitry Andric { 41*4824e7fdSDimitry Andric static const size_t value = _Rp + 1; 42*4824e7fdSDimitry Andric }; 43*4824e7fdSDimitry Andric 44*4824e7fdSDimitry Andric #ifndef _LIBCPP_HAS_NO_INT128 45*4824e7fdSDimitry Andric 46*4824e7fdSDimitry Andric template <__uint128_t _Xp, size_t _Rp> 47*4824e7fdSDimitry Andric struct __log2_imp<__uint128_t, _Xp, _Rp> 48*4824e7fdSDimitry Andric { 49*4824e7fdSDimitry Andric static const size_t value = (_Xp >> 64) 50*4824e7fdSDimitry Andric ? (64 + __log2_imp<unsigned long long, (_Xp >> 64), 63>::value) 51*4824e7fdSDimitry Andric : __log2_imp<unsigned long long, _Xp, 63>::value; 52*4824e7fdSDimitry Andric }; 53*4824e7fdSDimitry Andric 54*4824e7fdSDimitry Andric #endif // _LIBCPP_HAS_NO_INT128 55*4824e7fdSDimitry Andric 56*4824e7fdSDimitry Andric template <class _UIntType, _UIntType _Xp> 57*4824e7fdSDimitry Andric struct __log2 58*4824e7fdSDimitry Andric { 59*4824e7fdSDimitry Andric static const size_t value = __log2_imp< 60*4824e7fdSDimitry Andric #ifndef _LIBCPP_HAS_NO_INT128 61*4824e7fdSDimitry Andric typename conditional< 62*4824e7fdSDimitry Andric sizeof(_UIntType) <= sizeof(unsigned long long), 63*4824e7fdSDimitry Andric unsigned long long, 64*4824e7fdSDimitry Andric __uint128_t 65*4824e7fdSDimitry Andric >::type, 66*4824e7fdSDimitry Andric #else 67*4824e7fdSDimitry Andric unsigned long long, 68*4824e7fdSDimitry Andric #endif // _LIBCPP_HAS_NO_INT128 69*4824e7fdSDimitry Andric _Xp, sizeof(_UIntType) * __CHAR_BIT__ - 1>::value; 70*4824e7fdSDimitry Andric }; 71*4824e7fdSDimitry Andric 72*4824e7fdSDimitry Andric _LIBCPP_END_NAMESPACE_STD 73*4824e7fdSDimitry Andric 74*4824e7fdSDimitry Andric #endif // _LIBCPP___RANDOM_LOG2_H 75