1e78f53d1SNikolas Klauser //===----------------------------------------------------------------------===// 2e78f53d1SNikolas Klauser // 3e78f53d1SNikolas Klauser // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4e78f53d1SNikolas Klauser // See https://llvm.org/LICENSE.txt for license information. 5e78f53d1SNikolas Klauser // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6e78f53d1SNikolas Klauser // 7e78f53d1SNikolas Klauser //===----------------------------------------------------------------------===// 8e78f53d1SNikolas Klauser 9*ce777190SNikolas Klauser #ifndef _LIBCPP___CXX03___RANDOM_LOG2_H 10*ce777190SNikolas Klauser #define _LIBCPP___CXX03___RANDOM_LOG2_H 11e78f53d1SNikolas Klauser 1273fbae83SNikolas Klauser #include <__cxx03/__config> 1373fbae83SNikolas Klauser #include <__cxx03/__type_traits/conditional.h> 1473fbae83SNikolas Klauser #include <__cxx03/cstddef> 15e78f53d1SNikolas Klauser 16e78f53d1SNikolas Klauser #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 17e78f53d1SNikolas Klauser # pragma GCC system_header 18e78f53d1SNikolas Klauser #endif 19e78f53d1SNikolas Klauser 20e78f53d1SNikolas Klauser _LIBCPP_BEGIN_NAMESPACE_STD 21e78f53d1SNikolas Klauser 22e78f53d1SNikolas Klauser template <class _UIntType, _UIntType _Xp, size_t _Rp> 23e78f53d1SNikolas Klauser struct __log2_imp; 24e78f53d1SNikolas Klauser 25e78f53d1SNikolas Klauser template <unsigned long long _Xp, size_t _Rp> 26e78f53d1SNikolas Klauser struct __log2_imp<unsigned long long, _Xp, _Rp> { 27e78f53d1SNikolas Klauser static const size_t value = 28e78f53d1SNikolas Klauser _Xp & ((unsigned long long)(1) << _Rp) ? _Rp : __log2_imp<unsigned long long, _Xp, _Rp - 1>::value; 29e78f53d1SNikolas Klauser }; 30e78f53d1SNikolas Klauser 31e78f53d1SNikolas Klauser template <unsigned long long _Xp> 32e78f53d1SNikolas Klauser struct __log2_imp<unsigned long long, _Xp, 0> { 33e78f53d1SNikolas Klauser static const size_t value = 0; 34e78f53d1SNikolas Klauser }; 35e78f53d1SNikolas Klauser 36e78f53d1SNikolas Klauser template <size_t _Rp> 37e78f53d1SNikolas Klauser struct __log2_imp<unsigned long long, 0, _Rp> { 38e78f53d1SNikolas Klauser static const size_t value = _Rp + 1; 39e78f53d1SNikolas Klauser }; 40e78f53d1SNikolas Klauser 41e78f53d1SNikolas Klauser #ifndef _LIBCPP_HAS_NO_INT128 42e78f53d1SNikolas Klauser 43e78f53d1SNikolas Klauser template <__uint128_t _Xp, size_t _Rp> 44e78f53d1SNikolas Klauser struct __log2_imp<__uint128_t, _Xp, _Rp> { 45e78f53d1SNikolas Klauser static const size_t value = 46e78f53d1SNikolas Klauser (_Xp >> 64) ? (64 + __log2_imp<unsigned long long, (_Xp >> 64), 63>::value) 47e78f53d1SNikolas Klauser : __log2_imp<unsigned long long, _Xp, 63>::value; 48e78f53d1SNikolas Klauser }; 49e78f53d1SNikolas Klauser 50e78f53d1SNikolas Klauser #endif // _LIBCPP_HAS_NO_INT128 51e78f53d1SNikolas Klauser 52e78f53d1SNikolas Klauser template <class _UIntType, _UIntType _Xp> 53e78f53d1SNikolas Klauser struct __log2 { 54e78f53d1SNikolas Klauser static const size_t value = __log2_imp< 55e78f53d1SNikolas Klauser #ifndef _LIBCPP_HAS_NO_INT128 56e78f53d1SNikolas Klauser __conditional_t<sizeof(_UIntType) <= sizeof(unsigned long long), unsigned long long, __uint128_t>, 57e78f53d1SNikolas Klauser #else 58e78f53d1SNikolas Klauser unsigned long long, 59e78f53d1SNikolas Klauser #endif // _LIBCPP_HAS_NO_INT128 60e78f53d1SNikolas Klauser _Xp, 61e78f53d1SNikolas Klauser sizeof(_UIntType) * __CHAR_BIT__ - 1>::value; 62e78f53d1SNikolas Klauser }; 63e78f53d1SNikolas Klauser 64e78f53d1SNikolas Klauser _LIBCPP_END_NAMESPACE_STD 65e78f53d1SNikolas Klauser 66*ce777190SNikolas Klauser #endif // _LIBCPP___CXX03___RANDOM_LOG2_H 67