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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___RANDOM_LOG2_H10#define _LIBCPP___RANDOM_LOG2_H11 12#include <__config>13#include <__cstddef/size_t.h>14#include <__type_traits/conditional.h>15 16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)17# pragma GCC system_header18#endif19 20_LIBCPP_BEGIN_NAMESPACE_STD21 22template <class _UIntType, _UIntType _Xp, size_t _Rp>23struct __log2_imp;24 25template <unsigned long long _Xp, size_t _Rp>26struct __log2_imp<unsigned long long, _Xp, _Rp> {27 static const size_t value =28 _Xp & ((unsigned long long)(1) << _Rp) ? _Rp : __log2_imp<unsigned long long, _Xp, _Rp - 1>::value;29};30 31template <unsigned long long _Xp>32struct __log2_imp<unsigned long long, _Xp, 0> {33 static const size_t value = 0;34};35 36template <size_t _Rp>37struct __log2_imp<unsigned long long, 0, _Rp> {38 static const size_t value = _Rp + 1;39};40 41#if _LIBCPP_HAS_INT12842 43template <__uint128_t _Xp, size_t _Rp>44struct __log2_imp<__uint128_t, _Xp, _Rp> {45 static const size_t value =46 (_Xp >> 64) ? (64 + __log2_imp<unsigned long long, (_Xp >> 64), 63>::value)47 : __log2_imp<unsigned long long, _Xp, 63>::value;48};49 50#endif // _LIBCPP_HAS_INT12851 52template <class _UIntType, _UIntType _Xp>53struct __log2 {54 static const size_t value = __log2_imp<55#if _LIBCPP_HAS_INT12856 __conditional_t<sizeof(_UIntType) <= sizeof(unsigned long long), unsigned long long, __uint128_t>,57#else58 unsigned long long,59#endif // _LIBCPP_HAS_INT12860 _Xp,61 sizeof(_UIntType) * __CHAR_BIT__ - 1>::value;62};63 64_LIBCPP_END_NAMESPACE_STD65 66#endif // _LIBCPP___RANDOM_LOG2_H67