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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___RANDOM_LOG2_H
#define _LIBCPP___RANDOM_LOG2_H
#include <__config>
#include <cstddef>
#include <limits>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _UIntType, _UIntType _Xp, size_t _Rp>
struct __log2_imp;
template <unsigned long long _Xp, size_t _Rp>
struct __log2_imp<unsigned long long, _Xp, _Rp>
{
static const size_t value = _Xp & ((unsigned long long)(1) << _Rp) ? _Rp
: __log2_imp<unsigned long long, _Xp, _Rp - 1>::value;
};
template <unsigned long long _Xp>
struct __log2_imp<unsigned long long, _Xp, 0>
{
static const size_t value = 0;
};
template <size_t _Rp>
struct __log2_imp<unsigned long long, 0, _Rp>
{
static const size_t value = _Rp + 1;
};
#ifndef _LIBCPP_HAS_NO_INT128
template <__uint128_t _Xp, size_t _Rp>
struct __log2_imp<__uint128_t, _Xp, _Rp>
{
static const size_t value = (_Xp >> 64)
? (64 + __log2_imp<unsigned long long, (_Xp >> 64), 63>::value)
: __log2_imp<unsigned long long, _Xp, 63>::value;
};
#endif // _LIBCPP_HAS_NO_INT128
template <class _UIntType, _UIntType _Xp>
struct __log2
{
static const size_t value = __log2_imp<
#ifndef _LIBCPP_HAS_NO_INT128
typename conditional<
sizeof(_UIntType) <= sizeof(unsigned long long),
unsigned long long,
__uint128_t
>::type,
#else
unsigned long long,
#endif // _LIBCPP_HAS_NO_INT128
_Xp, sizeof(_UIntType) * __CHAR_BIT__ - 1>::value;
};
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___RANDOM_LOG2_H
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