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Add bit_ceil

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Peter Dimov
2020-12-29 00:29:44 +02:00
parent 3e41929dfb
commit 26728848b4
3 changed files with 127 additions and 3 deletions
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64
include/boost/core/bit.hpp
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@@ -197,15 +197,73 @@ BOOST_CONSTEXPR T bit_width( T x ) BOOST_NOEXCEPT
return std::numeric_limits<T>::digits - boost::core::countl_zero( x );
}
template<class T>
BOOST_CONSTEXPR T bit_ceil( T x ) BOOST_NOEXCEPT;
template<class T>
BOOST_CONSTEXPR T bit_floor( T x ) BOOST_NOEXCEPT
{
return x == 0? 0: T(1) << ( boost::core::bit_width( x ) - 1 );
}
namespace detail
{
BOOST_CXX14_CONSTEXPR inline boost::uint32_t bit_ceil_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
if( x == 0 )
{
return 0;
}
--x;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
++x;
return x;
}
BOOST_CXX14_CONSTEXPR inline boost::uint64_t bit_ceil_impl( boost::uint64_t x ) BOOST_NOEXCEPT
{
if( x == 0 )
{
return 0;
}
--x;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
x |= x >> 32;
++x;
return x;
}
} // namespace detail
template<class T>
BOOST_CXX14_CONSTEXPR T bit_ceil( T x ) BOOST_NOEXCEPT
{
BOOST_STATIC_ASSERT( sizeof(T) <= sizeof(boost::uint64_t) );
if( sizeof(T) <= sizeof(boost::uint32_t) )
{
return static_cast<T>( boost::core::detail::bit_ceil_impl( static_cast<boost::uint32_t>( x ) ) );
}
else
{
return static_cast<T>( boost::core::detail::bit_ceil_impl( static_cast<boost::uint64_t>( x ) ) );
}
}
// endian
#if !defined(BOOST_NO_CXX11_SCOPED_ENUMS)