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Add countl_zero, countl_one

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This commit is contained in:
Peter Dimov
2020-12-28 23:40:59 +02:00
parent 123b567051
commit cc877e6b5b
3 changed files with 99 additions and 6 deletions
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58
include/boost/core/bit.hpp
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@@ -45,20 +45,66 @@ To bit_cast( From const & from ) BOOST_NOEXCEPT
namespace detail
{
BOOST_CXX14_CONSTEXPR int countl_impl( boost::uint32_t x ) BOOST_NOEXCEPT
inline int countl_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
return 0;
static unsigned char const mod37[ 37 ] = { 32, 31, 6, 30, 9, 5, 0, 29, 16, 8, 2, 4, 21, 0, 19, 28, 25, 15, 0, 7, 10, 1, 17, 3, 22, 20, 26, 0, 11, 18, 23, 27, 12, 24, 13, 14, 0 };
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
return mod37[ x % 37 ];
}
inline int countl_impl( boost::uint64_t x ) BOOST_NOEXCEPT
{
return static_cast<boost::uint32_t>( x >> 32 ) != 0?
boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x >> 32 ) ):
boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) ) + 32;
}
inline int countl_impl( boost::uint8_t x ) BOOST_NOEXCEPT
{
return boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) ) - 24;
}
inline int countl_impl( boost::uint16_t x ) BOOST_NOEXCEPT
{
return boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) ) - 16;
}
} // namespace detail
template<class T>
BOOST_CORE_BIT_CONSTEXPR int countl_zero( T x ) BOOST_NOEXCEPT;
BOOST_CORE_BIT_CONSTEXPR int countl_zero( T x ) BOOST_NOEXCEPT
{
BOOST_STATIC_ASSERT( sizeof(T) == sizeof(boost::uint8_t) || sizeof(T) == sizeof(boost::uint16_t) || sizeof(T) == sizeof(boost::uint32_t) || sizeof(T) == sizeof(boost::uint64_t) );
if( sizeof(T) == sizeof(boost::uint8_t) )
{
return boost::core::detail::countl_impl( static_cast<boost::uint8_t>( x ) );
}
else if( sizeof(T) == sizeof(boost::uint16_t) )
{
return boost::core::detail::countl_impl( static_cast<boost::uint16_t>( x ) );
}
else if( sizeof(T) == sizeof(boost::uint32_t) )
{
return boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) );
}
else
{
return boost::core::detail::countl_impl( static_cast<boost::uint64_t>( x ) );
}
}
template<class T>
BOOST_CORE_BIT_CONSTEXPR int countl_one( T x ) BOOST_NOEXCEPT
{
return boost::core::countl_zero( ~x );
return boost::core::countl_zero( static_cast<T>( ~x ) );
}
namespace detail
@@ -66,7 +112,7 @@ namespace detail
inline int countr_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
static unsigned char const mod37[] = { 32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13, 4, 7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9, 5, 20, 8, 19, 18 };
static unsigned char const mod37[ 37 ] = { 32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13, 4, 7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9, 5, 20, 8, 19, 18 };
return mod37[ ( -(boost::int32_t)x & x ) % 37 ];
}
@@ -115,7 +161,7 @@ BOOST_CORE_BIT_CONSTEXPR int countr_zero( T x ) BOOST_NOEXCEPT
template<class T>
BOOST_CORE_BIT_CONSTEXPR int countr_one( T x ) BOOST_NOEXCEPT
{
return boost::core::countr_zero( ~x );
return boost::core::countr_zero( static_cast<T>( ~x ) );
}
template<class T>