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Add byteswap to bit.hpp

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This commit is contained in:
Peter Dimov
2023-05-30 19:09:09 +03:00
parent 6b9f0cbf57
commit b591214103
4 changed files with 120 additions and 0 deletions
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54
include/boost/core/bit.hpp
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@@ -792,6 +792,60 @@ typedef endian::type endian_type;
#undef BOOST_CORE_BIT_NATIVE_INITIALIZER
// byteswap
namespace detail
{
BOOST_CONSTEXPR inline boost::uint8_t byteswap_impl( boost::uint8_t x ) BOOST_NOEXCEPT
{
return x;
}
BOOST_CONSTEXPR inline boost::uint16_t byteswap_impl( boost::uint16_t x ) BOOST_NOEXCEPT
{
return (x << 8) | (x >> 8);
}
BOOST_CXX14_CONSTEXPR inline boost::uint32_t byteswap_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
boost::uint32_t step16 = x << 16 | x >> 16;
return ((step16 << 8) & 0xff00ff00) | ((step16 >> 8) & 0x00ff00ff);
}
BOOST_CXX14_CONSTEXPR inline boost::uint64_t byteswap_impl( boost::uint64_t x ) BOOST_NOEXCEPT
{
boost::uint64_t step32 = x << 32 | x >> 32;
boost::uint64_t step16 = (step32 & 0x0000FFFF0000FFFFULL) << 16 | (step32 & 0xFFFF0000FFFF0000ULL) >> 16;
return (step16 & 0x00FF00FF00FF00FFULL) << 8 | (step16 & 0xFF00FF00FF00FF00ULL) >> 8;
}
} // namespace detail
template<class T> BOOST_CXX14_CONSTEXPR T byteswap( T x ) BOOST_NOEXCEPT
{
BOOST_STATIC_ASSERT( std::numeric_limits<T>::is_integer );
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) );
BOOST_IF_CONSTEXPR ( sizeof(T) == sizeof(boost::uint8_t) )
{
return static_cast<T>( boost::core::detail::byteswap_impl( static_cast<boost::uint8_t>( x ) ) );
}
else BOOST_IF_CONSTEXPR ( sizeof(T) == sizeof(boost::uint16_t) )
{
return static_cast<T>( boost::core::detail::byteswap_impl( static_cast<boost::uint16_t>( x ) ) );
}
else BOOST_IF_CONSTEXPR ( sizeof(T) == sizeof(boost::uint32_t) )
{
return static_cast<T>( boost::core::detail::byteswap_impl( static_cast<boost::uint32_t>( x ) ) );
}
else
{
return static_cast<T>( boost::core::detail::byteswap_impl( static_cast<boost::uint64_t>( x ) ) );
}
}
} // namespace core
} // namespace boost