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Refactor detail/byteswap.hpp

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This commit is contained in:
Peter Dimov
2025-04-27 19:34:22 +03:00
parent 2b3e1fd6fa
commit 161b47e749
1 changed files with 39 additions and 50 deletions
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89
include/boost/hash2/detail/byteswap.hpp
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@@ -9,7 +9,7 @@
#include <boost/config.hpp>
#include <cstdint>
#if defined(BOOST_MSVC)
#if defined(_MSC_VER)
#include <intrin.h>
#endif
@@ -20,76 +20,65 @@ namespace hash2
namespace detail
{
#if defined(BOOST_GCC) || defined(BOOST_CLANG)
BOOST_CXX14_CONSTEXPR inline std::uint32_t byteswap_impl( std::uint32_t x ) noexcept
{
return __builtin_bswap32( x );
}
BOOST_CXX14_CONSTEXPR inline std::uint64_t byteswap_impl( std::uint64_t x ) noexcept
{
return __builtin_bswap64( x );
}
#elif defined(BOOST_MSVC)
BOOST_CXX14_CONSTEXPR inline std::uint32_t byteswap_impl( std::uint32_t x ) noexcept
{
if( !detail::is_constant_evaluated() )
{
return _byteswap_ulong( x );
}
else
{
// copy-paste the approach used by Core in bit.hpp
std::uint32_t step16 = x << 16 | x >> 16;
return ( ( step16 << 8 ) & 0xff00ff00 ) | ( ( step16 >> 8 ) & 0x00ff00ff );
}
}
BOOST_CXX14_CONSTEXPR inline std::uint64_t byteswap_impl( std::uint64_t x ) noexcept
{
if( !detail::is_constant_evaluated() )
{
return _byteswap_uint64( x );
}
else
{
// copy-paste the approach used by Core in bit.hpp
std::uint64_t step32 = x << 32 | x >> 32;
std::uint64_t step16 = ( step32 & 0x0000ffff0000ffffull ) << 16 | ( step32 & 0xffff0000ffff0000ull ) >> 16;
return ( step16 & 0x00ff00ff00ff00ffull ) << 8 | ( step16 & 0xff00ff00ff00ff00ull ) >> 8;
}
}
#else
BOOST_CXX14_CONSTEXPR inline std::uint32_t byteswap_impl( std::uint32_t x ) noexcept
{
// copy-paste the approach used by Core in bit.hpp
std::uint32_t step16 = x << 16 | x >> 16;
return ( ( step16 << 8 ) & 0xff00ff00 ) | ( ( step16 >> 8 ) & 0x00ff00ff );
}
BOOST_CXX14_CONSTEXPR inline std::uint64_t byteswap_impl( std::uint64_t x ) noexcept
{
// copy-paste the approach used by Core in bit.hpp
std::uint64_t step32 = x << 32 | x >> 32;
std::uint64_t step16 = ( step32 & 0x0000ffff0000ffffull ) << 16 | ( step32 & 0xffff0000ffff0000ull ) >> 16;
return ( step16 & 0x00ff00ff00ff00ffull ) << 8 | ( step16 & 0xff00ff00ff00ff00ull ) >> 8;
}
#endif
BOOST_CXX14_CONSTEXPR inline std::uint32_t byteswap( std::uint32_t x ) noexcept
{
#if defined(__GNUC__) || defined(__clang__)
return __builtin_bswap32( x );
#elif defined(_MSC_VER)
if( !detail::is_constant_evaluated() )
{
return _byteswap_ulong( x );
}
else
{
return byteswap_impl( x );
}
#else
return byteswap_impl( x );
#endif
}
BOOST_CXX14_CONSTEXPR inline std::uint64_t byteswap( std::uint64_t x ) noexcept
{
#if defined(__GNUC__) || defined(__clang__)
return __builtin_bswap64( x );
#elif defined(_MSC_VER)
if( !detail::is_constant_evaluated() )
{
return _byteswap_uint64( x );
}
else
{
return byteswap_impl( x );
}
#else
return byteswap_impl( x );
#endif
}
} // namespace detail