forked from boostorg/endian
118 lines
2.9 KiB
C++
118 lines
2.9 KiB
C++
#ifndef BOOST_ENDIAN_DETAIL_ENDIAN_REVERSE_HPP_INCLUDED
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#define BOOST_ENDIAN_DETAIL_ENDIAN_REVERSE_HPP_INCLUDED
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// Copyright 2019 Peter Dimov
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//
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// Distributed under the Boost Software License, Version 1.0.
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// http://www.boost.org/LICENSE_1_0.txt
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#include <boost/endian/detail/integral_by_size.hpp>
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#include <boost/endian/detail/intrinsic.hpp>
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#include <boost/type_traits/is_integral.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/static_assert.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/config.hpp>
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#include <cstddef>
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#include <cstring>
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#if defined(BOOST_ENDIAN_NO_INTRINSICS)
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# if defined(BOOST_NO_CXX14_CONSTEXPR)
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# define BOOST_ENDIAN_CONSTEXPR
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# else
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# define BOOST_ENDIAN_CONSTEXPR constexpr
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# endif
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#else
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# if defined(BOOST_ENDIAN_CONSTEXPR_INTRINSICS)
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# define BOOST_ENDIAN_CONSTEXPR BOOST_CONSTEXPR
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# else
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# define BOOST_ENDIAN_CONSTEXPR
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# endif
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#endif
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namespace boost
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{
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namespace endian
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{
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namespace detail
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{
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// -- portable approach suggested by tymofey, with avoidance of undefined behavior
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// as suggested by Giovanni Piero Deretta, with a further refinement suggested
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// by Pyry Jahkola.
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// -- intrinsic approach suggested by reviewers, and by David Stone, who provided
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// his Boost licensed macro implementation (detail/intrinsic.hpp)
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inline uint8_t BOOST_CONSTEXPR endian_reverse_impl( uint8_t x ) BOOST_NOEXCEPT
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{
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return x;
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}
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inline uint16_t BOOST_ENDIAN_CONSTEXPR endian_reverse_impl( uint16_t x ) BOOST_NOEXCEPT
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{
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#ifdef BOOST_ENDIAN_NO_INTRINSICS
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return (x << 8) | (x >> 8);
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#else
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return BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x);
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#endif
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}
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inline uint32_t BOOST_ENDIAN_CONSTEXPR endian_reverse_impl(uint32_t x) BOOST_NOEXCEPT
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{
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#ifdef BOOST_ENDIAN_NO_INTRINSICS
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uint32_t step16 = x << 16 | x >> 16;
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return ((step16 << 8) & 0xff00ff00) | ((step16 >> 8) & 0x00ff00ff);
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#else
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return BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x);
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#endif
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}
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inline uint64_t BOOST_ENDIAN_CONSTEXPR endian_reverse_impl(uint64_t x) BOOST_NOEXCEPT
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{
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#ifdef BOOST_ENDIAN_NO_INTRINSICS
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uint64_t step32 = x << 32 | x >> 32;
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uint64_t step16 = (step32 & 0x0000FFFF0000FFFFULL) << 16 | (step32 & 0xFFFF0000FFFF0000ULL) >> 16;
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return (step16 & 0x00FF00FF00FF00FFULL) << 8 | (step16 & 0xFF00FF00FF00FF00ULL) >> 8;
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#else
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return BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x);
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# endif
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}
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} // namespace detail
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// Requires:
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// T is non-bool integral
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template<class T> inline BOOST_CONSTEXPR T endian_reverse( T x ) BOOST_NOEXCEPT
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{
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BOOST_STATIC_ASSERT( is_integral<T>::value && !is_same<T, bool>::value );
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typedef typename detail::integral_by_size< sizeof(T) >::type uintN_t;
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return static_cast<T>( detail::endian_reverse_impl( static_cast<uintN_t>( x ) ) );
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}
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template <class EndianReversible>
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inline void endian_reverse_inplace(EndianReversible& x) BOOST_NOEXCEPT
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{
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x = endian_reverse( x );
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}
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} // namespace endian
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} // namespace boost
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#endif // BOOST_ENDIAN_DETAIL_ENDIAN_REVERSE_HPP_INCLUDED
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