diff options
Diffstat (limited to 'src/lib/util/endianness.h')
-rw-r--r-- | src/lib/util/endianness.h | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/src/lib/util/endianness.h b/src/lib/util/endianness.h index d983afe8c6b..aa83421f1d7 100644 --- a/src/lib/util/endianness.h +++ b/src/lib/util/endianness.h @@ -38,6 +38,37 @@ enum class endianness #endif }; + +// helper for accessing data adjusted for endianness +template <typename In, typename Out, endianness Endian> +class offset_endian_cast +{ +private: + static inline constexpr std::ptrdiff_t SWIZZLE = (sizeof(In) / sizeof(Out)) - 1; + + static_assert(!(sizeof(In) % sizeof(Out)), "input size must be a multiple of output size"); + static_assert(!((sizeof(In) / sizeof(Out)) & SWIZZLE), "ratio of input size to output size must be a power of two"); + + Out *m_ptr; + std::ptrdiff_t m_offs; + +public: + constexpr offset_endian_cast(In *ptr, std::ptrdiff_t offs) noexcept : m_ptr(reinterpret_cast<Out *>(ptr)), m_offs(offs) { } + + constexpr Out &operator[](std::ptrdiff_t i) const noexcept { return m_ptr[(m_offs + i) ^ ((Endian != endianness::native) ? SWIZZLE : 0)]; } + + constexpr offset_endian_cast operator+(std::ptrdiff_t i) const noexcept { return offset_endian_cast(*this) += i; } + constexpr offset_endian_cast operator-(std::ptrdiff_t i) const noexcept { return offset_endian_cast(*this) -= i; } + + offset_endian_cast &operator+=(std::ptrdiff_t i) noexcept { m_offs += i; return *this; } + offset_endian_cast &operator-=(std::ptrdiff_t i) noexcept { m_offs -= i; return *this; } + offset_endian_cast &operator++() noexcept { ++m_offs; return *this; } + offset_endian_cast &operator--() noexcept { --m_offs; return *this; } + offset_endian_cast operator++(int) noexcept { offset_endian_cast result(*this); ++m_offs; return result; } + offset_endian_cast operator--(int) noexcept { offset_endian_cast result(*this); --m_offs; return result; } +}; + + // helper for accessing data adjusted for endianness template <typename In, typename Out, endianness Endian> class endian_cast @@ -54,9 +85,24 @@ public: constexpr endian_cast(In *ptr) noexcept : m_ptr(reinterpret_cast<Out *>(ptr)) { } constexpr Out &operator[](std::ptrdiff_t i) const noexcept { return m_ptr[i ^ ((Endian != endianness::native) ? SWIZZLE : 0)]; } + + constexpr auto operator+(std::ptrdiff_t offs) const noexcept + { + using required_const = std::conditional_t<std::is_const_v<Out>, std::add_const_t<In>, In>; + using required_cv = std::conditional_t<std::is_volatile_v<Out>, std::add_volatile<required_const>, required_const>; + return offset_endian_cast<required_cv, Out, Endian>(reinterpret_cast<required_cv *>(m_ptr), offs); + } + + constexpr auto operator-(std::ptrdiff_t offs) const noexcept + { + using required_const = std::conditional_t<std::is_const_v<Out>, std::add_const_t<In>, In>; + using required_cv = std::conditional_t<std::is_volatile_v<Out>, std::add_volatile<required_const>, required_const>; + return offset_endian_cast<required_cv, Out, Endian>(reinterpret_cast<required_cv *>(m_ptr), -offs); + } }; + //************************************************************************** // MACROS AND INLINE FUNCTIONS //************************************************************************** |