common/swap: use template and tag for LE/BE specification

The tag can be useful for other type-generic templates like BitFields to forward the endianness specification
This commit is contained in:
Weiyi Wang 2019-01-25 12:09:12 -05:00
parent 8b047a49ae
commit 985cd878e6

View file

@ -645,64 +645,116 @@ protected:
}
};
struct SwapTag {}; // Use the different endianness from the system
struct KeepTag {}; // Use the same endianness as the system
template <typename T, typename Tag>
struct AddEndian;
// KeepTag specializations
template <typename T>
struct AddEndian<T, KeepTag> {
using type = T;
};
// SwapTag specializations
template <>
struct AddEndian<u8, SwapTag> {
using type = u8;
};
template <>
struct AddEndian<u16, SwapTag> {
using type = swap_struct_t<u16, swap_16_t<u16>>;
};
template <>
struct AddEndian<u32, SwapTag> {
using type = swap_struct_t<u32, swap_32_t<u32>>;
};
template <>
struct AddEndian<u64, SwapTag> {
using type = swap_struct_t<u64, swap_64_t<u64>>;
};
template <>
struct AddEndian<s8, SwapTag> {
using type = s8;
};
template <>
struct AddEndian<s16, SwapTag> {
using type = swap_struct_t<s16, swap_16_t<s16>>;
};
template <>
struct AddEndian<s32, SwapTag> {
using type = swap_struct_t<s32, swap_32_t<s32>>;
};
template <>
struct AddEndian<s64, SwapTag> {
using type = swap_struct_t<s64, swap_64_t<s64>>;
};
template <>
struct AddEndian<float, SwapTag> {
using type = swap_struct_t<float, swap_float_t<float>>;
};
template <>
struct AddEndian<double, SwapTag> {
using type = swap_struct_t<double, swap_double_t<double>>;
};
template <typename T>
struct AddEndian<T, SwapTag> {
static_assert(std::is_enum_v<T>);
using type = swap_enum_t<T>;
};
// Alias LETag/BETag as KeepTag/SwapTag depending on the system
#if COMMON_LITTLE_ENDIAN
using u16_le = u16;
using u32_le = u32;
using u64_le = u64;
using s16_le = s16;
using s32_le = s32;
using s64_le = s64;
using LETag = KeepTag;
using BETag = SwapTag;
template <typename T>
using enum_le = std::enable_if_t<std::is_enum_v<T>, T>;
using float_le = float;
using double_le = double;
using u64_be = swap_struct_t<u64, swap_64_t<u64>>;
using s64_be = swap_struct_t<s64, swap_64_t<s64>>;
using u32_be = swap_struct_t<u32, swap_32_t<u32>>;
using s32_be = swap_struct_t<s32, swap_32_t<s32>>;
using u16_be = swap_struct_t<u16, swap_16_t<u16>>;
using s16_be = swap_struct_t<s16, swap_16_t<s16>>;
template <typename T>
using enum_be = swap_enum_t<T>;
using float_be = swap_struct_t<float, swap_float_t<float>>;
using double_be = swap_struct_t<double, swap_double_t<double>>;
#else
using u64_le = swap_struct_t<u64, swap_64_t<u64>>;
using s64_le = swap_struct_t<s64, swap_64_t<s64>>;
using u32_le = swap_struct_t<u32, swap_32_t<u32>>;
using s32_le = swap_struct_t<s32, swap_32_t<s32>>;
using u16_le = swap_struct_t<u16, swap_16_t<u16>>;
using s16_le = swap_struct_t<s16, swap_16_t<s16>>;
template <typename T>
using enum_le = swap_enum_t<T>;
using float_le = swap_struct_t<float, swap_float_t<float>>;
using double_le = swap_struct_t<double, swap_double_t<double>>;
using u16_be = u16;
using u32_be = u32;
using u64_be = u64;
using s16_be = s16;
using s32_be = s32;
using s64_be = s64;
template <typename T>
using enum_be = std::enable_if_t<std::is_enum_v<T>, T>;
using float_be = float;
using double_be = double;
using BETag = KeepTag;
using LETag = SwapTag;
#endif
// Aliases for LE types
using u16_le = AddEndian<u16, LETag>::type;
using u32_le = AddEndian<u32, LETag>::type;
using u64_le = AddEndian<u64, LETag>::type;
using s16_le = AddEndian<s16, LETag>::type;
using s32_le = AddEndian<s32, LETag>::type;
using s64_le = AddEndian<s64, LETag>::type;
template <typename T>
using enum_le = std::enable_if_t<std::is_enum_v<T>, typename AddEndian<T, LETag>::type>;
using float_le = AddEndian<float, LETag>::type;
using double_le = AddEndian<double, LETag>::type;
// Aliases for BE types
using u16_be = AddEndian<u16, BETag>::type;
using u32_be = AddEndian<u32, BETag>::type;
using u64_be = AddEndian<u64, BETag>::type;
using s16_be = AddEndian<s16, BETag>::type;
using s32_be = AddEndian<s32, BETag>::type;
using s64_be = AddEndian<s64, BETag>::type;
template <typename T>
using enum_be = std::enable_if_t<std::is_enum_v<T>, typename AddEndian<T, BETag>::type>;
using float_be = AddEndian<float, BETag>::type;
using double_be = AddEndian<double, BETag>::type;