BAN: Update Endiannes API

Add functions to swap endiannes or convert host to big/little endian

This code should be very compiler friendly and should be optimized to
single bswap instruction on x86.
This commit is contained in:
Bananymous 2023-09-27 22:33:38 +03:00
parent cb76f1ea75
commit a8d74f604e
1 changed files with 51 additions and 16 deletions

View File

@ -7,20 +7,62 @@
namespace BAN namespace BAN
{ {
template<integral T>
constexpr T swap_endianness(T value)
{
if constexpr(sizeof(T) == 1)
return value;
if constexpr(sizeof(T) == 2)
return (((value >> 8) & 0xFF) << 0)
| (((value >> 0) & 0xFF) << 8);
if constexpr(sizeof(T) == 4)
return (((value >> 24) & 0xFF) << 0)
| (((value >> 16) & 0xFF) << 8)
| (((value >> 8) & 0xFF) << 16)
| (((value >> 0) & 0xFF) << 24);
if constexpr(sizeof(T) == 8)
return (((value >> 56) & 0xFF) << 0)
| (((value >> 48) & 0xFF) << 8)
| (((value >> 40) & 0xFF) << 16)
| (((value >> 32) & 0xFF) << 24)
| (((value >> 24) & 0xFF) << 32)
| (((value >> 16) & 0xFF) << 40)
| (((value >> 8) & 0xFF) << 48)
| (((value >> 0) & 0xFF) << 56);
T result { 0 };
for (size_t i = 0; i < sizeof(T); i++)
result |= ((value >> (i * 8)) & 0xFF) << ((sizeof(T) - i - 1) * 8);
return result;
}
template<integral T>
constexpr T host_to_little_endian(T value)
{
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
return value;
#else
return swap_endianness(value);
#endif
}
template<integral T>
constexpr T host_to_big_endian(T value)
{
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
return value;
#else
return swap_endianness(value);
#endif
}
template<integral T> template<integral T>
struct LittleEndian struct LittleEndian
{ {
constexpr operator T() const constexpr operator T() const
{ {
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ return host_to_little_endian(raw);
return raw;
#else
T result { 0 };
for (size_t i = 0; i < sizeof(T); i++)
result = (result << 8) | ((raw >> (sizeof(T) - i - 1) * 8) & 0xFF);
return result;
#endif
} }
private:
T raw; T raw;
}; };
@ -29,14 +71,7 @@ namespace BAN
{ {
constexpr operator T() const constexpr operator T() const
{ {
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ return host_to_big_endian(raw);
return raw;
#else
T result { 0 };
for (size_t i = 0; i < sizeof(T); i++)
result = (result << 8) | ((raw >> (i * 8)) & 0xFF);
return result;
#endif
} }
private: private:
T raw; T raw;