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endian: add signed byteswap

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This commit is contained in:
Danny Robson 2017-01-04 22:38:15 +11:00
parent f3fb385686
commit 0997bbbaac
1 changed files with 22 additions and 5 deletions
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25
endian.hpp
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@ -35,12 +35,29 @@ namespace util {
constexpr T
bswap (T);
//template <> constexpr int8_t bswap ( int8_t v) { return v; }
//template <> constexpr int16_t bswap (int16_t v) { return __builtin_bswap16 (v); }
//template <> constexpr int32_t bswap (int32_t v) { return __builtin_bswap32 (v); }
//template <> constexpr int64_t bswap (int64_t v) { return __builtin_bswap64 (v); }
// CXX: Update using "if constexpr" when available. It doesn't seem to be
// worth the dicking about to use enable_if_t to differentiate the
// signed/unsigned cases.
#define SIGNED_BSWAP(S) \
template <> \
constexpr \
int##S##_t \
bswap (int##S##_t v) { \
const union { \
int##S##_t s; \
uint##S##_t u; \
} vu = { v }; \
\
return __builtin_bswap##S (vu.u); \
}
SIGNED_BSWAP(16)
SIGNED_BSWAP(32)
SIGNED_BSWAP(64)
template <> constexpr int8_t bswap ( int8_t v) { return v; }
template <> constexpr uint8_t bswap (uint8_t v) { return v; }
template <> constexpr uint16_t bswap (uint16_t v) { return __builtin_bswap16 (v); }
template <> constexpr uint32_t bswap (uint32_t v) { return __builtin_bswap32 (v); }
template <> constexpr uint64_t bswap (uint64_t v) { return __builtin_bswap64 (v); }