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Replace serial byteswap macros with constexpr function

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This allows taking the input by-value instead of by-reference, while
still protecting against unwanted type conversion.

Add some basic static_assert tests that the swapped values are correct.
This commit is contained in:
Kp 2022-04-17 22:27:19 +00:00
parent 71b4c11f8c
commit cf2c7bbe80
1 changed files with 41 additions and 38 deletions
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79
common/include/serial.h
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@ -489,50 +489,53 @@ public:
template <typename... Args>
message(Args &&... args) -> message<Args && ...>;
#define SERIAL_DEFINE_SIZE_SPECIFIC_USWAP_BUILTIN(HBITS,BITS) \
static constexpr uint##BITS##_t bswap(const uint##BITS##_t &u) \
{ \
return __builtin_bswap##BITS(u); \
}
#define SERIAL_DEFINE_SIZE_SPECIFIC_USWAP_EXPLICIT(HBITS,BITS) \
static constexpr uint##BITS##_t bswap(const uint##BITS##_t &u) \
{ \
return (static_cast<uint##BITS##_t>(bswap(static_cast<uint##HBITS##_t>(u))) << HBITS) | \
static_cast<uint##BITS##_t>(bswap(static_cast<uint##HBITS##_t>(u >> HBITS))); \
}
#define SERIAL_DEFINE_SIZE_SPECIFIC_BSWAP(HBITS,BITS) \
SERIAL_DEFINE_SIZE_SPECIFIC_USWAP(HBITS,BITS); \
static constexpr int##BITS##_t bswap(const int##BITS##_t &i) \
{ \
return bswap(static_cast<uint##BITS##_t>(i)); \
}
static constexpr uint8_t bswap(const uint8_t &u)
template <typename T>
static constexpr T bswap(const T u)
{
return u;
}
static constexpr int8_t bswap(const int8_t &u)
{
return u;
}
if constexpr (std::is_same<T, int8_t>::value || std::is_same<T, uint8_t>::value)
/* Swapping a byte-sized value is a no-op. This is permitted here so
* that callers can swap without checking the size of the value.
*/
return u;
if constexpr (std::is_same<T, int16_t>::value || std::is_same<T, uint16_t>::value)
{
#ifdef DXX_HAVE_BUILTIN_BSWAP
#define SERIAL_DEFINE_SIZE_SPECIFIC_USWAP SERIAL_DEFINE_SIZE_SPECIFIC_USWAP_BUILTIN
return __builtin_bswap16(u);
#else
#define SERIAL_DEFINE_SIZE_SPECIFIC_USWAP SERIAL_DEFINE_SIZE_SPECIFIC_USWAP_EXPLICIT
return (static_cast<T>(static_cast<uint8_t>(u)) << 8) | static_cast<T>(static_cast<uint8_t>(u >> 8));
#endif
}
if constexpr (std::is_same<T, int32_t>::value || std::is_same<T, uint32_t>::value)
{
#ifdef DXX_HAVE_BUILTIN_BSWAP
return __builtin_bswap32(u);
#else
return (static_cast<T>(bswap(static_cast<uint16_t>(u))) << 16) | static_cast<T>(bswap(static_cast<uint16_t>(u >> 16)));
#endif
}
if constexpr (std::is_same<T, int64_t>::value || std::is_same<T, uint64_t>::value)
{
#ifdef DXX_HAVE_BUILTIN_BSWAP
return __builtin_bswap64(u);
#else
return (static_cast<T>(bswap(static_cast<uint32_t>(u))) << 32) | static_cast<T>(bswap(static_cast<uint32_t>(u >> 32)));
#endif
}
/* Unsupported type. Fall off the end of the function and trigger a
* compile error due to the missing `return` statement.
*/
}
SERIAL_DEFINE_SIZE_SPECIFIC_BSWAP(8, 16);
SERIAL_DEFINE_SIZE_SPECIFIC_BSWAP(16, 32);
SERIAL_DEFINE_SIZE_SPECIFIC_BSWAP(32, 64);
assert_equal(bswap(static_cast<uint8_t>(1)), 1, "");
#undef SERIAL_DEFINE_SIZE_SPECIFIC_BSWAP
#undef SERIAL_DEFINE_SIZE_SPECIFIC_USWAP
#undef SERIAL_DEFINE_SIZE_SPECIFIC_USWAP_BUILTIN
#undef SERIAL_DEFINE_SIZE_SPECIFIC_USWAP_EXPLICIT
assert_equal(bswap(static_cast<uint16_t>(0x12)), 0x1200, "");
assert_equal(bswap(static_cast<uint16_t>(0x92)), 0x9200, "");
assert_equal(bswap(static_cast<uint16_t>(0x9200)), 0x92, "");
assert_equal(bswap(static_cast<uint16_t>(0x102)), 0x201, "");
assert_equal(bswap(static_cast<uint32_t>(0x102)), 0x2010000, "");
assert_equal(bswap(static_cast<uint64_t>(0x102)), 0x201000000000000ull, "");
namespace reader {