nerdcruft/libcruft-util
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bitwise: add rotater

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This commit is contained in:
Danny Robson 2014-04-16 19:15:54 +10:00
parent fc935863ef
commit 028dee034a
2 changed files with 27 additions and 3 deletions
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17
bitwise.hpp
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@ -33,13 +33,24 @@ const uint8_t BITMASK_6BITS = 0x3F;
const uint8_t BITMASK_7BITS = 0x7F;
const uint8_t BITMASK_8BITS = 0xFF;
#define MODT(x) ((x) % (sizeof (T) * 8))
template <typename T>
T
constexpr T
rotatel (const T &value, size_t magnitude) {
magnitude %= sizeof (T) * 8;
return (value << magnitude) | (value >> sizeof (value) * 8 - magnitude);
return (value << MODT (magnitude)) |
(value >> sizeof (value) * 8 - MODT (magnitude));
}
template <typename T>
constexpr T
rotater (const T &value, size_t magnitude) {
return (value >> MODT (magnitude)) |
(value << sizeof (value) * 8 - MODT (magnitude));
}
#undef MODT
#endif

13
test/bitwise.cpp
View File

@ -7,15 +7,28 @@ main (int, char**) {
CHECK_EQ (rotatel (uint8_t (0xF0), 4), 0x0F);
CHECK_EQ (rotatel (uint8_t (0x0F), 8), 0x0F);
CHECK_EQ (rotater (uint8_t (0x0F), 0), 0x0F);
CHECK_EQ (rotater (uint8_t (0x0F), 4), 0xF0);
CHECK_EQ (rotater (uint8_t (0xF0), 4), 0x0F);
CHECK_EQ (rotater (uint8_t (0x0F), 8), 0x0F);
CHECK_EQ (rotatel (uint16_t (0xABCD), 0), 0xABCD);
CHECK_EQ (rotatel (uint16_t (0xABCD), 4), 0xBCDA);
CHECK_EQ (rotatel (uint16_t (0xABCD), 8), 0xCDAB);
CHECK_EQ (rotatel (uint16_t (0xABCD), 12), 0xDABC);
CHECK_EQ (rotatel (uint16_t (0xABCD), 16), 0xABCD);
CHECK_EQ (rotater (uint16_t (0xABCD), 0), 0xABCD);
CHECK_EQ (rotater (uint16_t (0xABCD), 4), 0xDABC);
CHECK_EQ (rotater (uint16_t (0xABCD), 8), 0xCDAB);
CHECK_EQ (rotater (uint16_t (0xABCD), 12), 0xBCDA);
CHECK_EQ (rotater (uint16_t (0xABCD), 16), 0xABCD);
CHECK_EQ (rotatel (uint32_t (0x12345670), 12), 0x45670123);
CHECK_EQ (rotater (uint32_t (0x12345670), 12), 0x67012345);
CHECK_EQ (rotatel (uint64_t (0x1234567890ABCDEF), 12), 0x4567890ABCDEF123);
CHECK_EQ (rotater (uint64_t (0x1234567890ABCDEF), 12), 0xDEF1234567890ABC);
return 0;
}