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Bitmath: Add utility functions for calculating bit masks

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Add tests
This commit is contained in:
Jonathan G Rennison
2024-01-28 15:41:50 +00:00
parent 0a16ba1bd7
commit be469405df
2 changed files with 48 additions and 0 deletions
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29
src/core/bitmath_func.hpp
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@@ -187,6 +187,35 @@ inline T ToggleBit(T &x, const uint8_t y)
return x = (T)(x ^ ((T)1U << y));
}
/**
* Return a bit mask of count bits starting at start.
*
* @param start The start bit
* @param count The number of bits
* @pre start + count < sizeof(T) * 8
* @return The bit mask
*/
template <typename T>
constexpr T GetBitMaskSC(const uint8_t start, const uint8_t count)
{
typename std::make_unsigned<T>::type mask = 1;
return (T)(((mask << count) - 1) << start);
}
/**
* Return a bit mask of bits from first to last (inclusive).
*
* @param first The first bit
* @param last The last bits (inclusive)
* @pre first <= last && last < sizeof(T) * 8
* @return The bit mask
*/
template <typename T>
constexpr T GetBitMaskFL(const uint8_t first, const uint8_t last)
{
return GetBitMaskSC<T>(first, 1 + last - first);
}
/**
* Search the first set bit in a value.
* When no bit is set, it returns 0.

19
src/tests/bitmath_func.cpp
View File

@@ -68,3 +68,22 @@ TEST_CASE("SetBitIterator tests")
CHECK(test_case(INT32_MIN, { 31 }));
CHECK(test_case(INT64_MIN, { 63 }));
}
TEST_CASE("GetBitMaskSC tests")
{
CHECK(GetBitMaskSC<uint>(4, 4) == 0xF0);
CHECK(GetBitMaskSC<uint>(28, 4) == 0xF0000000);
CHECK(GetBitMaskSC<uint8_t>(7, 1) == 0x80);
CHECK(GetBitMaskSC<uint8_t>(0, 1) == 1);
CHECK(GetBitMaskSC<uint8_t>(0, 0) == 0);
CHECK(GetBitMaskSC<uint8_t>(7, 0) == 0);
}
TEST_CASE("GetBitMaskFL tests")
{
CHECK(GetBitMaskFL<uint>(4, 7) == 0xF0);
CHECK(GetBitMaskFL<uint>(28, 31) == 0xF0000000);
CHECK(GetBitMaskFL<uint8_t>(7, 7) == 0x80);
CHECK(GetBitMaskFL<uint8_t>(0, 0) == 1);
CHECK(GetBitMaskFL<uint8_t>(3, 4) == 0x18);
}