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AK: Add count_required_bits

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This commit is contained in:
Tim Schumacher 2023-05-13 20:04:00 +02:00 • committed by Andreas Kling
parent 8434d76027
commit d194011570
2 changed files with 24 additions and 0 deletions
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11
AK/BuiltinWrappers.h
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@ -150,12 +150,23 @@ inline constexpr int bit_scan_forward(IntType value)
#endif
}
// Counts the minimum number of bits required to represent the value (i.e. ignoring leading null bits).
template<Unsigned IntType>
inline constexpr size_t count_required_bits(IntType value)
{
if (value == 0)
return 1;
return 8 * sizeof(value) - count_leading_zeroes(value);
}
}
#if USING_AK_GLOBALLY
using AK::bit_scan_forward;
using AK::count_leading_zeroes;
using AK::count_leading_zeroes_safe;
using AK::count_required_bits;
using AK::count_trailing_zeroes;
using AK::count_trailing_zeroes_safe;
using AK::popcount;

13
Tests/AK/TestBuiltinWrappers.cpp
View file

@ -52,3 +52,16 @@ TEST_CASE(wrapped_count_trailing_zeroes)
EXPECT_EQ(count_trailing_zeroes(static_cast<u64>(1)), 0);
EXPECT_EQ(count_trailing_zeroes(static_cast<u64>(2)), 1);
}
TEST_CASE(wrapped_count_required_bits)
{
EXPECT_EQ(count_required_bits(0b0u), 1ul);
EXPECT_EQ(count_required_bits(0b1u), 1ul);
EXPECT_EQ(count_required_bits(0b10u), 2ul);
EXPECT_EQ(count_required_bits(0b11u), 2ul);
EXPECT_EQ(count_required_bits(0b100u), 3ul);
EXPECT_EQ(count_required_bits(0b111u), 3ul);
EXPECT_EQ(count_required_bits(0b1000u), 4ul);
EXPECT_EQ(count_required_bits(0b1111u), 4ul);
EXPECT_EQ(count_required_bits(NumericLimits<u32>::max()), sizeof(u32) * 8);
}