Tools/TestWebKitAPI/Tests/WTF/StdLibExtras.cpp

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#include "config.h"
#include <wtf/StdLibExtras.h>

#include <wtf/MathExtras.h>
#include <wtf/RandomNumber.h>

namespace TestWebKitAPI {

template<typename WordType>
void testFindBitInWord()
{
    constexpr size_t bitsInWord = sizeof(WordType) * 8;
    constexpr size_t numberOfShiftValues = bitsInWord + 1;
    constexpr size_t testPermutationsPerShift = 100;

    constexpr size_t numberOfTestValues = numberOfShiftValues * testPermutationsPerShift;
    uint8_t startIndex[numberOfTestValues];
    uint8_t endIndex[numberOfTestValues];

    auto initTestValues = [&] () {
        // Set some internal and boundary cases.
        uint8_t specialCases[] = {
            0,
            bitsInWord / 2,
            bitsInWord - 1,
            bitsInWord,
        };

        constexpr size_t numberOfSpecialCases = sizeof(specialCases) / sizeof(specialCases[0]);

        size_t nextTestValue = 0;
        for (size_t i = 0; i < numberOfSpecialCases; ++i) {
            for (size_t j = 0; j < numberOfSpecialCases; ++j) {
                startIndex[nextTestValue] = specialCases[i];
                endIndex[nextTestValue++] = specialCases[j];
            }
        }

        // Fill in some random cases.
        for (size_t i = nextTestValue; i < numberOfTestValues; ++i) {
            startIndex[i] = static_cast<uint8_t>(randomNumber() * bitsInWord);
            uint8_t remainingBits = bitsInWord - startIndex[i];
            endIndex[i] = static_cast<uint8_t>(randomNumber() * remainingBits) + startIndex[i];
        }
    };

    auto expectedBitInWord = [] (WordType word, size_t& index, size_t endIndex, bool value) -> bool {
        word >>= index;
        while (index < endIndex) {
            if ((word & 1) == static_cast<WordType>(value))
                return true;
            index++;
            word >>= 1;
        }
        index = endIndex;
        return false;
    };

    auto test = [&] (bool value, size_t shift) {
        constexpr uint64_t baseWord = std::numeric_limits<uint64_t>::max();
        uint64_t word = (shift < bitsInWord) ? baseWord << shift : 0;

        for (size_t i = 0; i < numberOfTestValues; ++i) {
            size_t index = startIndex[i];
            bool result = findBitInWord(word, index, endIndex[i], value);

            size_t expectedIndex = startIndex[i];
            bool expectedResult = expectedBitInWord(word, expectedIndex, endIndex[i], value);

            ASSERT_EQ(result, expectedResult);
            ASSERT_EQ(index, expectedIndex);
        }
    };

    initTestValues();

    // Testing find a set bit.
    for (size_t i = 0; i < numberOfShiftValues; ++i)
        test(true, i);

    // Testing find a cleared bit.
    for (size_t i = 0; i < numberOfShiftValues; ++i)
        test(false, i);
}

TEST(WTF_StdLibExtras, findBitInWord_uint32_t) { testFindBitInWord<uint32_t>(); }
TEST(WTF_StdLibExtras, findBitInWord_uint64_t) { testFindBitInWord<uint64_t>(); }

} // namespace TestWebKitAPI