Tools/TestWebKitAPI/Tests/WTF/StringHasher.cpp

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#include "config.h"
#include <wtf/DataLog.h>
#include <wtf/MonotonicTime.h>
#include <wtf/Vector.h>
#include <wtf/text/StringHasherInlines.h>


namespace TestWebKitAPI {

static bool dumpHashingSpeedComparison = false;

TEST(WTF, StringHasher)
{
    auto generateLCharArray = [&](size_t size) {
        auto array = std::unique_ptr<LChar[]>(new LChar[size]);
        for (size_t i = 0; i < size; i++)
            array[i] = i;
        return array;
    };

    auto generateUCharArray = [&](size_t size) {
        auto array = std::unique_ptr<UChar[]>(new UChar[size]);
        for (size_t i = 0; i < size; i++)
            array[i] = i;
        return array;
    };

    StringHasher hash;
    unsigned max8Bit = std::numeric_limits<uint8_t>::max();
    for (size_t size = 0; size <= max8Bit; size++) {
        std::unique_ptr<const LChar[]> arr1 = generateLCharArray(size);
        std::unique_ptr<const UChar[]> arr2 = generateUCharArray(size);
        unsigned left = StringHasher::computeHashAndMaskTop8Bits(std::span { arr1.get(), size });
        unsigned right = StringHasher::computeHashAndMaskTop8Bits(std::span { arr2.get(), size });
        ASSERT_EQ(left, right);

        for (size_t i = 0; i < size; i++)
            hash.addCharacter(arr2.get()[i]);
        unsigned result1 = hash.hashWithTop8BitsMasked();
        ASSERT_EQ(right, result1);
    }
}

TEST(WTF, StringHasher_SuperFastHash_VS_WYHash)
{
    if (!dumpHashingSpeedComparison)
        return;

    size_t sum = 0;
    dataLogLn("UChar");
    for (size_t size = 2; size < (1 << 16); size *= 2) {
        Vector<UChar> vector;
        vector.resize(size);
        for (unsigned i = 0; i < size; ++i)
            vector[i] = i & 0x7f;
        sum += SuperFastHash::computeHashAndMaskTop8Bits(std::span<const UChar> { vector.data(), size });
        sum += WYHash::computeHashAndMaskTop8Bits(std::span<const UChar> { vector.data(), size });
        sum += StringHasher::computeHashAndMaskTop8Bits(std::span<const UChar> { vector.data(), size });
        auto start = MonotonicTime::now();
        for (unsigned i = 0; i < 1e5; ++i)
            sum += SuperFastHash::computeHashAndMaskTop8Bits(std::span<const UChar> { vector.data(), size });
        dataLogLn("SFH ", size, " -> ", MonotonicTime::now() - start);
        start = MonotonicTime::now();
        for (unsigned i = 0; i < 1e5; ++i)
            sum += WYHash::computeHashAndMaskTop8Bits(std::span<const UChar> { vector.data(), size });
        dataLogLn("WYH ", size, " -> ", MonotonicTime::now() - start);
        start = MonotonicTime::now();
        for (unsigned i = 0; i < 1e5; ++i)
            sum += StringHasher::computeHashAndMaskTop8Bits(std::span<const UChar> { vector.data(), size });
        dataLogLn("STH ", size, " -> ", MonotonicTime::now() - start);
    }

    dataLogLn("LChar");
    for (size_t size = 2; size < (1 << 16); size *= 2) {
        Vector<LChar> vector;
        vector.resize(size);
        for (unsigned i = 0; i < size; ++i)
            vector[i] = i & 0x7f;
        sum += SuperFastHash::computeHashAndMaskTop8Bits(std::span<const LChar> { vector.data(), size });
        sum += WYHash::computeHashAndMaskTop8Bits(std::span<const LChar> { vector.data(), size });
        sum += StringHasher::computeHashAndMaskTop8Bits(std::span<const LChar> { vector.data(), size });
        auto start = MonotonicTime::now();
        for (unsigned i = 0; i < 1e5; ++i)
            sum += SuperFastHash::computeHashAndMaskTop8Bits(std::span<const LChar> { vector.data(), size });
        dataLogLn("SFH ", size, " -> ", MonotonicTime::now() - start);
        start = MonotonicTime::now();
        for (unsigned i = 0; i < 1e5; ++i)
            sum += WYHash::computeHashAndMaskTop8Bits(std::span<const LChar> { vector.data(), size });
        dataLogLn("WYH ", size, " -> ", MonotonicTime::now() - start);
        start = MonotonicTime::now();
        for (unsigned i = 0; i < 1e5; ++i)
            sum += StringHasher::computeHashAndMaskTop8Bits(std::span<const LChar> { vector.data(), size });
        dataLogLn("STH ", size, " -> ", MonotonicTime::now() - start);
    }
    dataLogLn(sum);
}

} // namespace TestWebKitAPI