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// Copyright (C) 2021 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#include <QTest>
#include <qhashfunctions.h>
#if QT_CONFIG(process)
#include <qprocess.h>
#endif
class tst_QHashSeed : public QObject
{
Q_OBJECT
public:
static void initMain();
private Q_SLOTS:
void initTestCase();
void environmentVariable_data();
void environmentVariable();
void deterministicSeed();
void reseeding();
void quality();
#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
void compatibilityApi();
void deterministicSeed_compat();
#endif
};
void tst_QHashSeed::initMain()
{
qunsetenv("QT_HASH_SEED");
}
void tst_QHashSeed::initTestCase()
{
// in case the qunsetenv above didn't work
if (qEnvironmentVariableIsSet("QT_HASH_SEED"))
QSKIP("QT_HASH_SEED environment variable is set, please don't do that");
}
void tst_QHashSeed::environmentVariable_data()
{
#ifdef Q_OS_ANDROID
QSKIP("This test needs a helper binary, so is excluded from this platform.");
#endif
QTest::addColumn<QByteArray>("envVar");
QTest::addColumn<bool>("isZero");
QTest::newRow("unset-environment") << QByteArray() << false;
QTest::newRow("empty-environment") << QByteArray("") << false;
QTest::newRow("zero-seed") << QByteArray("0") << true;
}
void tst_QHashSeed::environmentVariable()
{
#if QT_CONFIG(process)
QFETCH(QByteArray, envVar);
QFETCH(bool, isZero);
QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
if (envVar.isNull())
env.remove("QT_HASH_SEED");
else
env.insert("QT_HASH_SEED", envVar);
QProcess helper;
helper.setProcessEnvironment(env);
helper.setProgram("./tst_qhashseed_helper");
helper.start();
QVERIFY2(helper.waitForStarted(5000), qPrintable(helper.errorString()));
QVERIFY2(helper.waitForFinished(5000), qPrintable(helper.errorString()));
QCOMPARE(helper.exitStatus(), 0);
QByteArray line1 = helper.readLine().trimmed();
QByteArray line2 = helper.readLine().trimmed();
QCOMPARE(line2, line1);
QCOMPARE(line1 == "0", isZero);
#endif
}
void tst_QHashSeed::deterministicSeed()
{
QHashSeed::setDeterministicGlobalSeed();
QCOMPARE(size_t(QHashSeed::globalSeed()), size_t(0));
// now reset
QHashSeed::resetRandomGlobalSeed();
QVERIFY(QHashSeed::globalSeed() != 0);
}
void tst_QHashSeed::reseeding()
{
constexpr int Iterations = 4;
size_t seeds[Iterations];
for (int i = 0; i < Iterations; ++i) {
seeds[i] = QHashSeed::globalSeed();
QHashSeed::resetRandomGlobalSeed();
}
// verify that they are all different
QString fmt = QStringLiteral("seeds[%1] = 0x%3, seeds[%2] = 0x%4");
for (int i = 0; i < Iterations; ++i) {
for (int j = i + 1; j < Iterations; ++j) {
QVERIFY2(seeds[i] != seeds[j],
qPrintable(fmt.arg(i).arg(j).arg(seeds[i], 16).arg(seeds[j], 16)));
}
}
}
void tst_QHashSeed::quality()
{
// this "bad seed" is used internally in qhash.cpp and should never leak!
constexpr size_t BadSeed = size_t(Q_UINT64_C(0x5555'5555'5555'5555));
constexpr int Iterations = 24; // nicely divisible by 3
int oneThird = 0;
int badSeeds = 0;
int seedsToMinus1 = 0;
size_t ored = 0;
for (int i = 0; i < Iterations; ++i) {
size_t seed = QHashSeed::globalSeed();
ored |= seed;
int bits = qPopulationCount(quintptr(seed));
QVERIFY2(bits > 0, QByteArray::number(bits)); // mandatory
if (bits >= std::numeric_limits<size_t>::digits / 3)
++oneThird;
if (seed == BadSeed)
++badSeeds;
if (ored != size_t(-1))
++seedsToMinus1;
QHashSeed::resetRandomGlobalSeed();
}
// report out
qInfo() << "Number of seeds until all bits became set:" << seedsToMinus1 << '/' << Iterations;
qInfo() << "Number of seeds with at least one third of the bits set:"
<< oneThird << '/' << Iterations;
// we must have set all bits after all the iterations
QCOMPARE(ored, size_t(-1));
// at least one third of the seeds must have one third of all the bits set
QVERIFY(oneThird > (Iterations/3));
// at most one seed can be the bad seed, if 32-bit, none on 64-bit
if (std::numeric_limits<size_t>::digits > 32)
QCOMPARE(badSeeds, 0);
else
QVERIFY2(badSeeds <= 1, "badSeeds = " + QByteArray::number(badSeeds));
// we must have taken at most two thirds of the iterations to have set each
// bit at least once
QVERIFY2(seedsToMinus1 < 2*Iterations/3,
"seedsToMinus1 = " + QByteArray::number(seedsToMinus1));
}
#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
QT_WARNING_DISABLE_DEPRECATED
void tst_QHashSeed::compatibilityApi()
{
int oldSeed = qGlobalQHashSeed();
size_t newSeed = QHashSeed::globalSeed();
QCOMPARE(size_t(oldSeed), newSeed & size_t(INT_MAX));
}
void tst_QHashSeed::deterministicSeed_compat()
{
// same as above, but using the compat API
qSetGlobalQHashSeed(0);
QCOMPARE(size_t(QHashSeed::globalSeed()), size_t(0));
QCOMPARE(qGlobalQHashSeed(), 0);
// now reset
qSetGlobalQHashSeed(-1);
QVERIFY(QHashSeed::globalSeed() != 0);
QVERIFY(qGlobalQHashSeed() != 0);
QVERIFY(qGlobalQHashSeed() != -1); // possible, but extremely unlikely
}
#endif // Qt 7
QTEST_MAIN(tst_QHashSeed)
#include "tst_qhashseed.moc"
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