qt-everywhere-src-5.15.1/qtbase/tests/benchmarks/corelib/mimetypes/qmimedatabase/main.cpp

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#include <QtTest/QtTest>

class tst_QMimeDatabase: public QObject
{

    Q_OBJECT

private slots:
    void inheritsPerformance();
    void benchMimeTypeForName();
};

void tst_QMimeDatabase::inheritsPerformance()
{
    // Check performance of inherits().
    // This benchmark (which started in 2009 in kmimetypetest.cpp) uses 40 mimetypes.
    QStringList mimeTypes;
    mimeTypes << QLatin1String("image/jpeg") << QLatin1String("image/png") << QLatin1String("image/tiff") << QLatin1String("text/plain") << QLatin1String("text/html");
    mimeTypes += mimeTypes;
    mimeTypes += mimeTypes;
    mimeTypes += mimeTypes;
    QCOMPARE(mimeTypes.count(), 40);
    QMimeDatabase db;
    QMimeType mime = db.mimeTypeForName(QString::fromLatin1("text/x-chdr"));
    QVERIFY(mime.isValid());
    QBENCHMARK {
        QString match;
        foreach (const QString &mt, mimeTypes) {
            if (mime.inherits(mt)) {
                match = mt;
                // of course there would normally be a "break" here, but we're testing worse-case
                // performance here
            }
        }
        QCOMPARE(match, QString::fromLatin1("text/plain"));
    }
    // Numbers from 2011, in release mode:
    // KDE 4.7 numbers: 0.21 msec / 494,000 ticks / 568,345 instr. loads per iteration
    // QMimeBinaryProvider (with Qt 5): 0.16 msec / NA / 416,049 instr. reads per iteration
    // QMimeXmlProvider (with Qt 5): 0.062 msec / NA / 172,889 instr. reads per iteration
    //   (but the startup time is way higher)
    // And memory usage is flat at 200K with QMimeBinaryProvider, while it peaks at 6 MB when
    // parsing XML, and then keeps being around 4.5 MB for all the in-memory hashes.
}

void tst_QMimeDatabase::benchMimeTypeForName()
{
    QMimeDatabase db;

    QBENCHMARK {
        const auto s = db.mimeTypeForName(QStringLiteral("text/plain"));
        QVERIFY(s.isValid());
    }
}

QTEST_MAIN(tst_QMimeDatabase)
#include "main.moc"