main.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QtCore>
 
void slowOperation1()
{
    static char buf[256];
    for (int i = 0; i < (1<<20); ++i)
        buf[i % sizeof buf] = i;
}
 
void slowOperation2(int) { slowOperation1(); }
 
void startExample()
{
    QElapsedTimer timer;
    timer.start();
 
    slowOperation1();
 
    qDebug() << "The slow operation took" << timer.elapsed() << "milliseconds";
}
 
void executeSlowOperations(int timeout)
{
    QElapsedTimer timer;
    timer.start();
    slowOperation1();
 
    int remainingTime = timeout - timer.elapsed();
    if (remainingTime > 0)
        slowOperation2(remainingTime);
}
 
void executeOperationsForTime(int ms)
{
    QElapsedTimer timer;
    timer.start();
 
    while (!timer.hasExpired(ms))
        slowOperation1();
}
 
int restartExample()
{
    QElapsedTimer timer;
 
    int count = 1;
    timer.start();
    do {
        count *= 2;
        slowOperation2(count);
    } while (timer.restart() < 250);
 
    return count;
}
 
int main(int argc, char **argv)
{
    QCoreApplication app(argc, argv);
 
    startExample();
    restartExample();
    executeSlowOperations(5);
    executeOperationsForTime(5);
}