qt-creator/src/libs/timeline/timelineformattime.cpp

/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt Creator.
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** GNU General Public License Usage
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** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
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#include "timelineformattime.h"

namespace Timeline {

QString formatTime(qint64 timestamp, qint64 reference)
{
    static const char *decimalUnits[] = {"ns", "\xb5s", "ms", "s"};
    static const double second = 1e9;
    static const double minute = 60;
    static const double hour = 60;

    int round = 0;
    int barrier = 1;

    auto roundTo3 = [](double time, int round) {
        // always show at least 3 significant digits
        if (time < 10 && round < 2)
            return 2;
        else if (time < 100 && round < 1)
            return 1;
        else
            return round;
    };

    for (uint i = 0, end = sizeof(decimalUnits) / sizeof(char *); i < end; ++i) {
        const double dividend = barrier;
        if (reference < barrier) {
            round += 3;
            barrier *= 1000;
        } else {
            barrier *= 10;
            if (reference < barrier) {
                round += 2;
                barrier *= 100;
            } else {
                barrier *= 10;
                if (reference < barrier)
                    round += 1;
                barrier *= 10;
            }
        }
        if (timestamp < barrier) {
            double time = timestamp;
            if (dividend > 1) {
                time /= dividend;
                round = roundTo3(time, round);
            }
            return QString::number(time, 'f', round)
                    + QString::fromLatin1(decimalUnits[i]);
        }
    }

    double seconds = timestamp / second;
    if (seconds < minute) {
        return QString::number(seconds, 'f', roundTo3(seconds, round)) + "s";
    } else {
        int minutes = seconds / minute;
        seconds -= minutes * minute;
        if (minutes < hour) {
            return QString::fromLatin1("%1m %2s").arg(QString::number(minutes),
                                                      QString::number(seconds, 'f', round));
        } else {
            int hours = minutes / hour;
            hours -= hours * hour;
            if (reference < barrier * minute) {
                return QString::fromLatin1("%1h %2m %3s").arg(QString::number(hours),
                                                              QString::number(minutes),
                                                              QString::number(seconds, 'f', round));
            } else {
                return QString::fromLatin1("%1h %2m").arg(QString::number(hours),
                                                          QString::number(minutes));
            }

        }
    }
}

}