format_data_size.cpp

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// QLocale::formatDataSize backported from Qt 5.10
// Ported by Max Schwarz <max.schwarz@uni-bonn.de>

#include "format_data_size.h"

#include <cmath>

#include <QtAlgorithms>
#include <QLocale>

namespace rqt_rosmon
{

static inline uint countLeadingZeroBits(quint64 v)
{
        return __builtin_clzll(v);
}

QString formattedDataSize(qint64 bytes, int precision)
{
        int power, base = 1000;
        if (!bytes) {
                power = 0;
        } else { // Compute log2(bytes) / 10:
                power = int((63 - countLeadingZeroBits(quint64(qAbs(bytes)))) / 10);
                base = 1024;
        }

        QLocale locale = QLocale::system();

        // Only go to doubles if we'll be using a quantifier:
        const QString number = power
                ? locale.toString(bytes / std::pow(double(base), power), 'f', qMin(precision, 3 * power))
                : locale.toString(bytes);

        // We don't support sizes in units larger than exbibytes because
        // the number of bytes would not fit into qint64.
        Q_ASSERT(power <= 6 && power >= 0);
        QString unit;
        if (power > 0) {
                switch(power)
                {
                        case 1: unit = "KiB"; break;
                        case 2: unit = "MiB"; break;
                        case 3: unit = "GiB"; break;
                        case 4: unit = "TiB"; break;
                        case 5: unit = "PiB"; break;
                        case 6: unit = "EiB"; break;
                }
        } else {
                unit = "B";
        }

        return number + QLatin1Char(' ') + unit;
}

}