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xyseriesiodevice.cpp Example File

audio/xyseriesiodevice.cpp
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Charts module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
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** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
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** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
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#include "xyseriesiodevice.h"

#include <QtCharts/QXYSeries>

XYSeriesIODevice::XYSeriesIODevice(QXYSeries *series, QObject *parent) :
    QIODevice(parent),
    m_series(series)
{
}

qint64 XYSeriesIODevice::readData(char *data, qint64 maxSize)
{
    Q_UNUSED(data)
    Q_UNUSED(maxSize)
    return -1;
}

qint64 XYSeriesIODevice::writeData(const char *data, qint64 maxSize)
{
    static const int resolution = 4;

    if (m_buffer.isEmpty()) {
        m_buffer.reserve(sampleCount);
        for (int i = 0; i < sampleCount; ++i)
            m_buffer.append(QPointF(i, 0));
    }

    int start = 0;
    const int availableSamples = int(maxSize) / resolution;
    if (availableSamples < sampleCount) {
        start = sampleCount - availableSamples;
        for (int s = 0; s < start; ++s)
            m_buffer[s].setY(m_buffer.at(s + availableSamples).y());
    }

    for (int s = start; s < sampleCount; ++s, data += resolution)
        m_buffer[s].setY(qreal(uchar(*data) -128) / qreal(128));

    m_series->replace(m_buffer);
    return (sampleCount - start) * resolution;
}
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