Game Programming 凯撒密码加密

凯撒密码加密

它使用一种非常简单的算法（凯撒密码）加密或解密流经它的数据。 加密时，它将明文中的每个字符移动由**定义的多个字符。 它在解密时进行相反的操作。 因此，如果**为 2，明文字符为 a，则密文变为 c。 用** 4 解密 z 将产生值 v。

CaesarCipherDevice.h

#ifndef CAESARCIPHERDEVICE_H
#define CAESARCIPHERDEVICE_H

#include <QIODevice>

class CaesarCipherDevice : public QIODevice
{
    Q_OBJECT
    Q_PROPERTY(int key READ key WRITE setKey)
public:
    explicit CaesarCipherDevice(QObject *parent = 0);
    void setBaseDevice(QIODevice *dev)
    {
        m_baseDevice = dev;
    }
    QIODevice *baseDevice() const
    {
        return m_baseDevice;
    }
    void setKey(int k)
    {
        m_key = k;
    }
    inline int key() const
    {
        return m_key;
    }
    bool open(OpenMode mode);
protected:
    qint64 writeData(const char *data, qint64 len);
    qint64 readData(char *data, qint64 maxlen);
private:
    int m_key;
    QIODevice *m_baseDevice;
};

#endif // CAESARCIPHERDEVICE_H

CaesarCipherDevice.cpp

#include "caesarcipherdevice.h"
#include <QDebug>

CaesarCipherDevice::CaesarCipherDevice(QObject *parent) : QIODevice(parent)
{
    m_key = 0;
    m_baseDevice = 0;
}

bool CaesarCipherDevice::open(OpenMode mode)
{
    if(!m_baseDevice)
    {
        qWarning("CaesarCipherDevice::open: No base device");
        setErrorString(tr("No base device"));
        return false;
    }
    if(!m_baseDevice->isOpen())
    {
        qWarning("CaesarCipherDevice::open: Base device is not open");
        setErrorString(tr("Base device is not open"));
        return false;
    }
    if(m_baseDevice->openMode() != mode)
    {
        qWarning("CaesarCipherDevice::open: Base device has a different openMode()");
        setErrorString(tr("Base device has a different openMode()"));
        return false;
    }
    return QIODevice::open(mode);
}

qint64 CaesarCipherDevice::writeData(const char *data, qint64 len)
{
    QByteArray byteArray;
    byteArray.resize(len);
    for(int i = 0; i < len; ++i) {
        byteArray[i] = data[i] + m_key;
    }
    int written = m_baseDevice->write(byteArray);
    emit bytesWritten(written);
    return written;
}

qint64 CaesarCipherDevice::readData(char *data, qint64 maxlen)
{
    QByteArray baseData = m_baseDevice->read(maxlen);
    const int size = baseData.size();
    for(int i = 0; i < size; ++i)
    {
        data[i] = baseData[i] - m_key;
    }
    return size;
}

main.cpp

#include <QByteArray>
#include <QBuffer>
#include <QtDebug>

#include "CaesarCipherDevice.h"

int main(int, char **)
{
    QByteArray ba = "plaintext";
    QBuffer buf;
    buf.open(QIODevice::WriteOnly);
    CaesarCipherDevice encrypt;
    encrypt.setKey(3);
    encrypt.setBaseDevice(&buf);
    encrypt.open(buf.openMode());
    encrypt.write(ba);
    qDebug() << buf.data();

    CaesarCipherDevice decrypt;
    decrypt.setKey(3);
    decrypt.setBaseDevice(&buf);
    buf.open(QIODevice::ReadOnly);
    decrypt.open(buf.openMode());
    qDebug() << decrypt.readAll();
    return 0;
}