Qt 多种方式读写二进制文件

将文本数据写入二进制文件，然后从二进制文件中读出，还原为文本数据。

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDataStream>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写二进制文件
    QFile file("F:/1.txt");
    if(!file.open(QIODevice::WriteOnly))
    {
        qDebug() << "Can't open file for writing";
        return 0;
    }
    QDataStream out(&file);
    out.setVersion(QDataStream::Qt_5_7);
    out << int(12) << QByteArray("123");
    file.close();

    //读二进制文件
    if (!file.open(QIODevice::ReadOnly))
    {
        qDebug() << "Cannot open file for reading: ";
        return 0;
    }
    QDataStream in(&file);
    in.setVersion(QDataStream::Qt_5_7);
    int n;
    QByteArray s;
    in >> n >>  s;
    file.close();
    qDebug() << n << s;

    return a.exec();
}

运行结果：

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDebug>

class T
{
public:
    int a;
    double b;
    QString c;

    T(int a1, double b1, QString c1);

    friend QDataStream& operator<<(QDataStream &out, const T &t);
    friend QDataStream& operator>>(QDataStream &in, T &t);
};

T::T(int a1, double b1, QString c1)
{
    a = a1;
    b = b1;
    c = c1;
}

QDataStream& operator <<(QDataStream &out, const T &t)
{
    out << t.a << t.b << t.c;
    return out;
}

QDataStream& operator >>(QDataStream &in, T &t)
{
    int a;
    double b;
    QString c;
    in >> a >> b >> c;
    t.a = a;
    t.b = b;
    t.c = c;
    return in;
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写二进制文件
    T t(1, 2, "3");
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    out << t;
    writeFile.close();

    //读二进制文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QDataStream in(&readFile);
    in >> t;
    readFile.close();
    qDebug() << t.a << t.b << t.c;

    return 0;
    return a.exec();
}

运行结果：

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDebug>

class T
{
public:
    int a;
    double b;
    QString c;

    T(int a1, double b1, QString c1);
};

T::T(int a1, double b1, QString c1)
{
    a = a1;
    b = b1;
    c = c1;
}


int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写文件
    T t(1, 2, "34");
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    out.writeRawData((char *)&t, sizeof(t));
    writeFile.close();

    //读文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QDataStream in(&readFile);
    in.readRawData((char *)&t, sizeof(t));
    readFile.close();
    qDebug() << t.a << t.b << t.c;

    return 0;
    return a.exec();
}

运行结果：

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写文件
    int aa = 1;
    char b = 'c';
    double c = 2;
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    out.writeRawData((char *)&aa, sizeof(int));
    out.writeRawData((char *)&b, sizeof(char));
    out.writeRawData((char *)&c, sizeof(double));
    writeFile.close();

    //读文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QDataStream in(&readFile);
    in.readRawData((char *)&aa, sizeof(int));
    in.readRawData((char *)&b, sizeof(char));
    in.readRawData((char *)&c, sizeof(double));
    readFile.close();
    qDebug() << aa << b << c;

    return 0;
    return a.exec();
}

运行结果：

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDebug>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写文件
    int aa = 1;
    char b = 'c';
    double c = 2;
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    out.writeRawData((char *)&aa, sizeof(int));
    out.writeRawData((char *)&b, sizeof(char));
    out.writeRawData((char *)&c, sizeof(double));
    writeFile.close();

    //读文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QDataStream in(&readFile);
    char bf[100];
    in.readRawData((char *)&bf, sizeof(int) + sizeof(char) + sizeof(double));
    readFile.close();

    memcpy(&aa, bf, sizeof(int));
    memcpy(&b, bf + 4, sizeof(char));
    memcpy(&c, bf + 5, sizeof(double));
    qDebug() << aa << b << c;

    return 0;
    return a.exec();
}

运行结果：

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写文件
    int aa = 1;
    char b = 'c';
    double c = 2;
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    out.writeRawData((char *)&aa, sizeof(int));
    out.writeRawData((char *)&b, sizeof(char));
    out.writeRawData((char *)&c, sizeof(double));
    writeFile.close();


    //读文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QByteArray by;
    char *bf;
    by = readFile.readAll();
    bf = by.data();
    readFile.close();

    memcpy(&aa, bf, sizeof(int));
    memcpy(&b, bf + 4, sizeof(char));
    memcpy(&c, bf + 5, sizeof(double));
    qDebug() << aa << b << c;

    return 0;
    return a.exec();
}

运行结果：

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写文件
    int aa = 1;
    char b = 'c';
    double c = 2;
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    char bbf[100];
    char *p;
    p = (char *)&aa;
    bbf[0] = p[0];
    bbf[1] = p[1];
    bbf[2] = p[2];
    bbf[3] = p[3];
    p = (char *)&b;
    bbf[4] = p[0];
    p = (char *)&c;
    bbf[5] = p[0];
    bbf[6] = p[1];
    bbf[7] = p[2];
    bbf[8] = p[3];
    bbf[9] = p[4];
    bbf[10] = p[5];
    bbf[11] = p[6];
    bbf[12] = p[7];

    out.writeRawData(bbf, 13);
    writeFile.close();


    //读文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QByteArray by;
    char *bf;
    by = readFile.readAll();
    bf = by.data();
    readFile.close();

    memcpy(&aa, bf, 4);
    memcpy(&b, bf + 4, 1);
    memcpy(&c, bf + 5, 8);
    qDebug() << aa << b << c;

    return 0;
    return a.exec();
}

运行结果：

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //写文件
    int aa = 1;
    char b = 'c';
    double c = 2;
    int d = (int)c;
    QFile writeFile("1.dat");
    writeFile.open(QIODevice::WriteOnly);
    QDataStream out(&writeFile);
    char bbf[100];
    char *p;
    p = (char *)&aa;
    bbf[0] = p[0];
    bbf[1] = p[1];
    bbf[2] = p[2];
    bbf[3] = p[3];
    p = (char *)&b;
    bbf[4] = p[0];
    p = (char *)&d;
    bbf[5] = p[0];
    bbf[6] = p[1];
    bbf[7] = p[2];
    bbf[8] = p[3];

    out.writeRawData(bbf, 9);
    writeFile.close();


    //读文件
    QFile readFile("1.dat");
    readFile.open(QIODevice::ReadOnly);
    QByteArray by;
    char *bf;
    by = readFile.readAll();
    bf = by.data();
    readFile.close();

    int cc;
    memcpy(&aa, bf, 4);
    memcpy(&b, bf + 4, 1);
    memcpy(&cc, bf + 5, 4);
    qDebug() << aa << b << cc;

    return 0;
    return a.exec();
}

运行结果：

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