Qt: 读写二进制文件(写对象, 原始数据等)

#include <iostream>
#include <QFile>
#include <QImage>
#include <QMap>
#include <QColor>

class C {
public:
C(quint32 value = 0) :
value(value) {
}

// Override operator << and >>.
friend QDataStream &operator<<(QDataStream &out, const C &obj);
friend QDataStream &operator>>(QDataStream &in, C &obj);

quint32 getValue() const {
return value;
}

private:
quint32 value;
};

QDataStream &operator<<(QDataStream &out, const C &obj) {
out << obj.value;

return out;
}

QDataStream &operator>>(QDataStream &in, C &obj) {
in >> obj.value;

return in;
}

/**
* Copy a file
*/
bool copy(const QString &source, const QString &dest) {
QFile sourceFile(source);
if (!sourceFile.open(QIODevice::ReadOnly)) {
#ifdef DEBUG
std::cerr << sourceFile.errorString().toStdString() << std::endl;
#endif
return false;
}

QFile destFile(dest);
if (!destFile.open(QIODevice::WriteOnly)) {
#ifdef DEBUG
std::cerr << destFile.errorString().toStdString() << std::endl;
#endif
return false;
}

destFile.write(sourceFile.readAll());

return sourceFile.error() == QFile::NoError && destFile.error()
== QFile::NoError;
}

/**
* Instantiate a QFile
* Open the file
* Access the file through q QDataStream object.
*
* Must ensure that we read all the types in exactly the same order
* as we wrote them.
*
* If the DataStream is being purely used to read and write basic C++ data types,
* we dont' even need to call setVersion().
*
* If we want to read or write a file in one go. WE can avoid using QDataStream altogether
* and instead using QIODevice's write() and readAll() function.
* For example copy a file.
*/
int main(int argc, char *argv[]) {
//********Write data in to the file.********
QImage image("Adium.png");
QMap<QString, QColor> map;
map.insert("red", Qt::red);
map.insert("green", Qt::green);
C c(23);
QFile file("data.dat");
if (!file.open(QIODevice::WriteOnly)) {
std::cerr << "Cannot open the file: Write." << file.errorString().toStdString() << std::endl;

return 1;
}

QDataStream out(&file);
out.setVersion(QDataStream::Qt_4_3);
out << quint32(7456) << map << c;
file.close();

//********Read data from the file.********
quint32 value;
QMap<QString, QColor> map2;
C c2;
if (!file.open(QIODevice::ReadOnly)) {
std::cerr << "Cannot open the file: Read." << file.errorString().toStdString() << std::endl;

return 2;
}
QDataStream in(&file);
in.setVersion(QDataStream::Qt_4_3);
in >> value >> map2 >> c2;
file.close();

std::cout << value << std::endl << c2.getValue();

copy(QString("Adium.png"), QString("Copy_Adium.png"));

return 0;
}

http://www.cppblog.com/biao/archive/2008/03/19/44810.html