Reading a file with differences type of data

[Alex22]

In the first step You saved to a file memory area with size 500 * sizeof (double) from the array g1. Exactly the same load the file into memory and have data array double [500]. Do not close the file between subsequent readings.

Thanks. I used this:

void read()
{
    QFile g1f, g2f, of, chf, namef;
    double g1[500];
    double g2[500];
    double ofse[500];
    int ch[500];
    QStringList names;
 
 
    g1f.setFileName("oneFile.th");
    if(!g1f.open(QFile::ReadOnly))
    {
        qDebug()<<"can not open to read";
    }
    g1f.read((char*)g1, (500)*sizeof(double));
 
 
    g2f.setFileName("oneFile.th");
    if(!g2f.open(QFile::Append))
    {
        qDebug()<<"can not open to read";
    }
    g2f.read((char*)g2, (500)*sizeof(double));
 
 
 
    of.setFileName("oneFile.th");
    if(!of.open(QFile::Append))
    {
        qDebug()<<"can not open to read";
    }
    of.read((char*)ofse, (500)*sizeof(double));
 
 
    chf.setFileName("oneFile.th");
    if(!chf.open(QFile::Append))
    {
        qDebug()<<"can not open to read";
    }
    chf.read((char*)ch, (500)*sizeof(int));
 
 
    namef.setFileName("oneFile.th");
    if(!namef.open(QFile::Append))
    {
        qDebug()<<"can not open to write";
    }
    QDataStream df(&namef);
    df >> names;
    namef.close();
 
    for(int y=0; y<500; y++)
    qDebug()<<ch[y];
}

void read()
{
    QFile g1f, g2f, of, chf, namef;
    double g1[500];
    double g2[500];
    double ofse[500];
    int ch[500];
    QStringList names;


    g1f.setFileName("oneFile.th");
    if(!g1f.open(QFile::ReadOnly))
    {
        qDebug()<<"can not open to read";
    }
    g1f.read((char*)g1, (500)*sizeof(double));


    g2f.setFileName("oneFile.th");
    if(!g2f.open(QFile::Append))
    {
        qDebug()<<"can not open to read";
    }
    g2f.read((char*)g2, (500)*sizeof(double));



    of.setFileName("oneFile.th");
    if(!of.open(QFile::Append))
    {
        qDebug()<<"can not open to read";
    }
    of.read((char*)ofse, (500)*sizeof(double));


    chf.setFileName("oneFile.th");
    if(!chf.open(QFile::Append))
    {
        qDebug()<<"can not open to read";
    }
    chf.read((char*)ch, (500)*sizeof(int));


    namef.setFileName("oneFile.th");
    if(!namef.open(QFile::Append))
    {
        qDebug()<<"can not open to write";
    }
    QDataStream df(&namef);
    df >> names;
    namef.close();
    
    for(int y=0; y<500; y++)
    qDebug()<<ch[y];
}

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now i have 2 issues. it gives me this when i want to read:
QIODevice::read (QFile, "oneFile.th"): WriteOnly device
QIODevice::read (QFile, "oneFile.th"): WriteOnly device
QIODevice::read (QFile, "oneFile.th"): WriteOnly device
QIODevice::read (QFile, "oneFile.th"): WriteOnly device

and for example in "int ch[500]", after reading, ch[499] must equal to 499 but it equals to 497! what is wrong?