Why is the QByteArray read from a file smaller than the newly downloaded QByteArray?

Question

I am attempting to compare a QByteArray of an already saved html file with a QByteArray that was just downloaded. I have to convert the QString of the file's contents to QByteArray in order to compare them (or vice versa) and comparing bytes seems like the cleanest method, however when converted from QString to QByteArray, the size of the new QByteArray is smaller than what it should be. QByteArray QString::toLocal8Bit() const states that if it is undefined, the characters will be suppressed or replaced. It also said that it uses toLatin1() by default and tried to use ASCII since that is what a website is encoded in. I still get the same results.

bool NewsBulletin::compareDownload(QByteArray new_contents, QString filename)
{
    bool return_what = false;
    qDebug() << "I am in compareDownload";
//    qDebug() << new_contents[1];
//    qDebug() << new_contents[1] << endl
//             << new_contents[2];
    QFile file(application_path + filename);
    if (file.exists())
    {
//        QString new_contents_qstr(new_contents);
        file.open(QIODevice::ReadOnly | QIODevice::Text);
        QTextStream in(&file);
        QTextCodec::setCodecForLocale(QTextCodec::codecForName("ASCII"));
        QString file_contents = in.readAll();
        QByteArray file_byte_array = file_contents.toLocal8Bit();
        qDebug() << "outputting new file array";
        qDebug() << new_contents[5] << new_contents.size();
        qDebug() << "outputting old file array";
        qDebug() << file_byte_array[5] << file_byte_array.size();
        for (int i=0; i<=file_byte_array.size(); i++)
        {
            if (file_byte_array[i] != new_contents[i])
            {
                return_what = true;
                break;
            }
            else if (i == file_byte_array.size())
            {
                qDebug() << "compareDownload will return false, duplicate file.";
                return_what = false;
            }
        }
    }
    else
    {
        qDebug() << "compareDownload will return true, DNE.";
        return_what = true;
    }
    return return_what;
}

The output of the qDebug() from the function is:

I am in compareDownload
outputting new file array
T 64704
outputting old file array
T 64576

score 0 · Accepted Answer · answered Jul 10 '15 at 02:19

After reading the api for hours, I found the reason for the bytes being different.

file.open(QIODevice::ReadOnly | QIODevice::Text);

QIODevice::Text needs to be removed. This flag changes end of line terminators into the terminator for cpp, "\n", thus giving a byte difference.

Why is the QByteArray read from a file smaller than the newly downloaded QByteArray?

1 Answers1