Qt C++ QString to QByteArray Conversion - c++

Question

I have created an encrypt/decrypt program, when encrypting I store the encrypted QByteArray in a text file.
When trying to decrypt I retrieved it and then put it into the decryption method, the problem is that I need a way to convert it to QByteArray without changing the format, otherwise it will not decrypt properly. What I mean is if the file gave me an encrypted value of 1234 and I converted that to QByteArray by going 1234.toLatin1() it changes the value and the decryption does not work. Any suggestions?
My Code:
QFile file(filename);
QString encrypted;
QString content;
if (file.open(QIODevice::ReadOnly)) {
QTextStream stream( &file );
content = stream.readAll();
}
encrypted = content.replace("\n", "");
qDebug() << encrypted; // Returns correct encrypted value
QByteArray a;
a += encrypted;
qDebug() << "2 " + a; // Returns different value than previous qDebug()
QByteArray decrypted = crypto.Decrypt(a, key);
return decrypted;

Answer 1

I guess you should use:
QString::fromUtf8(const QByteArray &str)
Or:
QString::QString(const QByteArray &ba)
to convert QByteArray to QString, then write it into file by QTextStream.
After that, read file by QTextStream, use:
QString::toUtf8()
to convert QString to QByteArray.
QString::QString(const QByteArray &ba)
Constructs a string initialized with the byte array ba. The given byte array is converted to Unicode using fromUtf8().
P.S:
Maybe use QFile::write and QFile::read is a better way.

Answer 2

try using toUtf8() .. it works fine with me

Answer 3

If I understand correctly, the text from the file is store in the QString content. I think you could create a new QByteArray. Because the constructor of a QByteArray does not allow a QString as input, I will probably have to append the QString to the empty QByteArray.
//After if:
QByteArray tempContent();
tempContent.append(content);
QByteArray decrypted = crypto.Decrypt(tempContent, key);
I do not have much experience in the Qt library, but I hope this helps.

Answer 4

Or simply go with b64 = data.toUtf8().toBase64();
First convert it to QByteArray with the toUtf8() and then immediately convert it to toBase64()

Answer 5

There's a simple way :
QByteArray ba;
QString qs = "String";
ba += qs;
More hard way:
QByteArray ba;
QDataStream in(&ba, QIODevice::WriteOnly);
in << QString("String");
Extreme way, for people who want to use QBuffer:
#include <QDebug>
#include <QBuffer>
#include <QDataStream>
#include <QIODevice>
#include <QByteArray>
#include <QString>
#include <qcoreapplication.h>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QByteArray byteArray;
QBuffer buffer(&byteArray);
buffer.open(QIODevice::ReadWrite);
QDataStream in( &buffer );
in << QString("String");
buffer.close();
for (int i = 0; i < byteArray.length(); ++i) {
printf("%c - %x\n", byteArray.at(i), byteArray.at(i));
}
printf("\n");
return a.exec();
}
Who run last code can ask me where does the null byte come from?
QDataStream serializes the QString as a little-endian. 4 bytes are read to create the 32-bit length value, followed by the string itself in UTF-16. This string length in UTF-16 is 12 bytes, so the first three bytes in QByteArray will be zero.
There is often a problem with reading the QByteArray in qDebug () The recording is fine.
Don't forget to remove QT_NO_CAST_FROM_BYTEARRAY in your .pro file, if it has