QByteArray saves wrong size with UTF8

JAVH

Hi, Im developing a tool who saves biometric data in MariaDB database, At the beggining of the program I do

QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));

And I can save and view text Ok (accents included), but when I try to save enrrollment to database (is a QByteArray) the database saves with a incorrect size, and cannot recognize fingerprint posteriorly, but, if I remove support forUTF8, I can save correctly the fingerprint in database, but text with accents shows incorrectly.

I did try change collation in MariaDb without luck, and I dont know how to deactivate LocaleCodec temporary for saving ifingerprint n database.

The way I create QByteArray and save data is this:

Var.HuellaBin = QByteArray ((char*)(m_pEnrollmentFmd),m_nEnrollmentFmdSize);

ChrisW67

@JAVH
What is the database column defined as?
How are you inserting values into that column?
What are you doing with the binary data that involves text encoding in any way?

JAVH

@ChrisW67 The column is longblob, charset is utf8mb4 and collation is utf8mb4_general_ci

I insert fingerprint in 2 ways, by a QSQlquery and calling a Stored procedure,

if(Huellas==0)
            {
                Data.Query.clear();
                Data.Query.prepare("insert t_huella (huellablob,id_empleado) values (?,?)");
                Data.Query.bindValue(0,Var.HuellaBin);
                Data.Query.bindValue(1,currentID);
                Data.Query.exec();
            }
            else
            {
                if(Var.saveHuella) //se modificó la huella
                {
                    Data.Query.clear();
                    Data.Query.prepare("update t_huella set huellablob=? where id_empleado=?");
                    Data.Query.bindValue(0,Var.HuellaBin);
                    Data.Query.bindValue(1,currentID);
                    Data.Query.exec();
                    Var.saveHuella=false;  //se restaura indicador de guardar huella una vez que ya se guardó
                }
            }

This works fine when I disable locale UTF8 at the beggining of the aplication, but its show wrong characters with accents, if I put this line at beggining:

QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));

Text show correctly, but if I want save a fingerprint, the long of QBytearray to save is more than double of large and fingerprint SDK cannot recognize data saved:

Values in Database:

Christian Ehrlicher

Why store a QString in a blob?
Please provide a minimal, compilable example. What is Var.HuellaBin ? How is it created?

JAVH

Ok I did solve, I encoded the QByteArray to base64 and I saved to Database, when I get it, I decode data and after compare fingerprint

Saving/Updating to DB

Data.Query.bindValue(0,Var.HuellaBin.toBase64());

Loading from DB:

Huella=QByteArray::fromBase64(Data.Query.value(2).toByteArray());

Thanks!

ChrisW67

@JAVH The longblob column should have the pseudo-character set "binary" (see, e.g., the second paragraph here) The blob is not a string with UTF-8 or any other encoding.