Restrict specified number of charecters in each row of Sqlite Db

[ChrisW67]

I cannot tell you what the logic of your program is or should be. The buffer will be emptied of whole records by the while loop which will exit if there is not a whole record in the buffer. Presumably, when more data is added to the buffer you will call this code again. If no more data is appended to the buffer then more records will never be written to the database.

If you want to throw away the content of the buffer the the clear() method is good for that.

[nagabathula]

Hello sir i have one more doubt .. I am actually doing this to save the data into the rsdata from rs232 port

QByteArray rsdata = (QByteArray::fromRawData(buff,numBytes));

QByteArray rsdata = (QByteArray::fromRawData(buff,numBytes));

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but i read the detail description of
QByteArray QByteArray::fromRawData ( const char * data, int size )

Constructs a QByteArray that uses the first size characters in the array data. The bytes in data are not copied. The caller must be able to guarantee that data will not be deleted or modified as long as the QByteArray (or an unmodified copy of it) exists.
Any attempts to modify the QByteArray or copies of it will cause it to create a deep copy of the data, ensuring that the raw data isn't modified.

but i am doing some bitwise shifting and aligining of the data so can it be the reason i am losing data sir, ?

I tried it this way i though i will append the data into an QByteArray rsdata; is this right sir it sud append the data in buff but i am not seeing the right data.

rsdata.append((QByteArray::fromRawData(buff,numBytes)).toHex());

rsdata.append((QByteArray::fromRawData(buff,numBytes)).toHex());

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thank you

[ChrisW67]

I cannot tell you why you are losing data.

It is easy enough to do a simple experiment to find out if the sort of manipulations you do will cause a deep copy:

#include <QtCore>
#include <QDebug>
 
int main(int argc, char **argv)
{
    QCoreApplication app(argc, argv);
 
    char buf[] = "....";
    QByteArray a = QByteArray::fromRawData(buf, 4);
    QByteArray b = a;   // shallow copy of a 
    qDebug() << buf << a << b;  // all point to buf and show same data
 
    buf[0] = 'X';   // modify original buffer directly
    qDebug() << buf << a << b;  // all changed because the share the buffer
 
    b[0] = 'Y';     // change using the byte array interface causes deep copy 
    qDebug() << buf << a << b;  //  only b changed after deep-copy
}

#include <QtCore>
#include <QDebug>

int main(int argc, char **argv)
{
    QCoreApplication app(argc, argv);

    char buf[] = "....";
    QByteArray a = QByteArray::fromRawData(buf, 4);
    QByteArray b = a;   // shallow copy of a 
    qDebug() << buf << a << b;  // all point to buf and show same data

    buf[0] = 'X';   // modify original buffer directly
    qDebug() << buf << a << b;  // all changed because the share the buffer

    b[0] = 'Y';     // change using the byte array interface causes deep copy 
    qDebug() << buf << a << b;  //  only b changed after deep-copy
}

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Output:

.... "...." "...." 
X... "X..." "X..." 
X... "X..." "Y..."

.... "...." "...." 
X... "X..." "X..." 
X... "X..." "Y..."

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