replacing “=” of encoded string in qt c++

Question

I have a Text Which is being encoded using base64 For example I have a String

string = "Hello"

It is encoded

Encoded string is :"SGVsbG9XQ1Q="

and then prepend the string with "||" (2-Pipe Character)

Now problem is I want to replace all = in that encoded string with | (one pipe) only at end of strings not in middle of any string

How will I replace all = only at end of the String with | in qt c++?

Here is my code:

#include <QCoreApplication>
#include <QString>
#include <QDebug>
#include <QByteArray>

QString base64_encode(QString string);
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QString srcString = "HelloWCT";
    QString encodedString = base64_encode(srcString);

    qDebug() << "Encoded string is" << encodedString;
    return a.exec();
 }

 QString base64_encode(QString string){
 QByteArray ba;
 ba = ba.append(string);
 ba = ba.toBase64();
 ba = ba.prepend("||");
 return(ba);
}

How to apply my replacing logic only at end of string?can anybody help me with the logic?

I have logic but dont know how to apply it?

Logic is: it will start checking from end of string if there is "=" it will replace it with "|" and it wil gain check if there exist another "=" before the last equal to it will again replace and then if before second "=" if there is another character it will stop replacing how can we do this ?

Answer 1

You can loop through the QByteArray from the end to the beginning (and break the loop when you find a character other than '=' ), replacing every occurrence of '=' by a '|' , something like this:

QByteArray ba("SGVsbG9XQ1Q=");
for(int i=ba.length()-1; i>=0 && ba[i]=='='; i--)
    ba[i] = '|';

Answer 2

I have found the exact solution:

for(int i=ba.length()-1; i>=0 ;i--)
         if(ba.at(i) == '=')
         {
            //replace with "|"
            ba.replace(i,1,QByteArray("|"));
         }
        else
           break;