issue char * hex buffer to QString conversion to print to textEdit Widget

[bobth12]

Hi,

I am new to QT, but have been programming in C/C++. I have a question regarding displaying hex values to TextEdit Widget. I have tried various method, but sometimes some of the hex values change or sometime the output is totally different.

So I have a char buffer like this:

1st implementation:

char * cHexData = new char [HexBuff_size+1];
memset(cHexData, '\0', HexBuff_size+1);
char * temp_iter = cHexData;
 
 for (int i = 0; i<(HexBuff_size+1); i++){ 
     sprintf(temp_iter ,"%X",(unsigned char)HexBuff[i]);   //HexBuff is char buffer of size 256 and it holds the some data
     temp_iter++;                                                       // I am printing putting the values to cHexData buffer which will hold hex values 
}                                                                          //ex: cHexData = FF6C69.....
 
 
//now i need to convert it to QString so that I can out the same Hex value in cHexData with formatting 
 for (int i = 0; i<(HexBuff_size+1); i++){
 
        if (i!=0 && i%2==0)             //append whitespace every 2 char
             QTtext_qsPrintData+=" ";
 
        if(i!=0 && i%16 ==0)           //every 16th hex value newline
             QTtext_qsPrintData+= "\n";
 
        QTtext_qsPrintData+=QString(QChar(cHexData[i]));
}
 
ui->textWid->setText(QTtext_qsPrintData);
 
//output i want is;
//FF 6C 69...  <- so same hex value as in cHexData.
//25 C8 95...
//...

char * cHexData = new char [HexBuff_size+1];
memset(cHexData, '\0', HexBuff_size+1);
char * temp_iter = cHexData;

 for (int i = 0; i<(HexBuff_size+1); i++){ 
     sprintf(temp_iter ,"%X",(unsigned char)HexBuff[i]);   //HexBuff is char buffer of size 256 and it holds the some data
     temp_iter++;                                                       // I am printing putting the values to cHexData buffer which will hold hex values 
}                                                                          //ex: cHexData = FF6C69.....


//now i need to convert it to QString so that I can out the same Hex value in cHexData with formatting 
 for (int i = 0; i<(HexBuff_size+1); i++){

        if (i!=0 && i%2==0)             //append whitespace every 2 char
             QTtext_qsPrintData+=" ";

        if(i!=0 && i%16 ==0)           //every 16th hex value newline
             QTtext_qsPrintData+= "\n";

        QTtext_qsPrintData+=QString(QChar(cHexData[i]));
}

ui->textWid->setText(QTtext_qsPrintData);

//output i want is;
//FF 6C 69...  <- so same hex value as in cHexData.
//25 C8 95...
//...

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So this implementation; when in Debug mode(breakpoints) has the correct Hex value for QTtext_qsPrintData as cHexData, which is good. But in the release version, on every run, some of the Hex values in QTtext_qsPrintData changes. That in turn will display the values wrong on the output
So after reading about hex value and QString conversion; I tried the following:

...
    iNumWhiteSpace = (HexBuff_size/2);                    //number of whitespace between 2 hex values
    iNumReturns = (HexBuff_size/16)-1;                    //\n every 16th hex value;
 
    for(int i = 0 ; i<HexBuff_size; i ++){
        if (i!=0 && i%2==0){
            *temp_iter=' ';
            temp_iter++;
        }
        if(i!=0 && i%16 ==0){
            *temp_iter='\n';
            temp_iter++;
        }
 
         sprintf(temp_iter ,"%X",(unsigned char)HexBuff[i]);
        temp_iter++;
 
    }
 
q_bHex = QByteArray(reinterpret_cast<char*>(cHexData ), HexBuff_size+iNumWhiteSpace+iNumReturns+1);
//and QByteArray q_bHex(cHexData , HexBuff_size+iNumWhiteSpace+iNumReturns+1);
ui->textWid->setText(QString(q_bHex));

...
    iNumWhiteSpace = (HexBuff_size/2);                    //number of whitespace between 2 hex values
    iNumReturns = (HexBuff_size/16)-1;                    //\n every 16th hex value;

    for(int i = 0 ; i<HexBuff_size; i ++){
        if (i!=0 && i%2==0){
            *temp_iter=' ';
            temp_iter++;
        }
        if(i!=0 && i%16 ==0){
            *temp_iter='\n';
            temp_iter++;
        }

         sprintf(temp_iter ,"%X",(unsigned char)HexBuff[i]);
        temp_iter++;

    }

q_bHex = QByteArray(reinterpret_cast<char*>(cHexData ), HexBuff_size+iNumWhiteSpace+iNumReturns+1);
//and QByteArray q_bHex(cHexData , HexBuff_size+iNumWhiteSpace+iNumReturns+1);
ui->textWid->setText(QString(q_bHex));

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// This implementation is also same as above

I have also looked into something like; but the values are decimal, and that make sense since my char * buffer already have hex values.

//for (int i=0 ; i < HexBuff_size; i++)
    //    QTtext_qsPrintData+= QString("%1").arg(cHexData[i],0,16);

//for (int i=0 ; i < HexBuff_size; i++)
    //    QTtext_qsPrintData+= QString("%1").arg(cHexData[i],0,16);

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please help with this. I was not too sure if I should post it here or QT newbie; If I have posted it in the wrong forum please move it.

Thanks!

[Infinity]

Just convert each character of your C-style character array to an integer and add it to a QString:

QString result;
result.reserve(3 * arraySize - 1);
for(char* i = array, end = array + arraySize; i < end; ++i) {
	if(!result.isEmpty()) {
		result += QLatin1Char(' ');
	}
	result += QString("%1").arg(static_cast<uint>(*i), 2, 16, QLatin1Char('0'));
}
hexLineEdit->setText(result);

QString result;
result.reserve(3 * arraySize - 1);
for(char* i = array, end = array + arraySize; i < end; ++i) {
	if(!result.isEmpty()) {
		result += QLatin1Char(' ');
	}
	result += QString("%1").arg(static_cast<uint>(*i), 2, 16, QLatin1Char('0'));
}
hexLineEdit->setText(result);

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That's just an quick draft. I haven't tested it.
I recommend to avoid the usage of C-style arrays and C-style casts in C++.

[ChrisW67]

This code is faulty and dangerous.

char * cHexData = new char [HexBuff_size+1];
memset(cHexData, '\0', HexBuff_size+1);
char * temp_iter = cHexData;
 
 for (int i = 0; i<(HexBuff_size+1); i++){ 
     sprintf(temp_iter ,"%X",(unsigned char)HexBuff[i]);   //HexBuff is char buffer of size 256 and it holds the some data
     temp_iter++;                                                       // I am printing putting the values to cHexData buffer which will hold hex values 
}                                                                          //ex: cHexData = FF6C69.....

char * cHexData = new char [HexBuff_size+1];
memset(cHexData, '\0', HexBuff_size+1);
char * temp_iter = cHexData;

 for (int i = 0; i<(HexBuff_size+1); i++){ 
     sprintf(temp_iter ,"%X",(unsigned char)HexBuff[i]);   //HexBuff is char buffer of size 256 and it holds the some data
     temp_iter++;                                                       // I am printing putting the values to cHexData buffer which will hold hex values 
}                                                                          //ex: cHexData = FF6C69.....

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If you are going to convert N bytes into a hexadecimal string you need a target buffer at least 2N+1 bytes long to avoid the possibility of overrunning the buffer. In this case, your 256 source bytes require a 513 byte output buffer.

You convert each successive byte into one (i.e. no 0 padding for values < 16) or two hexadecimal digits in the target buffer and then advance the pointer by one character. You need to consistently convert each byte to two characters ("%02X") and advance by two chars.

If you already have the input buffer and know its size:

QByteArray temp = QByteArray::fromRawData(input, inputBufferSize);
QString output = QString(temp.toHex());

QByteArray temp = QByteArray::fromRawData(input, inputBufferSize);
QString output = QString(temp.toHex());

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