Searching for a string in QByteArray

[wysota]

i am converting it from binary to Hexadecimal

No, you are not. Binary data is already hexadecimal. It's like you said "I'm converting my sentences from letters to words".

How can i pass the value of k as the index position for the QByteArray data; so that i can append only from the start of the frame.

Let me solve this one for you but promise you will learn what "hexadecimal", "binary" and "ascii" really means.

From what I understand you are trying to find some data beginning with 0x1A2C11000000. To do that you need to construct such a pattern - a binary pattern, not a textual one.

So here goes...
this is a text pattern:

QByteArray pattern("1A2C11000000");

QByteArray pattern("1A2C11000000");

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And this is a binary pattern:

QByteArray pattern("\x1A\x2C\x11\x00\x00\x00");

QByteArray pattern("\x1A\x2C\x11\x00\x00\x00");

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Now use QByteArrayMatcher to find your byte array.

QByteArrayMatcher matcher(pattern);
int pos = 0;
while((pos = matcher.indexIn(data, pos)) != -1) {
  qDebug() << "pattern found at pos" << pos;
}

QByteArrayMatcher matcher(pattern);
int pos = 0;
while((pos = matcher.indexIn(data, pos)) != -1) {
  qDebug() << "pattern found at pos" << pos;
}

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Note, you have to care about a situation when a chunk of data ends in the middle of the pattern.