Question

I am trying to extract some information from a binary file. It looks like this:

AUTHCODE(here goes 3 bytes, that I don't need)part_that_i_need(here goes a NULL byte).

How to I match the portion of alpha-numeric characters qszjlbnkmctkkezgd_qyzkyptqigudilzpkp_qgetefvmigwimrihudk that is between bytes {11} {00} {38} and {00}.

Here’s what I’ve done so far:

            string ReadFileMF;
            using (StreamReader reader = new StreamReader(pathCopy))
            {
                ReadFileMF = reader.ReadToEnd();
            }

            ///match the whole string
            Match passMF = Regex.Match(ReadFileMF, @"(AUTHCODE).+?(www)");
            String passMFs = passMF.Value;

            //convert to array of bytes
            byte[] bpass = StrToByteArray(passMFs);

            //replace the 3 bytes after AUTHCODE with spaces
            bpass[8] = 0x20;
            bpass[9] = 0x20;
            bpass[10] = 0x20;

Ok, so now I have just to match the nullbyte at the end. Somthing like (AUTHCODE).+?(NULL_BYTE). Any ideas?

Answer 1

This might be easiest with a few simple for-loops or Copy() actions over the byte data. Too few specs to be exact. Like:

// untested, I could be off-by-1 somewhere
int start = "AUTHCODE".Length + 3;
int end = text.Indexof('\0', start);
string result = text.SubString(start, end-start);

If you do want/need Regex, you’ll have to turn it into a string first. Your only safe bet seems to be ASCII encoding.

 string text = Encoding.ASCII.GetString(data);

and then (untested)

 Regex.Match(text, "AUTHCODE.{3}([^\0x00]+)\0x00);