How to search sequence of bytes in an byte array[] of a bin file?

Question

I'm trying to code a program where I can:

Load a file
Input a start and beginning offset addresses where to scan data from
Scan that offset range in search of specific sequence of bytes (such as "05805A6C")
Retrieve the offset of every match and write them to a .txt file

i66.tinypic.com/2zelef5.png

As the picture shows I need to search the file for "05805A6C" and then print to a .txt file the offset "0x21F0".

I'm using Java Swing for this. So far I've been able to load the file as a Byte array[]. But I haven't found a way how to search for the specific sequence of bytes, nor setting that search between a range of offsets.

This is my code that opens and reads the file into byte array[]

public class Read { static public byte[] readBytesFromFile () { try { JFileChooser chooser = new JFileChooser(); int returnVal = chooser.showOpenDialog(null); if (returnVal == JFileChooser.APPROVE_OPTION) { FileInputStream input = new FileInputStream(chooser.getSelectedFile()); byte[] data = new byte[input.available()]; input.read(data); input.close(); return data; } return null; } catch (IOException e) { System.out.println("Unable to read bytes: " + e.getMessage()); return null; } } }

And my code where I try to search among the bytes.

byte[] model = Read.readBytesFromFile(); String x = new String(model); boolean found = false; for (int i = 0; i < model.length; i++) { if(x.contains("05805A6C")){ found = true; } } if(found == true){ System.out.println("Yes"); }else{ System.out.println("No"); }

"pmdl" is a String (not a byte[]).

Elliott Frisch
– Elliott Frisch

2016-02-07 02:18:55 +00:00
Commented Feb 7, 2016 at 2:18 — Elliott Frisch
– Elliott Frisch, Commented Feb 7, 2016 at 2:18
"05805A6C" is a String, not a sequence of bytes

Ken Bekov
– Ken Bekov

2016-02-07 02:28:02 +00:00
Commented Feb 7, 2016 at 2:28 — Ken Bekov
– Ken Bekov, Commented Feb 7, 2016 at 2:28
Right, but how should I go to search for that sequence?

Midori_hige
– Midori_hige

2016-02-07 02:34:43 +00:00
Commented Feb 7, 2016 at 2:34 — Midori_hige
– Midori_hige, Commented Feb 7, 2016 at 2:34

Stephen C · Accepted Answer · 2016-02-07 04:14:11Z

Here's a bomb-proof¹ way to search for a sequence of bytes in a byte array:

public boolean find(byte[] buffer, byte[] key) { for (int i = 0; i <= buffer.length - key.length; i++) { int j = 0; while (j < key.length && buffer[i + j] == key[j]) { j++; } if (j == key.length) { return true; } } return false; }

There are more efficient ways to do this for large-scale searching; e.g. using the Boyer-Moore algorithm. However:

converting the byte array a String and using Java string search is NOT more efficient, and it is potentially fragile depending on what encoding you use when converting the bytes to a string.
converting the byte array to a hexadecimal encoded String is even less efficient ... and memory hungry ... though not fragile if you have enough memory. (You may need up to 5 times the memory as the file size while doing the conversion ...)

^{1 - bomb-proof, modulo any bugs :-)}

1) You call it from your code, passing in the buffer and the key as parameters. 2) No. It is a method. You can put it into a class. Or you copy the code / method body into something else, refactoring as required.
I don't understand how to use this. What buffer and key suppose to be?. I only got one byte array[] which is the data from the file (model)
Buffer is the data you got from the file. Key is a byte array containing the byte sequence that you are search for.
Yeah, I got that method working and yes it does work in doing the search. However how can I get the offset address of every match? Also, how to do many search with different byte sequences from top to bottom?

Pooya · Accepted Answer · 2016-02-07 04:09:17Z

0

EDIT It seems the charset from system to system is different so you may get different results so I approach it with another method:

String x = HexBin.encode(model); String b = new String("058a5a6c"); int index = 0; while((index = x.indexOf(b,index)) != -1 ) { System.out.println("0x"+Integer.toHexString(index/2)); index = index + 2; } ...