Searching byte sequence in file. Problem with certain byte values

Hello,

I'm coding a little utility that searches for a given byte sequence in a file. The source code is as follows:
#include "stdafx.h"
#include <fstream>
#include <iostream>
using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{
      char readChar;
      unsigned char searchPattern[] = { 0xEB, 0x34, 0x54, 0x44 };
      fstream fileReader;
      fileReader.open("d:\\Development\\TestData\\test.txt", ios::in | ios::binary);
      
      cout << "Searching for pattern: ";
      for(int i = 0; i < sizeof(searchPattern); i++){
            printf("0x%x ", searchPattern[i]);
            
      }
      cout << endl;

      if(fileReader.is_open()){
            cout << "File opened" << endl;
            while(!fileReader.eof()){
                  fileReader.read(&readChar, sizeof(readChar));
                  printf("Current byte: 0x%x\n", readChar);

                  /*First byte of search pattern is found. Seek pointer in file is
                   *adjusted by -1. sizeof(searchPattern) bytes are read from that
                   *position and then compared to the searchPattern. If there is a
                   *match, the file-offset is saved. If no match, seek pointer is
                   *adjusted again to continue search
                  */
                  if(readChar == searchPattern[0]){
                        
                        char compareBuffer[sizeof(searchPattern)];
                        fileReader.seekg((int)fileReader.tellg()-1);                        
                        fileReader.read(compareBuffer, sizeof(compareBuffer));
                        bool match = true;
                        for(int i = 0; i < sizeof(compareBuffer); i++){
                              match = compareBuffer[i] == searchPattern[i];
                              if(!match){
                                    break;
                              }
                              printf("Byte match found: 0x%x for searchPattern byte %d\n", compareBuffer[i], i+1);
                        }
                        if(!match){
                              //No match, adjust file pointer
                              fileReader.seekg((int)fileReader.tellg() - sizeof(searchPattern) + 1);
                              cout << "No match, offset adjusted to: " << (int)fileReader.tellg()<< endl;

                        } else {
                              //Save file offset of match
                              cout << "Offset of first byte for match: " << (int)fileReader.tellg() - sizeof(searchPattern) << endl;

                        }
                  }
            }
      } else {
            cout << "Error opening file";
      }
      fileReader.close();
      return 0;
}

It works fine when searching for numbers and letters. But as soon as i put something like 0xEB into the search pattern, the pattern wont be found anymore, even the pattern is in my test file. Here is the output i get when running the tool on my test-file which includes the 0xEB byte:

Searching for pattern: 0xeb 0x34 0x54 0x4
File opened
Current byte: 0x67
Current byte: 0xffffffeb
Current byte: 0x38
Current byte: 0x37
Current byte: 0x32
Current byte: 0x38
Current byte: 0x37
Current byte: 0x36
Current byte: 0x38
Current byte: 0x36
Current byte: 0x38
Current byte: 0x37
Current byte: 0x67
Current byte: 0x66
Current byte: 0x68
Current byte: 0x67
Current byte: 0x66
Current byte: 0x68
Current byte: 0x67
Current byte: 0x6b
Current byte: 0x67
Current byte: 0x67
Current byte: 0x38
Current byte: 0xffffffeb
Current byte: 0xffffffeb

The problem seems to be that for the 0xEB bytes there are FFFFFF added. I dont know why this happens, can someone help me with this?
b3n_Asked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Deepu AbrahamR & D Engineering ManagerCommented:
It 0xffffffff shows because it shows the full 4 bytes.
(Hex)0xffffffff = 11111111111111111111111111111111 (in binary)

Since you are using int, it will show full 4 bytes, make it to 'short i' or downcast it to  (short)

Best Regards,
DeepuAbrahamK
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Infinity08Commented:
Try using unsigned char instead of char.
0
Infinity08Commented:
Did DeepuAbrahamK's post help you ?

Changing i from int to short will not change anything for your problem as far as I can see ...

And short is usually 2 bytes, not 1 byte.
0
Cloud Class® Course: Certified Penetration Testing

This CPTE Certified Penetration Testing Engineer course covers everything you need to know about becoming a Certified Penetration Testing Engineer. Career Path: Professional roles include Ethical Hackers, Security Consultants, System Administrators, and Chief Security Officers.

b3n_Author Commented:
it helped because he pointed out the general problem. i gave you points too cause your solution helped me fix the program. maybe i should have given you some more points, sorry for that.
0
Infinity08Commented:
No, that's not the reason I asked - I just wanted to make sure that you knew that using "short" will not fix the problem.

I wasn't critiquing the way you allocated points, because that's your decision - you alone know which posts helped you :)
0
Deepu AbrahamR & D Engineering ManagerCommented:
b3n, I have overlooked that, I think you got my intension correctly.. Thanks
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
C++

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.