How to Search for a Piece of Text in Binary File by Using fstream - C/C++?

[f.ben.isaac]

I got a binary file, i opened the file. I need to look for this "255.255.255.255", and then replace it with the user newly inserted IP...

I know there is something called seekp(), but it needs me to determine where to point in the file. I do not know yet. Once i find the spot 255.255... I will have to write from the iso::beg, right?

1. I can go through the file line by line by using getline()...Is there another solution?

2. Assume i went through the file & i found 255.255.255.255, to overwrite it do i t have to start from 2, or before 2? I guess ios::beg has to be involved in someway.

3.

ofstream file1;
file1.open("OutputTrial1.txt", ios::binary );
file1.write(temp,sizeof(temp));
file1.close();

In this line file1.open("OutputTrial1.txt", ios::binary ); OutputTrial1.txt is not binary, so how come we specified it as a binary in parameter two?

Regards

[Lindley]

Unless it's a really huge file, it's probably easiest to just read the entire file contents into a single string using getline() with EOF as the delimiter, then do the replace, then write the whole thing back out.

If it *is* a really huge file, reading byte by byte until you find a '2' and then special-casing from there might be the easiest way. (At the furthest extent of this approach, you'd essentially have the DFA-based substring matching algorithm.)

[GNiewerth]

Unless it's a really huge file, it's probably easiest to just read the entire file contents into a single string using getline() with EOF as the delimiter, then do the replace, then write the whole thing back out.

If it *is* a really huge file, reading byte by byte until you find a '2' and then special-casing from there might be the easiest way. (At the furthest extent of this approach, you'd essentially have the DFA-based substring matching algorithm.)

The best may be a mixture of both of them. Read a fixed size chunk of data, replace the relevant occurences and read the next chunk. There´s a special case that must be handled when the text exceeds one chunk and is continued in the next one.

[f.ben.isaac]

1. Here is what i did! I do not know how good this piece of code is, it works %90 i need to fix it little bit, but the main disadvantage is i have to use Hex Workshop to get the offset of ip & offset of port then pass it manually to the parameter. I find it inefficient thats why i though to do it through fstream since its more flexible. I want to locate IP then overwrite it, same thing with port. Please look at the code & give suggestions if you don't mind

//get offsets through parameters and data to be inserted in place offset
editBinary(long offsetOfIP, long offsetOfPortNumber, const char *IPAddress, const char *portNumber)
{
    const DWORD MAX_NUMBER_OF_BYTES_IN_IP = 15;
    const DWORD MAX_NUMBER_OF_BYTES_IN_PORT = 5;

       DWORD numOfBytesWritten = 0;    
  
       HANDLE hFile = CreateFile(L"application.exe", GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    
       if(hFile == INVALID_HANDLE_VALUE){
        cout<<"CreateFile() error: "<<GetLastError()<<endl;
        cout<<"*Make sure the file app.exe exists in the folder."<<endl;
        cout<<"Please press any key to go back"<<endl;
        cin.get();
        //get back
        }

       //point to IP offset
       DWORD successResult = SetFilePointer(hFile, offsetOfIP, NULL, FILE_CURRENT);
       if(successResult == INVALID_SET_FILE_POINTER)
       {
        cout<<"SetFilePointer() error: "<<GetLastError()<<endl;
        cout<<"Please press any key to go back"<<endl;
        cin.get();
        //get back
    }
  
       //overwrite the old IP - IPAddress contains the new IP
       BOOL numberOfIPBytesWrittenToFile = WriteFile(hFile, IPAddress, MAX_NUMBER_OF_BYTES_IN_IP, &numOfBytesWritten, NULL);

       if(numberOfIPBytesWrittenToFile == 0)
       {
        cout<<"WriteFile() error: "<<GetLastError()<<endl;
        cout<<"Please press any key to go back"<<endl;
        cin.get();
        //get back
        }

        //point to where port is located
    successResult = SetFilePointer(hFile, offsetOfPortNumber, NULL, FILE_BEGIN);
    if(successResult == INVALID_SET_FILE_POINTER)
    {
        cout<<"SetFilePointer() error: "<<GetLastError()<<endl;
        cout<<"Please press any key to go back"<<endl;
        cin.get();
        //get back
    }

        //overwrite the old port number - portNumber contains the new port number
    numOfBytesWritten = 0;  
        BOOL numberOfPortBytesWrittenToFile = WriteFile(hFile, portNumber, MAX_NUMBER_OF_BYTES_IN_PORT, &numOfBytesWritten, NULL);

     if(numberOfPortBytesWrittenToFile == 0)
     {
        cout<<"WriteFile() error: "<<GetLastError()<<endl;
        cout<<"Please press any key to go back"<<endl;
        cin.get();
        //get back
     }

        //close file
        BOOL isFileClosed = CloseHandle(hFile);

    if(isFileClosed == 0)
    {
        cout<<"CloseHandle() error: "<<GetLastError()<<endl;
        cout<<"Please press any key to go back"<<endl;
        cin.get();
        //get back
    }

        cout<<"Editing Succeeded."<<endl;
}

2.

then do the replace, then write the whole thing back out.

All data resides in the other file i just need to go through it. Once i find the spot i want to change, i start writing from there until data get fully replaced, then close the file. Can you clarify about why do i have to write the whole thing back out - this is right if i moved everything in a temp file afaik.Correct me if i'm wrong

Ignore boundary checking for now...