Reading Binary

[UnknownBlue]

Hi.

I am trying to read .dat files which is in binary using visual C++ 6.0. I want to display the first 100 char (in hex). But instead some weird char are being display. I opened the file through hex editor and this is what i am supposed to get: 2EFACCF69FFC84...

Can anyone help me in this? Thanks in advance!

char *memblock;
ifstream::pos_type size;
ifstream file;
 
int main ()
{
    int size, i;
    char n;
 
    file.open ("s0455_re.dat", ios::in|ios::binary|ios::ate);
 
    if (file.is_open())
    {
        cout << "Able to open file!";    
                               // Able to get the size since it is at the end
        size = (int) file.tellg(); 
 
        // allocate memory
        memblock = new char [size]; 
 
        file.seekg (0, ios::beg);
 
        for (i=0; i<100; i++)
        {    
            file.seekg (0, ios::cur);
            file.read (memblock, 1);
            n = *memblock;
            cout << n;
        }
 
        file.close();
    }
    else cout << "Unable to open file";
    return 0;
}
 

[willakawill]

Hi.

I am trying to read .dat files which is in binary using visual C++ 6.0. I want to display the first 100 char (in hex). But instead some weird char are being display. I opened the file through hex editor and this is what i am supposed to get: 2EFACCF69FFC84...

Can anyone help me in this? Thanks in advance!

char *memblock;
ifstream::pos_type size;
ifstream file;

int main ()
{
int size, i;
char n;

file.open ("s0455_re.dat", ios::in|ios::binary|ios::ate);

if (file.is_open())
{
cout << "Able to open file!";
// Able to get the size since it is at the end
size = (int) file.tellg();

// allocate memory
memblock = new char [size];

file.seekg (0, ios::beg);

for (i=0; i<100; i++)
{
file.seekg (0, ios::cur);
file.read (memblock, 1);
n = *memblock;
cout << n;
}

file.close();
}
else cout << "Unable to open file";
return 0;
}

Hi. If you compare your code to this you may discover how to make it work:

#include <iostream>
#include <fstream>
using namespace std;
 
int main () {
  int length;
  char * buffer;
 
  ifstream is;
  is.open ("test.txt", ios::binary );
 
  // get length of file:
  is.seekg (0, ios::end);
  length = is.tellg();
  is.seekg (0, ios::beg);
 
  // allocate memory:
  buffer = new char [length];
 
  // read data as a block:
  is.read (buffer,length);
 
  is.close();
 
  cout.write (buffer,length);
 
  return 0;
}

[UnknownBlue]

Hi.

Thanks for replying.
I have tried that but it gives an output of two lines like =.
Its not in terms of hex.

[willakawill]

Hi.

Thanks for replying.
I have tried that but it gives an output of two lines like =.
Its not in terms of hex.

Adjusted

#include <iostream>
#include <fstream>
using namespace std;
 
int main () {
  int length;
  char * buffer;
  char output[2];
  int lp;
 
  ifstream is;
  is.open ("test.txt", ios::binary );
 
  // get length of file:
  is.seekg (0, ios::end);
  length = is.tellg();
  is.seekg (0, ios::beg);
 
  // allocate memory:
  buffer = new char [length];
 
  // read data as a block:
  is.read (buffer,length);
 
  is.close();
 
  if (length > 100) length = 100;
 
  for (lp = 0; lp < length; lp++) {
    sprintf(output, "%X", atoi(buffer[lp]));
    cout << output;
  }
  return 0;
}

[willakawill]

That last part will not work.
this piece of code will print out in hex so maybe you can adapt it

char ar[30] = {0};
char buffer[20] = {0};
sprintf(ar, "%d", 123456789);
sprintf(buffer, "%X", atol(ar));
cout << buffer;

If you read the file 4 chars at a time into a long variable you could achieve what you need rather than into a char array.

[UnknownBlue]

It sort of work!
Thanks!

[horace1]

with a few minor modifications your original program would work, e.g. in particular cast the byte read as a char to an int and use the io manipulator to print it as hex

#include <iostream>
#include <fstream>
using namespace std;
 
char memblock;  // ** remove *
ifstream::pos_type size;
ifstream file;
 
int main ()
{
int size, i;
char n;
 
file.open ("s0455_re.dat", ios::in|ios::binary|ios::ate);
 
if (file.is_open())
{
cout << "Able to open file!";
// Able to get the size since it is at the end
size = (int) file.tellg();
 
// allocate memory
//memblock = new char [size];  // ** not needed
 
file.seekg (0, ios::beg);
 
for (i=0; i<100; i++)
{
file.seekg (0, ios::cur);
file.read (&memblock, 1);  // ** added &
//n = *memblock;  // ** remove
cout << hex << (int) memblock;  // ** output as hex
}
 
file.close();
}
else cout << "Unable to open file";
cin.get();
return 0;
}
 

[LSB]

You sure may want to make some minor changes:

int size100;
……………..
size100 = (size < 100) ? size : 100;
……………..
for (i =0; i<size100; i++)
..................