Reading Binary files

Hey,

I've looked over the binary I/O post and read over some tutorials on line, but I still can't make the program read in a binary number properly.

I've tried:

Code:

---

char num[5];
  int DataFormat;

  inp>>DataFormat;

  // and

  inp.read(num, sizeof(long));
  num[5] = '\0';
  DataFormat = atoi(num);

---

It doesn't interprit DataFormat properly in either case. The input file is binary. to place the poiter at the correct position I use:

Code:

---

ifstream inp;
  inp.open("test.baf", ios_base::binary);

    inp.seekg(549,ios::beg);

---

is there another way to read in 4 bytes into a longint variable fro ma binary file?

Try

Code:

---

long x;

inp.read(&x, sizeof(long);

---

You might need to cast &x to char*.

Nope, doesn't work either.
Thanks though.

Check out this line:

num[5] = '\0';

Post an example of the bytes that is read from the file and the incorrect value assigned to DataFormat.

Kuphryn

Code:

---

        DataFormat        -858993460
        &DataFormat        0x0012f5bc

---

thant's using : inp.read((char*)&DataFormat, sizeof(long));

If I use

Code:

---

inp.read(num, sizeof(long));
  num[5] = '\0';
  DataFormat = atoi(num);

---

I get

Code:

---

        DataFormat        -858993460
-        num        0x0012f5c0 "ÌÌÌÌÌ"
        [0]        -52 'Ì'
        [1]        -52 'Ì'
        [2]        -52 'Ì'
        [3]        -52 'Ì'
        [4]        -52 'Ì'
        num[5]        0 ''

---

Code:

---

inp.read((char*)&DataFormat, sizeof(long));

---

is correct (assuming a 4 byte int). Or better is:

Code:

---

inp.read((char*)&DataFormat, sizeof(DataFormat));

---

What's actually in your file at locations 549-552?

this is advance but i remember that you have to treat the file as binary while opening it

Code:

---

ofstream file ( "file.file", ios::binary );

---

>What's actually in your file at locations 549-552?

It should be 0,1 or 2 as a long int.

>you have to treat the file as binary while opening it
I do use ios::binary

god im stupid lol didnt read all of it hahaha sry

I would verify the data with this then (first seek to appropriate location):

Code:

---

char ch;

inp.read((char*)&ch, sizeof(ch));
cout << (int) ch << " ";
inp.read((char*)&ch, sizeof(ch));
cout << (int) ch << " ";
inp.read((char*)&ch, sizeof(ch));
cout << (int) ch << " ";
inp.read((char*)&ch, sizeof(ch));
cout << (int) ch << " ";
cout << endl;

---

It's possible the bytes are reversed (endian problem), but first see if the data looks right.

I've tried everything above. It doesn't come back properly. let me look into the file structure a bit more. Maybe I'm forgetting something there. Maybe later I'll be back with a new problem.
Thanks for all the help,

AS.