Thread: 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 ''

>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

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.