Reading a binary file (byte swapping?): HELP!

Question

Hi,
Below are 2 simple programs, one in C and the other in Java that read a binary file. The first 3 integer numbers read by the C program are:
910, 1024437292, 100002
The first 3 integer numbers read by the Java program are:
-1912406016, 749473597, -1568276224
The file was written with another C program. The values read by the C program listed here are correct.
I supect that I have a byte swapping problem. Do you know how I can solve this problem? I really can't change the format of the input file.
Thanks for your help,
Miguel
#include <stdio.h>
void main(int argc, char *argv[]) {
long buff[600];
FILE *fp = fopen("c:\\inetpub\\wwwroot\\super\\wvdot3.awg","r");
fread(buff,sizeof(int),512,fp);
int sz = sizeof(int);
import java.io.*;
public class test {
public static void main(String[] args) {
try {
DataInputStream din = new DataInputStream(new BufferedInputStream
(new FileInputStream("c:\\inetpub\\wwwroot\\super\\wvdot3.awg")));
int nrecs = din.readInt();
int version = din.readInt();
int routetype = din.readInt();
System.out.println("read: " + nrecs + " " + version + " " + routetype);
} catch (IOException exc) {
System.out.println("IOException: " + exc);

Answer 1

Yeah, the problem is byte ordering. I had to deal with the same thing, since Java is always big endian, and intel and DEC Alpha are both little endian. I assume you're original program runs on Intel.
I ended up creating a new LittleEndianDataInputStream. Unfortunately, you can't just extend DataInputStream since all it's methods are final. You can however copy the source, rename it, and then change all the multi-byte numeric methods to reverse the byte ordering.
For example, here is the code for the original and little endian version of readInt()
<code>
// DataInputStream
public final int readInt() throws IOException {
InputStream in = this.in;
int ch1 = in.read();
int ch2 = in.read();
int ch3 = in.read();
int ch4 = in.read();
if ((ch1 | ch2 | ch3 | ch4) < 0)
throw new EOFException();
return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
// LittleEndianDataInputStream
public int readInt() throws IOException
int ch1 = in.read();
int ch2 = in.read();
int ch3 = in.read();
int ch4 = in.read();
if ((ch1 | ch2 | ch3 | ch4) < 0)
throw new EOFException();
// here's the change
return ( (ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1 << 0) );
</code>