Question

Okay, so I’ve got a game map creater programmed in Java which writes the map out to file using ObjectOutputStream.writeInt()

Now I’m converting the game engine to C# XNA and I’m trying to load the map. I’m getting numerical errors though, so I’m wondering if anyone knows what I’m doing wrong?

Java writes as int 32 Big Endian I believe (I could be wrong though).

Here is the code I’m using to read the height and width of the map in C#.

Edit: br is BinaryReader.

width = (int)IPAddress.NetworkToHostOrder(BitConverter.ToInt32(br.ReadBytes(sizeof(int)), 0));
height = (int)IPAddress.NetworkToHostOrder(BitConverter.ToInt32(br.ReadBytes(sizeof(int)), 0));

Can anyone please tell me what I’m doing wrong? Or how to read the bytes from ObjectOutputStream.writeInt() properly in C#?

Edit: 2nd try failed. here is the current code:

public byte[] ReadBigEndianBytes(int count, BinaryReader br)
        {
            byte[] bytes = new byte[count];
            for (int i = count - 1; i >= 0; i--)
                bytes[i] = br.ReadByte();

            return bytes;
        }

        public void loadFile(int level)
        {
            FileStream fs = new FileStream("map" + level + ".lv", FileMode.Open, FileAccess.Read);
            BinaryReader br = new BinaryReader(fs, System.Text.Encoding.BigEndianUnicode);

            width =  BitConverter.ToInt32(ReadBigEndianBytes(4, br), 0);
            height = BitConverter.ToInt32(ReadBigEndianBytes(4, br), 0);

            tile = new int[width, height];

            for (int x = 0; x < width; x++)
            {
                for (int y = 0; y < height; y++)
                {
                    tile[x, y] = BitConverter.ToInt32(ReadBigEndianBytes(4, br), 0);
                }
            }

        }
    }

Answer 1

Absolutely correct:

Java writes as int 32 Big Endian I believe (I could be wrong though).

Remember, though: a .Net Int32 is Little-Endian 😉

[Edit] SOLUTION:

1) Here is Java code that writes 10 integers (Java int’s are 32-bit, Big-endian))

    import java.io.*;

    public class WriteBinary {

      public static void main (String[] args) {
        int[] data = {
          1, 2, 3, 4, 5, 6, 7, 8, 9, 10
        };

        String fname = "myfile.bin";
        try
        {
          System.out.println("Opening " + fname + "...");      
          FileOutputStream fos = 
            new FileOutputStream(fname);
          int ibyte;
          for (int i = 0; i < data.length; i++) {
            ibyte = ((data[i] >>> 24) & 0xff); fos.write(ibyte);
            ibyte = ((data[i] >>> 16) & 0xff); fos.write(ibyte);
            ibyte = ((data[i] >>> 8) & 0xff); fos.write(ibyte);
            ibyte = (data[i] & 0xff); fos.write(ibyte);
          }
          fos.close();
          System.out.println("File write complete.");      
        }
        catch (IOException e) {
          System.out.println ("I/O error: " + e.getMessage());
        }
      }
    }

2) Here is the C# code that reads it. You’ll notice the “using System.Net”, in order to get .Net’s equivalent of “ntohl()”:

using System;
using System.IO;
using System.Net;

namespace ReadBinary
{
    class Program
    {
        static void Main(string[] args)
        {
            string fname = "myfile.bin";
            try
            {
                Console.WriteLine("Opening " + fname + "...");
                BinaryReader br =
                  new BinaryReader(
                        File.Open(fname, FileMode.Open));
                for (int i = 0; i < (int)(br.BaseStream.Length / 4); i++)
                {
                    int j =
                        System.Net.IPAddress.NetworkToHostOrder (br.ReadInt32());
                    Console.WriteLine("array[" + i + "]=" + j + "...");
                }
                br.Close();
                Console.WriteLine("Read complete.");
            }
            catch (IOException ex)
            {
                Console.WriteLine("I/O error" + ex.Message);
            }
        }
    }
}