Extracting the ARK version from the windows client

App.java

package qowyn.ark.ave;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * The thing we are searching for:
 * c705xxxxxxxx(high xxxx0000)
 * c705xxxxxxxx(low xxxx0000)
 * a801
 * 751a
 * xxxxxx
 * xxxxxxxxxxxx
 * xxxxxxxxxx
 * xxxxxxxxxxxxxx
 * xxxxxxxxxx
 * xxxxxxxxxxxxxx
 * xxxxxxxxxxxxxx
 * 41b9(low xxxx0000)
 * 41b8(high xxxx0000)
 */

public class App 
{
  private static final int MIN_LENGTH = 10 + 10 + 2 + 2 + 3 + 6 + 5 + 7 + 5 + 7 + 7 + 6 + 6;

  public static void main( String[] args )
  {
    if (args.length != 1) {
      System.exit(3);
      return;
    }

    Path pathToExe = Paths.get(args[0]);
    try (FileChannel channel = FileChannel.open(pathToExe)) {
      ByteBuffer buffer = ByteBuffer.allocate(0x1000000);
      channel.read(buffer);
      buffer.order(ByteOrder.LITTLE_ENDIAN).clear();

      while (buffer.position() < buffer.capacity() - MIN_LENGTH) {
        short value = buffer.getShort();
        if (value == (short)0x05c7) {
          // Found a potential match
          buffer.mark();
          if (search(buffer)) {
            System.exit(0);
            return;
          } else {
            buffer.reset();
          }
        } else if ((value & 0xFF00) == 0xc700) {
          // Don't skip potential matches
          buffer.position(buffer.position() - 1);
        }
      }

      System.exit(1);
    } catch (IOException e) {
      e.printStackTrace();
      System.exit(2);
    }
  }
  
  private static boolean search(ByteBuffer buffer) {
    buffer.position(buffer.position() + 4);
    int high = buffer.getInt();

    // this will fail with ARK version above 65535
    if ((high & 0xFFFF0000) != 0) {
      return false;
    }

    if (buffer.getShort() != (short)0x05c7) {
      return false;
    }

    buffer.position(buffer.position() + 4);
    int low = buffer.getInt();

    if (buffer.getInt() != 0x1a7501a8) {
      return false;
    }

    buffer.position(buffer.position() + 3 + 6 + 5 + 7 + 5 + 7 + 7);

    if (buffer.getShort() != (short)0xb941) {
      return false;
    }

    if (buffer.getInt() != low) {
      return false;
    }

    if (buffer.getShort() != (short)0xb841) {
      return false;
    }

    if (buffer.getInt() != high) {
      return false;
    }

    System.out.println(Integer.toString(high) + "." + Integer.toString(low));

    return true;
  }
}