Add serialization versioning

core/src/io/github/lonamiwebs/klooni/serializer/BinSerializer.java

@@ -5,12 +5,23 @@ import java.io.DataOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.util.Arrays;
 
 public class BinSerializer {
+
+    // ascii (klooni) and binary (1010b)
+    private static byte[] HEADER = { 0x6B, 0x6C, 0x6F, 0x6F, 0x6E, 0x69, 0xa };
+
+    // MODIFY THIS VALUE EVERY TIME A BinSerializable IMPLEMENTATION CHANGES
+    // Or unwanted results will happen and corrupt the game in an unknown way.
+    private static int VERSION = 1;
+
     public static void serialize(final BinSerializable serializable, final OutputStream output)
             throws IOException {
         DataOutputStream out = new DataOutputStream(output);
         try {
+            out.write(HEADER);
+            out.writeInt(VERSION);
             serializable.write(out);
         } finally {
             try {
@@ -23,6 +34,19 @@ public class BinSerializer {
             throws IOException {
         DataInputStream in = new DataInputStream(input);
         try {
+            // Read the HEADER and the VERSION (checks)
+            byte[] savedBuffer = new byte[HEADER.length];
+            in.readFully(savedBuffer);
+            if (!Arrays.equals(savedBuffer, HEADER))
+                throw new IOException("Invalid saved header found.");
+
+            int savedVersion = in.readInt();
+            if (savedVersion != VERSION) {
+                throw new IOException(
+                        "Invalid saved version found. Should be " + VERSION + ", not " + savedVersion);
+            }
+
+            // Read the saved data if the checks passed
             serializable.read(in);
         } finally {
             try {