gamemode on savegame format

src/net/torvald/terrarum/savegame/DiskSkimmer.kt

@@ -392,7 +392,7 @@ removefile:
 
     fun setSaveSnapshotVersion(snapshot: Snapshot?) {
         val fa = RandomAccessFile(diskFile, "rwd")
-        fa.seek(51L)
+        fa.seek(52L)
         if (snapshot == null)
             fa.write(byteArrayOf(0, 0))
         else
@@ -400,6 +400,13 @@ removefile:
         fa.close()
     }
 
+    fun setGameMode(bits: Int) {
+        val fa = RandomAccessFile(diskFile, "rwd")
+        fa.seek(54L)
+        fa.writeByte(bits)
+        fa.close()
+    }
+
     /**
      * @return Save type (0b 0000 00ab)
      *                   b: unset - full save; set - quicksave (only applicable to worlds -- quicksave just means the disk is in dirty state)
@@ -440,6 +447,12 @@ removefile:
         else Snapshot(byteArrayOf(b1, b2))
     }
 
+    fun getGameMode(): Int {
+        val fa = RandomAccessFile(diskFile, "rwd")
+        fa.seek(54L)
+        return fa.read().also { fa.close() }
+    }
+
 
 
     override fun getDiskName(charset: Charset): String {

src/net/torvald/terrarum/savegame/VirtualDisk.kt

@@ -87,7 +87,12 @@ Version 254 is a customised version of TEVD tailored to be used as a savegame fo
                    w: ISO Week Number (1-53)
                    Aaa: Alphabet (a->000, b->001, ... e->100, f->101, ..., h->111)
                  e.g. 23w40f is encoded as 1_0010111 101000_01
-    Int8[10]    Extra info bytes reserved for future usage
+    Int8        Game Mode (0b ww tttttt)
+                t: 0 - Undecided
+                   1 - Survival (0.4.0+)
+                w: 0 - Singleplayer
+                   2 - Multiplayer
+    Int8[9]    Extra info bytes reserved for future usage
 
     -- END extraInfoBytes --
     UInt8[236]  Rest of the long disk name (268 bytes total)
@@ -183,6 +188,9 @@ class VirtualDisk(
                 Snapshot(extraInfoBytes.sliceArray(4..5))
             }
         }
+    var gamemode: Int
+        set(value) { extraInfoBytes[6] = value.toByte() }
+        get() = extraInfoBytes[6].toUint()
 
     override fun getDiskName(charset: Charset) = diskName.toCanonicalString(charset)
     val root: DiskEntry