(DameganeCrypt): another decryption scheme.

ArcFormats/ArcXP3.cs

@@ -92,6 +92,7 @@ namespace GameRes.Formats.KiriKiri
             { arcStrings.ArcNoEncryption, NoCryptAlgorithm },
             { "Cafe Sourire",       new XorCrypt (0xcd) },
             { "Coμ",                new ComyuCrypt() },
+            { "Damegane",           new DameganeCrypt() },
             { "Fate/hollow ataraxia", new FateHACrypt() },
             { "Fate/stay night",    new FateCrypt() },
             { "Imouto Style",       new ImoutoStyleCrypt() },
@@ -1055,4 +1056,31 @@ NextEntry:
             }
         }
     }
+
+    internal class DameganeCrypt : ICrypt
+    {
+        public override byte Decrypt (Xp3Entry entry, long offset, byte value)
+        {
+            if (0 != (offset & 1))
+                return (byte)(value ^ entry.Hash);
+            else
+                return (byte)(value ^ offset);
+        }
+
+        public override void Decrypt (Xp3Entry entry, long offset, byte[] values, int pos, int count)
+        {
+            for (int i = 0; i < count; ++i, ++offset)
+            {
+                if (0 != (offset & 1))
+                    values[pos+i] ^= (byte)entry.Hash;
+                else
+                    values[pos+i] ^= (byte)offset;
+            }
+        }
+
+        public override void Encrypt (Xp3Entry entry, long offset, byte[] values, int pos, int count)
+        {
+            Decrypt (entry, offset, values, pos, count);
+        }
+    }
 }