write headers for data processing

src/dat/mcx.h

@@ -0,0 +1,19 @@
+// Copyright (c) 2025 Quinn
+// Licensed under the MIT Licence. See LICENSE for details
+#pragma once
+
+/* the MCR (Minecraft region) and MCA (Minecraft anvil) files are similar
+ * MCA is the newer variant, where it includes:
+ *  - a world height of 256, rather than 128.
+ *  - block IDs have been extended to 4096 from 256
+ *  - block ordering is now YZX, rather than XZY.
+ *  - biomes are included in the data per XZ column.
+ * MCR start with an 8KiB header, split in two 4KiB tables
+ * - the first containing the offsets of chunks in the region file itself.
+ * - the second providing timestamps on when they were last updated.
+ * -
+ *
+ *
+ *
+ *
+ */