added rom decoding

utils/decode_cloanto_rom.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""
+Convert Cloanto ROM to normal Kickstart ROM
+"""
+import argparse
+
+CLOANTO_ID = b'AMIROMTYPE1'
+SIZE_CLASSIC = 0x40000
+SIZE_MODERN  = 0x80000
+MAX_ROM_SIZE = SIZE_MODERN
+
+def decode_cloanto(rom, key, real_size):
+    rom = bytearray(rom)
+    key = bytearray(key)
+    result = bytearray(len(rom))
+    key_size = len(key)
+    key_index = 0
+
+    for i in range(len(rom)):
+        result[i] = rom[i] ^ key[key_index]
+        key_index = (key_index + 1) % key_size
+
+    return result
+        
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description="Cloanto Decoder 1.0")
+    parser.add_argument('romfile')
+    parser.add_argument('keyfile')
+    parser.add_argument('target')
+    args = parser.parse_args()
+
+    with open(args.keyfile, 'rb') as infile:
+        key_data = infile.read()
+
+    with open(args.romfile, 'rb') as infile:
+        file_id = infile.read(len(CLOANTO_ID))
+        if file_id == CLOANTO_ID:
+            data = infile.read()            
+            size = len(data)
+            if size != SIZE_CLASSIC and size != SIZE_MODERN:
+                raise Exception("invalid rom size")
+            decoded = decode_cloanto(data, key_data, len(data))
+            with open(args.target, 'wb') as outfile:
+                outfile.write(bytes(decoded))
+        else:
+            raise Exception('not a cloanto rom: ', file_id)