Calculate and verify checksum for RGN binary payloads.

grmn/rgnbin.py

@@ -2,6 +2,7 @@
 # Thanks to Herbert Oppmann (herby) for all your work!
 
 from . import devices
+from .ansi import RESET, RED, GREEN
 from .chksum import ChkSum
 from struct import unpack
 
@@ -30,6 +31,20 @@ class RgnBin:
         self.load_from_bytes(rawdata)
 
     def load_from_bytes(self, payload: bytes):
+        self.payload = payload
         print(repr(payload[0:10]))
         jmp = unpack("<L", payload[0:4])[0]
         print("{:08x}".format(jmp))
+
+    def __str__(self):
+        txt = "Binary payload, {} Bytes".format(len(self.payload))
+        cksum = ChkSum()
+        cksum.add(self.payload)
+        exp_byte = cksum.get_expected()
+        last_byte = cksum.get_last_byte()
+        txt += "\n  - Checksum: {:02x} (expected: {:02x}) = ".format(last_byte, exp_byte)
+        if cksum.is_valid():
+            txt += GREEN + "OK" + RESET
+        else:
+            txt += RED + "INVALID" + RESET
+        return txt