From 66e28d6ef8a293bca0d741c218b41510f6511800 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juhani=20Krekel=C3=A4?= <juhani@krekelä.fi>
Date: Tue, 10 May 2022 11:19:22 +0200
Subject: [PATCH] =?UTF-8?q?Properly=20handle=20non-instruction=20bytes=20i?=
 =?UTF-8?q?n=20the=20range=200xa0=E2=80=A60xbf?=
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Previously address arguments were extracted without verifying the start
byte corresponded to a valid instruction. In case of a non-instruction
byte this would result in the two following bytes to be silently
skipped.
---
 .gitignore            |  1 +
 thingamajig_disasm.py | 19 +++++++++----------
 2 files changed, 10 insertions(+), 10 deletions(-)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a8a0dce
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.bin
diff --git a/thingamajig_disasm.py b/thingamajig_disasm.py
index 1655643..fda93b6 100644
--- a/thingamajig_disasm.py
+++ b/thingamajig_disasm.py
@@ -41,23 +41,22 @@ def segment(binary, origin):
 		rx = (byte >> 2) & 3
 		ry = byte & 3
 
-		addr = None
-		if opcodes[opcode].addr:
-			addr = (binary[ip + 1] << 8) + binary[ip + 2]
-
 		valid = True
 		if not opcodes[opcode].rx and rx != 0: valid = False
 		if not opcodes[opcode].ry and ry != 0: valid = False
 
-		if valid:
+		if not valid:
+			statements.append(Statement(ip, Data(byte)))
+			ip += 1
+		elif opcodes[opcode].addr:
+			addr = (binary[ip + 1] << 8) + binary[ip + 2]
 			instruction = Instruction(opcode, rx, ry, addr)
 			statements.append(Statement(ip, instruction))
+			ip += 3
 		else:
-			statements.append(Statement(ip, Data(byte)))
-
-		ip += 1
-		if opcodes[opcode].addr:
-			ip += 2
+			instruction = Instruction(opcode, rx, ry, None)
+			statements.append(Statement(ip, instruction))
+			ip += 1
 
 	return statements