Fix disassembly output when instruction wraps past the top of memory

CHANGES.txt

@@ -18,6 +18,9 @@
   - Assembling now shows an Overflow Error if the statement won't
     fit at the top of memory.
 
+  - Fixed a bug in the disassembler where instructions that wrap past
+    the top of memory would not be displayed properly.
+
 0.13 (2012-11-15)
 
   - Fixed a bug where negative numbers could be entered

py65/monitor.py

@@ -369,14 +369,23 @@ class Monitor(cmd.Cmd):
             self._output(self._format_disassembly(address, bytes, disasm))
             address += bytes
 
-    def _format_disassembly(self, address, bytes, disasm):
-        mem = ''
-        for byte in self._mpu.memory[address:address + bytes]:
-            mem += self.byteFmt % byte + " "
+    def _format_disassembly(self, address, length, disasm):
+        cur_address = address
+        max_address = (2 ** self._mpu.ADDR_WIDTH) - 1
+
+        bytes_remaining = length
+        dump = ''
+
+        while bytes_remaining:
+            if cur_address > max_address:
+                cur_address = 0
+            dump += self.byteFmt % self._mpu.memory[cur_address] + " "
+            cur_address += 1
+            bytes_remaining -= 1
 
         fieldwidth = 1 + (1 + self.byteWidth / 4) * 3
         fieldfmt = "%%-%ds" % fieldwidth
-        return "$" + self.addrFmt % address + "  " + fieldfmt % mem + disasm
+        return "$" + self.addrFmt % address + "  " + fieldfmt % dump + disasm
 
     def help_disassemble(self):
         self._output("disassemble <address_range>")

py65/tests/test_disassembler.py

@@ -7,6 +7,19 @@ from py65.utils.addressing import AddressParser
 
 
 class DisassemblerTests(unittest.TestCase):
+    def test_disassemble_wraps_after_top_of_mem(self):
+        mpu = MPU()
+        mpu.memory[0xFFFF] = 0x20  # JSR
+        mpu.memory[0x0000] = 0xD2  #
+        mpu.memory[0x0001] = 0xFF  # $FFD2
+
+        dis = Disassembler(mpu)
+#        length, disasm = dis.instruction_at(0xFFFF)
+        from pprint import pprint as pp
+#        pp(disasm)
+
+#        return disasm.instruction_at(pc)
+
     def test_disassembles_00(self):
         length, disasm = self.disassemble([0x00])
         self.assertEqual(1, length)

py65/tests/test_monitor.py

@@ -301,6 +301,18 @@ class MonitorTests(unittest.TestCase):
         disasm = "$c000  ea        NOP\n$c001  ea        NOP\n"
         self.assertEqual(out, disasm)
 
+    def test_disassemble_wraps_to_0_after_to_of_memory(self):
+        stdout = StringIO()
+        mon = Monitor(stdout=stdout)
+        mon._mpu.memory[0xffff] = 0x20  # => JSR
+        mon._mpu.memory[0x0000] = 0xD2  #
+        mon._mpu.memory[0x0001] = 0xFF  # => $FFD2
+        mon.do_disassemble("ffff")
+
+        out = stdout.getvalue()
+        disasm = "$ffff  20 d2 ff  JSR $ffd2\n"
+        self.assertEqual(out, disasm)
+
     # fill
 
     def test_shortcut_f_for_fill(self):