checkpoint: VT1200 reverse-engineering workspace before board-model work

test_ptr_constants.py

@@ -0,0 +1,62 @@
+"""Tests for tools/ptr_constants.py.
+
+The VT1200 firmware stores TMS34010 *bit* addresses: a 32-bit value P refers to
+physical byte P >> 3.  ptr_constants.scan() finds those constants in an
+address-ordered image and resolves where they point.
+"""
+import os
+import struct
+import sys
+import unittest
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, os.path.join(HERE, "tools"))
+
+import ptr_constants
+
+ROM_BASE = 0x07E40000
+
+
+class ScanSyntheticTest(unittest.TestCase):
+    def test_finds_string_pointer(self):
+        img = bytearray(0x1000)
+        img[0x100:0x100 + 11] = b"HELLO WORLD"
+        ptr = (ROM_BASE + 0x100) << 3           # bit address of the string
+        struct.pack_into("<I", img, 0x10, ptr)
+        hits = list(ptr_constants.scan(bytes(img)))
+        self.assertIn((0x10, ptr, 0x100, "string"), hits)
+
+    def test_ignores_values_that_do_not_resolve(self):
+        self.assertEqual(list(ptr_constants.scan(b"\xff" * 0x100)), [])
+
+
+class ClassifyTest(unittest.TestCase):
+    def test_printable_run_is_a_string(self):
+        img = b"\x00" * 8 + b"ABCDEFGH"
+        self.assertEqual(ptr_constants.classify(img, 8), "string")
+
+    def test_non_printable_is_other(self):
+        img = b"\x00" * 16
+        self.assertEqual(ptr_constants.classify(img, 8), "other")
+
+    def test_out_of_range_returns_none(self):
+        self.assertIsNone(ptr_constants.classify(b"\x00\x01", 99))
+
+
+class RealImageTest(unittest.TestCase):
+    def test_known_pointer_resolves_to_its_string(self):
+        path = os.path.join(HERE, "vt1200_v21.bin")
+        if not os.path.exists(path):
+            self.skipTest("image not built")
+        with open(path, "rb") as fh:
+            img = fh.read()
+        by_value = {v: (off, tgt, kind) for off, v, tgt, kind in ptr_constants.scan(img)}
+        self.assertIn(0x3F816ED8, by_value)
+        off, tgt, kind = by_value[0x3F816ED8]
+        self.assertEqual(tgt, 0xC2DDB)
+        self.assertEqual(kind, "string")
+        self.assertEqual(img[tgt:tgt + 15], b"Messages re-xmt")
+
+
+if __name__ == "__main__":
+    unittest.main()