framing: fix data

amodem/framing.py

@@ -64,13 +64,13 @@ class Framer(object):
         length = struct.calcsize(fmt)
         chunk = bytearray(itertools.islice(data, length))
         if len(chunk) < length:
-            raise StopIteration()
+            raise ValueError('missing prefix data')
         return struct.unpack(fmt, chunk)
 
     def _take_len(self, data, length):
         chunk = bytearray(itertools.islice(data, length))
         if len(chunk) < length:
-            raise StopIteration()
+            raise ValueError('missing payload data')
         return chunk
 
 

tests/test_framing.py

@@ -33,3 +33,17 @@ def test_main(data):
     encoded = framing.encode(data)
     decoded = framing.decode(encoded)
     assert bytearray(decoded) == data
+
+def test_fail():
+    encoded = list(framing.encode(''))
+    encoded[-1] = not encoded[-1]
+    with pytest.raises(ValueError):
+        list(framing.decode(encoded))
+
+def test_missing():
+    f = framing.Framer()
+    with pytest.raises(ValueError):
+        list(f.decode(b'\x00'))
+    with pytest.raises(ValueError):
+        list(f.decode(b'\x01\x02\x03\x04'))
+