Fix float type (Single/Double) deserialization. (#164)

* Fix float type deserialization.
* Refactor float types.
Raise if buffer size is incorrect.

tests/test_types.py

@@ -13,15 +13,27 @@ def test_int_too_short():
 
 
 def test_single():
-    v = t.Single(1.25)
+    value = 1.25
+    extra = b'ab12!'
+    v = t.Single(value)
     ser = v.serialize()
-    assert t.Single.deserialize(ser) == (1.25, b'')
+    assert t.Single.deserialize(ser) == (value, b'')
+    assert t.Single.deserialize(ser + extra) == (value, extra)
+
+    with pytest.raises(ValueError):
+        t.Double.deserialize(ser[1:])
 
 
 def test_double():
-    v = t.Double(1.25)
+    value = 1.25
+    extra = b'ab12!'
+    v = t.Double(value)
     ser = v.serialize()
-    assert t.Double.deserialize(ser) == (1.25, b'')
+    assert t.Double.deserialize(ser) == (value, b'')
+    assert t.Double.deserialize(ser + extra) == (value, extra)
+
+    with pytest.raises(ValueError):
+        t.Double.deserialize(ser[1:])
 
 
 def test_lvbytes():

zigpy/types/basic.py

@@ -125,21 +125,22 @@ class bitmap64(uint64_t):  # noqa: N801
 
 
 class Single(float):
+    _fmt = '<f'
+
     def serialize(self):
-        return struct.pack('<f', self)
+        return struct.pack(self._fmt, self)
 
     @classmethod
     def deserialize(cls, data):
-        return struct.unpack('<f', data)[0], data[4:]
+        size = struct.calcsize(cls._fmt)
+        if len(data) < size:
+            raise ValueError('Data is too short to contain %s float' % cls.__name__)
 
+        return struct.unpack(cls._fmt, data[0:size])[0], data[size:]
 
-class Double(float):
-    def serialize(self):
-        return struct.pack('<d', self)
 
-    @classmethod
-    def deserialize(cls, data):
-        return struct.unpack('<d', data)[0], data[8:]
+class Double(Single):
+    _fmt = '<d'
 
 
 class LVBytes(bytes):