add support for extended types: you can now pack/unpack custom python objects by subclassing Packer and Unpacker

test/test_extension.py

@@ -0,0 +1,24 @@
+import array
+import msgpack
+
+def test_extension_type():
+    class MyPacker(msgpack.Packer):
+        def handle_extended_type(self, obj):
+            if isinstance(obj, array.array):
+                fmt = "ext 32"
+                typecode = 123 # application specific typecode
+                data = obj.tostring()
+                return fmt, typecode, data
+
+    class MyUnpacker(msgpack.Unpacker):
+        def handle_extended_type(self, typecode, data):
+            assert typecode == 123
+            obj = array.array('d')
+            obj.fromstring(data)
+            return obj
+
+    obj = [42, 'hello', array.array('d', [1.1, 2.2, 3.3])]
+    s = msgpack.packb(obj, MyPacker)
+    obj2 = msgpack.unpackb(s, MyUnpacker)
+    assert obj == obj2
+