support deepcopy & copy by serialize and deserialize

src/fastpb/template/module.jinjacc

@@ -203,6 +203,25 @@ namespace {
       return PyString_FromStringAndSize(result.data(), result.length());
   }
 
+  PyObject *
+  {{ message.name }}_Copy({{ message.name }}* self)
+  {
+      std::string result;
+      {{ message.name }}* cloned = NULL;
+      Py_BEGIN_ALLOW_THREADS
+      self->protobuf->SerializeToString(&result);
+      cloned = ({{ message.name }}*){{ message.name }}_new(&{{ message.name }}Type, NULL, NULL);
+      cloned->protobuf->ParseFromString(result);
+      Py_END_ALLOW_THREADS
+      return (PyObject*)cloned;
+  }
+
+  PyObject *
+  {{ message.name }}_DeepCopy({{ message.name }}* self, PyObject* /*memo*/)
+  {
+      return {{ message.name }}_Copy(self);
+  }
+
 
   PyObject *
   {{ message.name }}_ParseFromString({{ message.name }}* self, PyObject *value)
@@ -658,6 +677,12 @@ namespace {
       {"ParseMany", (PyCFunction){{ message.name }}_ParseMany, METH_VARARGS | METH_CLASS,
        "Parses many protocol buffers of this type from a string."
       },
+      {"__copy__", (PyCFunction){{ message.name }}_DeepCopy, METH_NOARGS,
+       "copy a pb message."
+      },
+      {"__deepcopy__", (PyCFunction){{ message.name }}_DeepCopy, METH_O,
+       "deep copy a pb message."
+      },
       {NULL}  // Sentinel
   };