Add some comments
diff --git a/include/grpc++/completion_queue.h b/include/grpc++/completion_queue.h
index 665f293..c5267f8 100644
--- a/include/grpc++/completion_queue.h
+++ b/include/grpc++/completion_queue.h
@@ -84,6 +84,8 @@
grpc_completion_queue *cq() { return cq_; }
private:
+ // Friend synchronous wrappers so that they can access Pluck(), which is
+ // a semi-private API geared towards the synchronous implementation.
template <class R>
friend class ::grpc::ClientReader;
template <class W>
@@ -103,6 +105,8 @@
const google::protobuf::Message &request,
google::protobuf::Message *result);
+ // Wraps grpc_completion_queue_pluck.
+ // Cannot be mixed with calls to Next().
bool Pluck(CompletionQueueTag *tag);
grpc_completion_queue *cq_; // owned