Code cleanup

src/pipe.hpp

@@ -69,7 +69,7 @@ namespace zmq
         //  This allows pipepair to create pipe objects.
         friend int pipepair (zmq::object_t *parents_ [2], zmq::pipe_t* pipes_ [2],
             int hwms_ [2], bool conflate_ [2]);
-            
+
     public:
 
         //  Specifies the object to send events to.
@@ -105,7 +105,7 @@ namespace zmq
         //  all the messages on the fly. Causes 'hiccuped' event to be generated
         //  in the peer.
         void hiccup ();
-        
+
         // Ensure the pipe wont block on receiving pipe_term.
         void set_nodelay ();
 
@@ -119,7 +119,7 @@ namespace zmq
         void set_hwms (int inhwm_, int outhwm_);
 
         // check HWM
-        bool check_hwm ();
+        bool check_hwm () const;
         // provide a way to link pipe to engine fd. Set on session initialization
         fd_t assoc_fd; //=retired_fd
     private: