Do not pass a message to the check_write method

The check_write method does not use the passed message.
The parameter was needed to implement the swap.
As the swap is not supported anymore, it is safe to remove this parameter.

src/lb.cpp

@@ -131,17 +131,9 @@ bool zmq::lb_t::has_out ()
 
     while (active > 0) {
 
-        //  Check whether zero-sized message can be written to the pipe.
+        //  Check whether a pipe has room for another message.
-        msg_t msg;
+        if (pipes [current]->check_write ())
-        int rc = msg.init ();
-        errno_assert (rc == 0);
-        if (pipes [current]->check_write (&msg)) {
-            rc = msg.close ();
-            errno_assert (rc == 0);
             return true;
-        }
-        rc = msg.close ();
-        errno_assert (rc == 0);
 
         //  Deactivate the pipe.
         active--;

src/pair.cpp

@@ -108,13 +108,7 @@ bool zmq::pair_t::xhas_out ()
     if (!pipe)
         return false;
 
-    msg_t msg;
+    return pipe->check_write ();
-    int rc = msg.init ();
-    errno_assert (rc == 0);
-    bool result = pipe->check_write (&msg);
-    rc = msg.close ();
-    errno_assert (rc == 0);
-    return result;
 }
 
 zmq::pair_session_t::pair_session_t (io_thread_t *io_thread_, bool connect_,

src/pipe.cpp

@@ -146,7 +146,7 @@ bool zmq::pipe_t::read (msg_t *msg_)
     return true;
 }
 
-bool zmq::pipe_t::check_write (msg_t *msg_)
+bool zmq::pipe_t::check_write ()
 {
     if (unlikely (!out_active || state != active))
         return false;
@@ -163,7 +163,7 @@ bool zmq::pipe_t::check_write (msg_t *msg_)
 
 bool zmq::pipe_t::write (msg_t *msg_)
 {
-    if (unlikely (!check_write (msg_)))
+    if (unlikely (!check_write ()))
         return false;
 
     bool more = msg_->flags () & msg_t::more ? true : false;

src/pipe.hpp

@@ -87,7 +87,7 @@ namespace zmq
 
         //  Checks whether messages can be written to the pipe. If writing
         //  the message would cause high watermark the function returns false.
-        bool check_write (msg_t *msg_);
+        bool check_write ();
 
         //  Writes a message to the underlying pipe. Returns false if the
         //  message cannot be written because high watermark was reached.

src/router.cpp

@@ -152,21 +152,15 @@ int zmq::router_t::xsend (msg_t *msg_, int flags_)
 
             if (it != outpipes.end ()) {
                 current_out = it->second.pipe;
-                msg_t empty;
+                if (!current_out->check_write ()) {
-                int rc = empty.init ();
-                errno_assert (rc == 0);
-                if (!current_out->check_write (&empty)) {
                     it->second.active = false;
                     more_out = false;
                     current_out = NULL;
                 }
-                rc = empty.close ();
-                errno_assert (rc == 0);
             } else if(fail_unroutable) {
                 more_out = false;
                 retval = EHOSTUNREACH;
             }
-
         }
 
         int rc = msg_->close ();