Implement flow control

This commit introduces the necessary changes necessary
for implementing flow control. None of the socket types
implements the flow control yet. The code will crash when
the flow control is enabled and the thw lwm is reached.

The following commits will add flow-control support for
individual socket types.

1 files changed, 22 insertions, 27 deletions

diff --git a/src/lb.cpp b/src/lb.cpp
index 4743ac6..d7193f1 100644
--- a/src/lb.cpp
+++ b/src/lb.cpp
@@ -54,15 +54,6 @@ void zmq::lb_t::detach (writer_t *pipe_)
     pipes.erase (pipe_);
 }
 
-void zmq::lb_t::kill (writer_t *pipe_)
-{
-    //  Move the pipe to the list of inactive pipes.
-    active--;
-    if (current == active)
-        current = 0;
-    pipes.swap (pipes.index (pipe_), active);
-}
-
 void zmq::lb_t::revive (writer_t *pipe_)
 {
     //  Move the pipe to the list of active pipes.
@@ -72,42 +63,46 @@ void zmq::lb_t::revive (writer_t *pipe_)
 
 int zmq::lb_t::send (zmq_msg_t *msg_, int flags_)
 {
+    while (active > 0) {
+        if (pipes [current]->write (msg_))
+            break;
+
+        active--;
+        if (current < active)
+            pipes.swap (current, active);
+        else
+            current = 0;
+    }
+
     //  If there are no pipes we cannot send the message.
-    if (pipes.empty ()) {
+    if (active == 0) {
         errno = EAGAIN;
         return -1;
     }
 
-    //  TODO: Implement this once queue limits are in-place.
-    zmq_assert (pipes [current]->check_write (zmq_msg_size (msg_)));
-
-    //  Push message to the selected pipe.
-    pipes [current]->write (msg_);
-    pipes [current]->flush ();
+    if (!(flags_ & ZMQ_NOFLUSH))
+        pipes [current]->flush ();
 
     //  Detach the message from the data buffer.
     int rc = zmq_msg_init (msg_);
     zmq_assert (rc == 0);
 
     //  Move to the next pipe (load-balancing).
-    current++;
-    if (current >= active)
-        current = 0;
+    current = (current + 1) % active;
 
     return 0;
 }
 
 bool zmq::lb_t::has_out ()
 {
-    for (int count = active; count != 0; count--) {
-
-        //  We should be able to write at least 1-byte message to interrupt
-        //  polling for POLLOUT.
-        //  TODO: Shouldn't we use a saner value here?
-        if (pipes [current]->check_write (1))
+    while (active > 0) {
+        if (pipes [current]->check_write ())
             return true;
-        current++;
-        if (current >= active)
+
+        active--;
+        if (current < active)
+            pipes.swap (current, active);
+        else
             current = 0;
     }