zmq_encoder/decoder are able to add/trim prefixes from messages; fair queueing and load balancing algorithms factorised into separate classes

1 files changed, 111 insertions, 0 deletions

diff --git a/src/lb.cpp b/src/lb.cpp
new file mode 100644
index 0000000..4db8594
--- /dev/null
+++ b/src/lb.cpp
@@ -0,0 +1,111 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../bindings/c/zmq.h"
+
+#include "lb.hpp"
+#include "pipe.hpp"
+#include "err.hpp"
+
+zmq::lb_t::lb_t () :
+    active (0),
+    current (0)
+{
+}
+
+zmq::lb_t::~lb_t ()
+{
+    for (pipes_t::size_type i = 0; i != pipes.size (); i++)
+        pipes [i]->term ();
+}
+
+void zmq::lb_t::attach (writer_t *pipe_)
+{
+    pipes.push_back (pipe_);
+    pipes.swap (active, pipes.size () - 1);
+    active++;
+}
+
+void zmq::lb_t::detach (writer_t *pipe_)
+{
+    //  Remove the pipe from the list; adjust number of active pipes
+    //  accordingly.
+    if (pipes.index (pipe_) < active)
+        active--;
+    pipes.erase (pipe_);
+}
+
+void zmq::lb_t::kill (writer_t *pipe_)
+{
+    //  Move the pipe to the list of inactive pipes.
+    active--;
+    pipes.swap (pipes.index (pipe_), active);
+}
+
+void zmq::lb_t::revive (writer_t *pipe_)
+{
+    //  Move the pipe to the list of active pipes.
+    pipes.swap (pipes.index (pipe_), active);
+    active++;
+}
+
+int zmq::lb_t::send (zmq_msg_t *msg_, int flags_)
+{
+    //  If there are no pipes we cannot send the message.
+    if (pipes.empty ()) {
+        errno = EAGAIN;
+        return -1;
+    }
+
+    //  Move to the next pipe (load-balancing).
+    current++;
+    if (current >= active)
+        current = 0;
+
+    //  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 ();
+
+    //  Detach the message from the data buffer.
+    int rc = zmq_msg_init (msg_);
+    zmq_assert (rc == 0);
+
+    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))
+            return true;
+        current++;
+        if (current >= active)
+            current = 0;
+    }
+
+    return false;
+}
+