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

1 files changed, 106 insertions, 0 deletions

diff --git a/src/fq.cpp b/src/fq.cpp
new file mode 100644
index 0000000..2c6fffb
--- /dev/null
+++ b/src/fq.cpp
@@ -0,0 +1,106 @@
+/*
+    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 "fq.hpp"
+#include "pipe.hpp"
+#include "err.hpp"
+
+zmq::fq_t::fq_t () :
+    active (0),
+    current (0)
+{
+}
+
+zmq::fq_t::~fq_t ()
+{
+    for (pipes_t::size_type i = 0; i != pipes.size (); i++)
+        pipes [i]->term ();
+}
+
+void zmq::fq_t::attach (reader_t *pipe_)
+{
+    pipes.push_back (pipe_);
+    pipes.swap (active, pipes.size () - 1);
+    active++;
+}
+
+void zmq::fq_t::detach (reader_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::fq_t::kill (reader_t *pipe_)
+{
+    //  Move the pipe to the list of inactive pipes.
+    active--;
+    pipes.swap (pipes.index (pipe_), active);
+}
+
+void zmq::fq_t::revive (reader_t *pipe_)
+{
+    //  Move the pipe to the list of active pipes.
+    pipes.swap (pipes.index (pipe_), active);
+    active++;
+}
+
+int zmq::fq_t::recv (zmq_msg_t *msg_, int flags_)
+{
+    //  Deallocate old content of the message.
+    zmq_msg_close (msg_);
+
+    //  Round-robin over the pipes to get next message.
+    for (int count = active; count != 0; count--) {
+        bool fetched = pipes [current]->read (msg_);
+        current++;
+        if (current >= active)
+            current = 0;
+        if (fetched)
+            return 0;
+    }
+
+    //  No message is available. Initialise the output parameter
+    //  to be a 0-byte message.
+    zmq_msg_init (msg_);
+    errno = EAGAIN;
+    return -1;
+}
+
+bool zmq::fq_t::has_in ()
+{
+    //  Note that messing with current doesn't break the fairness of fair
+    //  queueing algorithm. If there are no messages available current will
+    //  get back to its original value. Otherwise it'll point to the first
+    //  pipe holding messages, skipping only pipes with no messages available.
+    for (int count = active; count != 0; count--) {
+        if (pipes [current]->check_read ())
+            return true;
+        current++;
+        if (current >= active)
+            current = 0;
+    }
+
+    return false;
+}
+