Merge commit 'e988fee1679536137b87d10e939eff5c1f27c8ab' as 'libs/libzmq'

libs/libzmq/src/lb.cpp

@@ -0,0 +1,180 @@
+/*
+    Copyright (c) 2007-2018 Contributors as noted in the AUTHORS file
+
+    This file is part of libzmq, the ZeroMQ core engine in C++.
+
+    libzmq is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser General Public License (LGPL) as published
+    by the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    As a special exception, the Contributors give you permission to link
+    this library with independent modules to produce an executable,
+    regardless of the license terms of these independent modules, and to
+    copy and distribute the resulting executable under terms of your choice,
+    provided that you also meet, for each linked independent module, the
+    terms and conditions of the license of that module. An independent
+    module is a module which is not derived from or based on this library.
+    If you modify this library, you must extend this exception to your
+    version of the library.
+
+    libzmq 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 GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "precompiled.hpp"
+#include "lb.hpp"
+#include "pipe.hpp"
+#include "err.hpp"
+#include "msg.hpp"
+
+zmq::lb_t::lb_t () : _active (0), _current (0), _more (false), _dropping (false)
+{
+}
+
+zmq::lb_t::~lb_t ()
+{
+    zmq_assert (_pipes.empty ());
+}
+
+void zmq::lb_t::attach (pipe_t *pipe_)
+{
+    _pipes.push_back (pipe_);
+    activated (pipe_);
+}
+
+void zmq::lb_t::pipe_terminated (pipe_t *pipe_)
+{
+    const pipes_t::size_type index = _pipes.index (pipe_);
+
+    //  If we are in the middle of multipart message and current pipe
+    //  have disconnected, we have to drop the remainder of the message.
+    if (index == _current && _more)
+        _dropping = true;
+
+    //  Remove the pipe from the list; adjust number of active pipes
+    //  accordingly.
+    if (index < _active) {
+        _active--;
+        _pipes.swap (index, _active);
+        if (_current == _active)
+            _current = 0;
+    }
+    _pipes.erase (pipe_);
+}
+
+void zmq::lb_t::activated (pipe_t *pipe_)
+{
+    //  Move the pipe to the list of active pipes.
+    _pipes.swap (_pipes.index (pipe_), _active);
+    _active++;
+}
+
+int zmq::lb_t::send (msg_t *msg_)
+{
+    return sendpipe (msg_, NULL);
+}
+
+int zmq::lb_t::sendpipe (msg_t *msg_, pipe_t **pipe_)
+{
+    //  Drop the message if required. If we are at the end of the message
+    //  switch back to non-dropping mode.
+    if (_dropping) {
+        _more = (msg_->flags () & msg_t::more) != 0;
+        _dropping = _more;
+
+        int rc = msg_->close ();
+        errno_assert (rc == 0);
+        rc = msg_->init ();
+        errno_assert (rc == 0);
+        return 0;
+    }
+
+    while (_active > 0) {
+        if (_pipes[_current]->write (msg_)) {
+            if (pipe_)
+                *pipe_ = _pipes[_current];
+            break;
+        }
+
+        // If send fails for multi-part msg rollback other
+        // parts sent earlier and return EAGAIN.
+        // Application should handle this as suitable
+        if (_more) {
+            _pipes[_current]->rollback ();
+            // At this point the pipe is already being deallocated
+            // and the first N frames are unreachable (_outpipe is
+            // most likely already NULL so rollback won't actually do
+            // anything and they can't be un-written to deliver later).
+            // Return EFAULT to socket_base caller to drop current message
+            // and any other subsequent frames to avoid them being
+            // "stuck" and received when a new client reconnects, which
+            // would break atomicity of multi-part messages (in blocking mode
+            // socket_base just tries again and again to send the same message)
+            // Note that given dropping mode returns 0, the user will
+            // never know that the message could not be delivered, but
+            // can't really fix it without breaking backward compatibility.
+            // -2/EAGAIN will make sure socket_base caller does not re-enter
+            // immediately or after a short sleep in blocking mode.
+            _dropping = (msg_->flags () & msg_t::more) != 0;
+            _more = false;
+            errno = EAGAIN;
+            return -2;
+        }
+
+        _active--;
+        if (_current < _active)
+            _pipes.swap (_current, _active);
+        else
+            _current = 0;
+    }
+
+    //  If there are no pipes we cannot send the message.
+    if (_active == 0) {
+        errno = EAGAIN;
+        return -1;
+    }
+
+    //  If it's final part of the message we can flush it downstream and
+    //  continue round-robining (load balance).
+    _more = (msg_->flags () & msg_t::more) != 0;
+    if (!_more) {
+        _pipes[_current]->flush ();
+
+        if (++_current >= _active)
+            _current = 0;
+    }
+
+    //  Detach the message from the data buffer.
+    const int rc = msg_->init ();
+    errno_assert (rc == 0);
+
+    return 0;
+}
+
+bool zmq::lb_t::has_out ()
+{
+    //  If one part of the message was already written we can definitely
+    //  write the rest of the message.
+    if (_more)
+        return true;
+
+    while (_active > 0) {
+        //  Check whether a pipe has room for another message.
+        if (_pipes[_current]->check_write ())
+            return true;
+
+        //  Deactivate the pipe.
+        _active--;
+        _pipes.swap (_current, _active);
+        if (_current == _active)
+            _current = 0;
+    }
+
+    return false;
+}