thread safety

src/mailbox_safe.cpp

@@ -0,0 +1,111 @@
+/*
+    Copyright (c) 2007-2015 Contributors as noted in the AUTHORS file
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser 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
+    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 "mailbox_safe.hpp"
+#include "err.hpp"
+
+zmq::mailbox_safe_t::mailbox_safe_t (mutex_t* socket_mutex_) :
+    socket_mutex (socket_mutex_)
+{
+    //  Get the pipe into passive state. That way, if the users starts by
+    //  polling on the associated file descriptor it will get woken up when
+    //  new command is posted.
+    const bool ok = cpipe.read (NULL);
+    zmq_assert (!ok);
+}
+
+zmq::mailbox_safe_t::~mailbox_safe_t ()
+{
+    //  TODO: Retrieve and deallocate commands inside the cpipe.
+
+    // Work around problem that other threads might still be in our
+    // send() method, by waiting on the mutex before disappearing.
+    sync.lock ();
+    sync.unlock ();
+}
+
+void zmq::mailbox_safe_t::add_signaler(signaler_t* signaler)
+{
+    sync.lock();
+    signalers.push_back(signaler);
+    sync.unlock();
+}
+
+void zmq::mailbox_safe_t::remove_signaler(signaler_t* signaler)
+{
+    sync.lock();
+    std::vector<signaler_t*>::iterator it = signalers.begin();
+
+    // TODO: make a copy of array and signal outside the lock
+    for (; it != signalers.end(); ++it){
+        if (*it == signaler)
+           break;        
+    }
+
+    if (it != signalers.end())
+        signalers.erase(it);
+    sync.unlock();
+}
+
+void zmq::mailbox_safe_t::send (const command_t &cmd_)
+{
+    sync.lock ();
+    cpipe.write (cmd_, false);
+    const bool ok = cpipe.flush ();
+
+    if (!ok) {
+        for (std::vector<signaler_t*>::iterator it = signalers.begin(); it != signalers.end(); ++it){
+            (*it)->send();
+        }
+    }
+
+    sync.unlock ();
+    
+    if (!ok)
+        cond_var.broadcast ();
+}
+
+int zmq::mailbox_safe_t::recv (command_t *cmd_, int timeout_)
+{
+    //  Try to get the command straight away.
+    if (cpipe.read (cmd_))
+        return 0;
+
+    if (timeout_ == 0) {
+        errno = EAGAIN;
+        return -1;
+    }
+    
+    //  Wait for signal from the command sender.
+    int rc = cond_var.wait (socket_mutex, timeout_);
+    if (rc == -1) {
+        errno_assert (errno == EAGAIN || errno == EINTR);
+        return -1;
+    }
+
+    //  Another thread may already fetch the command
+    const bool ok = cpipe.read (cmd_);
+
+    if (!ok) {
+        errno = EAGAIN;
+        return -1;
+    }
+
+    return 0;
+}