--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/OrthancFramework/Sources/MultiThreading/SharedMessageQueue.cpp	Wed Jun 10 20:30:34 2020 +0200
@@ -0,0 +1,211 @@
+/**
+ * Orthanc - A Lightweight, RESTful DICOM Store
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2020 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * In addition, as a special exception, the copyright holders of this
+ * program give permission to link the code of its release with the
+ * OpenSSL project's "OpenSSL" library (or with modified versions of it
+ * that use the same license as the "OpenSSL" library), and distribute
+ * the linked executables. You must obey the GNU General Public License
+ * in all respects for all of the code used other than "OpenSSL". If you
+ * modify file(s) with this exception, you may extend this exception to
+ * your version of the file(s), but you are not obligated to do so. If
+ * you do not wish to do so, delete this exception statement from your
+ * version. If you delete this exception statement from all source files
+ * in the program, then also delete it here.
+ * 
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#include "../PrecompiledHeaders.h"
+#include "SharedMessageQueue.h"
+
+
+#include "../Compatibility.h"
+
+
+/**
+ * FIFO (queue):
+ * 
+ *            back                         front
+ *            +--+--+--+--+--+--+--+--+--+--+--+
+ * Enqueue -> |  |  |  |  |  |  |  |  |  |  |  |
+ *            |  |  |  |  |  |  |  |  |  |  |  | -> Dequeue
+ *            +--+--+--+--+--+--+--+--+--+--+--+
+ *                                            ^
+ *                                            |
+ *                                      Make room here
+ *
+ *
+ * LIFO (stack):
+ * 
+ *            back                         front
+ *            +--+--+--+--+--+--+--+--+--+--+--+
+ *            |  |  |  |  |  |  |  |  |  |  |  | <- Enqueue
+ *            |  |  |  |  |  |  |  |  |  |  |  | -> Dequeue
+ *            +--+--+--+--+--+--+--+--+--+--+--+
+ *              ^
+ *              |
+ *        Make room here
+ **/
+
+
+namespace Orthanc
+{
+  SharedMessageQueue::SharedMessageQueue(unsigned int maxSize) :
+    isFifo_(true),
+    maxSize_(maxSize)
+  {
+  }
+
+
+  SharedMessageQueue::~SharedMessageQueue()
+  {
+    for (Queue::iterator it = queue_.begin(); it != queue_.end(); ++it)
+    {
+      delete *it;
+    }
+  }
+
+
+  void SharedMessageQueue::Enqueue(IDynamicObject* message)
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+
+    if (maxSize_ != 0 && queue_.size() > maxSize_)
+    {
+      if (isFifo_)
+      {
+        // Too many elements in the queue: Make room
+        delete queue_.front();
+        queue_.pop_front();
+      }
+      else
+      {
+        // Too many elements in the stack: Make room
+        delete queue_.back();
+        queue_.pop_back();
+      }
+    }
+
+    if (isFifo_)
+    {
+      // Queue policy (FIFO)
+      queue_.push_back(message);
+    }
+    else
+    {
+      // Stack policy (LIFO)
+      queue_.push_front(message);
+    }
+
+    elementAvailable_.notify_one();
+  }
+
+
+  IDynamicObject* SharedMessageQueue::Dequeue(int32_t millisecondsTimeout)
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+
+    // Wait for a message to arrive in the FIFO queue
+    while (queue_.empty())
+    {
+      if (millisecondsTimeout == 0)
+      {
+        elementAvailable_.wait(lock);
+      }
+      else
+      {
+        bool success = elementAvailable_.timed_wait
+          (lock, boost::posix_time::milliseconds(millisecondsTimeout));
+        if (!success)
+        {
+          return NULL;
+        }
+      }
+    }
+
+    std::unique_ptr<IDynamicObject> message(queue_.front());
+    queue_.pop_front();
+
+    if (queue_.empty())
+    {
+      emptied_.notify_all();
+    }
+
+    return message.release();
+  }
+
+
+
+  bool SharedMessageQueue::WaitEmpty(int32_t millisecondsTimeout)
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+    
+    // Wait for the queue to become empty
+    while (!queue_.empty())
+    {
+      if (millisecondsTimeout == 0)
+      {
+        emptied_.wait(lock);
+      }
+      else
+      {
+        if (!emptied_.timed_wait
+            (lock, boost::posix_time::milliseconds(millisecondsTimeout)))
+        {
+          return false;
+        }
+      }
+    }
+
+    return true;
+  }
+
+
+  void SharedMessageQueue::SetFifoPolicy()
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+    isFifo_ = true;
+  }
+
+  void SharedMessageQueue::SetLifoPolicy()
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+    isFifo_ = false;
+  }
+
+  void SharedMessageQueue::Clear()
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+
+    if (queue_.empty())
+    {
+      return;
+    }
+    else
+    {
+      while (!queue_.empty())
+      {
+        std::unique_ptr<IDynamicObject> message(queue_.front());
+        queue_.pop_front();
+      }
+
+      emptied_.notify_all();
+    }
+  }
+}