--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/OrthancFramework/Sources/MultiThreading/Semaphore.h	Wed Jun 10 20:30:34 2020 +0200
@@ -0,0 +1,108 @@
+/**
+ * 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/>.
+ **/
+
+
+#pragma once
+
+#include <boost/noncopyable.hpp>
+#include <boost/thread.hpp>
+
+namespace Orthanc
+{
+  class Semaphore : public boost::noncopyable
+  {
+  private:
+    unsigned int availableResources_;
+    boost::mutex mutex_;
+    boost::condition_variable condition_;
+    
+    void Release();
+
+    void Acquire();
+
+    bool TryAcquire();
+  public:
+    explicit Semaphore(unsigned int availableResources);
+
+    unsigned int GetAvailableResourcesCount() const
+    {
+      return availableResources_;
+    }
+
+
+    class Locker : public boost::noncopyable
+    {
+    private:
+      Semaphore&  that_;
+
+    public:
+      explicit Locker(Semaphore& that) :
+        that_(that)
+      {
+        that_.Acquire();
+      }
+
+      ~Locker()
+      {
+        that_.Release();
+      }
+    };
+
+    class TryLocker : public boost::noncopyable
+    {
+    private:
+      Semaphore&  that_;
+      bool        isAcquired_;
+
+    public:
+      explicit TryLocker(Semaphore& that) :
+        that_(that)
+      {
+        isAcquired_ = that_.TryAcquire();
+      }
+
+      ~TryLocker()
+      {
+        if (isAcquired_)
+        {
+          that_.Release();
+        }
+      }
+
+      bool IsAcquired() const
+      {
+        return isAcquired_;
+      }
+    };
+
+  };
+}