FairMQ: Introduce callbacks for the FairMQUnmanagedRegion.

Callbacks are called when the data buffer of the message assiciated
with the corresponding region is no longer needed by the transport.
Example in examples/advanced/Region/

fairmq/shmem/Common.h

@@ -0,0 +1,76 @@
+/********************************************************************************
+ *    Copyright (C) 2014 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH    *
+ *                                                                              *
+ *              This software is distributed under the terms of the             *
+ *         GNU Lesser General Public Licence version 3 (LGPL) version 3,        *
+ *                  copied verbatim in the file "LICENSE"                       *
+ ********************************************************************************/
+#ifndef FAIR_MQ_SHMEM_COMMON_H_
+#define FAIR_MQ_SHMEM_COMMON_H_
+
+#include <atomic>
+
+#include <boost/interprocess/managed_shared_memory.hpp>
+
+namespace fair
+{
+namespace mq
+{
+namespace shmem
+{
+
+struct DeviceCounter
+{
+    DeviceCounter(unsigned int c)
+        : fCount(c)
+    {}
+
+    std::atomic<unsigned int> fCount;
+};
+
+struct RegionCounter
+{
+    RegionCounter(unsigned int c)
+        : fCount(c)
+    {}
+
+    std::atomic<unsigned int> fCount;
+};
+
+struct MonitorStatus
+{
+    MonitorStatus()
+        : fActive(true)
+    {}
+
+    bool fActive;
+};
+
+struct alignas(32) MetaHeader
+{
+    uint64_t fSize;
+    uint64_t fRegionId;
+    boost::interprocess::managed_shared_memory::handle_t fHandle;
+};
+
+struct RegionBlock
+{
+    RegionBlock()
+        : fHandle()
+        , fSize(0)
+    {}
+
+    RegionBlock(boost::interprocess::managed_shared_memory::handle_t handle, size_t size)
+        : fHandle(handle)
+        , fSize(size)
+    {}
+
+    boost::interprocess::managed_shared_memory::handle_t fHandle;
+    size_t fSize;
+};
+
+} // namespace shmem
+} // namespace mq
+} // namespace fair
+
+#endif /* FAIR_MQ_SHMEM_COMMON_H_ */