#include <boost/interprocess/sync/interprocess_upgradable_mutex.hpp>

   struct shared_data
   {
      enum { NumItems = 100 };
      enum { LineSize = 100 };

      shared_data()
         :  current_line(0)
         ,  end_a(false)
         ,  end_b(false)
      {}

      //Mutex to protect access to the queue
      boost::interprocess::interprocess_upgradable_mutex upgradable_mutex;

      //Items to fill
      char   items[NumItems][LineSize];
      int    current_line;
      bool   end_a;
      bool   end_b;
   };