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//
// G4TWorkspacePool
//
// Class description:
//
// Create and hold a pointer to Workspace.
// This class holds a thread-private static instance of the template
// parameter workspace.
//
// The concrete implementation of workspace objects are responsible for
// instantiating a singleton instance of this pool.
//
// Recycling of this pool can enable reuse among different threads in
// task-based - or 'on-demand' - simulation.

// Authors: J.Apostolakis, A.Dotti - 24 October 2014
// Revisions: G.Cosmo - 21 Obctober 2016, revised pool initialisation
// ------------------------------------------------------------
#ifndef G4TWORKSPACEPOOL_HH
#define G4TWORKSPACEPOOL_HH 1

#include "globals.hh"
#include "tls.hh"

template <class T>
class G4TWorkspacePool
{
 public:
  inline T* CreateWorkspace();
  // For use with simple MT mode - each thread gets a workspace
  // and uses it until end

  inline void CreateAndUseWorkspace();
  // Create it (as above) and use it

  inline T* FindOrCreateWorkspace();
  // For use with 'dynamic' model of threading - workspaces can be recycled
  // Reuse an existing workspace - or create a new one if needed.
  // This will never fail, except if system is out of resources

  inline T* GetWorkspace() { return fMyWorkspace; }
  // Give back the existing, active workspace for my thread / task

  inline void Recycle(T* myWrkSpace);
  // Keep the unused Workspace - for recycling

  inline void CleanUpAndDestroyAllWorkspaces();
  // To be called once at the end of the job

  G4TWorkspacePool() {}
  ~G4TWorkspacePool() {}

 private:
  static G4ThreadLocal T* fMyWorkspace;
  // The thread's workspace - if assigned
};

template <typename T>
G4ThreadLocal T* G4TWorkspacePool<T>::fMyWorkspace = nullptr;

// -----------------------------
// Inline methods implementation
// -----------------------------

template <class T>
T* G4TWorkspacePool<T>::CreateWorkspace()
{
  T* wrk = nullptr;
  if(fMyWorkspace == nullptr)
  {
    wrk = new T;
    if(wrk == nullptr)
    {
      G4Exception("G4TWorspacePool<someType>::CreateWorkspace()", "MemoryError",
                  FatalException, "Failed to create workspace.");
    }
    else
    {
      fMyWorkspace = wrk;
    }
  }
  else
  {
    G4Exception("ParticlesWorspacePool::CreateWorkspace()", "InvalidCondition",
                FatalException,
                "Cannot create workspace twice for the same thread.");
    wrk = fMyWorkspace;
  }
  return wrk;
}

template <class T>
void G4TWorkspacePool<T>::CreateAndUseWorkspace()
{
  (this->CreateWorkspace())->UseWorkspace();
}

template <class T>
T* G4TWorkspacePool<T>::FindOrCreateWorkspace()
{
  T* wrk = fMyWorkspace;
  if(wrk == nullptr)
  {
    wrk = this->CreateWorkspace();
  }
  wrk->UseWorkspace();

  fMyWorkspace = wrk;  // assign it for use by this thread.
  return wrk;
}

template <class T>
void G4TWorkspacePool<T>::Recycle(T* myWrkSpace)
{
  myWrkSpace->ReleaseWorkspace();
  delete myWrkSpace;
}

template <class T>
void G4TWorkspacePool<T>::CleanUpAndDestroyAllWorkspaces()
{
  if(fMyWorkspace != nullptr)
  {
    fMyWorkspace->DestroyWorkspace();
    delete fMyWorkspace;
    fMyWorkspace = nullptr;
  }
}

#endif