BodyNodePtr.hpp

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#ifndef DART_DYNAMICS_DETAIL_BODYNODEPTR_HPP_
#define DART_DYNAMICS_DETAIL_BODYNODEPTR_HPP_
 
#include <memory>
#include <mutex>
#include <atomic>
 
namespace dart{
namespace dynamics {
 
class Skeleton;
 
//==============================================================================
struct MutexedWeakSkeletonPtr
{
  std::mutex mMutex;
  std::weak_ptr<const Skeleton> mSkeleton;
};
 
//==============================================================================
class SkeletonRefCountingBase
{
public:
  template<class> friend class TemplateBodyNodePtr;
  template<class> friend class TemplateWeakBodyNodePtr;
 
  std::shared_ptr<Skeleton> getSkeleton();
 
  std::shared_ptr<const Skeleton> getSkeleton() const;
 
private:
 
  //--------------------------------------------------------------------------
  // Reference counting
  //--------------------------------------------------------------------------
 
  void incrementReferenceCount() const;
 
  void decrementReferenceCount() const;
 
protected:
 
  SkeletonRefCountingBase();
 
  std::weak_ptr<Skeleton> mSkeleton;
 
  mutable std::atomic<int> mReferenceCount;
 
  mutable std::shared_ptr<Skeleton> mReferenceSkeleton;
 
  std::shared_ptr<MutexedWeakSkeletonPtr> mLockedSkeleton;
 
};
 
template <class BodyNodeT>
class TemplateBodyNodePtr
{
public:
  TemplateBodyNodePtr() : mPtr(nullptr) { }
 
  TemplateBodyNodePtr(BodyNodeT* _ptr) : mPtr(nullptr) { set(_ptr); }
 
  TemplateBodyNodePtr(const TemplateBodyNodePtr& _bnp)
    : mPtr(nullptr)
  {
    set(_bnp.get());
  }
 
  template <class OtherBodyNodeT>
  TemplateBodyNodePtr(const TemplateBodyNodePtr<OtherBodyNodeT>& _bnp)
    : mPtr(nullptr)
  {
    set(_bnp.get());
  }
 
  ~TemplateBodyNodePtr() { set(nullptr); }
 
  template <class OtherBodyNodeT>
  TemplateBodyNodePtr& operator = (
      const TemplateBodyNodePtr<OtherBodyNodeT>& _bnp)
  {
    set(_bnp.get());
    return *this;
  }
 
  TemplateBodyNodePtr& operator = (BodyNodeT* _ptr)
  {
    set(_ptr);
    return *this;
  }
 
  operator BodyNodeT*() const { return mPtr; }
 
  BodyNodeT& operator*() const { return *mPtr; }
 
  BodyNodeT* operator->() const { return mPtr; }
 
  BodyNodeT* get() const { return mPtr; }
 
  void set(BodyNodeT* _ptr)
  {
    if(mPtr == _ptr)
      return;
 
    if(nullptr != mPtr)
    {
      static_cast<const SkeletonRefCountingBase*>(mPtr)->
          decrementReferenceCount();
    }
 
    if(nullptr != _ptr)
    {
      static_cast<const SkeletonRefCountingBase*>(_ptr)->
          incrementReferenceCount();
    }
 
    mPtr = _ptr;
  }
 
private:
  BodyNodeT* mPtr;
};
 
template <class BodyNodeT>
class TemplateWeakBodyNodePtr
{
public:
 
  template<class> friend class TemplateWeakBodyNodePtr;
 
  TemplateWeakBodyNodePtr() : mPtr(nullptr) { }
 
  TemplateWeakBodyNodePtr(BodyNodeT* _ptr) : mPtr(nullptr) { set(_ptr); }
 
  template <class OtherBodyNodeT>
  TemplateWeakBodyNodePtr(
      const TemplateWeakBodyNodePtr<OtherBodyNodeT>& _weakPtr)
    : mPtr(nullptr) { set(_weakPtr); }
 
  TemplateWeakBodyNodePtr& operator = (BodyNodeT* _ptr)
  {
    set(_ptr);
    return *this;
  }
 
  template <class OtherBodyNodeT>
  TemplateWeakBodyNodePtr& operator = (
      const TemplateWeakBodyNodePtr<OtherBodyNodeT>& _weakPtr)
  {
    set(_weakPtr);
    return *this;
  }
 
  TemplateBodyNodePtr<BodyNodeT> lock() const
  {
    if(nullptr == mLocker)
      return nullptr;
 
    // We do not use the expired() function here, because we want to ensure that
    // the Skeleton's reference count remains up while we create the strong
    // BodyNodePtr that we're going to return.
    std::lock_guard<std::mutex> lock(mLocker->mMutex);
    std::shared_ptr<const Skeleton> skeleton = mLocker->mSkeleton.lock();
    if(nullptr == skeleton)
      return nullptr;
 
    return TemplateBodyNodePtr<BodyNodeT>(mPtr);
  }
 
  void set(BodyNodeT* _ptr)
  {
    mPtr = _ptr;
 
    if(nullptr == mPtr)
      mLocker = nullptr;
    else
      mLocker = static_cast<const SkeletonRefCountingBase*>(_ptr)->
          mLockedSkeleton;
  }
 
  template <class OtherBodyNodeT>
  void set(const TemplateWeakBodyNodePtr<OtherBodyNodeT>& _weakPtr)
  {
    if(nullptr == _weakPtr.mLocker)
    {
      set(nullptr);
      return;
    }
 
    std::lock_guard<std::mutex> lock(_weakPtr.mLocker->mMutex);
    std::shared_ptr<const Skeleton> skeleton =
        _weakPtr.mLocker->mSkeleton.lock();
    if(nullptr == skeleton)
    {
      set(nullptr);
      return;
    }
 
    set(_weakPtr.mPtr);
  }
 
  bool expired() const
  {
    if(nullptr == mLocker)
      return true;
 
    // It is okay for 'lock' to go "unused", because it is managed by RAII after
    // it has been initialized
    std::lock_guard<std::mutex> lock(mLocker->mMutex);
    std::shared_ptr<const Skeleton> skeleton = mLocker->mSkeleton.lock();
    if(nullptr == skeleton)
      return true;
 
    return false;
  }
 
private:
  BodyNodeT* mPtr;
 
  std::shared_ptr<MutexedWeakSkeletonPtr> mLocker;
};
 
 
} // namespace dynamics
} // namespace dart
 
#endif // DART_DYNAMICS_DETAIL_BODYNODEPTR_HPP_