vtkWeakPointer.h

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/*=========================================================================
 
  Program:   Visualization Toolkit
  Module:    vtkWeakPointer.h
 
  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
 
     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.
 
=========================================================================*/
#ifndef vtkWeakPointer_h
#define vtkWeakPointer_h
 
#include "vtkWeakPointerBase.h"
 
#include "vtkMeta.h" // for IsComplete
#include "vtkNew.h"  // for vtkNew
 
#include <type_traits> // for is_base_of
#include <utility>     // for std::move
 
template <class T>
class vtkWeakPointer : public vtkWeakPointerBase
{
  // These static asserts only fire when the function calling CheckTypes is
  // used. Thus, this smart pointer class may still be used as a member variable
  // with a forward declared T, so long as T is defined by the time the calling
  // function is used.
  template <typename U = T>
  static void CheckTypes() noexcept
  {
    static_assert(vtk::detail::IsComplete<T>::value,
      "vtkWeakPointer<T>'s T type has not been defined. Missing "
      "include?");
    static_assert(vtk::detail::IsComplete<U>::value,
      "Cannot store an object with undefined type in "
      "vtkWeakPointer. Missing include?");
    static_assert(std::is_base_of<T, U>::value,
      "Argument type is not compatible with vtkWeakPointer<T>'s "
      "T type.");
    static_assert(std::is_base_of<vtkObjectBase, T>::value,
      "vtkWeakPointer can only be used with subclasses of "
      "vtkObjectBase.");
  }
 
public:
  vtkWeakPointer() noexcept
    : vtkWeakPointerBase()
  {
  }
 
  vtkWeakPointer(const vtkWeakPointer& r)
    : vtkWeakPointerBase(r)
  {
  }
 
  template <class U>
  vtkWeakPointer(const vtkWeakPointer<U>& r)
    : vtkWeakPointerBase(r)
  {
    vtkWeakPointer::CheckTypes<U>();
  }
  /* @} **/
 
  vtkWeakPointer(vtkWeakPointer&& r) noexcept
    : vtkWeakPointerBase(std::move(r))
  {
  }
 
  template <class U>
  vtkWeakPointer(vtkWeakPointer<U>&& r) noexcept
    : vtkWeakPointerBase(std::move(r))
  {
    vtkWeakPointer::CheckTypes<U>();
  }
  /* @} **/
 
  vtkWeakPointer(T* r)
    : vtkWeakPointerBase(r)
  {
    vtkWeakPointer::CheckTypes();
  }
 
  template <typename U>
  vtkWeakPointer(const vtkNew<U>& r)
    : vtkWeakPointerBase(r.Object)
  { // Create a new reference on copy
    vtkWeakPointer::CheckTypes<U>();
  }
 
 
  vtkWeakPointer& operator=(const vtkWeakPointer& r)
  {
    this->vtkWeakPointerBase::operator=(r);
    return *this;
  }
 
  template <class U>
  vtkWeakPointer& operator=(const vtkWeakPointer<U>& r)
  {
    vtkWeakPointer::CheckTypes<U>();
 
    this->vtkWeakPointerBase::operator=(r);
    return *this;
  }
 
 
  vtkWeakPointer& operator=(vtkWeakPointer&& r) noexcept
  {
    this->vtkWeakPointerBase::operator=(std::move(r));
    return *this;
  }
 
  template <class U>
  vtkWeakPointer& operator=(vtkWeakPointer<U>&& r) noexcept
  {
    vtkWeakPointer::CheckTypes<U>();
 
    this->vtkWeakPointerBase::operator=(std::move(r));
    return *this;
  }
 
 
  vtkWeakPointer& operator=(T* r)
  {
    vtkWeakPointer::CheckTypes();
    this->vtkWeakPointerBase::operator=(r);
    return *this;
  }
 
  template <typename U>
  vtkWeakPointer& operator=(const vtkNew<U>& r)
  {
    vtkWeakPointer::CheckTypes<U>();
 
    this->vtkWeakPointerBase::operator=(r.Object);
    return *this;
  }
 
 
  T* GetPointer() const noexcept { return static_cast<T*>(this->Object); }
  T* Get() const noexcept { return static_cast<T*>(this->Object); }
  operator T*() const noexcept { return static_cast<T*>(this->Object); }
 
  T& operator*() const noexcept { return *static_cast<T*>(this->Object); }
 
  T* operator->() const noexcept { return static_cast<T*>(this->Object); }
 
  // Work-around for HP and IBM overload resolution bug.  Since
  // NullPointerOnly is a private type the only pointer value that can
  // be passed by user code is a null pointer.  This operator will be
  // chosen by the compiler when comparing against null explicitly and
  // avoid the bogus ambiguous overload error.
#if defined(__HP_aCC) || defined(__IBMCPP__)
#define VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(op)                                            \
  bool operator op(NullPointerOnly*) const { return ::operator op(*this, 0); }
 
private:
  class NullPointerOnly
  {
  };
 
public:
  VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(==)
  VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(!=)
  VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(<)
  VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(<=)
  VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(>)
  VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND(>=)
#undef VTK_WEAK_POINTER_DEFINE_OPERATOR_WORKAROUND
#endif
protected:
  vtkWeakPointer(T* r, const NoReference& n)
    : vtkWeakPointerBase(r, n)
  {
  }
 
private:
  // These are purposely not implemented to prevent callers from
  // trying to take references from other smart pointers.
  void TakeReference(const vtkWeakPointerBase&) = delete;
  static void Take(const vtkWeakPointerBase&) = delete;
};
 
#define VTK_WEAK_POINTER_DEFINE_OPERATOR(op)                                                       \
  template <class T, class U>                                                                      \
  inline bool operator op(const vtkWeakPointer<T>& l, const vtkWeakPointer<U>& r)                  \
  {                                                                                                \
    return (l.GetPointer() op r.GetPointer());                                                     \
  }                                                                                                \
  template <class T, class U>                                                                      \
  inline bool operator op(T* l, const vtkWeakPointer<U>& r)                                        \
  {                                                                                                \
    return (l op r.GetPointer());                                                                  \
  }                                                                                                \
  template <class T, class U>                                                                      \
  inline bool operator op(const vtkWeakPointer<T>& l, U* r)                                        \
  {                                                                                                \
    return (l.GetPointer() op r);                                                                  \
  }                                                                                                \
  template <class T, class U>                                                                      \
  inline bool operator op(const vtkNew<T>& l, const vtkWeakPointer<U>& r)                          \
  {                                                                                                \
    return (l.GetPointer() op r.GetPointer());                                                     \
  }                                                                                                \
  template <class T, class U>                                                                      \
  inline bool operator op(const vtkWeakPointer<T>& l, const vtkNew<U>& r)                          \
  {                                                                                                \
    return (l.GetPointer() op r.GetPointer);                                                       \
  }
 
VTK_WEAK_POINTER_DEFINE_OPERATOR(==)
VTK_WEAK_POINTER_DEFINE_OPERATOR(!=)
VTK_WEAK_POINTER_DEFINE_OPERATOR(<)
VTK_WEAK_POINTER_DEFINE_OPERATOR(<=)
VTK_WEAK_POINTER_DEFINE_OPERATOR(>)
VTK_WEAK_POINTER_DEFINE_OPERATOR(>=)
 
#undef VTK_WEAK_POINTER_DEFINE_OPERATOR
 
namespace vtk
{
 
template <typename T>
vtkWeakPointer<T> TakeWeakPointer(T* obj)
{
  return vtkWeakPointer<T>(obj);
}
 
} // end namespace vtk
 
template <class T>
inline ostream& operator<<(ostream& os, const vtkWeakPointer<T>& p)
{
  return os << static_cast<const vtkWeakPointerBase&>(p);
}
 
#endif
 
// VTK-HeaderTest-Exclude: vtkWeakPointer.h