/src/poco/Foundation/include/Poco/AutoPtr.h

Source
//
// AutoPtr.h
//
// Library: Foundation
// Package: Core
// Module:  AutoPtr
//
// Definition of the AutoPtr template class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//


#ifndef Foundation_AutoPtr_INCLUDED
#define Foundation_AutoPtr_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include <algorithm>
#include <cstddef>


namespace Poco {


template <class C>
class AutoPtr
  /// AutoPtr is a "smart" pointer for classes implementing
  /// reference counting based garbage collection.
  /// To be usable with the AutoPtr template, a class must
  /// implement the following behaviour:
  /// A class must maintain a reference count.
  /// The constructors of the object initialize the reference
  /// count to one.
  /// The class must implement a public duplicate() method:
  ///     void duplicate();
  /// that increments the reference count by one.
  /// The class must implement a public release() method:
  ///     void release()
  /// that decrements the reference count by one, and,
  /// if the reference count reaches zero, deletes the
  /// object.
  ///
  /// AutoPtr works in the following way:
  /// If an AutoPtr is assigned an ordinary pointer to
  /// an object (via the constructor or the assignment operator),
  /// it takes ownership of the object and the object's reference
  /// count remains unchanged.
  /// If the AutoPtr is assigned another AutoPtr, the
  /// object's reference count is incremented by one by
  /// calling duplicate() on its object.
  /// The destructor of AutoPtr calls release() on its
  /// object.
  /// AutoPtr supports dereferencing with both the ->
  /// and the * operator. An attempt to dereference a null
  /// AutoPtr results in a NullPointerException being thrown.
  /// AutoPtr also implements all relational operators.
  /// Note that AutoPtr allows casting of its encapsulated data types.
{
public:
  AutoPtr(): _ptr(nullptr)
  {
  }

  AutoPtr(C* ptr): _ptr(ptr)
  {
  }

  AutoPtr(C* ptr, bool shared): _ptr(ptr)
  {
    if (shared && _ptr) _ptr->duplicate();
  }

  AutoPtr(const AutoPtr& ptr): _ptr(ptr._ptr)
  {
    if (_ptr) _ptr->duplicate();
  }

  AutoPtr(AutoPtr&& ptr) noexcept: _ptr(std::move(ptr._ptr))
  {
    ptr._ptr = nullptr;
  }

  template <class Other>
  AutoPtr(const AutoPtr<Other>& ptr): _ptr(const_cast<Other*>(ptr.get()))
  {
    if (_ptr) _ptr->duplicate();
  }

  ~AutoPtr()
  {
    if (_ptr) _ptr->release();
  }

  AutoPtr& assign(C* ptr)
  {
    if (_ptr != ptr)
    {
      if (_ptr) _ptr->release();
      _ptr = ptr;
    }
    return *this;
  }

  AutoPtr& assign(C* ptr, bool shared)
  {
    if (_ptr != ptr)
    {
      if (shared && ptr) ptr->duplicate();
      std::swap(_ptr, ptr);
      if (ptr) ptr->release();
    }
    return *this;
  }

  AutoPtr& assign(const AutoPtr& ptr)
  {
    return assign(ptr._ptr, true);
  }

  template <class Other>
  AutoPtr& assign(const AutoPtr<Other>& ptr)
  {
    C* nptr = const_cast<Other*>(ptr.get());
    return assign(nptr, true);
  }

  void reset()
  {
    if (_ptr)
    {
      _ptr->release();
      _ptr = nullptr;
    }
  }

  void reset(C* ptr)
  {
    assign(ptr);
  }

  void reset(C* ptr, bool shared)
  {
    assign(ptr, shared);
  }

  void reset(const AutoPtr& ptr)
  {
    assign(ptr);
  }

  template <class Other>
  void reset(const AutoPtr<Other>& ptr)
  {
    assign<Other>(ptr);
  }

  AutoPtr& operator = (C* ptr)
  {
    return assign(ptr);
  }

  AutoPtr& operator = (const AutoPtr& ptr)
  {
    return assign(ptr);
  }

  AutoPtr& operator = (AutoPtr&& ptr) noexcept
  {
    if (_ptr) _ptr->release();
    _ptr = ptr._ptr;
    ptr._ptr = nullptr;
    return *this;
  }

  template <class Other>
  AutoPtr& operator = (const AutoPtr<Other>& ptr)
  {
    return assign<Other>(ptr);
  }

  void swap(AutoPtr& ptr) noexcept
  {
    std::swap(_ptr, ptr._ptr);
  }

  template <class Other>
  [[nodiscard]] AutoPtr<Other> cast() const
    /// Casts the AutoPtr via a dynamic cast to the given type.
    /// Returns an AutoPtr containing nullptr if the cast fails.
    /// Example: (assume class Sub: public Super)
    ///    AutoPtr<Super> super(new Sub());
    ///    AutoPtr<Sub> sub = super.cast<Sub>();
    ///    poco_assert (sub.get());
  {
    Other* pOther = dynamic_cast<Other*>(_ptr);
    return AutoPtr<Other>(pOther, true);
  }

  template <class Other>
  [[nodiscard]] AutoPtr<Other> unsafeCast() const
    /// Casts the AutoPtr via a static cast to the given type.
    /// Example: (assume class Sub: public Super)
    ///    AutoPtr<Super> super(new Sub());
    ///    AutoPtr<Sub> sub = super.unsafeCast<Sub>();
    ///    poco_assert (sub.get());
  {
    Other* pOther = static_cast<Other*>(_ptr);
    return AutoPtr<Other>(pOther, true);
  }

  C* operator -> ()
  {
    if (_ptr)
      return _ptr;
    else
      throw NullPointerException();
  }

  const C* operator -> () const
  {
    if (_ptr)
      return _ptr;
    else
      throw NullPointerException();
  }

  C& operator * ()
  {
    if (_ptr)
      return *_ptr;
    else
      throw NullPointerException();
  }

  const C& operator * () const
  {
    if (_ptr)
      return *_ptr;
    else
      throw NullPointerException();
  }

  [[nodiscard]] C* get()
  {
    return _ptr;
  }

  [[nodiscard]] const C* get() const
  {
    return _ptr;
  }

  [[nodiscard]] operator C* ()
  {
    return _ptr;
  }

  [[nodiscard]] operator const C* () const
  {
    return _ptr;
  }

  [[nodiscard]] bool operator ! () const
  {
    return _ptr == nullptr;
  }

  [[nodiscard]] bool isNull() const
  {
    return _ptr == nullptr;
  }

  [[nodiscard]] C* duplicate()
  {
    if (_ptr) _ptr->duplicate();
    return _ptr;
  }

  [[nodiscard]] bool operator == (const AutoPtr& ptr) const
  {
    return _ptr == ptr._ptr;
  }

  [[nodiscard]] bool operator == (const C* ptr) const
  {
    return _ptr == ptr;
  }

  [[nodiscard]] bool operator == (C* ptr) const
  {
    return _ptr == ptr;
  }

  [[nodiscard]] bool operator == (std::nullptr_t ptr) const
  {
    return _ptr == ptr;
  }

  [[nodiscard]] bool operator != (const AutoPtr& ptr) const
  {
    return _ptr != ptr._ptr;
  }

  [[nodiscard]] bool operator != (const C* ptr) const
  {
    return _ptr != ptr;
  }

  [[nodiscard]] bool operator != (C* ptr) const
  {
    return _ptr != ptr;
  }

  [[nodiscard]] bool operator != (std::nullptr_t ptr) const
  {
    return _ptr != ptr;
  }

  [[nodiscard]] bool operator < (const AutoPtr& ptr) const
  {
    return _ptr < ptr._ptr;
  }

  [[nodiscard]] bool operator < (const C* ptr) const
  {
    return _ptr < ptr;
  }

  [[nodiscard]] bool operator < (C* ptr) const
  {
    return _ptr < ptr;
  }

  [[nodiscard]] bool operator <= (const AutoPtr& ptr) const
  {
    return _ptr <= ptr._ptr;
  }

  [[nodiscard]] bool operator <= (const C* ptr) const
  {
    return _ptr <= ptr;
  }

  [[nodiscard]] bool operator <= (C* ptr) const
  {
    return _ptr <= ptr;
  }

  [[nodiscard]] bool operator > (const AutoPtr& ptr) const
  {
    return _ptr > ptr._ptr;
  }

  [[nodiscard]] bool operator > (const C* ptr) const
  {
    return _ptr > ptr;
  }

  [[nodiscard]] bool operator > (C* ptr) const
  {
    return _ptr > ptr;
  }

  [[nodiscard]] bool operator >= (const AutoPtr& ptr) const
  {
    return _ptr >= ptr._ptr;
  }

  [[nodiscard]] bool operator >= (const C* ptr) const
  {
    return _ptr >= ptr;
  }

  [[nodiscard]] bool operator >= (C* ptr) const
  {
    return _ptr >= ptr;
  }

private:
  C* _ptr;
};


template <class C>
inline void swap(AutoPtr<C>& p1, AutoPtr<C>& p2) noexcept
{
  p1.swap(p2);
}


template <typename T, typename... Args>
[[nodiscard]] AutoPtr<T> makeAuto(Args&&... args)
{
  return AutoPtr<T>(new T(std::forward<Args>(args)...));
}


} // namespace Poco


#endif // Foundation_AutoPtr_INCLUDED

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Created: 2026-10-28 06:40