/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2005,2006 INRIA

 * All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#ifndef PTR_H

#define PTR_H

#include <stdint.h>

#include <cassert>

namespace ns3 {

/**

 * \brief smart pointer class similar to boost::shared_ptr

 *

 * This smart-pointer class is supposed to be used to manage

 * heap-allocated objects: when it decides it does not need

 * the object it references, it invokes operator delete on it.

 * This implementation allows you to manipulate the smart pointer

 * as if it was a normal pointer: you can compare it with zero,

 * compare it against other pointers, etc. However, the only 

 * operation we are careful to avoid is the conversion back to

 * raw pointers: if you need to convert back, you need to invoke

 * the Ptr<T>::Remove method which returns a raw pointer and

 * makes the smart pointer forget about the raw pointer.

 */

template <typename T>

class Ptr 

{

private:

  T *m_ptr;

  uint32_t *m_count;

  class Tester {

  private:

    void operator delete (void *);

  };

  static uint32_t *AllocCount (void);

  static void DeallocCount (uint32_t *count);

public:

  /**

   * Create an empty smart pointer

   */

  Ptr ();

  /**

   * \param ptr raw pointer to manage

   *

   * Create a smart pointer which points to the

   * input raw pointer. This method takes ownershipt

   * of the input raw pointer. That is, the smart pointer

   * becomes responsible for calling delete on the

   * raw pointer when needed.

   */

  Ptr (T *ptr);

  Ptr (Ptr const&o);

  // allow conversions from T to T const.

  template <typename U>

  Ptr (Ptr<U> const &o);

  ~Ptr () ;

  Ptr<T> &operator = (Ptr const& o);

  T *operator -> () const;

  T *operator -> ();

  // allow if (!sp)

  bool operator! ();

  // allow if (sp)

  operator Tester * () const;

  // allow if (sp == 0)

  template <typename T1, typename T2>

  inline friend bool operator == (Ptr<T1> const &lhs, T2 const *rhs);

  // allow if (0 == sp)

  template <typename T1, typename T2>

  inline friend bool operator == (T1 const *lhs, Ptr<T2> &rhs);

  // allow if (sp != 0)

  template <typename T1, typename T2>

  inline friend bool operator != (Ptr<T1> const &lhs, T2 const *rhs);

  // allow if (0 != sp)

  template <typename T1, typename T2>

  inline friend bool operator != (T1 const *lhs, Ptr<T2> &rhs);

  /**

   * \returns raw pointer

   *

   * It is a programming error to invoke this method when

   * the reference count of the smart pointer is not one.

   * If you try to do it anyway, an assert will be triggered.

   * If asserts are disabled, bad things will happen.

   * Once you have successfully called Ptr<T>::Remove on

   * a smart pointer, the smart pointer will forget 

   * about the raw pointer and will stop managing it. As such,

   * you, as the caller, become responsible for invoking

   * operator delete on the returned raw pointer.

   */

  T *Remove (void);

};

template <typename T>

uint32_t *

Ptr<T>::AllocCount (void)

{

  return new uint32_t [1] ();

}

template <typename T>

void 

Ptr<T>::DeallocCount (uint32_t *count)

{

  delete [] count;

}

template <typename T>

Ptr<T>::Ptr ()

  : m_ptr (0),

    m_count (Ptr::AllocCount ())

{}

template <typename T>

Ptr<T>::Ptr (T *ptr) 

  : m_ptr (ptr),

    m_count (Ptr::AllocCount ())

{

  if (m_ptr != 0)

    {

      *m_count = 1;

    }

}

template <typename T>

Ptr<T>::Ptr (Ptr const&o) 

  : m_ptr (o.m_ptr),

    m_count (o.m_count)

{

  if (m_ptr != 0) 

    {

      (*m_count)++;

    }

}

template <typename T>

template <typename U>

Ptr<T>::Ptr (Ptr<U> const &o)

  : m_ptr (o.m_ptr),

    m_count (o.m_count)

{

  if (m_ptr != 0) 

    {

      (*m_count)++;

    }

}

template <typename T>

Ptr<T>::~Ptr () 

{

  if (m_ptr != 0) 

    {

      (*m_count)--;

      if ((*m_count) == 0) 

        {

          delete m_ptr;

          Ptr::DeallocCount (m_count);

        }

    }

}

template <typename T>

Ptr<T> &

Ptr<T>::operator = (Ptr const& o) 

{

  if (o.m_ptr != 0) 

    {

      (*(o.m_count))++;

    }

  if (m_ptr != 0) 

    {

      (*m_count)--;

      if ((*m_count) == 0) 

        {

          delete m_ptr;

          Ptr::DeallocCount (m_count);

        }

    }

  m_ptr = o.m_ptr;

  m_count = o.m_count;

  return *this;

}

template <typename T>

T *

Ptr<T>::operator -> () 

{

  return m_ptr;

}

template <typename T>

T *

Ptr<T>::operator -> () const

{

  return m_ptr;

}

template <typename T>

bool 

Ptr<T>::operator! () 

{

  return m_ptr == 0;

}

template <typename T>

Ptr<T>::operator Tester * () const

{

  if (m_ptr == 0) 

    {

      return 0;

    }

  static Tester test;

  return &test;

}

template <typename T>

T *

Ptr<T>::Remove (void) 

{

  T *retval = m_ptr;

  m_ptr = 0;

  return retval;

}

// non-member friend functions.

template <typename T1, typename T2>

bool 

operator == (Ptr<T1> const &lhs, T2 const *rhs)

{

  return lhs.m_ptr == rhs;

}

template <typename T1, typename T2>

bool 

operator == (T1 const *lhs, Ptr<T2> &rhs)

{

  return lhs == rhs.m_ptr;

}

template <typename T1, typename T2>

bool 

operator != (Ptr<T1> const &lhs, T2 const *rhs)

{

  return lhs.m_ptr != rhs;

}

template <typename T1, typename T2>

bool 

operator != (T1 const *lhs, Ptr<T2> &rhs)

{

  return lhs != rhs.m_ptr;

}

}; // namespace ns3

#endif /* PTR_H */