/* -*- C++ -*- */

//=============================================================================
/**
 *  @file    Bound_Ptr.h
 *
 *  $Id$
 *
 *  @author Christopher Kohlhoff <chris@kohlhoff.com>
 */
//=============================================================================

#ifndef ACE_BOUND_PTR_H
#define ACE_BOUND_PTR_H
#include "ace/pre.h"

#include "ace/OS.h"
#include "ace/Auto_Ptr.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

/**
 * @class ACE_Bound_Ptr_Counter
 *
 * @brief An ACE_Bound_Ptr_Counter<ACE_LOCK> object encapsulates an object
 * reference count. Do not use this class directly, use ACE_Strong_Bound_Ptr
 * or ACE_Weak_Bound_Ptr instead.
 */
template <class ACE_LOCK>
class ACE_Bound_Ptr_Counter
{
public:
  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

  ACE_Bound_Ptr_Counter (int init_obj_ref_count = 0);
  ~ACE_Bound_Ptr_Counter (void);

  /// Create a ACE_Bound_Ptr_Counter<ACE_LOCK> and initialize the reference
  /// count to indicate ownership by a strong pointer.
  static ACE_Bound_Ptr_Counter<ACE_LOCK> *create_strong (void);

  /// Increase both the object and counter reference counts and return the new
  /// object reference count. A return value of -1 indicates that the object
  /// has already been destroyed.
  static int attach_strong (ACE_Bound_Ptr_Counter<ACE_LOCK> *counter);

  /// Decreases both the object and counter reference counts and deletes
  /// whichever has no more references. Returns the new object reference count.
  static int detach_strong (ACE_Bound_Ptr_Counter<ACE_LOCK> *counter);

  /// Create a ACE_Bound_Ptr_Counter<ACE_LOCK> and initialize the reference
  /// count to indicate no ownership.
  static ACE_Bound_Ptr_Counter<ACE_LOCK> *create_weak (void);

  /// Increase the counter reference count and return argument.
  static void attach_weak (ACE_Bound_Ptr_Counter<ACE_LOCK> *counter);

  /// Decreases the counter reference count and deletes the counter if it has
  /// no more references.
  static void detach_weak (ACE_Bound_Ptr_Counter<ACE_LOCK> *counter);

  /// Determine whether the object has been deleted.
  static int object_was_deleted (ACE_Bound_Ptr_Counter<ACE_LOCK> *counter);

private:
  /// Allocate a new ACE_Bound_Ptr_Counter<ACE_LOCK> instance, returning NULL
  /// if it cannot be created.
  static ACE_Bound_Ptr_Counter<ACE_LOCK> *internal_create (int init_obj_ref_count);

  /// Reference count of underlying object. Is set to -1 once the object has
  /// been destroyed to indicate to all weak pointers that it is no longer valid.
  int obj_ref_count_;

  /// Reference count of this counter.
  int self_ref_count_;

  /// Mutex variable to synchronize access to the reference counts.
  ACE_LOCK lock_;
};

// Forward decl.
template <class X, class ACE_LOCK> class ACE_Weak_Bound_Ptr;

/**
 * @class ACE_Strong_Bound_Ptr
 *
 * @brief This class implements support for a reference counted pointer.
 * Assigning or copying instances of an ACE_Strong_Bound_Ptr will
 * automatically increment the reference count of the underlying object.
 * When the last instance of an ACE_Strong_Bound_Ptr that references a
 * particular object is destroyed or overwritten, it will invoke delete
 * on its underlying pointer.
 */
template <class X, class ACE_LOCK>
class ACE_Strong_Bound_Ptr
{
public:
  /// Constructor that initializes an ACE_Strong_Bound_Ptr to point to the
  /// object <p> immediately.
  ACE_EXPLICIT ACE_Strong_Bound_Ptr (X *p = 0);

  /// Constructor that initializes an ACE_Strong_Bound_Ptr by stealing
  /// ownership of an object from an auto_ptr.
  ACE_EXPLICIT ACE_Strong_Bound_Ptr (auto_ptr<X> p);

  /// Copy constructor binds <this> and <r> to the same object.
  ACE_Strong_Bound_Ptr (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r);

  /// Constructor binds <this> and <r> to the same object.
  ACE_Strong_Bound_Ptr (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r);

  /// Destructor.
  ~ACE_Strong_Bound_Ptr (void);

  /// Assignment operator that binds <this> and <r> to the same object.
  void operator = (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r);

  /// Assignment operator that binds <this> and <r> to the same object.
  void operator = (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r);

  /// Equality operator that returns 1 if both ACE_Strong_Bound_Ptr instances
  /// point to the same underlying object. Attention: It also returns 1 if
  /// both objects have just been instantiated and not used yet.
  int operator == (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Equality operator that returns 1 if the ACE_Strong_Bound_Ptr and
  /// ACE_Weak_Bound_Ptr objects point to the same underlying object.
  /// Attention: It also returns 1 if both objects have just been
  /// instantiated and not used yet.
  int operator == (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Equality operator that returns 1 if the ACE_Strong_Bound_Ptr and the raw
  /// pointer point to the same underlying object.
  int operator == (X *p) const;

  /// Inequality operator, which is the opposite of equality.
  int operator != (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Inequality operator, which is the opposite of equality.
  int operator != (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Inequality operator, which is the opposite of equality.
  int operator != (X *p) const;

  /// Redirection operator
  X *operator-> (void) const;

  /// Dereference operator
  X &operator * (void) const;

  /// Get the pointer value.
  X *get (void);

  /// Resets the ACE_Strong_Bound_Ptr to refer to a different underlying
  /// object.
  void reset (X *p = 0);

  /// Resets the ACE_Strong_Bound_Ptr to refer to a different underlying
  /// object, ownership of which is stolen from the auto_ptr.
  void reset (auto_ptr<X> p);

  /// Allows us to check for NULL on all ACE_Strong_Bound_Ptr objects.
  int null (void) const;

  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

private:
  friend class ACE_Weak_Bound_Ptr<X, ACE_LOCK>;

  /// The ACE_Bound_Ptr_Counter type.
  typedef ACE_Bound_Ptr_Counter<ACE_LOCK> COUNTER;

  /// The reference counter.
  COUNTER *counter_;

  /// The underlying object.
  X *ptr_;
};

/**
 * @class ACE_Weak_Bound_Ptr
 *
 * @brief This class implements support for a weak pointer that complements
 * ACE_Strong_Bound_Ptr. Unlike ACE_Strong_Bound_Ptr, assigning or copying
 * instances of an ACE_Weak_Bound_Ptr will not automatically increment the
 * reference count of the underlying object. What ACE_Weak_Bound_Ptr does is
 * preserve the knowledge that the object is in fact reference counted, and
 * thus provides an alternative to raw pointers where non-ownership
 * associations must be maintained. When the last instance of an
 * ACE_Strong_Bound_Ptr that references a particular object is destroyed or
 * overwritten, the corresponding ACE_Weak_Bound_Ptr instances are set to
 * null.
 */
template <class X, class ACE_LOCK>
class ACE_Weak_Bound_Ptr
{
public:
  /// Constructor that initializes an ACE_Weak_Bound_Ptr to point to the
  /// object <p> immediately.
  ACE_EXPLICIT ACE_Weak_Bound_Ptr (X *p = 0);

  /// Copy constructor binds <this> and <r> to the same object.
  ACE_Weak_Bound_Ptr (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r);

  /// Constructor binds <this> and <r> to the same object.
  ACE_Weak_Bound_Ptr (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r);

  /// Destructor.
  ~ACE_Weak_Bound_Ptr (void);

  /// Assignment operator that binds <this> and <r> to the same object.
  void operator = (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r);

  /// Assignment operator that binds <this> and <r> to the same object.
  void operator = (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r);

  /// Equality operator that returns 1 if both ACE_Weak_Bound_Ptr objects
  /// point to the same underlying object. Attention: It also returns 1 if
  /// both objects have just been instantiated and not used yet.
  int operator == (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Equality operator that returns 1 if the ACE_Weak_Bound_Ptr and
  /// ACE_Strong_Bound_Ptr objects point to the same underlying object.
  /// Attention: It also returns 1 if both objects have just been instantiated
  /// and not used yet.
  int operator == (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Equality operator that returns 1 if the ACE_Weak_Bound_Ptr and the raw
  /// pointer point to the same underlying object.
  int operator == (X *p) const;

  /// Inequality operator, which is the opposite of equality.
  int operator != (const ACE_Weak_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Inequality operator, which is the opposite of equality.
  int operator != (const ACE_Strong_Bound_Ptr<X, ACE_LOCK> &r) const;

  /// Inequality operator, which is the opposite of equality.
  int operator != (X *p) const;

  /// Redirection operator. It returns a temporary strong pointer and makes
  /// use of the chaining properties of operator-> to ensure that the
  /// underlying object does not disappear while you are using it. If
  /// you are certain of the lifetimes of the object, and do not want to incur
  /// the locking overhead, then use the unsafe_get method instead.
  ACE_Strong_Bound_Ptr<X, ACE_LOCK> operator-> (void) const;

  /// Obtain a strong pointer corresponding to this weak pointer. This function
  /// is useful to create a temporary strong pointer for conversion to a
  /// reference.
  ACE_Strong_Bound_Ptr<X, ACE_LOCK> strong (void) const;

  /// Get the pointer value. Warning: this does not affect the reference count
  /// of the underlying object, so it may disappear on you while you are using
  /// it if you are not careful.
  X *unsafe_get (void) const;

  /// Resets the ACE_Weak_Bound_Ptr to refer to a different underlying object.
  void reset (X *p = 0);

  /// Increment the reference count on the underlying object. Returns the new
  /// reference count on the object. This function may be used to integrate the
  /// bound pointers into an external reference counting mechanism such as
  /// those used by COM or CORBA servants.
  int add_ref (void);

  /// Decrement the reference count on the underlying object, which is deleted
  /// if the count has reached zero. Returns the new reference count on the
  /// object. This function may be used to integrate the bound pointers into an
  /// external reference counting mechanism such as those used by COM or CORBA
  /// servants.
  int remove_ref (void);

  /// Allows us to check for NULL on all ACE_Weak_Bound_Ptr objects.
  int null (void) const;

  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

private:
  friend class ACE_Strong_Bound_Ptr<X, ACE_LOCK>;

  /// The ACE_Bound_Ptr_Counter type.
  typedef ACE_Bound_Ptr_Counter<ACE_LOCK> COUNTER;

  /// The reference counter.
  COUNTER *counter_;

  /// The underlying object.
  X *ptr_;
};

#include "ace/Bound_Ptr.i"

#include "ace/post.h"
#endif /* ACE_BOUND_PTR_H */