unison/src/core/model/object.h

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2007 INRIA, Gustavo Carneiro
 *
 * 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
 *
 * Authors: Gustavo Carneiro <gjcarneiro@gmail.com>,
 *          Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 */
#ifndef OBJECT_H
#define OBJECT_H

#include <stdint.h>
#include <string>
#include <vector>
#include "ptr.h"
#include "attribute.h"
#include "object-base.h"
#include "attribute-construction-list.h"
#include "simple-ref-count.h"


namespace ns3 {

class Object;
class AttributeAccessor;
class AttributeValue;
class TraceSourceAccessor;

struct ObjectDeleter
{
  inline static void Delete (Object *object);
};

/**
 * \ingroup core
 * \defgroup object Object
 */
/**
 * \ingroup object
 * \brief a base class which provides memory management and object aggregation
 *
 * The memory management scheme is based on reference-counting with dispose-like
 * functionality to break the reference cycles. The reference count is increamented
 * and decremented with the methods Object::Ref and Object::Unref. If a reference cycle is
 * present, the user is responsible for breaking it by calling Object::Dispose in
 * a single location. This will eventually trigger the invocation of Object::DoDispose 
 * on itself and all its aggregates. The Object::DoDispose method is always automatically
 * invoked from the Object::Unref method before destroying the object, even if the user 
 * did not call Object::Dispose directly.
 */
class Object : public SimpleRefCount<Object,ObjectBase,ObjectDeleter>
{
public:
  static TypeId GetTypeId (void);

  /**
   * \brief Iterate over the objects aggregated to an ns3::Object.
   *
   * This iterator does not allow you to iterate over the initial
   * object used to call Object::GetAggregateIterator. 
   *
   * Note: this is a java-style iterator.
   */
  class AggregateIterator
  {
public:
    AggregateIterator ();

    /**
     * \returns true if HasNext can be called and return a non-null
     *          pointer, false otherwise.
     */
    bool HasNext (void) const;

    /**
     * \returns the next aggregated object.
     */
    Ptr<const Object> Next (void);
private:
    friend class Object;
    AggregateIterator (Ptr<const Object> object);
    Ptr<const Object> m_object;
    uint32_t m_current;
  };

  Object ();
  virtual ~Object ();

  /*
   * Implement the GetInstanceTypeId method defined in ObjectBase.
   */
  virtual TypeId GetInstanceTypeId (void) const;

  /**
   * \returns a pointer to the requested interface or zero if it could not be found.
   */
  template <typename T>
  inline Ptr<T> GetObject (void) const;
  /**
   * \param tid the interface id of the requested interface
   * \returns a pointer to the requested interface or zero if it could not be found.
   */
  template <typename T>
  Ptr<T> GetObject (TypeId tid) const;
  /**
   * Run the DoDispose methods of this object and all the
   * objects aggregated to it.
   * After calling this method, the object is expected to be
   * totally unusable except for the Ref and Unref methods.
   *
   * Note that you can call Dispose many times on the same object or
   * different objects aggregated together, and DoDispose will be
   * called only once for each aggregated object.
   *
   * This method is typically used to break reference cycles.
   */
  void Dispose (void);
  /**
   * \param other another object pointer
   *
   * This method aggregates the two objects together: after this
   * method returns, it becomes possible to call GetObject
   * on one to get the other, and vice-versa. 
   *
   * This method calls the virtual method NotifyNewAggregates to
   * notify all aggregated objects that they have been aggregated
   * together.
   *
   * \sa NotifyNewAggregate
   */
  void AggregateObject (Ptr<Object> other);

  /**
   * \returns an iterator to the first object aggregated to this
   *          object.
   *
   * If no objects are aggregated to this object, then, the returned
   * iterator will be empty and AggregateIterator::HasNext will
   * always return false.
   */
  AggregateIterator GetAggregateIterator (void) const;

  /**
   * This method calls the virtual DoInitialize method on all the objects
   * aggregated to this object. DoInitialize will be called only once over
   * the lifetime of an object, just like DoDispose is called only
   * once.
   *
   * \sa DoInitialize
   */
  void Initialize (void);

protected:
  /**
   * This method is invoked whenever two sets of objects are aggregated together.
   * It is invoked exactly once for each object in both sets.
   * This method can be overriden by subclasses who wish to be notified of aggregation
   * events. These subclasses must chain up to their base class NotifyNewAggregate method.
   * It is safe to call GetObject and AggregateObject from within this method.
   */
  virtual void NotifyNewAggregate (void);
  /**
   * This method is called only once by Object::Initialize. If the user
   * calls Object::Initialize multiple times, DoInitialize is called only the
   * first time.
   *
   * Subclasses are expected to override this method and _chain up_
   * to their parent's implementation once they are done. It is
   * safe to call GetObject and AggregateObject from within this method.
   */
  virtual void DoInitialize (void);
  /**
   * This method is called by Object::Dispose or by the object's 
   * destructor, whichever comes first.
   *
   * Subclasses are expected to implement their real destruction
   * code in an overriden version of this method and chain
   * up to their parent's implementation once they are done.
   * i.e., for simplicity, the destructor of every subclass should
   * be empty and its content should be moved to the associated
   * DoDispose method.
   *
   * It is safe to call GetObject from within this method.
   */
  virtual void DoDispose (void);
  /**
   * \param o the object to copy.
   *
   * Allow subclasses to implement a copy constructor.
   * While it is technically possible to implement a copy
   * constructor in a subclass, we strongly discourage you
   * to do so. If you really want to do it anyway, you have
   * to understand that this copy constructor will _not_
   * copy aggregated objects. i.e., if your object instance
   * is already aggregated to another object and if you invoke
   * this copy constructor, the new object instance will be
   * a pristine standalone object instance not aggregated to
   * any other object. It is thus _your_ responsability
   * as a caller of this method to do what needs to be done
   * (if it is needed) to ensure that the object stays in a
   * valid state.
   */
  Object (const Object &o);
private:

  template <typename T>
  friend Ptr<T> CopyObject (Ptr<T> object);
  template <typename T>
  friend Ptr<T> CopyObject (Ptr<const T> object);
  template <typename T>
  friend Ptr<T> CompleteConstruct (T *object);

  friend class ObjectFactory;
  friend class AggregateIterator;
  friend struct ObjectDeleter;

  /**
   * This data structure uses a classic C-style trick to 
   * hold an array of variable size without performing
   * two memory allocations: the declaration of the structure
   * declares a one-element array but when we allocate
   * memory for this struct, we effectively allocate a larger
   * chunk of memory than the struct to allow space for a larger
   * variable sized buffer whose size is indicated by the element
   * 'n'
   */
  struct Aggregates {
    uint32_t n;
    Object *buffer[1];
  };

  Ptr<Object> DoGetObject (TypeId tid) const;
  bool Check (void) const;
  bool CheckLoose (void) const;
  /**
   * \param tid an TypeId
   *
   * Invoked from ns3::CreateObject only.
   * Initialize the m_tid member variable to
   * keep track of the type of this object instance.
   */
  void SetTypeId (TypeId tid);
  /**
  * \param attributes the attribute values used to initialize
  *        the member variables of this object's instance.
  *
  * Invoked from ns3::ObjectFactory::Create and ns3::CreateObject only.
  * Initialize all the member variables which were
  * registered with the associated TypeId.
  */
  void Construct (const AttributeConstructionList &attributes);

  void UpdateSortedArray (struct Aggregates *aggregates, uint32_t i) const;
  /**
   * Attempt to delete this object. This method iterates
   * over all aggregated objects to check if they all 
   * have a zero refcount. If yes, the object and all
   * its aggregates are deleted. If not, nothing is done.
   */
  void DoDelete (void);

  /**
   * Identifies the type of this object instance.
   */
  TypeId m_tid;
  /**
   * Set to true when the DoDispose method of the object
   * has run, false otherwise.
   */
  bool m_disposed;
  /**
   * Set to true once the DoInitialize method has run,
   * false otherwise
   */
  bool m_initialized;
  /**
   * a pointer to an array of 'aggregates'. i.e., a pointer to
   * each object aggregated to this object is stored in this 
   * array. The array is shared by all aggregated objects
   * so the size of the array is indirectly a reference count.
   */
  struct Aggregates * m_aggregates;
  /**
   * Indicates the number of times the object was accessed with a
   * call to GetObject. This integer is used to implement a
   * heuristic to sort the array of aggregates to put at the start
   * of the array the most-frequently accessed elements.
   */
  uint32_t m_getObjectCount;
};

/**
 * \param object a pointer to the object to copy.
 * \returns a copy of the input object.
 *
 * This method invoke the copy constructor of the input object
 * and returns the new instance.
 */
template <typename T>
Ptr<T> CopyObject (Ptr<const T> object);
template <typename T>
Ptr<T> CopyObject (Ptr<T> object);

} // namespace ns3

namespace ns3 {

void 
ObjectDeleter::Delete (Object *object)
{
  object->DoDelete ();
}

/*************************************************************************
 *   The Object implementation which depends on templates
 *************************************************************************/

template <typename T>
Ptr<T> 
Object::GetObject () const
{
  // This is an optimization: if the cast works (which is likely),
  // things will be pretty fast.
  T *result = dynamic_cast<T *> (m_aggregates->buffer[0]);
  if (result != 0)
    {
      return Ptr<T> (result);
    }
  // if the cast does not work, we try to do a full type check.
  Ptr<Object> found = DoGetObject (T::GetTypeId ());
  if (found != 0)
    {
      return Ptr<T> (static_cast<T *> (PeekPointer (found)));
    }
  return 0;
}

template <typename T>
Ptr<T> 
Object::GetObject (TypeId tid) const
{
  Ptr<Object> found = DoGetObject (tid);
  if (found != 0)
    {
      return Ptr<T> (static_cast<T *> (PeekPointer (found)));
    }
  return 0;
}

/*************************************************************************
 *   The helper functions which need templates.
 *************************************************************************/

template <typename T>
Ptr<T> CopyObject (Ptr<T> object)
{
  Ptr<T> p = Ptr<T> (new T (*PeekPointer (object)), false);
  NS_ASSERT (p->GetInstanceTypeId () == object->GetInstanceTypeId ());
  return p;
}

template <typename T>
Ptr<T> CopyObject (Ptr<const T> object)
{
  Ptr<T> p = Ptr<T> (new T (*PeekPointer (object)), false);
  NS_ASSERT (p->GetInstanceTypeId () == object->GetInstanceTypeId ());
  return p;
}

template <typename T>
Ptr<T> CompleteConstruct (T *p)
{
  p->SetTypeId (T::GetTypeId ());
  p->Object::Construct (AttributeConstructionList ());
  return Ptr<T> (p, false);
}

template <typename T>
Ptr<T> CreateObject (void)
{
  return CompleteConstruct (new T ());
}

template <typename T, typename T1>
Ptr<T> CreateObject (T1 a1)
{
  return CompleteConstruct (new T (a1));
}

template <typename T, typename T1, typename T2>
Ptr<T> CreateObject (T1 a1, T2 a2)
{
  return CompleteConstruct (new T (a1,a2));
}

template <typename T, typename T1, typename T2, typename T3>
Ptr<T> CreateObject (T1 a1, T2 a2, T3 a3)
{
  return CompleteConstruct (new T (a1,a2,a3));
}

template <typename T, typename T1, typename T2, typename T3, typename T4>
Ptr<T> CreateObject (T1 a1, T2 a2, T3 a3, T4 a4)
{
  return CompleteConstruct (new T (a1,a2,a3,a4));
}

template <typename T, typename T1, typename T2, typename T3, typename T4, typename T5>
Ptr<T> CreateObject (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5)
{
  return CompleteConstruct (new T (a1,a2,a3,a4,a5));
}

template <typename T, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6>
Ptr<T> CreateObject (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5, T6 a6)
{
  return CompleteConstruct (new T (a1,a2,a3,a4,a5,a6));
}

template <typename T, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7>
Ptr<T> CreateObject (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5, T6 a6, T7 a7)
{
  return CompleteConstruct (new T (a1,a2,a3,a4,a5,a6,a7));
}


} // namespace ns3

#endif /* OBJECT_H */