get rid of scary implementation details of Attribute.
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2008 INRIA
*
* 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
*/
#ifndef ATTRIBUTE_H
#define ATTRIBUTE_H
#include <string>
#include <stdint.h>
#include "ptr.h"
#include "ref-count-base.h"
namespace ns3 {
class AttributeAccessor;
class AttributeChecker;
class Attribute;
class ObjectBase;
/**
* \brief Hold a value for an Attribute.
*
* Instances of this class should always be wrapped into an Attribute object.
* Most subclasses of this base class are implemented by the
* ATTRIBUTE_HELPER_* macros.
*/
class AttributeValue : public RefCountBase
{
public:
AttributeValue ();
virtual ~AttributeValue ();
/**
* \returns a deep copy of this class, wrapped into an Attribute object.
*/
virtual Attribute Copy (void) const = 0;
/**
* \param checker the checker associated to the attribute
* \returns a string representation of this value.
*
* In most cases, this method will not make any use of the checker argument.
* However, in a very limited set of cases, the checker argument is needed to
* perform proper serialization. A nice example of code which needs it is
* the EnumValue::SerializeToString code.
*/
virtual std::string SerializeToString (Ptr<const AttributeChecker> checker) const = 0;
/**
* \param value a string representation of the value
* \param checker a pointer to the checker associated to the attribute.
* \returns true if the input string was correctly-formatted and could be
* successfully deserialized, false otherwise.
*
* Upon return of this function, this AttributeValue instance contains
* the deserialized value.
* In most cases, this method will not make any use of the checker argument.
* However, in a very limited set of cases, the checker argument is needed to
* perform proper serialization. A nice example of code which needs it is
* the EnumValue::SerializeToString code.
*/
virtual bool DeserializeFromString (std::string value, Ptr<const AttributeChecker> checker) = 0;
private:
friend class Attribute;
uint32_t m_count;
};
/**
* \brief an opaque wrapper around a value to set or retrieved
* from an attribute.
*
* This class is really a smart pointer to an instance of AttributeValue.
* Of course, the question is "why not use a Ptr<AttributeValue>" ?. The
* answer is long and complicated but the crux of the issue is that if we
* do not reproduce the smart pointer code in this class, we cannot provide
* transparent handling of Ptr<T> values through the attribute system.
*/
class Attribute
{
public:
Attribute ();
/**
* Forward to AttributeValue::Copy
*/
Attribute Copy (void) const;
/**
* Forward to AttributeValue::SerializeToString
*/
std::string SerializeToString (Ptr<const AttributeChecker> checker) const;
/**
* Forward to AttributeValue::DeserializeFromString
*/
bool DeserializeFromString (std::string value, Ptr<const AttributeChecker> checker);
/**
* This method performs a dynamic_cast on the underlying AttributeValue.
* This method is typically used to implement conversion operators
* from the type Attribute. In most cases, these conversion operators
* will be generated for you by the ATTRIBUTE_HELPER_* macros.
* \returns the casted pointer.
*/
template <typename T>
T DynCast (void) const;
Attribute (Ptr<AttributeValue> value);
private:
Ptr<AttributeValue> m_value;
};
/**
* \brief allow setting and getting the value of an attribute.
*
* The goal of this class is to hide from the user how an attribute
* is actually set or get to or from a class instance. Implementations
* of this base class are usually provided through the MakeAccessorHelper
* template functions, hidden behind an ATTRIBUTE_HELPER_* macro.
*/
class AttributeAccessor
{
public:
AttributeAccessor ();
void Ref (void) const;
void Unref (void) const;
virtual ~AttributeAccessor ();
/**
* \param object the object instance to set the value in
* \param value the value to set
* \returns true if the value could be set successfully, false otherwise.
*
* This method expects that the caller has checked that the input value is
* valid with AttributeChecker::Check.
*/
virtual bool Set (ObjectBase * object, Attribute value) const = 0;
/**
* \param object the object instance to get the value from
* \param attribute a pointer to where the value should be set.
* \returns true if the value could be read successfully, and
* stored in the input value, false otherwise.
*
* This method expects that the caller has checked that the input value is
* valid with AttributeChecker::Check.
*/
virtual bool Get (const ObjectBase * object, Attribute attribute) const = 0;
private:
mutable uint32_t m_count;
};
/**
* \brief Represent the type of an attribute
*
* Each type of attribute has an associated unique AttributeChecker
* subclass. The type of the subclass can be safely used by users
* to infer the type of the associated attribute. i.e., we expect
* binding authors to use the checker associated to an attribute
* to detect the type of the associated attribute.
*
* Most subclasses of this base class are implemented by the
* ATTRIBUTE_HELPER_* macros.
*/
class AttributeChecker
{
public:
AttributeChecker ();
void Ref (void) const;
void Unref (void) const;
virtual ~AttributeChecker ();
/**
* \param value a pointer to the value to check
* \returns true if the input value is both of the right type
* and if its value is within the requested range. Returns
* false otherwise.
*/
virtual bool Check (Attribute value) const = 0;
virtual std::string GetType (void) const = 0;
virtual bool HasTypeConstraints (void) const = 0;
virtual std::string GetTypeConstraints (void) const = 0;
/**
* \returns a new instance of an AttributeValue (wrapper in an Attribute
* instance) which matches the type of the underlying attribute.
*
* This method is typically used to create a temporary variable prior
* to calling Attribute::DeserializeFromString.
*/
virtual Attribute Create (void) const = 0;
private:
mutable uint32_t m_count;
};
} // namespace ns3
namespace ns3 {
/********************************************************
* The implementation of the Attribute
* class template methods.
********************************************************/
template <typename T>
T
Attribute::DynCast (void) const
{
return dynamic_cast<T> (PeekPointer (m_value));
}
} // namespace ns3
#endif /* ATTRIBUTE_H */