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  Licensed to Accellera Systems Initiative Inc. (Accellera) under one or
  more contributor license agreements.  See the NOTICE file distributed
  with this work for additional information regarding copyright ownership.
  Accellera licenses this file to you under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with the
  License.  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
  implied.  See the License for the specific language governing
  permissions and limitations under the License.

 *****************************************************************************/
 
/*
Instance specific extensions, are extension that only a single instance of a module
may access. They are invisible to all other modules; they are private to this
instance so to speak.

As they are only of value to a certain instance, this instance knows very well
when it needs them and when it does not need them any longer (usually when
a transaction passes through a module for the last time).
It does not have to care if anyone else in the system may still have a
reference to the transaction as this one is not able to access the extension
anyway.
Therefore the instance is obliged to call set_extension when it wants to add a
private extension and clear_extension when it does not need it any more.

To get access to an instance specifc extension the module must own a so called
instance_specific_extension_accessor that provides the exclusive access rights.
Assuming the instance_specific_extension_accessor of a given module is called m_accessor
and the transaction of which the private extension is about to be accessed
is called txn, then the calls have to be

m_accessor(txn).set_extension(...);
or
m_accessor(txn).clear_extension(...);

The owner of the private extension is responsible to allocate/deallocate
the extension before/after setting/clearing the extension.
*/
 
#ifndef TLM_UTILS_INSTANCE_SPECIFIC_EXTENSIONS_H_INCLUDED_
#define TLM_UTILS_INSTANCE_SPECIFIC_EXTENSIONS_H_INCLUDED_

#include "tlm_utils/instance_specific_extensions_int.h"

namespace tlm_utils {

//The templated private extension. Similar to normal extension
template <typename T>
class instance_specific_extension : public ispex_base {
public:
    virtual ~instance_specific_extension() {}
    const static unsigned int priv_id;
};

template <typename T>
const unsigned int instance_specific_extension<T>::priv_id
  = ispex_base::register_private_extension(typeid(T));

// ----------------------------------------------------------------------------

// This is the class that actually sits in the extension array
// - we keep this small since that one gets allocated and deallocated all the times
// - we keep the implementation in the header to avoid registration
//   of the extension itself unless used in the model
class instance_specific_extension_carrier
  : public tlm::tlm_extension<instance_specific_extension_carrier>
{
  friend class instance_specific_extension_accessor;
public:
  instance_specific_extension_carrier()
    : m_container()
  {}

  virtual tlm::tlm_extension_base* clone() const {
    //we don't clone since private info is instance specific and associated to a given txn (the original)
    //so the deep copied txn will be virgin in terms of private info
    return NULL;
  }

  void copy_from(tlm::tlm_extension_base const &) { return; }
  void free() { return; }

private:
  instance_specific_extension_container* m_container;
};

// ----------------------------------------------------------------------------

template<typename T>
instance_specific_extensions_per_accessor&
instance_specific_extension_accessor::operator()(T& txn)
{
  instance_specific_extension_carrier* carrier = NULL;
  txn.get_extension(carrier);
  if (!carrier) {
    carrier = new instance_specific_extension_carrier();
    carrier->m_container = instance_specific_extension_container::create();
    carrier->m_container->attach_carrier(carrier, &txn, &release_carrier<T>);
    txn.set_extension(carrier);
  }
  return *carrier->m_container->get_accessor(m_index);
}

template<typename T>
void
instance_specific_extension_accessor::
  release_carrier(instance_specific_extension_carrier* carrier, void* txn)
{
  T* typed_txn = static_cast<T*>(txn);
  typed_txn->clear_extension(carrier);
  delete carrier;
}

} // namespace tlm_utils

#endif // TLM_UTILS_INSTANCE_SPECIFIC_EXTENSIONS_H_INCLUDED_