instance_specific_extensions.h

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/*
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 __INSTANCE_SPECIFIC_EXTENSIONS_H__
#define __INSTANCE_SPECIFIC_EXTENSIONS_H__

#include <tlm>

namespace tlm_utils {

//Helper to do the numbering of private extension accessors
inline unsigned int max_num_ispex_accessors(bool increment=false)
{
    static unsigned int max_num = 0;
    if (increment) ++max_num;
    return max_num;
}

//Helper to do the index generation for private extensions
inline unsigned int max_num_ispex(bool increment=false)
{
    static unsigned int max_num = 0;
    if (increment) ++max_num;
    return max_num;
}

//The private extension base. Similar to normal extension base, but without clone and free
class ispex_base
{
public:
    virtual ~ispex_base() {}
protected:
    static unsigned int register_private_extension()
    {
        return (max_num_ispex(true) - 1);
    };
};

//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();


//this thing is basically a snippet of the generic_payload
// it contains all the extension specific code (the extension API so to speak)
// the differences are:
// - it calls back to its owner whenever a real (==non-NULL) extension gets set for the first time
// - it calls back to its owner whenever a living (==non-NULL) extension gets cleared
template<typename U>
class instance_specific_extensions_per_accessor{
public:

  typedef void (U::*cb)();

  instance_specific_extensions_per_accessor(U* container, cb inc, cb dec): m_container(container), m_inc(inc), m_dec(dec){
  }

  template <typename T> T* set_extension(T* ext)
  {
      resize_extensions();
      T* tmp = static_cast<T*>(m_extensions[T::priv_id]);
      m_extensions[T::priv_id] = static_cast<ispex_base*>(ext);
      if (!tmp && ext) (m_container->*m_inc)();
      return tmp;
  }
  // non-templatized version with manual index:
  ispex_base* set_extension(unsigned int index,
                                    ispex_base* ext)
  {
      resize_extensions();
      ispex_base* tmp = m_extensions[index];
      m_extensions[index] = ext;
      if (!tmp && ext) (m_container->*m_inc)();
      return tmp;
  }

  // Check for an extension, ext will point to 0 if not present
  template <typename T> void get_extension(T*& ext) const
  {
      ext = static_cast<T*>(m_extensions[T::priv_id]);
  }
  // Non-templatized version:
   ispex_base* get_extension(unsigned int index) const
  {
      return m_extensions[index];
  }

  // Clear extension, the argument is needed to find the right index:
  template <typename T> void clear_extension(const T* ext)
  {
      resize_extensions();
      if (m_extensions[T::priv_id]) (m_container->*m_dec)();
      m_extensions[T::priv_id] = static_cast<ispex_base*>(0);
  }
  // Non-templatized version with manual index
  void clear_extension(unsigned int index)
  {
      if (index < m_extensions.size())
      {
          if (m_extensions[index]) (m_container->*m_dec)();
          m_extensions[index] = static_cast<ispex_base*>(0);
      }
  }

  // Make sure the extension array is large enough. Can be called once by
  // an initiator module (before issuing the first transaction) to make
  // sure that the extension array is of correct size. This is only needed
  // if the initiator cannot guarantee that the generic payload object is
  // allocated after C++ static construction time.
  void resize_extensions()
  {
      m_extensions.expand(max_num_ispex());
  }
  
private:
  tlm::tlm_array<ispex_base*> m_extensions;
  U* m_container;
  cb m_inc, m_dec;
  
};

class instance_specific_extension_container;


//the pool for the container, plain as can be
class instance_specific_extension_container_pool{
  friend class instance_specific_extension_carrier;
  friend class instance_specific_extension_container;
  instance_specific_extension_container_pool() : unused(NULL){}
  inline ~instance_specific_extension_container_pool();
  inline static instance_specific_extension_container_pool& get_ispexcont_pool(){ static instance_specific_extension_container_pool tmp; return tmp;}
  inline instance_specific_extension_container* create();
  inline void free(instance_specific_extension_container*);
  
  instance_specific_extension_container* unused;
};

class instance_specific_extension_carrier;

//this thing contains the vector of extensions per accessor
//which can be really large so this one should be pool allocated
// therefore it keeps a use_count of itself to automatically free itself
// - to this end it provides callbacks to the extensions per accessor
//   to increment and decrement the use_count
class instance_specific_extension_container{
  friend class instance_specific_extension_container_pool;
  friend class instance_specific_extension_accessor;
  friend class instance_specific_extension_carrier;
  
  instance_specific_extension_container(): use_count(0), next(NULL){resize();}
  
  void resize(){
    m_ispex_per_accessor.resize(max_num_ispex_accessors());
    for (unsigned int i=0; i<m_ispex_per_accessor.size(); i++) {
      m_ispex_per_accessor[i]=new instance_specific_extensions_per_accessor<instance_specific_extension_container>(this, 
                                                                                   &instance_specific_extension_container::inc_use_count, 
                                                                                   &instance_specific_extension_container::dec_use_count
                                                                                   );
      m_ispex_per_accessor[i]->resize_extensions();
    }
  }
 
  ~instance_specific_extension_container(){
    for (unsigned int i=0; i<m_ispex_per_accessor.size(); i++) delete m_ispex_per_accessor[i];
  }
 
  void inc_use_count(){use_count++;}
  inline void dec_use_count();
  
  std::vector<instance_specific_extensions_per_accessor<instance_specific_extension_container>* > m_ispex_per_accessor; 
  unsigned int use_count;
  tlm::tlm_generic_payload* my_txn;
  instance_specific_extension_carrier* my_carrier;
  instance_specific_extension_container* next; //for pooling
};


inline instance_specific_extension_container_pool::~instance_specific_extension_container_pool(){
  while(unused) { instance_specific_extension_container* tmp=unused; unused=unused->next; delete tmp;}
}

instance_specific_extension_container* instance_specific_extension_container_pool::create(){
  if (!unused) {unused=new instance_specific_extension_container();}
  instance_specific_extension_container* tmp=unused;
  unused=unused->next;
  return tmp; 
}

void instance_specific_extension_container_pool::free(instance_specific_extension_container* cont){
  cont->next=unused;
  unused=cont;
}

//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
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=instance_specific_extension_container_pool::get_ispexcont_pool().create();
    m_container->my_carrier=this;
  }
  
  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;
};

inline void instance_specific_extension_container::dec_use_count(){
  if ((--use_count)==0) { //if this container isn't used any more
    instance_specific_extension_container_pool::get_ispexcont_pool().free(this);  //we send it back to our pool
    //we have to do that manually, as we cannot rely on the fact that there is MM in the txn
    my_txn->clear_extension(my_carrier); //and remove it from the transaction's extension array
    delete my_carrier;
  }
}


//This class 'hides' all the instance specific extension stuff from the user
// he instantiates one of those (e.g. instance_specific_extension_accessor extAcc;) and can then access
// the private extensions
//    extAcc(txn).extensionAPIFnCall()
//  where extensionAPIFnCall is set_extension, get_extension, clear_extension,...
class instance_specific_extension_accessor{
public:
  instance_specific_extension_accessor(): m_index(max_num_ispex_accessors(true)-1){}
  
  template<typename T>
  inline instance_specific_extensions_per_accessor<instance_specific_extension_container>& operator()(T& txn){
    instance_specific_extension_carrier* carrier;
    txn.get_extension(carrier);
    if (!carrier){
      carrier=new instance_specific_extension_carrier();
      carrier->m_container->my_txn=&txn;
      txn.set_extension(carrier);
    }
    return *(carrier->m_container->m_ispex_per_accessor[m_index]);
  }
  
protected:
  unsigned int m_index;
};

}

#endif