tlm_quantumkeeper.h

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  source code Copyright (c) 1996-2014 by all Contributors.
  All Rights reserved.

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  set forth in the SystemC Open Source License (the "License");
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// 20-Mar-2009  John Aynsley  Add set_and_sync() method


#ifndef __TLM_QUANTUMKEEPER_H__
#define __TLM_QUANTUMKEEPER_H__

#include "tlm_core/tlm_2/tlm_quantum/tlm_global_quantum.h"

namespace tlm_utils {

  //
  // tlm_quantumkeeper class
  //
  // The tlm_quantumkeeper class is used to keep track of the local time in
  // an initiator (how much it has run ahead of the SystemC time), to
  // synchronize with SystemC time etc.
  //
  class tlm_quantumkeeper
  {
  public:
    //
    // Static setters/getters for the global quantum value.
    //
    // The global quantum is the maximum time an initiator can run ahead of
    // systemC time. All initiators will synchronize on timingpoints that are
    // multiples of the global quantum value.
    //
    static void set_global_quantum(const sc_core::sc_time& t)
    {
      tlm::tlm_global_quantum::instance().set(t);
    }

    static const sc_core::sc_time& get_global_quantum()
    {
      return tlm::tlm_global_quantum::instance().get();
    }

  public:
    tlm_quantumkeeper() :
      m_next_sync_point(sc_core::SC_ZERO_TIME),
      m_local_time(sc_core::SC_ZERO_TIME)
    {
    }

    virtual ~tlm_quantumkeeper() {}

    //
    // Increment the local time (the time the initiator is ahead of the
    // systemC time) After incrementing the local time an initiator should
    // check (with the need_sync method) if a sync is required.
    //
    virtual void inc(const sc_core::sc_time& t)
    {
      m_local_time += t;
    }

    //
    // Sets the local time (the time the initiator is ahead of the
    // systemC time) After changing the local time an initiator should
    // check (with the need_sync method) if a sync is required.
    //
    virtual void set(const sc_core::sc_time& t)
    {
      m_local_time = t;
    }

    //
    // Checks if a sync to systemC is required for this initiator. This will
    // be the case if the local time becomes greater than the local (current)
    // quantum value for this initiator.
    //
    virtual bool need_sync() const
    {
      return sc_core::sc_time_stamp() + m_local_time >= m_next_sync_point;
    }

    //
    // Synchronize to systemC. This call will do a wait for the time the
    // initiator was running ahead of systemC time and reset the
    // tlm_quantumkeeper.
    //
    virtual void sync()
    {
      sc_core::wait(m_local_time);
      reset();
    }

    //
    // Non-virtual convenience method to set the local time and sync only if needed
    //
    void set_and_sync(const sc_core::sc_time& t)
    {
      set(t);
      if (need_sync())
        sync();
    }

    //
    // Resets the local time to SC_ZERO_TIME and computes the value of the
    // next local quantum. This method should be called by an initiator after
    // a wait because of a synchronization request by a target (TLM_ACCEPTED,
    // or TLM_UPDATED).
    //
    virtual void reset()
    {
      m_local_time = sc_core::SC_ZERO_TIME;
      m_next_sync_point = sc_core::sc_time_stamp() + compute_local_quantum();
    }

    //
    // Helper function to get the current systemC time, taken the local time
    // into account. The current systemC time is calculated as the time
    // returned by sc_time_stamp incremeneted with the time the initiator is
    // running ahead.
    //
    virtual sc_core::sc_time get_current_time() const
    {
      return sc_core::sc_time_stamp() + m_local_time;
    }

    //
    // Helper functions to get the time the initiator is running ahead of
    // systenC (local time). This time should be passed to a target in the
    // nb_transport call
    //
    virtual sc_core::sc_time get_local_time() const
    {
      return m_local_time;
    }

  protected:
    //
    // Calculate the next local quantum for this initiator.
    //
    // The method can be overloaded in a derived object if an initiator wants
    // to use another local quantum. This derived object should also take the
    // global quantum into account. It's local quantum should not be set to a
    // value that is larger than the quantum returned by the
    // compute_local_quantum of the tlm_global_quantum singleton.
    //
    virtual sc_core::sc_time compute_local_quantum()
    {
      return tlm::tlm_global_quantum::instance().compute_local_quantum();
    }

  protected:
    sc_core::sc_time m_next_sync_point;
    sc_core::sc_time m_local_time;
  };

} // namespace tlm

#endif