signal.hh

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 * Copyright 2022 Google, Inc.
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 * modification, are permitted provided that the following conditions are
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 * notice, this list of conditions and the following disclaimer;
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 * neither the name of the copyright holders nor the names of its
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 * this software without specific prior written permission.
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 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 */
 
#ifndef __SIM_SIGNAL_HH__
#define __SIM_SIGNAL_HH__
 
#include <functional>
 
#include "base/logging.hh"
#include "sim/port.hh"
 
namespace gem5
{
 
template <typename State>
class SignalSourcePort;
 
template <typename State>
class SignalSinkPort : public Port
{
  public:
    using OnChangeFunc = std::function<void(const State &new_val)>;
 
  private:
    friend SignalSourcePort<State>;
 
    SignalSourcePort<State> *_source = nullptr;
 
    State _state = {};
 
  protected:
    // if bypass_on_change is specified true, it will not call the _onChange
    // function. Only _state will be updated if needed.
    virtual void
    set(const State &new_state, const bool bypass_on_change = false)
    {
        if (new_state == _state)
            return;
 
        _state = new_state;
        if (!bypass_on_change && _onChange)
            _onChange(_state);
    }
 
    OnChangeFunc _onChange;
 
  public:
    SignalSinkPort(const std::string &_name, PortID _id=InvalidPortID) :
        Port(_name, _id)
    {}
 
    const State &state() const { return _state; }
    void onChange(OnChangeFunc func) { _onChange = std::move(func); }
 
    void
    bind(Port &peer) override
    {
        _source = dynamic_cast<SignalSourcePort<State> *>(&peer);
        fatal_if(!_source, "Attempt to bind signal pin %s to "
                "incompatible pin %s", name(), peer.name());
        // The state of sink has to match the state of source.
        _state = _source->state();
        Port::bind(peer);
    }
    void
    unbind() override
    {
        _source = nullptr;
        Port::unbind();
    }
};
 
template <typename State>
class SignalSourcePort : public Port
{
  private:
    SignalSinkPort<State> *sink = nullptr;
    State _state;
 
  public:
    SignalSourcePort(const std::string &_name, PortID _id = InvalidPortID)
        : Port(_name, _id)
    {
        _state = {};
    }
 
    // Give an initial value to the _state instead of using a default value.
    SignalSourcePort(const std::string &_name, PortID _id,
                     const State &init_state)
        : SignalSourcePort(_name, _id)
    {
        _state = init_state;
    }
 
    // if bypass_on_change is specified true, it will not call the _onChange
    // function. Only _state will be updated if needed.
    void
    set(const State &new_state, const bool bypass_on_change = false)
    {
        _state = new_state;
        sink->set(new_state, bypass_on_change);
    }
 
    const State &state() const { return _state; }
 
    void
    bind(Port &peer) override
    {
        sink = dynamic_cast<SignalSinkPort<State> *>(&peer);
        fatal_if(!sink, "Attempt to bind signal pin %s to "
                "incompatible pin %s", name(), peer.name());
        Port::bind(peer);
    }
    void
    unbind() override
    {
        sink = nullptr;
        Port::unbind();
    }
};
 
}  // namespace gem5
 
#endif  //__SIM_SIGNAL_HH__