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Interrupt CRC

Responsibilities:

class Interrupt {
  public:
    Interrupt();                        // initialize the interrupt simulation
    ~Interrupt();                       // de-allocate data structures

    IntStatus SetLevel(IntStatus level);// Disable or enable interrupts
                                        // and return previous setting.

    void Enable();                      // Enable interrupts.
    IntStatus getLevel() {return level;}// Return whether interrupts
                                        // are enabled or disabled

    void Idle();                        // The ready queue is empty, roll
                                        // simulated time forward until the
                                        // next interrupt

    void Halt();                        // quit and print out stats

    void YieldOnReturn();               // cause a context switch on return
                                        // from an interrupt handler

    MachineStatus getStatus() { return status; } // idle, kernel, user
    void setStatus(MachineStatus st) { status = st; }

    void DumpState();                   // Print interrupt state


    // NOTE: the following are internal to the hardware simulation code.
    // DO NOT call these directly.  I should make them "private",
    // but they need to be public since they are called by the
    // hardware device simulators.

    void Schedule(VoidFunctionPtr handler,// Schedule an interrupt to occur
        int arg, int when, IntType type);// at time ``when''.  This is called
                                        // by the hardware device simulators.

    void OneTick();                     // Advance simulated time

  private:
    IntStatus level;            // are interrupts enabled or disabled?
    List *pending;              // the list of interrupts scheduled
                                // to occur in the future
    bool inHandler;             // TRUE if we are running an interrupt handler
    bool yieldOnReturn;         // TRUE if we are to context switch
                                // on return from the interrupt handler
    MachineStatus status;       // idle, kernel mode, user mode

    // these functions are internal to the interrupt simulation code

    bool CheckIfDue(bool advanceClock); // Check if an interrupt is supposed   
                                        // to occur now

    void ChangeLevel(IntStatus old,     // SetLevel, without advancing the
        IntStatus now);                 // simulated time
};