Package mars.simulator

Class BackStepper

java.lang.Object
mars.simulator.BackStepper
public class BackStepper extends Object
Used to "step backward" through execution, undoing each instruction.
Author:
Pete Sanderson, February 2006; Sean Clarke, November 2024

  • Constructor Summary

    Constructors
    Constructor
    Description
    BackStepper()
    Create a fresh BackStepper.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    backStep()
    Carry out a "back step", which will undo the latest execution step.
    void
    finishStep()
     
    boolean
    isEmpty()
    Test whether there are steps that can be undone.
    boolean
    isEnabled()
    Determine whether execution "undo" steps are currently being recorded.
    void
    registerChanged(Register register, int restoreValue)
    Add a new "back step" (the undo action) to the stack.
    void
    reset()
     
    void
    setEnabled(boolean state)
    Set enable status.
    void
    statementWritten(int address, BasicStatement restoreStatement)
    Add a new "back step" (the undo action) to the stack.
    void
    wordWritten(int address, int restoreValue)
    Add a new "back step" (the undo action) to the stack.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • BackStepper

      public BackStepper()
      Create a fresh BackStepper. It is enabled, which means all subsequent instruction executions will have their "undo" action recorded here.

  • Method Details

    • reset

      public void reset()

    • isEnabled

      public boolean isEnabled()
      Determine whether execution "undo" steps are currently being recorded.
      Returns:
      true if undo steps being recorded, false if not.

    • setEnabled

      public void setEnabled(boolean state)
      Set enable status.
      Parameters:
      state - If true, will begin (or continue) recoding "undo" steps. If false, will stop.

    • isEmpty

      public boolean isEmpty()
      Test whether there are steps that can be undone.
      Returns:
      true if there are no steps to be undone, false otherwise.

    • finishStep

      public void finishStep()

    • backStep

      public void backStep()
      Carry out a "back step", which will undo the latest execution step. Does nothing if backstepping not enabled or if there are no steps to undo.

    • registerChanged

      public void registerChanged(Register register, int restoreValue)
      Add a new "back step" (the undo action) to the stack. The action here is to restore a register file register value.
      Parameters:
      register - The affected register number.
      restoreValue - The "restore" value to be stored there.

    • wordWritten

      public void wordWritten(int address, int restoreValue)
      Add a new "back step" (the undo action) to the stack. The action here is to restore a memory word value.
      Parameters:
      address - The affected memory address.
      restoreValue - The "restore" value to be stored there.

    • statementWritten

      public void statementWritten(int address, BasicStatement restoreStatement)
      Add a new "back step" (the undo action) to the stack. The action here is to restore a memory word value.
      Parameters:
      address - The affected memory address.
      restoreStatement - The "restore" value to be stored there.