code: /**
   * Copyright (c) 2004-2005, Regents of the University of California
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * Redistributions of source code must retain the above copyright notice,
   * this list of conditions and the following disclaimer.
   *
   * Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * Neither the name of the University of California, Los Angeles nor the
   * names of its contributors may be used to endorse or promote products
   * derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package avrora.stack;
  
  import avrora.arch.legacy.LegacyRegister;
  import cck.util.Util;
  
  /**
   * The <code>MutableState</code> class represents an abstract state of the processor that is mutable. This is
   * used in computation of next states, but is not used in the state space.
   *
   * @author Ben L. Titzer
   * @see AbstractArithmetic
   * @see StateCache
   */
  public class MutableState extends AbstractState implements IORegisterConstants {
  
      /**
       * The constructor of the <code>MutableState</code> class builds the default values of each of the
       * registers and each IO register that is being modelled. The default is that all registers are known
       * zero, all IO registers are known zero, and the program counter is zero.
       */
      public MutableState() {
          av_SREG = AbstractArithmetic.ZERO;
          av_EIMSK = AbstractArithmetic.ZERO;
          av_TIMSK = AbstractArithmetic.ZERO;
          for (int cntr = 0; cntr < NUM_REGS; cntr++) {
              av_REGISTERS[cntr] = AbstractArithmetic.ZERO;
          }
      }
  
      public MutableState(int npc, char nSREG, char nEIMSK, char nTIMSK, char[] nregs) {
          av_REGISTERS = new char[NUM_REGS];
          System.arraycopy(nregs, 0, av_REGISTERS, 0, NUM_REGS);
          pc = npc;
          av_SREG = nSREG;
          av_EIMSK = nEIMSK;
          av_TIMSK = nTIMSK;
      }
  
      /**
       * The <code>merge()</code> method merges this abstract state with another abstract state and returns a
       * new copy. This abstract state is not updated. The operation is a simple pointwise merging operation:
       * each value is merged with its corresponding abstract value in the other abstract state.
       *
       * @param s the abstract state to merge with
       * @return a new abstract state that represents the merged abstract states
       * @see AbstractArithmetic
       */
      public MutableState merge(MutableState s) {
  
          if (pc != s.pc)
              throw Util.failure("cannot merge abstract states with different program counters");
  
          MutableState n = copy();
  
          n.av_SREG = AbstractArithmetic.merge(this.av_SREG, s.av_SREG);
          for (int cntr = 0; cntr < NUM_REGS; cntr++)
              n.av_REGISTERS[cntr] = AbstractArithmetic.merge(this.av_REGISTERS[cntr], s.av_REGISTERS[cntr]);
  
          return n;
      }
  
      /**
       * The <code>hashCode()</code> method computes an integer hash code for this state. A good hash code is
       * needed to make hashtables in <code>StateSpace</code> efficient.
       *
       * @throws Util.InternalError
       */
      public int hashCode() {
          throw Util.failure("cannot compute hash code of MutableState");
      }
  
      /**
       * The <code>equals()</code> method implements the standard <code>java.lang.Object</code> equality testing
       * contract.
       *
       * @param o the object to test equality against.
       * @throws Util.InternalError
       */
      public boolean equals(Object o) {
          throw Util.failure("cannot perform .equals() on MutableState");
      }
  
      /**
       * The <code>setPC()</code> method updates the concrete value of the program counter. The program counter
       * is known in ever abstract state.
       *
       * @param npc the new concrete value of the program counter
       */
      public void setPC(int npc) {
          pc = npc;
      }
  
      /**
       * The <code>writeSREG</code> method updates the abstract value of the status register.
       *
       * @param val the new abstract value to write to the status register.
       */
      public void writeSREG(char val) {
          av_SREG = AbstractArithmetic.canon(val);
      }
  
      /**
       * The <code>writeSREG</code> method updates one bit of the abstract value of the status register.
       *
       * @param val the new abstract value of the bit
       */
      public void setSREG_bit(int bit, char val) {
          av_SREG = AbstractArithmetic.setBit(av_SREG, bit, val);
      }
  
      /**
       * The <code>setFlag_I()</code> method updates the abstract value of the I flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_I(char val) {
          setSREG_bit(SREG_I, val);
      }
  
      /**
       * The <code>setFlag_T()</code> method updates the abstract value of the T flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_T(char val) {
          setSREG_bit(SREG_T, val);
      }
  
      /**
       * The <code>setFlag_H()</code> method updates the abstract value of the H flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_H(char val) {
          setSREG_bit(SREG_H, val);
      }
  
      /**
       * The <code>setFlag_S()</code> method updates the abstract value of the S flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_S(char val) {
          setSREG_bit(SREG_S, val);
      }
  
      /**
       * The <code>setFlag_V()</code> method updates the abstract value of the V flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_V(char val) {
          setSREG_bit(SREG_V, val);
      }
  
      /**
       * The <code>setFlag_N()</code> method updates the abstract value of the N flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_N(char val) {
          setSREG_bit(SREG_N, val);
      }
  
      /**
       * The <code>setFlag_Z()</code> method updates the abstract value of the Z flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_Z(char val) {
          setSREG_bit(SREG_Z, val);
      }
  
      /**
       * The <code>setFlag_C()</code> method updates the abstract value of the C flag.
       *
       * @param val the new abstract bit of the flag
       */
      public void setFlag_C(char val) {
          setSREG_bit(SREG_C, val);
      }
  
      /**
       * The <code>setIORegisterAV()</code> method writes the abstract value of an IO register. If the register
       * is being modelled, then its value will be updated. Otherwise, the write will be ignored.
       *
       * @param num the IO register number to be updated
       * @param val the new abstract value of the IO register
       */
      public void setIORegisterAV(int num, char val) {
          if (num == IORegisterConstants.SREG) av_SREG = val;
          if (num == IORegisterConstants.EIMSK) av_EIMSK = val;
          if (num == IORegisterConstants.TIMSK) av_TIMSK = val;
      }
  
      /**
       * The <code>setRegisterAV()</code> method writes the abstract value of a register in the abstract state
       *
       * @param r   the register to write
       * @param val the new abstract value of the register
       */
      public void setRegisterAV(LegacyRegister r, char val) {
          av_REGISTERS[r.getNumber()] = AbstractArithmetic.canon(val);
      }
  
  }
  