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;
  
  /**
   * The <code>Policy</code> interface allows for more modular, composable analysis. An instance of this class
   * is passed to the <code>AbstractInterpreter</code> and that instance determines how to handle calls,
   * returns, indirect jumps, and stack operations in the abstract interpretation. Thus, multiple anlayses can
   * share the same core abstract interpreter in a clean way.
   *
   * @author Ben L. Titzer
   * @see AbstractInterpreter
   */
  public interface AnalyzerPolicy {
  
      /**
       * The <code>call()</code> method is called by the abstract interpreter when it encounters a call
       * instruction within the program. Different policies may handle calls differently. For example, a
       * context-sensitive analysis might fork and start analysis the called method in this context, which a
       * context insensitive analsysis may just merge the current state into the entrance state for that address
       * and then reanalyze that code.
       *
       * @param s              the current calling abstract state
       * @param target_address the concrete target address of the call
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState call(MutableState s, int target_address);
  
      /**
       * The <code>interrupt()</code> is called by the abstract interrupt when it encounters a place in the
       * program when an interrupt might occur.
       *
       * @param s   the abstract state just before interrupt
       * @param num the interrupt number that might occur
       * @return the state of the program after the interrupt, null if there is no next state
       */
      public MutableState interrupt(MutableState s, int num);
  
      /**
       * The <code>ret()</code> method is called by the abstract interpreter when it encounters a return within
       * the program.
       *
       * @param s the current abstract state
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState ret(MutableState s);
  
      /**
       * The <code>reti()</code> method is called by the abstract interpreter when it encounters a return from
       * an interrupt within the program.
       *
       * @param s the current abstract state
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState reti(MutableState s);
  
      /**
       * The <code>indirectCall()</code> method is called by the abstract interpreter when it encounters an
       * indirect call within the program. The abstract values of the address are given as parameters, so that a
       * policy can choose to compute possible targets or be conservative or whatever it so chooses.
       *
       * @param s        the current abstract state
       * @param addr_low the (abstract) low byte of the address
       * @param addr_hi  the (abstract) high byte of the address
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState indirectCall(MutableState s, char addr_low, char addr_hi);
  
      /**
       * The <code>indirectJump()</code> method is called by the abstract interpreter when it encounters an
       * indirect jump within the program. The abstract values of the address are given as parameters, so that a
       * policy can choose to compute possible targets or be conservative or whatever it so chooses.
       *
       * @param s        the current abstract state
       * @param addr_low the (abstract) low byte of the address
       * @param addr_hi  the (abstract) high byte of the address
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState indirectJump(MutableState s, char addr_low, char addr_hi);
  
      /**
       * The <code>indirectCall()</code> method is called by the abstract interpreter when it encounters an
       * indirect call within the program. The abstract values of the address are given as parameters, so that a
       * policy can choose to compute possible targets or be conservative or whatever it so chooses.
       *
       * @param s        the current abstract state
       * @param addr_low the (abstract) low byte of the address
       * @param addr_hi  the (abstract) high byte of the address
       * @param ext      the (abstract) extended part of the address
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState indirectCall(MutableState s, char addr_low, char addr_hi, char ext);
  
      /**
       * The <code>indirectJump()</code> method is called by the abstract interpreter when it encounters an
       * indirect jump within the program. The abstract values of the address are given as parameters, so that a
       * policy can choose to compute possible targets or be conservative or whatever it so chooses.
       *
       * @param s        the current abstract state
       * @param addr_low the (abstract) low byte of the address
       * @param addr_hi  the (abstract) high byte of the address
       * @param ext      the (abstract) extended part of the address
       * @return the state of the program after the call, null if there is no next state
       */
      public MutableState indirectJump(MutableState s, char addr_low, char addr_hi, char ext);
  
      /**
       * The <code>push()</code> method is called by the abstract interpreter when a push to the stack is
       * encountered in the program. The policy can then choose what outgoing and/or modelling of the stack
       * needs to be done.
       *
       * @param s   the current abstract state
       * @param val the abstract value to push onto the stack
       */
      public void push(MutableState s, char val);
  
      /**
       * The <code>pop()</code> method is called by the abstract interpreter when a pop from the stack is
       * ecountered in the program. The policy can then choose to either return whatever information it has
       * about the stack contents, or return an UNKNOWN value.
       *
       * @param s the current abstract state
       * @return the abstract value popped from the stack
       */
      public char pop(MutableState s);
  
      /**
       * The <code>pushState</code> method is called by the abstract interpreter when a state is forked by the
       * abstract interpreter (for example when a branch condition is not known and both branches must be
       * taken.
       *
       * @param newState the new state created
       */
      public void pushState(MutableState newState);
  
  }
  