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.sim;
  
  import avrora.arch.legacy.*;
  import avrora.core.Program;
  import avrora.sim.util.MulticastProbe;
  import cck.util.Util;
  import java.util.Arrays;
  
  /**
   * The <code>CodeSegment</code> class represents a segment of memory that stores executable
   * code. The program memory on the AVR chips, for example, is a flash segment.
   *
   * @author Ben L. Titzer
   */
  public class CodeSegment extends Segment {
  
      protected final AtmelInterpreter interpreter;
  
      /**
       * The <code>replaceInstr()</code> method is used internally to update an instruction in the flash segment
       * without losing all of its attached instrumentation (i.e. probes and watches).
       * @param address the address in the code segment of the instruction
       * @param i the new instruction to place at this location in the flash
       */
      protected void replaceInstr(int address, LegacyInstr i) {
          LegacyInstr instr = getInstr(address);
          if ( instr == null || !(instr instanceof ProbedLegacyInstr) ) {
              writeInstr(address, i);
          } else {
              ProbedLegacyInstr pi = new ProbedLegacyInstr(i, (ProbedLegacyInstr)instr);
              writeInstr(address, pi);
          }
      }
  
      /**
       * The <code>CodeSegment.Factory</code> class is used to create a new code segment for a new interpreter.
       */
      public interface Factory {
          public CodeSegment newCodeSegment(String name, AtmelInterpreter bi, Program p);
      }
  
      /**
       * The <code>DefaultFactory</code> class represents a factory capable of creating a simple code segment
       * that is not reprogrammable.
       */
      public static class DefaultFactory implements Factory {
          final int size;
  
          public DefaultFactory(int s) {
              size = s;
          }
  
          public CodeSegment newCodeSegment(String name, AtmelInterpreter bi, Program p) {
              return new CodeSegment(name, size, bi);
          }
      }
  
      /**
       * The <code>DEFAULT_VALUE</code> field stores the default value that is used to
       * initialize the flash memory.
       */
      public static final byte DEFAULT_VALUE = (byte)0xff;
  
      /**
       * The <code>segment_instr</code> field stores a reference to an array that contains the
       * disassembled instructions that correspond to the machine code.
       */
      protected LegacyInstr[] segment_instr;
  
      protected final NoLegacyInstr NO_INSTR = new NoLegacyInstr();
  
      protected CodeSharer codeSharer;
  
      /**
       * The <code>CodeSharer</code> interface is used to allow sharing of the underlying array
       * representing the code. Only the interpreter should share this representation. If there
       * is an update to this array (e.g. it must be grown), the sharer will be notified to
       * update its reference.
       */
      public interface CodeSharer {
          public void update(LegacyInstr[] segment);
      }
  
      /**
       * The constructor for the <code>CodeSegment</code> class creates a new code segment, complete
       * with binary and instruction representations.
       * @param name the name of the segment as a string
       * @param size the size of the segment in bytes
       * @param bi the interpreter that will use this segment
       */
      public CodeSegment(String name, int size, AtmelInterpreter bi) {
          super(name, size, DEFAULT_VALUE, bi.state);
          interpreter = bi;
          segment_instr = new LegacyInstr[size];
      }
  
      /**
       * The <code>update()</code> method is called when the program attempts an update
       * to the flash memory through the SPM instruction. This is only supported on some
       * flash memory types.
       */
      public void update() {
          throw Util.failure("Update of flash memory not supported for this segment");
      }
  
      public LegacyInstr[] shareCode(CodeSharer s) {
          codeSharer = s;
          return segment_instr;
      }
  
      /**
       * The <code>load()</code> method loads a program into the flash memory, writing the
       * binary machine code and the disassembled instructions. This should only be done
       * once for a <code>FlashMemory</code> object, before any instrumentation is added.
       * @param p the program to be loaded into the flash memory
       */
      public void load(Program p) {
          Arrays.fill(segment_instr, NO_INSTR);
          for (int cntr = p.program_start; cntr < p.program_end;) {
              LegacyInstr i = (LegacyInstr)p.readInstr(cntr);
              if (i != null) {
                  segment_instr[cntr] = i;
                  cntr += i.getSize();
              } else {
                  cntr += 2;
              }
          }
  
          // now initialize the flash data
          for (int cntr = p.program_start; cntr < p.program_end; cntr++)
              segment_data[cntr] = p.readProgramByte(cntr);
      }
  
      /**
       * The <code>readInstr()</code> method reads an LegacyInstr from the specified address in
       * the flash. For misaligned accesses and accesses to places in the flash where there
       * are no valid instructions, this method returns <code>null</code>. This method does
       * not return <code>ProbedLegacyInstr</code> or <code>DisassembleLegacyInstr</code> objects which
       * are used internally to accomplish probing and dynamically updated code.
       *
       * @param address the address in the flash from which to read the instruction
       * @return a reference to the <code>LegacyInstr</code> object at this address in the flash;
       * <code>null</code> if there is no instruction at this address.
       */
      public LegacyInstr readInstr(int address) {
          try {
              return segment_instr[address].asInstr();
          } catch ( ArrayIndexOutOfBoundsException e) {
              throw new AddressOutOfBoundsException(address);
          }
      }
  
      /**
       * The <code>getInstr()</code> method reads an LegacyInstr from the specified address in
       * the flash. For misaligned accesses and accesses to places in the flash where there
       * are no valid instructions, this method may return instances of <code>MisalignedLegacyInstr</code>
       * or <code>DisassembleLegacyInstr</code> objects which are used internally to check for errors
       * and support dynamically updated code. Additionally, this method may return instances of
       * <code>ProbedLegacyInstr</code> that are used internally to support probing of instructions.
       *
       * @param address the address in the flash from which to read the instruction
       * @return a reference to the <code>LegacyInstr</code> object at this address in the flash;
       * <code>null</code> if there is no instruction at this address.
       */
      public LegacyInstr getInstr(int address) {
          try {
              return segment_instr[address];
          } catch ( ArrayIndexOutOfBoundsException e) {
              throw new AddressOutOfBoundsException(address);
          }
      }
  
      /**
       * The <code>insertProbe()</code> method inserts a probe on an instruction at the
       * specified address. No equality testing is done; i.e. inserting the same probe
       * on the same address more than once will result in it being triggered more than
       * once when the instruction executes.
       * @param address the address of the instruction on which to insert the probe
       * @param p the probe to insert on this instruction
       */
      public void insertProbe(int address, Simulator.Probe p) {
          LegacyInstr instr = getInstr(address);
          if ( instr instanceof ProbedLegacyInstr ) {
              ProbedLegacyInstr pri = (ProbedLegacyInstr)instr;
              pri.add(p);
          } else {
              ProbedLegacyInstr pri = new ProbedLegacyInstr(instr, address);
              pri.add(p);
              writeInstr(address, pri);
          }
      }
  
      /**
       * The <code>removeProbe()</code> method removes a probe from a particular instruction
       * in the program. The probe will no longer be triggered for subsequent executions of
       * this instruction. Reference equality is used for testing whether the probe should be
       * removed; i.e. the <code>Object.equals()</code> method is not consulted.
       * @param address the address of the instructiobn on which to insert the probe
       * @param p the probe to isnert on this instruction
       */
      public void removeProbe(int address, Simulator.Probe p) {
          LegacyInstr instr = getInstr(address);
          if ( instr instanceof ProbedLegacyInstr ) {
              ProbedLegacyInstr pri = (ProbedLegacyInstr)instr;
              pri.remove(p);
          }
      }
  
      protected void writeInstr(int address, LegacyInstr i) {
          segment_instr[address] = i;
      }
  
      /**
       * The ProbedLegacyInstr class represents a wrapper around an instruction in the program that executes the
       * probes before executing the instruction and after the instruction. For most methods on the
       * <code>LegacyInstr</code> class, it simply forwards the call to the original instruction.
       */
      protected class ProbedLegacyInstr extends LegacyInstr {
          protected final int address;
          protected final LegacyInstr instr;
          protected final MulticastProbe probe;
  
          public ProbedLegacyInstr(LegacyInstr i, int a) {
              super(new LegacyInstrProperties(i.properties.name, i.properties.variant, i.properties.size, 0));
              instr = i;
              address = a;
              probe = new MulticastProbe();
          }
  
          public ProbedLegacyInstr(LegacyInstr i, ProbedLegacyInstr prev) {
              super(new LegacyInstrProperties(i.properties.name, i.properties.variant, i.properties.size, 0));
              instr = i;
              address = prev.address;
              probe = prev.probe;
          }
  
          void add(Simulator.Probe p) {
              probe.add(p);
          }
  
          void remove(Simulator.Probe p) {
              probe.remove(p);
          }
  
          boolean isEmpty() {
              return probe.isEmpty();
          }
  
          public void accept(LegacyInstrVisitor v) {
              probe.fireBefore(interpreter.state, address);
              instr.accept(interpreter);
              interpreter.commit();
              probe.fireAfter(interpreter.state, address);
  
              if ( probe.isEmpty() ) {
                  // if the probed instruction has no more probes, remove it altogether
                  writeInstr(address, instr);
              }
          }
  
          public LegacyInstr build(int address, LegacyOperand[] ops) {
              throw Util.failure("ProbedLegacyInstr should be confined to BaseInterpreter");
          }
  
          public String getOperands() {
              return instr.getOperands();
          }
  
          public LegacyInstr asInstr() {
              return instr;
          }
      }
  
      static LegacyInstrProperties NO_INSTR_PROPS = new LegacyInstrProperties("<none>", "<none>", 2, 1);
  
      private class NoLegacyInstr extends LegacyInstr {
  
          NoLegacyInstr() {
              super(NO_INSTR_PROPS);
          }
  
          /**
           * The <code>getOperands()</code> method returns a string representation of the operands of the
           * instruction. This is useful for printing and tracing of instructions as well as generating
           * listings.
           *
           * @return a string representing the operands of the instruction
           */
          public String getOperands() {
              throw Util.failure("no instruction here");
          }
  
          /**
           * The <code>accept()</code> method is part of the visitor pattern for instructions. The visitor
           * pattern uses two virtual dispatches combined with memory overloading to achieve dispatching on
           * multiple types. The result is clean and modular code.
           *
           * @param v the visitor to accept
           */
          public void accept(LegacyInstrVisitor v) {
              throw new InterpreterError.NoSuchInstructionException(interpreter.getState().getPC());
          }
  
          /**
           * The <code>build()</code> method constructs a new <code>LegacyInstr</code> instance with the given
           * operands, checking the operands against the constraints that are specific to each instruction.
           *
           * @param pc  the address at which the instruction will be located
           * @param ops the operands to the instruction
           * @return a new <code>LegacyInstr</code> instance representing the instruction with the given operands
           */
          public LegacyInstr build(int pc, LegacyOperand[] ops) {
              throw Util.failure("no instruction here");
          }
  
          public LegacyInstr asInstr() {
              return null;
          }
      }
  
  }
  