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.sim.util.MulticastWatch;
  import cck.text.StringUtil;
  import cck.util.Util;
  import java.util.Arrays;
  
  /**
   * The <code>Segment</code> class represents a segment of byte-addressable memory that
   * supports probing. It is used to represent the SRAM, the flash, and the EEPROM. For
   * efficiency, it allows sharing of the underlying byte array representing the memory.
   *
   * @author Ben L. Titzer
   */
  public class Segment {
  
      public final int length;
  
      protected final State state;
      public final String name;
      public final byte value;
      protected byte[] segment_data;
      protected MulticastWatch[] segment_watches;
      protected MulticastWatch error_watch;
  
      protected Sharer sharer;
  
      /**
       * The constructor for the <code>Segment</code> class creates an object that represents this segment.
       * The segment is byte-addressable and allows watches to be placed on individual bytes in memory.
       * @param name the name of the segment as a string
       * @param size the size of the segment in bytes
       * @param defvalue the default value of bytes in this segment
       * @param st the state object to pass to watches when fired
       */
      public Segment(String name, int size, byte defvalue, State st) {
          this.name = name;
          this.length = size;
          this.value = defvalue;
          this.segment_data = new byte[size];
          this.state = st;
  
          // if the default value is something other than zero, initialize the array
          if ( defvalue != 0 ) Arrays.fill(segment_data, defvalue);
      }
  
      /**
       * The <code>Sharer</code> interface must be implemented by a class that needs to
       * share the underlying data representation for efficiency reasons. Whenever the
       * reference to the underlying data is changed (i.e. the array is resized), the
       * sharer will be notified and it must update its reference.
       */
      public interface Sharer {
          public void update(byte[] segment);
      }
  
      /**
       * The <code>AddressOutOfBoundsException</code> class represents an error when
       * using the <code>get()</code> and <code>set()</code> methods where the user
       * specifies an address that is out of the bounds of the segment. Note that this
       * exception is not thrown in the case of <code>read()</code> and <code>write()</code>
       * methods making accesses out of bounds; in that case, the <code>ErrorReporter</code>
       * object is consulted.
       */
      public class AddressOutOfBoundsException extends Util.Error {
          private static final long serialVersionUID = 1L;
          public final int data_addr;
  
          protected AddressOutOfBoundsException(int da) {
              super("Segment access error", "illegal access of "+ StringUtil.quote(name) + " at " + StringUtil.addrToString(da));
              this.data_addr = da;
          }
      }
  
      /**
       * The <code>share()</code> method allows sharing of the underlying array representing the values of
       * memory. This is used for performance.
       * @param s the sharer to allow access to this segment's internal data
       * @return the byte array that is the underlying representation of the memory
       */
      public byte[] share(Sharer s) {
          sharer = s;
          return segment_data;
      }
  
      /**
       * The <code>read()</code> method of the segment reads a byte from a location in the segment,
       * firing any watches on the address before and after the read. This is intended to be called
       * ONLY by the interpreter and device implementations, and NOT by other parts of the simulation
       * that simply want to inspect the state of simulation. A call to the <code>read()</code> method
       * will result in a call to the <code>readError()</code> method of the <code>ErrorReporter</code>
       * object associated with this segment if the access is not within the bounds of the segment.
       * @param address the address in the segment from which to read the byte
       * @return the byte value at this location
       */
      public byte read(int address) {
          MulticastWatch p;
          // FAST PATH 1: no watches
          if ( segment_watches == null ) {
              return checked_read(address);
          }
  
          // FAST PATH 2: no watches for this address
          p = segment_watches[address];
          if ( p == null) {
              return checked_read(address);
          }
  
          // SLOW PATH: consult with memory watches
          p.fireBeforeRead(state, address);
          byte val = checked_read(address);
          p.fireAfterRead(state, address, val);
          return val;
      }
  
      /**
       * The <code>checked_read()</code> method simply reads from the segment's array representing the
       * actual raw values of memory. It will catch out of bounds accesses and notify the
       * <code>ErrorReporter</code> instance for this segment.
       * @param address the address in the segment from which to read the byte
       * @return the byte value at this location if the access is within the bounds of the segment; the
       * result of the <code>readError()</code> method of the <code>ErrorReporter</code> object associated
       * with this segment otherwise
       */
      private byte checked_read(int address) {
          try {
              return direct_read(address);
          } catch ( ArrayIndexOutOfBoundsException e ) {
              if ( error_watch != null ) error_watch.fireBeforeRead(state, address);
              return this.value;
          }
      }
  
      /**
       * The <code>direct_read()</code> method accesses the actual values stored in the segment, after
       * watches and instrumentation have been applied. It is intended to be used ONLY internally to the
       * segment. It is protected to allow architecture-specific implementations such as sparse memories
       * or memory mapped IO.
       * @param address the address in the segment to read
       * @return the value of the of segment at the specified address
       */
      protected byte direct_read(int address) {
          return segment_data[address];
      }
  
      /**
       * The <code>get()</code> method simply retrieves the value of a byte at a particular location in the
       * segment. This method will NOT result in triggering any watches installed for this address. This method
       * is intended for use by user code outside of the simulation (such as probes and watches) to inspect
       * the values in this segment.
       * @param address the address in the segment for which to retrieve the value
       * @return the value of the byte at the specified location, without triggering any monitors on this location
       * @throws AddressOutOfBoundsException if the specified address is not within the bounds of this segment
       */
      public byte get(int address) {
          try {
              return direct_read(address);
          } catch (ArrayIndexOutOfBoundsException e) {
              throw new AddressOutOfBoundsException(address);
          }
      }
  
      /**
       * The <code>write()</code> method of the segment writes a byte to a location in the segment,
       * firing any watches on the address before and after the write. This is intended to be called
       * ONLY by the interpreter and device implementations, and NOT by other parts of the simulation
       * that want to alter the state of the simulation. A call to the <code>write()</code> method
       * will result in a call to the <code>writeError()</code> method of the <code>ErrorReporter</code>
       * object associated with this segment if the access is not within the bounds of the segment.
       * @param address the address in the segment which should be written
       * @param val the value to write to the location in the segment
       */
      public void write(int address, byte val) {
          MulticastWatch p;
          // FAST PATH 1: no watches
          if ( segment_watches == null ) {
              checked_write(address, val);
              return;
          }
  
          // FAST PATH 2: no watches for this address
          p = segment_watches[address];
          if ( p == null) {
              checked_write(address, val);
              return;
          }
  
          // SLOW PATH: consult with memory watches
          p.fireBeforeWrite(state, address, val);
          checked_write(address, val);
          p.fireAfterWrite(state, address, val);
      }
  
      /**
       * The <code>checked_write()</code> method simply writes to the segment's array representing the
       * actual raw values of memory. It will catch out of bounds accesses and notify the
       * <code>ErrorReporter</code> instance for this segment.
       * @param address the address in the segment which should be written
       * @param val the value to write to this byte in memory
       */
      private void checked_write(int address, byte val) {
          try {
              direct_write(address, val);
          } catch (ArrayIndexOutOfBoundsException e) {
              if ( error_watch != null ) error_watch.fireBeforeWrite(state, address, val);
          }
      }
  
      /**
       * The <code>direct_write()</code> method writes the value directly into the array. This
       * method is protected and is ONLY used internally. It is protected to allow architecture-
       * specific implementations such as segments that are not contiguous, contain active register
       * ranges, etc.
       * @param address the address to write
       * @param val the value to write into the segment
       */
      protected void direct_write(int address, byte val) {
          segment_data[address] = val;
      }
  
      /**
       * The <code>set()</code> method simply sets the value of a byte at a particular location in the
       * segment. This method will NOT result in triggering any watches installed for this address. This method
       * is intended for use by code outside of the simulation (such as probes and watches) to alter the
       * state of the memory segment, which should not be done by user code.
       * @param address the address in the segment which should be written
       * @param val the value to write to this byte in memory
       * @throws AddressOutOfBoundsException if the specified address is not within the bounds of this segment
       */
      public void set(int address, byte val) {
          try {
              direct_write(address, val);
          } catch (ArrayIndexOutOfBoundsException e) {
              throw new AddressOutOfBoundsException(address);
          }
      }
  
      /**
       * The <code>insertWatch()</code> allows user code to insert a watch on a particular memory location.
       * The watch will be triggered when a <code>read()</code> or <code>write()</code> to the memory location
       * occurs in during simulation.
       * @param data_addr the address of the byte in memory for which to insert the watch
       * @param p the watch to insert on the memory byte
       */
      public void insertWatch(int data_addr, Simulator.Watch p) {
          if (segment_watches == null)
              segment_watches = new MulticastWatch[length];
  
          // add the probe to the multicast probe present at the location (if there is one)
          MulticastWatch mcw = segment_watches[data_addr];
          if (mcw == null) mcw = segment_watches[data_addr] = new MulticastWatch();
          mcw.add(p);
      }
  
      public void insertErrorWatch(Simulator.Watch p) {
          if (error_watch == null) error_watch = new MulticastWatch();
          error_watch.add(p);
      }
  
      /**
       * The <code>removeWatch()</code> removes a watch on a particular memory location.
       * The watch will no longer be triggered for subseqent <code>read()</code>s or <code>write()</code>s
       * occur in during simulation. Reference equality is used to match watches, and NOT <code>Object.equals()</code>.
       * @param data_addr the address of the byte in memory for which to remove the watch
       * @param p the watch to remove
       */
      public void removeWatch(int data_addr, Simulator.Watch p) {
          if (segment_watches == null)
              return;
  
          // remove the probe from the multicast probe present at the location (if there is one)
          MulticastWatch w = segment_watches[data_addr];
          if (w == null) return;
          w.remove(p);
      }
  }
  