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.platform;
  
  import avrora.sim.Simulator;
  import avrora.sim.clock.Clock;
  import avrora.sim.mcu.SPI;
  import avrora.sim.mcu.SPIDevice;
  import cck.text.Terminal;
  import cck.util.Util;
  import java.io.*;
  import java.net.ServerSocket;
  import java.net.Socket;
  
  /**
   * The <code>SerialForwarder</code> class implements a serial forwarder that takes traffic to and from a socket and
   * directs it into the UART chip of a simulated device.
   *
   * @author Olaf Landsiedel
   * @author Ben L. Titzer
   */
  public class SPIForwarder implements SPIDevice {
  
      public static final int BPS = 2400;
  
      private ServerSocket serverSocket;
      protected int portNumber;
      private Socket socket;
  
      private OutputStream out;
      private InputStream in;
  
      private SPI spi;
      private SFTicker ticker;
      private byte[] buffer;
      protected int bitsPerSecond;
  
      public SPIForwarder(SPI spdv, int pn, int bps, boolean master) {
          spdv.connect(this);
  
          spi = spdv;
          portNumber = pn;
          bitsPerSecond = bps;
          buffer = new byte[1];
  
          if ( master ) {
              ticker = new SFTicker(spdv.getClock());
              ticker.start();
          }
  
          try {
              serverSocket = new ServerSocket(portNumber);
              Terminal.print("Waiting for spi connection on port " + portNumber + "...");
              Terminal.flush();
              socket = serverSocket.accept();
              Terminal.println("connected to " + socket.getRemoteSocketAddress());
              out = socket.getOutputStream();
              in = socket.getInputStream();
          } catch (IOException e) {
              throw Util.unexpected(e);
          }
      }
  
  
      public SPI.Frame nextFrame() {
          try {
              // called when we are expected to supply data to the SPI.
              byte data = 0;
              if ( in.available() > 0 ) {
                  // if there is something available in the socket, transfer it
                  if ( in.read(buffer, 0, 1) > 0 ) data = buffer[0];
              }
              return SPI.newFrame(data);
          } catch (IOException e) {
              throw Util.unexpected(e);
          }
      }
  
  
      public SPI.Frame exchange(SPI.Frame frame) {
          try {
              receive(frame);
              return nextFrame();
          } catch (IOException e) {
              throw Util.unexpected(e);
          }
      }
  
      private void receive(SPI.Frame frame) throws IOException {
          out.write(frame.data);
      }
  
      public void connect(SPIDevice d) {
          // do nothing.
      }
  
      private class SFTicker implements Simulator.Event {
  
          private final long delta;
          private final Clock clock;
  
          SFTicker(Clock c) {
              delta = c.getHZ() / bitsPerSecond;
              clock = c;
          }
  
          public void fire() {
              try {
                  if (in.available() >= 1) {
                      // send our frame to the SPI
                      receive(spi.exchange(nextFrame()));
                  }
              } catch (IOException e) {
                  throw Util.unexpected(e);
              }
              clock.insertEvent(this, delta);
          }
  
          void start() {
              clock.insertEvent(this, delta);
          }
      }
  }
  