// $Id: Message.java,v 1.6 2007/05/29 16:44:50 rincon Exp $

/*									tab:4
 * "Copyright (c) 2000-2003 The Regents of the University  of California.  
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice, the following
 * two paragraphs and the author appear in all copies of this software.
 * 
 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
 * CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
 *
 * Copyright (c) 2002-2003 Intel Corporation
 * All rights reserved.
 *
 * This file is distributed under the terms in the attached INTEL-LICENSE     
 * file. If you do not find these files, copies can be found by writing to
 * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300, Berkeley, CA, 
 * 94704.  Attention:  Intel License Inquiry.
 */
/* Authors:  David Gay  <dgay@intel-research.net>
 *           Intel Research Berkeley Lab
 *
 */

/**
 * Message class (encode/decode tinyos messages).<p>
 *
 * The base class for encoding and decoding tinyos messages.  Provides
 * methods to read and write bit fields at an offset for a particular bit
 * length.  Intended for use by the Java code generated by mig.
 *
 * @version	1, 15 Jul 2002
 * @author	David Gay
 * @author David Gay <dgay@intel-research.net>
 * @author Intel Research Berkeley Lab
 */
package net.tinyos.message;

public class Message implements Cloneable {

  /**
   * The maximum number of characters read from an 8-bit array field being
   * converted into a Java String.
   */
  public static final int MAX_CONVERTED_STRING_LENGTH = 512;

  /**
   * The underlying byte array storing the data for this message. This is
   * private to enforce access to the data through the accessor methods in this
   * class, which do bounds checking and manage the base_offset for embedded
   * messages.
   */
  private byte[] data;

  /**
   * The base offset into the data. This allows the message data to exist at
   * some non-zero offset into the actual data.
   */
  protected int base_offset;

  /**
   * The actual length of the message data. Must be less than or equal to
   * (data.length - base_offset).
   */
  protected int data_length;

  /**
   * The AM type corresponding to this object. Set to -1 if no AM type is known.
   */
  protected int am_type;

  /** The serial packet this message originated from */
  private SerialPacket serialPacket;
  
  /** Limit no-arg instantiation. */
  protected Message() {
  }

  /**
   * Construct a new message of the given size.
   * 
   * @param data_length
   *          The size of the message to create.
   */
  public Message(int data_length) {
    init(data_length);
  }

  public void init(int data_length) {
    init(new byte[data_length]);
  }

  /**
   * Construct a new message of the given size and base offset. Allocates a new
   * byte array of size data_length+base_offset.
   * 
   * @param data_length
   *          The size of the message to create.
   * @param base_offset
   *          The base offset into the newly created message.
   */
  public Message(int data_length, int base_offset) {
    init(data_length, base_offset);
  }

  protected void init(int data_length, int base_offset) {
    init(new byte[data_length + base_offset], base_offset);
  }

  /**
   * Construct a message using data as the storage. The length of data
   * determines the length of this message.
   * 
   * @param data
   *          the storage for this message
   */
  public Message(byte[] data) {
    init(data);
  }

  protected void init(byte[] data) {
    init(data, 0);
  }

  /**
   * Construct a message using data as the storage. Use the given base_offset as
   * the base offset into the data array. The data length will be (data.length -
   * base_offset).
   * 
   * @param data
   *          the storage for this message
   * @param base_offset
   *          the base offset into the data array
   */
  public Message(byte[] data, int base_offset) {
    init(data, base_offset);
  }

  protected void init(byte[] data, int base_offset) {
    init(data, base_offset, data.length - base_offset);
  }

  /**
   * Construct a message using data as the storage. Use the given base_offset as
   * the base offset into the data array, and the specified data length.
   * 
   * @param data
   *          the storage for this message
   * @param base_offset
   *          the base offset into the data array
   * @param data_length
   *          the length of the message data
   */
  public Message(byte[] data, int base_offset, int data_length) {
    init(data, base_offset, data_length);
  }

  protected void init(byte[] data, int base_offset, int data_length) {
    this.data = data;
    this.base_offset = base_offset;
    this.data_length = data_length;
    if (base_offset + data_length > data.length)
      throw new ArrayIndexOutOfBoundsException(
          "Cannot create Message with base_offset " + base_offset
              + ", data_length " + data_length + " and data array size "
              + data.length);
  }

  /**
   * Construct an embedded message within the given 'msg'. Use the given
   * base_offset as the base offset into the data array, and the specified data
   * length.
   * 
   * @param msg
   *          the message to embed this message into
   * @param base_offset
   *          the base offset into the data array
   * @param data_length
   *          the length of the message data
   */
  public Message(Message msg, int base_offset, int data_length) {
    init(msg, base_offset, data_length);
  }

  protected void init(Message msg, int base_offset, int data_length) {
    init(msg.dataGet(), msg.base_offset + base_offset, data_length);
  }

  private Message cloneself() {
    Message copy;

    try {
      copy = (Message) super.clone();
    } catch (CloneNotSupportedException e) {
      System.err
          .println("Message: WARNING: CloneNotSupportedException in cloneself(): "
              + e);
      System.err
          .println("Message: This is a bug - please contact dgay@intel-research.net");
      copy = null;
      System.exit(2);
    }
    return copy;
  }

  /**
   * Clone this Message, including making a copy of its data
   */
  public Object clone() {
    Message copy = cloneself();
    copy.init((byte[]) data.clone(), base_offset, data_length);
    copy.am_type = this.am_type;
    return copy;
  }

  /**
   * Clone this Message, but give it a new unitialised data array of size size
   * 
   * @param size
   *          size of the new data array
   */
  public Message clone(int size) {
    Message copy = cloneself();
    copy.init(new byte[size], 0, size);
    copy.am_type = this.am_type;
    return copy;
  }

  /**
   * Copy new data for this message from 'data'. Copies min(data.length,
   * this.data_length) bytes.
   * 
   * @param data
   *          the array containing the data to be copied
   * @exception ArrayIndexOutOfBoundsException
   *              if any of data[0..getData().length - 1] are invalid
   */
  public void dataSet(byte[] data) {
    dataSet(data, 0, this.base_offset, Math.min(this.data_length, data.length));
  }

  /**
   * Copy new data for this message from offsetFrom in data to offsetTo in this
   * message. Copies a total of length bytes
   * 
   * @param data
   *          the array containing the data to be copied
   * @param offsetFrom
   *          the offset in data to start copying from
   * @param offsetTo
   *          the offset at which to start copying data into this message.
   * @param length
   *          bytes are copied.
   * @exception ArrayIndexOutOfBoundsException
   *              if any of the source or target indices are invalid
   */
  public void dataSet(byte[] data, int offsetFrom, int offsetTo, int length) {
    System.arraycopy(data, offsetFrom, this.data, offsetTo + base_offset,
        length);
  }

  /**
   * Copy new data for this message from the raw data in msg to offsetTo in this
   * message. Copies a total of msg.dataLength() bytes
   * 
   * @param msg
   *          the message containing the data to be copied
   * @param offsetTo
   *          the offset at which to start copying data into this message.
   * @exception ArrayIndexOutOfBoundsException
   *              if any of the target indices are invalid
   */
  public void dataSet(Message msg, int offsetTo) {
    System.arraycopy(msg.dataGet(), msg.baseOffset(), this.data, offsetTo
        + base_offset, msg.dataLength());
  }

  /**
   * Return the raw byte array representing the data of this message. Note that
   * only indices in the range (this.baseOffset(),
   * this.baseOffset()+this.dataLength()) are valid.
   */
  public byte[] dataGet() {
    return data;
  }

  /**
   * Return the base offset into the data array for this message.
   */
  public int baseOffset() {
    return base_offset;
  }

  /**
   * Return the length of the data (in bytes) contained in this message.
   */
  public int dataLength() {
    return data_length;
  }

  /**
   * Return the active message type of this message (-1 if unknown)
   */
  public int amType() {
    return am_type;
  }

  /**
   * Set the active message type of this message
   */
  public void amTypeSet(int type) {
    this.am_type = type;
  }

  // Check that length bits from offset are in bounds
  private void checkBounds(int offset, int length) {
    if (offset < 0 || length <= 0 || offset + length > (data_length * 8))
      throw new ArrayIndexOutOfBoundsException(
          "Message.checkBounds: bad offset (" + offset + ") or length ("
              + length + "), for data_length " + data_length + " in class "
              + this.getClass());
  }

  // Check that value is valid for a bitfield of length length
  private void checkValue(int length, long value) {
    if (length != 64 && (value < 0 || value >= 1L << length))
      throw new IllegalArgumentException("Message.checkValue: bad length ("
          + length + " or value (" + value + ")");
  }

  // Unsigned byte read
  private int ubyte(int offset) {
    int val = data[base_offset + offset];