/*
 *                             Sun Public License
 *
 * The contents of this file are subject to the Sun Public License Version
 * 1.0 (the "License").  You may not use this file except in compliance with
 * the License.  A copy of the License is available at http://www.sun.com/
 *
 * The Original Code is the SLAMD Distributed Load Generation Engine.
 * The Initial Developer of the Original Code is Neil A. Wilson.
 * Portions created by Neil A. Wilson are Copyright (C) 2004-2010.
 * Some preexisting portions Copyright (C) 2002-2006 Sun Microsystems, Inc.
 * All Rights Reserved.
 *
 * Contributor(s):  Neil A. Wilson
 */
package com.slamd.protocol;



import java.util.HashMap;

import com.slamd.asn1.ASN1Element;
import com.slamd.asn1.ASN1Null;
import com.slamd.common.SLAMDException;



/**
 * This class defines a SLAMD message with no real payload, which is used to
 * ensure that the communication between the client and the server remains
 * valid.  It can be used to help prevent network hardware from "timing out" an
 * idle connection, and it can also be used to verify that an existing
 * connection is still valid (because an error would be generated if the attempt
 * to send it failed).
 *
 *
 * @author   Neil A. Wilson
 */
public class KeepAlive
       extends SLAMDMessage
{
  /**
   * Creates a new instance of this keepalive message with the provided
   * information.
   *
   * @param  messageID        The message ID for this SLAMD message.
   * @param  extraProperties  The "extra" properties for this SLAMD message.
   *                          Both the names and values for the properties must
   *                          be strings.
   */
  public KeepAlive(int messageID, HashMap<String,String> extraProperties)
  {
    super(messageID, extraProperties);
  }



  /**
   * Encodes the payload component of this SLAMD message to an ASN.1 element for
   * inclusion in the message envelope.
   *
   * @return  The ASN.1 element containing the encoded message payload.
   */
  @Override()
  public ASN1Element encodeMessagePayload()
  {
    // There is no real payload for a keepalive message.

    return new ASN1Null();
  }



  /**
   * Decodes the provided ASN.1 element and uses it as the payload for this
   * SLAMD message.
   *
   * @param  payloadElement  The ASN.1 element to decode as the payload for this
   *                         SLAMD message.
   *
   * @throws  SLAMDException  If a problem occurs while attempting to decode the
   *                          provided ASN.1 element as the payload for this
   *                          SLAMD message.
   */
  @Override()
  public void decodeMessagePayload(ASN1Element payloadElement)
         throws SLAMDException
  {
    // No action is required, since there should not be any real payload.
  }



  /**
   * Appends a string representation of the payload for this SLAMD message to
   * the provided buffer.  The string representation may contain multiple lines,
   * but the last line should not end with an end-of-line marker.
   *
   * @param  buffer  The buffer to which the string representation is to be
   *                 appended.
   * @param  indent  The number of spaces to indent the payload content.
   */
  @Override()
  public void payloadToString(StringBuilder buffer, int indent)
  {
    // No action is required, since there is no payload.
  }
}