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This package supports the parsing of AIS messages in Java. AIS, the Automatic Identification System, is a system aiming at improving maritime safety by exchanging messages between ships, other vehicles in particular aircraft involved in search-and-rescue (SAR), and (fixed) base stations. To be precise, this package support the ITU-R M.1371-4 AIS standard. See our extensive javadoc and in particular the class AISParser for more information on how to use this package. The parser was used in the Poseidon project, and is improved in the Metis project to better handle uncertain information. Both projects were led by the Embedded Systems Institute. In both projects Thales Nederlands was the carrying industrial partner, and multiple Dutch universities participated.

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package nl.esi.metis.aisparser;

import cern.colt.bitvector.BitVector;

/* ESI AIS Parser
 * 
 * Copyright 2011/2012 by Pierre van de Laar (Embedded Systems Institute)
 * Copyright 2008 by Brian C. Lane 
 * All Rights Reserved
 */

/** This class provides functions to get the individual components of the dimensions BitVector that is returned by 
 * {@link AISMessage05#getDimension} or {@link AISMessage19#getDimension()}.
 * Together these components specify the size of the ship and the place of the reference point of which the position is reported in AIS messages.
 * 
 * @author Pierre van de Laar
 * @author Pierre America
 * @author Brian C. Lane
 */

/*  * Field Nr     Field Name                          NrOf Bits   (from, to )
 * ------------------------------------------------------------------------
 *  1	bow                                     	   9	(  21,  29)
 *  2	stern                                   	   9	(  12,  20)
 *  3	port                                    	   6	(   6,  11)
 *  4	starboard                               	   6	(   0,   5)
 *                                                    ---- +
 *                        (maximum) number of bits    30
 * 
 */
public class UtilsDimensions30 {
	
	/** The position of the first bit of the bow component. */
	private static final int BOW_FROM = 21;

	/** The position of the last bit of the bow component. */
	private static final int BOW_TO = 29;

	/** Returns the distance from the reference point to the bow of the ship.
	 * @param dimension a {@code BitVector} containing the dimensions of the ship, as returned by
     * {@link AISMessage05#getDimension} or {@link AISMessage19#getDimension()}.
	 * @return > 0: the distance from the reference point to the bow in meters 

	 *         0: reference point not available, in which case the stern component could indicate the length of the ship or be zero as well.
	 */
	public static int getBow(BitVector dimension) { 
		return (int)dimension.getLongFromTo(BOW_FROM,BOW_TO); 
	}

	/** The position of the first bit of the stern component. */
	private static final int STERN_FROM = 12;

	/** The position of the last bit of the stern component. */
	private static final int STERN_TO = 20;

	/** Returns the distance from the reference point to the stern of the ship.
	 * @param dimension a {@code BitVector} containing the dimensions of the ship, as returned by
     * {@link AISMessage05#getDimension} or {@link AISMessage19#getDimension()}.
	 * @return > 0: the distance from the reference point to the stern in meters or, if the bow component is zero, the length of the ship 

	 *         0: ship size and reference point not available, in which case the bow component should be zero as well.
	 */
	public static int getStern(BitVector dimension) { 
		return (int) dimension.getLongFromTo(STERN_FROM,STERN_TO);
	}

	/** The position of the first bit of the port component. */
	private static final int PORT_FROM = 6;

	/** The position of the last bit of the port component. */
	private static final int PORT_TO = 11;

	/** Returns the distance from the reference point to the port side of the ship.
	 * @param dimension a {@code BitVector} containing the dimensions of the ship, as returned by
     * {@link AISMessage05#getDimension} or {@link AISMessage19#getDimension()}.
	 * @return > 0: the distance from the reference point to the port side in meters 

	 *         0: reference point not available, in which case the starboard component could indicate the width of the ship or be zero as well.
	 */
	public static int getPort(BitVector dimension) { 
		return (int)dimension.getLongFromTo(PORT_FROM,PORT_TO);
	}
	
	/** The position of the first bit of the starboard component. */
	private static final int STARBOARD_FROM = 0;

	/** The position of the first bit of the starboard component. */
	private static final int STARBOARD_TO = 5;

	/** Returns the distance from the reference point to the starboard side of the ship.
	 * @param dimension a {@code BitVector} containing the dimensions of the ship, as returned by
     * {@link AISMessage05#getDimension} or {@link AISMessage19#getDimension()}.
	 * @return  > 0: the distance from the reference point to the starboard in meters or, if the port component is zero, the width of the ship 

	 *          0: ship size and reference point not available, in which case the port component should be zero as well.
	 */
	public static int getStarboard(BitVector dimension) {
		return (int) dimension.getLongFromTo(STARBOARD_FROM,STARBOARD_TO);
	}
	
	/** Returns a string representing the components of the given dimensions.
	 * The components are separated by commas, in the order: bow, stern, port, starboard.
	 * @param dimension a {@code BitVector} containing the dimensions of the ship, as returned by
     * {@link AISMessage05#getDimension} or {@link AISMessage19#getDimension()}.
	 * @return a string representing the dimensions
	 */
	public static String toString(BitVector dimension) {
		int bow = getBow(dimension);
		int stern = getStern(dimension);
		int port = getPort(dimension);
		int starboard = getStarboard(dimension);
		String result = bow + "," + stern + "," + port + "," + starboard;
		return result;
	}

	/** This constructor is made private to indicate that clients should not construct instances of this class. */
	private UtilsDimensions30 () {
	}
}