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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.impl;

import nl.esi.metis.aisparser.AISMessage19;
import nl.esi.metis.aisparser.Sixbit;
import nl.esi.metis.aisparser.UtilsDimensions30;
import nl.esi.metis.aisparser.UtilsPositioningDevice;
import nl.esi.metis.aisparser.UtilsShipType8;
import nl.esi.metis.aisparser.UtilsSpare;
import nl.esi.metis.aisparser.UtilsString;
import nl.esi.metis.aisparser.annotations.AISIllegalValueAnnotation;
import nl.esi.metis.aisparser.provenance.VDMMessageProvenance;
import cern.colt.bitvector.BitVector;

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

/** Implementation of AIS Message 19:  Extended Class B Equipment Position Report.
 * Several fields are covered by the superclass {@link AISMessageClassBPositionReportImpl}.
 * Here are the remaining fields:
 *  * Field Nr     Field Name                          NrOf Bits   (from, to )
 * ------------------------------------------------------------------------
 * 12           spare2                                     4    ( 140, 143)
 * 13           name                                     120    ( 144, 263)
 * 14           typeOfShipAndCargoType                     8    ( 264, 271)
 * 15           dimension                                 30    ( 272, 301)
 * 16           typeOfElectronicPositionFixingDevice       4    ( 302, 305)
 * 17           raimFlag                                   1    ( 306, 306)
 * 18           dte                                        1    ( 307, 307)
 * 19           assignedModeFlag                           1    ( 308, 308)
 * 20           spare3                                     4    ( 309, 312)
 *                                                      ---- +
 *                           (maximum) number of bits    312
 * 
 * @author Pierre van de Laar
 * @author Pierre America
 * @author Brian C. Lane
 */
class AISMessage19Impl extends AISMessageClassBPositionReportImpl implements AISMessage19 {

	/** The first position of the second set of spare bits. */
	protected static final int SPARE2_FROM = 140;

	/** The last position of the second set of spare bits.
	 * Note that this is different from type 18 messages, 
	 * and therefore not covered by the superclass {@link AISMessageClassBPositionReportImpl}.*/
	protected static final int SPARE2_TO = 143;

	/** The position of the first bit of the name. */
	private static final int NAME_FROM = 144;

	/** The position of the last bit of the name. */
	private static final int NAME_TO = 263;

	/** The name. */
	private String name;

	/** Returns the name of the transmitting ship.
	 * @return a String value, containing maximum 20 characters, representing the name. 

	 * "" = not available.
	 */
	public String getName() { return name; }

	/** The position of the first bit of the type of ship and cargo type. */
	private static final int TYPEOFSHIPANDCARGOTYPE_FROM = 264;

	/** The position of the last bit of the type of ship and cargo type. */
	private static final int TYPEOFSHIPANDCARGOTYPE_TO = 271;

	/** The  type of ship and cargo type. */
	private int typeOfShipAndCargoType;

	/** Returns the type of ship and cargo type. This can be converted to a String by utility class {@link UtilsShipType8}.
	 * @return an integer value representing the type of ship and cargo type: 

	 * 0 = not available or no ship 

	 * 1-99 = as defined in the standard (see {@link UtilsShipType8}) 

	 * 100-199 = reserved for regional use 

	 * 200-255 = reserved for future use  

	 */
	public int getTypeOfShipAndCargoType() { return typeOfShipAndCargoType; }

	/** The position of the first bit of the dimensions. */
	private static final int DIMENSION_FROM = 272;

	/** The position of the last bit of the dimensions. */
	private static final int DIMENSION_TO = 301;

	/** The dimensions. */
	private BitVector dimension;

	/** Returns the dimensions of the ship and the reference point for the reported position.
	 * These can be analyzed further with utility class {@link UtilsDimensions30}.
	 * @return a BitVector value representing the dimensions.
	 */
	public BitVector getDimension() { return dimension; }

	/** The position of the first bit of the electronic position fixing device. */
	private static final int TYPEOFELECTRONICPOSITIONFIXINGDEVICE_FROM = 302;

	/** The position of the last bit of the electronic position fixing device. */
	private static final int TYPEOFELECTRONICPOSITIONFIXINGDEVICE_TO = 305;

	/** The electronic position fixing device. */
	private int typeOfElectronicPositionFixingDevice;

	/** Returns the type of electronic position fixing device.
	 * @return an integer value representing of the type of electronic position fixing device: 

	 * 0 = undefined (default) 

	 * 1 = global positioning system (GPS) 

	 * 2 = GNSS (GLONASS) 

	 * 3 = combined GPS/GLONASS 

	 * 4 = Loran-C 

	 * 5 = Chayka 

	 * 6 = integrated navigation system 

	 * 7 = surveyed 

	 * 8 = Galileo 

	 * 9-14 = not used 

	 * 15 = internal GNSS
	 */
	public int getTypeOfElectronicPositionFixingDevice() { return typeOfElectronicPositionFixingDevice; }

	/** The position of the RAIM flag.
	 * Note that the position of this flag is different for type 18 messages. */
	private static final int RAIMFLAG_BITINDEX = 306;

	/** The position of the DTE status. */
	private static final int DTE_BITINDEX = 307;

	/** The DTE status */
	private boolean dte;
	/** Returns the data terminal equipment (DTE) status.
	 * @return a boolean value describing whether the data terminal equipment is ready: 

	 * false = available 

	 * true = not available
	 */
	public boolean getDte() { return dte; }

	/** The position of the assigned mode flag. 
	 * Note that the position of this flag is different for type 18 messages. */
	private static final int ASSIGNEDMODEFLAG_BITINDEX = 308;

	/** The first position of the third set of spare bits. */
	private static final int SPARE3_FROM = 309;

	/** The last position of the third set of spare bits. */
	private static final int SPARE3_TO = 312;

	/** The value of the third set of spare bits. */
	protected int spare3;

	/** Returns the third set of spare bits.
	 * @return the value of the third set of spare bits. This should be zero.
	 */
	public int getSpare3() { return spare3; }

	/** The length in bytes that a valid AIS message 19 should have */
	public static final int LENGTH = 312;

	/** Checks whether the given number can be the length in bytes of the contents of a valid AIS message 19.
	 * @param length an integer value representing the length of a message in bytes
	 * @return true if this can be the length of a valid AIS message 19
	 */
	public static boolean validLength(int length)
	{
		return (length == LENGTH);
	}
	
	/**
	 * Return the difference in available and needed bits to parse this sixbit as an AISMessage
	 * A positive difference indicates that there are more bits available than needed by the standard.
	 * @param sb
	 * @return
	 */
	public static int differenceInBits(Sixbit sb)
	{
		return (sb.available() - LENGTH);
	}


	/** AISMessage 19 constructor
	 * @param content AIS content
	 * @param prov the provenance of the message
	 * @precondition validLength(content.length()) && AISMessageBase.getMessageId(content)==19
	 */
	public AISMessage19Impl(Sixbit content, VDMMessageProvenance prov)
	{
		super(content, prov);
		assert(validLength(content.length()));
		assert(getMessageID() == 19);

		spare2 = content.getIntFromTo(SPARE2_FROM,SPARE2_TO);
	    if (!UtilsSpare.isSpareSemanticallyCorrect(spare2))
	    {
	    	annotations.add(new AISIllegalValueAnnotation("getSpare2", spare2, UtilsSpare.range));
	    }
		name = UtilsString.stripAtSigns(content.getStringFromTo(NAME_FROM,NAME_TO));
		typeOfShipAndCargoType = content.getIntFromTo(TYPEOFSHIPANDCARGOTYPE_FROM,TYPEOFSHIPANDCARGOTYPE_TO);
		dimension = content.getBitVectorFromTo(DIMENSION_FROM,DIMENSION_TO);
		typeOfElectronicPositionFixingDevice = content.getIntFromTo(TYPEOFELECTRONICPOSITIONFIXINGDEVICE_FROM,TYPEOFELECTRONICPOSITIONFIXINGDEVICE_TO);
		raimFlag = content.getBoolean(RAIMFLAG_BITINDEX);
		dte = content.getBoolean(DTE_BITINDEX);
		assignedModeFlag = content.getBoolean(ASSIGNEDMODEFLAG_BITINDEX);
		spare3 = content.getIntFromTo(SPARE3_FROM,SPARE3_TO);
	    if (!UtilsSpare.isSpareSemanticallyCorrect(spare3))
	    {
	    	annotations.add(new AISIllegalValueAnnotation("getSpare3", spare3, UtilsSpare.range));
	    }
	}
	
	/** Generates a String representing the AIS message. 
	 * Format: all fields are shown in the order and units as specified by the standard separated by the SEPARATOR string.
	 */
	@Override
	public String toString () {
		String result = super.toString();
		result += SEPARATOR + name;
		result += SEPARATOR + UtilsShipType8.shipTypeToString(typeOfShipAndCargoType);
		result += SEPARATOR + UtilsDimensions30.toString(dimension);
		result += SEPARATOR + UtilsPositioningDevice.toString(typeOfElectronicPositionFixingDevice);
		result += SEPARATOR + "RAIM " + (raimFlag ? "in use" : "not in use");
		result += SEPARATOR + (dte ? "no DTE" : "with DTE");
		result += SEPARATOR + (assignedModeFlag ? "assigned" : "autonomous") + " mode";
		return result;		
	}
}