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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;

/** This class provides utilities to deal with Strings.
 * This is used internally by classes in this package.
 * 
 * According to the standard (paragraph 3.3.7 'Message structure' on page 38):
 * Character strings are presented left to right most significant bit first. 
 * All unused characters should be represented by the @ symbol, and they should be placed at the end of the string.
 * 
 * Note that according to TABLE 44 on page 100, @ symbol is a valid character.
 * 
 * We have found no info how to handle the special case that @ is the last character of the string.
 * 
 * @author Pierre America
 * @author Pierre van de Laar
 */
public class UtilsString {
	/** Removes the trailing at signs (@) at the end of a string.
	 * @param orig a string with possibly trailing at signs
	 * @return the string with the at signs at the end removed
	 */
	static public String stripAtSigns (String orig) {
		int x = orig.length()-1;
		int y = -1;
		while (x != y)
		{
			if (orig.charAt(x) == '@')
			{
				x = x -1;
			}
			else
			{
				y = x;
			}
		}
		return orig.substring(0, x+1);
	}

}