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A Mode S and ADS-B decoding library for Java
There is a newer version: 3.4.0
package org.opensky.libadsb;

/*
 *  This file is part of org.opensky.libadsb.
 *
 *  org.opensky.libadsb is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  org.opensky.libadsb is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with org.opensky.libadsb.  If not, see .
 */

/**
 * Some useful functions when working with libadsb. Mostly we need these
 * functions since the library often works with arrays of bytes which are
 * not really readable for humans or basic operations are missing.
 * @author Matthias Schäfer ([email protected])
 */
public class tools {
	private static final char[] hexDigits =
			{'0', '1', '2', '3', '4', '5', '6', '7',
					'8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

	/**
	 * Converts a byte into a hex string (e.g. 164 -> "a4")
	 * @param b input byte
	 * @return hex representation of input byte
	 */
	public static String toHexString(byte b) {
		final char[] out = new char[2];
		out[0] = hexDigits[(0xF0 & b) >>> 4];
		out[1] = hexDigits[0x0F & b];
		return new String(out);
	}


	/**
	 * Converts an array of bytes in a hex string; Taken from 
	 * org.apache.commons.codec.binary.Hex.
	 * @param bytes array of bytes
	 * @return concatenated hex representation of input byte array
	 */
	public static String toHexString(byte[] bytes) {
		final int l = bytes.length;
		final char[] out = new char[l << 1];

		for (int i = 0, j = 0; i < l; i++) {
			out[j++] = hexDigits[(0xF0 & bytes[i]) >>> 4];
			out[j++] = hexDigits[0x0F & bytes[i]];
		}
		return new String(out);
	}

	/**
	 * Converts a hex string to an array of bytes.

	 * Source: https://stackoverflow.com/a/140861/3485023
	 * @param str the hex string to convert
	 * @return the byte array
	 */
	public static byte[] hexStringToByteArray(String str) {
		int len = str.length();
		byte[] data = new byte[len / 2];
		for (int i = 0; i < len; i += 2) {
			data[i / 2] = (byte) ((Character.digit(str.charAt(i), 16) << 4)
					+ Character.digit(str.charAt(i+1), 16));
		}
		return data;
	}

	/**
	 * Compares two byte arrays element by element
	 * @param array1 first array
	 * @param array2 second array
	 * @return array1 == array2
	 */
	public static boolean areEqual(byte[] array1, byte[] array2) {
		if (array1.length != array2.length) return false;

		for (int i=0; i