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There is a newer version: 3.6.2_1

// Copyright (c) 1999-2004 Brian Wellington ([email protected])

package org.xbill.DNS.utils;

import java.io.*;

/**
 * Routines for converting between Strings of hex-encoded data and arrays of
 * binary data.  This is not actually used by DNS.
 *
 * @author Brian Wellington
 */

public class base16 {

private static final String Base16 = "0123456789ABCDEF";

private
base16() {}

/**
 * Convert binary data to a hex-encoded String
 * @param b An array containing binary data
 * @return A String containing the encoded data
 */
public static String
toString(byte [] b) {
	ByteArrayOutputStream os = new ByteArrayOutputStream();

	for (int i = 0; i < b.length; i++) {
		short value = (short) (b[i] & 0xFF);
		byte high = (byte) (value >> 4);
		byte low = (byte) (value & 0xF);
		os.write(Base16.charAt(high));
		os.write(Base16.charAt(low));
	}
	return new String(os.toByteArray());
}

/**
 * Convert a hex-encoded String to binary data
 * @param str A String containing the encoded data
 * @return An array containing the binary data, or null if the string is invalid
 */
public static byte []
fromString(String str) {
	ByteArrayOutputStream bs = new ByteArrayOutputStream();
	byte [] raw = str.getBytes();
	for (int i = 0; i < raw.length; i++) {
		if (!Character.isWhitespace((char)raw[i]))
			bs.write(raw[i]);
	}
	byte [] in = bs.toByteArray();
	if (in.length % 2 != 0) {
		return null;
	}

	bs.reset();
	DataOutputStream ds = new DataOutputStream(bs);

	for (int i = 0; i < in.length; i += 2) {
		byte high = (byte) Base16.indexOf(Character.toUpperCase((char)in[i]));
		byte low = (byte) Base16.indexOf(Character.toUpperCase((char)in[i+1]));
		try {
			ds.writeByte((high << 4) + low);
		}
		catch (IOException e) {
		}
	}
	return bs.toByteArray();
}

}