Java tutorial
package org.bouncycastle.util.encoders; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.OutputStream; import org.bouncycastle.util.Strings; /** * Utility class for converting hex data to bytes and back again. */ public class Hex { private static final HexEncoder encoder = new HexEncoder(); public static String toHexString(byte[] data) { return toHexString(data, 0, data.length); } public static String toHexString(byte[] data, int off, int length) { byte[] encoded = encode(data, off, length); return Strings.fromByteArray(encoded); } /** * encode the input data producing a Hex encoded byte array. * * @return a byte array containing the Hex encoded data. */ public static byte[] encode(byte[] data) { return encode(data, 0, data.length); } /** * encode the input data producing a Hex encoded byte array. * * @return a byte array containing the Hex encoded data. */ public static byte[] encode(byte[] data, int off, int length) { ByteArrayOutputStream bOut = new ByteArrayOutputStream(); try { encoder.encode(data, off, length, bOut); } catch (Exception e) { throw new EncoderException("exception encoding Hex string: " + e.getMessage(), e); } return bOut.toByteArray(); } /** * Hex encode the byte data writing it to the given output stream. * * @return the number of bytes produced. */ public static int encode(byte[] data, OutputStream out) throws IOException { return encoder.encode(data, 0, data.length, out); } /** * Hex encode the byte data writing it to the given output stream. * * @return the number of bytes produced. */ public static int encode(byte[] data, int off, int length, OutputStream out) throws IOException { return encoder.encode(data, off, length, out); } /** * decode the Hex encoded input data. It is assumed the input data is valid. * * @return a byte array representing the decoded data. */ public static byte[] decode(byte[] data) { ByteArrayOutputStream bOut = new ByteArrayOutputStream(); try { encoder.decode(data, 0, data.length, bOut); } catch (Exception e) { throw new DecoderException("exception decoding Hex data: " + e.getMessage(), e); } return bOut.toByteArray(); } /** * decode the Hex encoded String data - whitespace will be ignored. * * @return a byte array representing the decoded data. */ public static byte[] decode(String data) { ByteArrayOutputStream bOut = new ByteArrayOutputStream(); try { encoder.decode(data, bOut); } catch (Exception e) { throw new DecoderException("exception decoding Hex string: " + e.getMessage(), e); } return bOut.toByteArray(); } /** * decode the Hex encoded String data writing it to the given output stream, * whitespace characters will be ignored. * * @return the number of bytes produced. */ public static int decode(String data, OutputStream out) throws IOException { return encoder.decode(data, out); } /** * Decode the hexadecimal-encoded string strictly i.e. any non-hexadecimal characters will be * considered an error. * * @return a byte array representing the decoded data. */ public static byte[] decodeStrict(String str) { try { return encoder.decodeStrict(str, 0, str.length()); } catch (Exception e) { throw new DecoderException("exception decoding Hex string: " + e.getMessage(), e); } } /** * Decode the hexadecimal-encoded string strictly i.e. any non-hexadecimal characters will be * considered an error. * * @return a byte array representing the decoded data. */ public static byte[] decodeStrict(String str, int off, int len) { try { return encoder.decodeStrict(str, off, len); } catch (Exception e) { throw new DecoderException("exception decoding Hex string: " + e.getMessage(), e); } } }