001// Copyright 2021 Paul Schaub, @maybeWeCouldStealAVan, @Dave L.
002// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
003//
004// SPDX-License-Identifier: Apache-2.0
005
006package sop.util;
007
008public class HexUtil {
009
010    private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
011
012    /**
013     * Encode a byte array to a hex string.
014     *
015     * @see <a href="https://stackoverflow.com/a/9855338">
016     *     How to convert a byte array to a hex string in Java?</a>
017     * @param bytes bytes
018     * @return hex encoding
019     */
020    public static String bytesToHex(byte[] bytes) {
021        char[] hexChars = new char[bytes.length * 2];
022        for (int j = 0; j < bytes.length; j++) {
023            int v = bytes[j] & 0xFF;
024            hexChars[j * 2] = HEX_ARRAY[v >>> 4];
025            hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
026        }
027        return new String(hexChars);
028    }
029
030    /**
031     * Decode a hex string into a byte array.
032     *
033     * @see <a href="https://stackoverflow.com/a/140861">
034     *     Convert a string representation of a hex dump to a byte array using Java?</a>
035     * @param s hex string
036     * @return decoded byte array
037     */
038    public static byte[] hexToBytes(String s) {
039        int len = s.length();
040        byte[] data = new byte[len / 2];
041        for (int i = 0; i < len; i += 2) {
042            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
043                    + Character.digit(s.charAt(i + 1), 16));
044        }
045        return data;
046    }
047}