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jDLMS is a library implementing the DLMS/COSEM (IEC 62056) communication standard.
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/*
 * Copyright 2012-2023 Fraunhofer ISE
 *
 * This file is part of jDLMS.
 * For more information visit http://www.openmuc.org
 *
 * jDLMS 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.
 *
 * jDLMS 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 jDLMS.  If not, see .
 *
 */
package org.openmuc.jdlms;

public class HexConverter {

    public static String toHexString(byte b) {
        StringBuilder builder = new StringBuilder();
        appendHexString(b, builder);
        return builder.toString();
    }

    public static String toHexString(byte[] bytes) {
        return toHexString(bytes, 0, bytes.length);
    }

    public static String toHexString(byte[] bytes, int offset, int length) {
        StringBuilder builder = new StringBuilder();

        int l = 1;
        for (int i = offset; i < (offset + length); i++) {
            if ((l != 1) && ((l - 1) % 8 == 0)) {
                builder.append(' ');
            }
            if ((l != 1) && ((l - 1) % 16 == 0)) {
                builder.append('\n');
            }
            l++;
            appendHexString(bytes[i], builder);
            if (i != offset + length - 1) {
                builder.append(' ');
            }
        }

        return builder.toString();
    }

    /**
     * Returns the integer value as hex string filled with leading zeros. If you do not want leading zeros use
     * Integer.toHexString(int i) instead.
     * 
     * @param i
     *            the integer value to be converted
     * @return the hex string
     */
    public static String toShortHexString(int i) {
        byte[] bytes = new byte[] { (byte) (i >> 24), (byte) (i >> 16), (byte) (i >> 8), (byte) (i) };
        return toShortHexString(bytes);
    }

    /**
     * Returns the long value as hex string filled with leading zeros. If you do not want leading zeros use
     * Long.toHexString(long i) instead.
     * 
     * @param l
     *            the long value to be converted
     * @return the hex string
     */
    public static String toShortHexString(long l) {
        byte[] bytes = new byte[] { (byte) (l >> 56), (byte) (l >> 48), (byte) (l >> 40), (byte) (l >> 32),
                (byte) (l >> 24), (byte) (l >> 16), (byte) (l >> 8), (byte) (l) };
        return toShortHexString(bytes);
    }

    /**
     * Returns the byte as a hex string. If b is less than 16 the hex string returned contains a leading zero.
     * 
     * @param b
     *            the byte to be converted
     * @return the byte as a hex string.
     */
    public static String toShortHexString(byte b) {
        return toShortHexString(new byte[] { b });
    }

    private static final char[] hexArray = "0123456789ABCDEF".toCharArray();

    public static String toShortHexString(byte[] bytes) {
        return toShortHexString(bytes, 0, bytes.length);
    }

    public static String toShortHexString(byte[] bytes, int offset, int length) {
        char[] hexChars = new char[length * 2];
        for (int j = offset; j < (offset + length); j++) {
            int v = bytes[j] & 0xff;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0f];
        }
        return new String(hexChars);
    }

    public static byte[] fromShortHexString(String shortHexString) throws NumberFormatException {

        validate(shortHexString);

        int length = shortHexString.length();

        byte[] data = new byte[length / 2];
        for (int i = 0; i < length; i += 2) {
            int firstCharacter = Character.digit(shortHexString.charAt(i), 16);
            int secondCharacter = Character.digit(shortHexString.charAt(i + 1), 16);

            if (firstCharacter == -1 || secondCharacter == -1) {
                throw new NumberFormatException("string is not a legal hex string.");
            }

            data[i / 2] = (byte) ((firstCharacter << 4) + secondCharacter);
        }
        return data;
    }

    public static void appendShortHexString(byte b, StringBuilder builder) {
        builder.append(toShortHexString(b));
    }

    public static void appendShortHexString(StringBuilder builder, byte[] bytes, int offset, int length) {
        builder.append(toShortHexString(bytes, offset, length));
    }

    public static void appendHexString(byte b, StringBuilder builder) {
        builder.append("0x");
        appendShortHexString(b, builder);
    }

    public static void appendHexString(StringBuilder builder, byte[] byteArray, int offset, int length) {
        int l = 1;
        for (int i = offset; i < (offset + length); i++) {
            if ((l != 1) && ((l - 1) % 8 == 0)) {
                builder.append(' ');
            }
            if ((l != 1) && ((l - 1) % 16 == 0)) {
                builder.append('\n');
            }
            l++;
            appendHexString(byteArray[i], builder);
            if (i != offset + length - 1) {
                builder.append(' ');
            }
        }
    }

    private static void validate(String s) {
        if (s == null) {
            throw new IllegalArgumentException("string s may not be null");
        }

        if ((s.length() == 0) || ((s.length() % 2) != 0)) {
            throw new NumberFormatException("string is not a legal hex string.");
        }
    }

    /**
     * Don't let anyone instantiate this class.
     */
    private HexConverter() {
    }
}