tsi-consumer/src/main/java/com/tsi/app/common/utils/HexString.java

package com.tsi.app.common.utils;

import java.nio.ByteBuffer;
import java.util.Objects;

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

    private HexString() {}

    public static String fromByte(byte b) {
        return fromBytes(new byte[] {b});
    }

    public static String fromByte(int b) {
        return fromBytes(new byte[] {(byte) b});
    }

    public static String fromInt(int i) {
        byte[] bytes = new byte[] {(byte) (i >> 24), (byte) (i >> 16), (byte) (i >> 8), (byte) (i)};
        return fromBytes(bytes);
    }

    public static String fromLong(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 fromBytes(bytes);
    }

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

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

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

    public static String fromBytesSpace(byte[] bytes, int offset, int length) {
        char[] hexChars = new char[length * 3];
        for (int j = 0; j < length; j++) {
            int v = bytes[j + offset] & 0xff;
            hexChars[j * 2    ] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0f];
            hexChars[j * 2 + 2] = ' ';
        }
        return new String(hexChars);
    }

    public static String fromBytes(ByteBuffer buffer) {
        return fromBytes(buffer.array(), buffer.arrayOffset(), buffer.arrayOffset() + buffer.limit());
    }

    public static String fromBytesFormatted(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++;
            appendFromByte(bytes[i], builder);
            if (i != offset + length - 1) {
                builder.append(' ');
            }
        }
        return builder.toString();
    }

    public static byte[] toBytes(String hexString) {

        Objects.requireNonNull(hexString);
        if ((hexString.length() == 0) || ((hexString.length() % 2) != 0)) {
            throw new NumberFormatException("argument is not a valid hex string");
        }

        int length = hexString.length();

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

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

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

    public static void appendFromByte(byte b, StringBuilder builder) {
        builder.append(fromByte(b));
    }

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