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Resolution library that talks with etherium .crypto registry to resolve various information attached to .crypto domain

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package com.unstoppabledomains.resolution.artifacts;

/** This code was taken from web3J and adapted accordingly
 *  https://github.com/web3j/web3j/blob/5877c308e11c0de8e24e50c882effa84354a8e57/utils/src/main/java/org/web3j/utils/Numeric.java#L27
 */
public final class Numeric {
    private Numeric() {}

    public static String cleanHexPrefix(String input) {
        if (containsHexPrefix(input)) {
            return input.substring(2);
        } else {
            return input;
        }
    }


    public static boolean containsHexPrefix(String input) {
        return !Strings.isEmpty(input)
                && input.length() > 1
                && input.charAt(0) == '0'
                && input.charAt(1) == 'x';
    }


    public static byte[] hexStringToByteArray(String input) {
        String cleanInput = cleanHexPrefix(input);

        int len = cleanInput.length();

        if (len == 0) {
            return new byte[] {};
        }

        byte[] data;
        int startIdx;
        if (len % 2 != 0) {
            data = new byte[(len / 2) + 1];
            data[0] = (byte) Character.digit(cleanInput.charAt(0), 16);
            startIdx = 1;
        } else {
            data = new byte[len / 2];
            startIdx = 0;
        }

        for (int i = startIdx; i < len; i += 2) {
            data[(i + 1) / 2] =
                    (byte)
                            ((Character.digit(cleanInput.charAt(i), 16) << 4)
                                    + Character.digit(cleanInput.charAt(i + 1), 16));
        }
        return data;
    }

    public static String toHexString(byte[] input, int offset, int length, boolean withPrefix) {
        StringBuilder stringBuilder = new StringBuilder();
        if (withPrefix) {
            stringBuilder.append("0x");
        }
        for (int i = offset; i < offset + length; i++) {
            stringBuilder.append(String.format("%02x", input[i] & 0xFF));
        }

        return stringBuilder.toString();
    }

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