com.arxanfintech.common.util.ByteUtils Maven / Gradle / Ivy

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/*******************************************************************************
Copyright ArxanFintech Technology Ltd. 2018 All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

                 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*******************************************************************************/

package com.arxanfintech.common.util;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;

import com.arxanfintech.common.crypto.Hash;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;

/**
 * generic byte array utilities
 */
public class ByteUtils {
    private static final char[] b58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray();
    private static final int[] r58 = new int[256];

    static {
        for (int i = 0; i < 256; ++i) {
            r58[i] = -1;
        }
        for (int i = 0; i < b58.length; ++i) {
            r58[b58[i]] = i;
        }
    }

    /**
     * convert a byte array to a human readable base58 string. Base58 is a Bitcoin
     * specific encoding similar to widely used base64 but avoids using characters
     * of similar shape, such as 1 and l or O an 0
     *
     * @param b
     *            byte data
     * @return base58 data
     */
    public static String toBase58(byte[] b) {
        if (b.length == 0) {
            return "";
        }

        int lz = 0;
        while (lz < b.length && b[lz] == 0) {
            ++lz;
        }

        StringBuilder s = new StringBuilder();
        BigInteger n = new BigInteger(1, b);
        while (n.compareTo(BigInteger.ZERO) > 0) {
            BigInteger[] r = n.divideAndRemainder(BigInteger.valueOf(58));
            n = r[0];
            char digit = b58[r[1].intValue()];
            s.append(digit);
        }
        while (lz > 0) {
            --lz;
            s.append("1");
        }
        return s.reverse().toString();
    }

    /**
     * Encode in base58 with an added checksum of four bytes.
     *
     * @param b
     *            byte[] data
     * @return toBase58WithChecksum
     */
    public static String toBase58WithChecksum(byte[] b) {
        byte[] cs = Hash.hash(b);
        byte[] extended = new byte[b.length + 4];
        System.arraycopy(b, 0, extended, 0, b.length);
        System.arraycopy(cs, 0, extended, b.length, 4);
        return toBase58(extended);
    }

    /**
     * reverse a byte array in place WARNING the parameter array is altered and
     * returned.
     *
     * @param data
     *            ori data
     * @return reverse data
     */
    public static byte[] reverse(byte[] data) {
        for (int i = 0, j = data.length - 1; i < data.length / 2; i++, j--) {
            data[i] ^= data[j];
            data[j] ^= data[i];
            data[i] ^= data[j];
        }
        return data;
    }

    /**
     * convert a byte array to hexadecimal
     *
     * @param data
     *            byte[] data
     * @return hex data
     */
    public static String toHex(byte[] data) {
        return new String(Hex.encodeHex(data));
    }

    /**
     * recreate a byte array from hexadecimal
     *
     * @param hex
     *            string data
     * @return byte[] data
     */
    public static byte[] fromHex(String hex) {
        try {
            return Hex.decodeHex(hex.toCharArray());
        } catch (DecoderException e) {
            return null;
        }
    }
}