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package com.netease.cloud.util;

import java.io.UnsupportedEncodingException;
import java.util.Locale;

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utilities for encoding and decoding binary data to and from different forms.
 */
public class BinaryUtils {

    /** Default encoding when extracting binary data from a String */
    private static final String DEFAULT_ENCODING = "UTF-8";

    private static final Logger log = LoggerFactory.getLogger(BinaryUtils.class);

    /**
     * Converts byte data to a Hex-encoded string.
     *
     * @param data
     *            data to hex encode.
     *
     * @return hex-encoded string.
     */
    public static String toHex(byte[] data) {
        StringBuilder sb = new StringBuilder(data.length * 2);
        for (int i = 0; i < data.length; i++) {
            String hex = Integer.toHexString(data[i]);
            if (hex.length() == 1) {
                // Append leading zero.
                sb.append("0");
            } else if (hex.length() == 8) {
                // Remove ff prefix from negative numbers.
                hex = hex.substring(6);
            }
            sb.append(hex);
        }
        return sb.toString().toLowerCase(Locale.getDefault());
    }

    /**
     * Converts a Hex-encoded data string to the original byte data.
     *
     * @param hexData
     *            hex-encoded data to decode.
     * @return decoded data from the hex string.
     */
    public static byte[] fromHex(String hexData) {
        byte[] result = new byte[(hexData.length() + 1) / 2];
        String hexNumber = null;
        int stringOffset = 0;
        int byteOffset = 0;
        while (stringOffset < hexData.length()) {
            hexNumber = hexData.substring(stringOffset, stringOffset + 2);
            stringOffset += 2;
            result[byteOffset++] = (byte) Integer.parseInt(hexNumber, 16);
        }
        return result;
    }

    /**
     * Converts byte data to a Base64-encoded string.
     *
     * @param data
     *            data to Base64 encode.
     * @return encoded Base64 string.
     */
    public static String toBase64(byte[] data) {
        byte[] b64 = Base64.encodeBase64(data);
        return new String(b64);
    }

    /**
     * Converts a Base64-encoded string to the original byte data.
     *
     * @param b64Data
     *            a Base64-encoded string to decode.
     *
     * @return bytes decoded from a Base64 string.
     */
    public static byte[] fromBase64(String b64Data) {
        byte[] decoded;
        try {
            decoded = Base64.decodeBase64(b64Data.getBytes(DEFAULT_ENCODING));
        } catch (UnsupportedEncodingException uee) {
            // Shouldn't happen if the string is truly Base64 encoded.
            log.warn("Tried to Base64-decode a String with the wrong encoding: ", uee);
            decoded = Base64.decodeBase64(b64Data.getBytes());
        }
        return decoded;
    }

}