package com.xkl;

import java.security.MessageDigest;

/**
 * Created by win7 on 2016/12/25.
 */
public class EncodeTools {
    private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
            'e', 'f' };

    public static String encode(String algorithm, String str) {
        if (str == null) {
            return null;
        }
        try {
            MessageDigest messageDigest = MessageDigest.getInstance(algorithm);
            messageDigest.update(str.getBytes());
            return getFormattedText(messageDigest.digest());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

    }

    /**
     * Takes the raw bytes from the digest and formats them correct.
     *
     * @param bytes
     *            the raw bytes from the digest.
     * @return the formatted bytes.
     */
    private static String getFormattedText(byte[] bytes) {
        int len = bytes.length;
        StringBuilder buf = new StringBuilder(len * 2);
        // 把密文转换成十六进制的字符串形式
        for (int j = 0; j < len; j++) {
            buf.append(HEX_DIGITS[(bytes[j] >> 4) & 0x0f]);
            buf.append(HEX_DIGITS[bytes[j] & 0x0f]);
        }
        return buf.toString();
    }


}