package com.fdkankan.common.util;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {

    public static String md5Str(String str) {
        if (str == null) return "";
        return md5Str(str, 0);
    }


    public static String md5Str(String str, int offset) {
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            byte[] b = str.getBytes("UTF8");
            md5.update(b, offset, b.length);
            return byteArrayToHexString(md5.digest());
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
            return null;
        } catch (UnsupportedEncodingException ex) {
            ex.printStackTrace();
            return null;
        }
    }

    /**
     * @param b byte[]
     * @return String
     */
    public static String byteArrayToHexString(byte[] b) {
        String result = "";
        for (int i = 0; i < b.length; i++) {
            result += byteToHexString(b[i]);
        }
        return result;
    }

    private static String[] hexDigits =
            {
                    "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b",
                    "c", "d", "e", "f"};

    public static String byteToHexString(byte b) {
        int n = b;
        if (n < 0) {
            n = 256 + n;
        }
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    public static void main(String[] args) {
        System.out.println(byteToHexString((byte) -99));
        String str =
                "eeeeeeeeeeeeeewrw213123122222222222222222222222213123213213213erwer";
        String ened = MD5.md5Str(str);
        System.out.println(ened.length());
        System.out.println(ened);
    }


    public final static String getMessageDigest(byte[] buffer) {
        char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
        try {
            MessageDigest mdTemp = MessageDigest.getInstance("MD5");
            mdTemp.update(buffer);
            byte[] md = mdTemp.digest();
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            return null;
        }
    }
}