//实现MD5算法的类，提供一个静态的函数toMD5()供调用；
//还提供一个getMD5ofStr()函数生成一个MD5加密串；
public class MD5
{
    static final int S11 = 7;
    static final int S12 = 12;
    static final int S13 = 17;
    static final int S14 = 22;
    static final int S21 = 5;
    static final int S22 = 9;
    static final int S23 = 14;
    static final int S24 = 20;
    static final int S31 = 4;
    static final int S32 = 11;
    static final int S33 = 16;
    static final int S34 = 23;
    static final int S41 = 6;
    static final int S42 = 10;
    static final int S43 = 15;
    static final int S44 = 21;
    static final char Hex[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
    static final byte PADDING[] = {
        -128, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0
    };
    private long state[];
    private long count[];
    private byte buffer[];
    public String digestHexStr;
    private byte digest[];
    private byte test;
    public String getMD5ofStr(String s)
    {//返回MD5串；
        int i;
        md5Init();
        md5Update(s.getBytes(), s.length());
        md5Final();
        digestHexStr = "";
        for(i = 0;i<16;i++)
          digestHexStr=digestHexStr+byteHEX(digest[i]);
        return digestHexStr;
    }
    public MD5()
    {
        state = new long[4];
        count = new long[2];
        buffer = new byte[64];
        digest = new byte[16];
        md5Init();
    }
    private void md5Init()
    {//初始化部分变量；
        count[0] = 0L;
        count[1] = 0L;
        state[0] = 0x67452301L;
        state[1] = 0xefcdab89L;
        state[2] = 0x98badcfeL;
        state[3] = 0x10325476L;
    }
    private long F(long l, long l1, long l2)
    {
        return l & l1 | ~l & l2;
    }
    private long G(long l, long l1, long l2)
    {
        return l & l2 | l1 & ~l2;
    }
    private long H(long l, long l1, long l2)
    {
        return l ^ l1 ^ l2;
    }
    private long I(long l, long l1, long l2)
    {
        return l1 ^ (l | ~l2);
    }
    private long FF(long l, long l1, long l2, long l3, long l4, long l5, long l6)
    {
        l += F(l1, l2, l3) + l4 + l6;
        l = (int)l << (int)l5 | (int)l >>> (int)(32L - l5);
        l += l1;
        return l;
    }
    private long GG(long l, long l1, long l2, long l3, long l4, long l5, long l6)
    {
        l += G(l1, l2, l3) + l4 + l6;
        l = (int)l << (int)l5 | (int)l >>> (int)(32L - l5);
        l += l1;
        return l;
    }
    private long HH(long l, long l1, long l2, long l3, long l4, long l5, long l6)
    {
        l += H(l1, l2, l3) + l4 + l6;
        l = (int)l << (int)l5 | (int)l >>> (int)(32L - l5);
        l += l1;
        return l;
    }
    private long II(long l, long l1, long l2, long l3, long l4, long l5, long l6)
    {
        l += I(l1, l2, l3) + l4 + l6;
        l = (int)l << (int)l5 | (int)l >>> (int)(32L - l5);
        l += l1;
        return l;
    }
    private void md5Update(byte abyte0[], int i)
    {//补位操作，abyte0为需要进行MD5加密的字符串，i为字符串长度；
        byte abyte1[] = new byte[64];
        int k = (int)(count[0] >>> 3) & 0x3f;
        if((count[0] += i << 3) < (long)(i << 3))
            count[1]++;
        count[1] += i >>> 29;
        int l = 64 - k;
        int j;
        if(i >= l)
        {
            md5Memcpy(buffer, abyte0, k, 0, l);
            md5Transform(buffer);
            for(j = l; j + 63 < i; j += 64)
            {
                md5Memcpy(abyte1, abyte0, 0, j, 64);
                md5Transform(abyte1);
            }
            k = 0;
        } else
        {
            j = 0;
        }
        md5Memcpy(buffer, abyte0, k, j, i - j);
    }
    private void md5Final()
    {//最终处理，将得到的128位（16字节）MD5码存放在digest数组中
        byte abyte0[] = new byte[8];
        Encode(abyte0, count, 8);
        int i = (int)(count[0] >>> 3) & 0x3f;
        int j = i >= 56 ? 120 - i : 56 - i;
        md5Update(PADDING, j);
        md5Update(abyte0, 8);
        Encode(digest, state, 16);
    }
    private void md5Memcpy(byte abyte0[], byte abyte1[], int i, int j, int k)
    {
        for(int l = 0; l < k; l++)
            abyte0[i + l] = abyte1[j + l];
    }
    private void md5Transform(byte abyte0[])
    {
        long l = state[0];
        long l1 = state[1];
        long l2 = state[2];
        long l3 = state[3];
        long al[] = new long[16];
        Decode(al, abyte0, 64);
        l = FF(l, l1, l2, l3, al[0], 7L, 0xd76aa478L);
        l3 = FF(l3, l, l1, l2, al[1], 12L, 0xe8c7b756L);
        l2 = FF(l2, l3, l, l1, al[2], 17L, 0x242070dbL);
        l1 = FF(l1, l2, l3, l, al[3], 22L, 0xc1bdceeeL);
        l = FF(l, l1, l2, l3, al[4], 7L, 0xf57c0fafL);
        l3 = FF(l3, l, l1, l2, al[5], 12L, 0x4787c62aL);
        l2 = FF(l2, l3, l, l1, al[6], 17L, 0xa8304613L);
        l1 = FF(l1, l2, l3, l, al[7], 22L, 0xfd469501L);
        l = FF(l, l1, l2, l3, al[8], 7L, 0x698098d8L);
        l3 = FF(l3, l, l1, l2, al[9], 12L, 0x8b44f7afL);
        l2 = FF(l2, l3, l, l1, al[10], 17L, 0xffff5bb1L);
        l1 = FF(l1, l2, l3, l, al[11], 22L, 0x895cd7beL);
        l = FF(l, l1, l2, l3, al[12], 7L, 0x6b901122L);
        l3 = FF(l3, l, l1, l2, al[13], 12L, 0xfd987193L);
        l2 = FF(l2, l3, l, l1, al[14], 17L, 0xa679438eL);
        l1 = FF(l1, l2, l3, l, al[15], 22L, 0x49b40821L);
        l = GG(l, l1, l2, l3, al[1], 5L, 0xf61e2562L);
        l3 = GG(l3, l, l1, l2, al[6], 9L, 0xc040b340L);
        l2 = GG(l2, l3, l, l1, al[11], 14L, 0x265e5a51L);
        l1 = GG(l1, l2, l3, l, al[0], 20L, 0xe9b6c7aaL);
        l = GG(l, l1, l2, l3, al[5], 5L, 0xd62f105dL);
        l3 = GG(l3, l, l1, l2, al[10], 9L, 0x2441453L);
        l2 = GG(l2, l3, l, l1, al[15], 14L, 0xd8a1e681L);
        l1 = GG(l1, l2, l3, l, al[4], 20L, 0xe7d3fbc8L);
        l = GG(l, l1, l2, l3, al[9], 5L, 0x21e1cde6L);
        l3 = GG(l3, l, l1, l2, al[14], 9L, 0xc33707d6L);
        l2 = GG(l2, l3, l, l1, al[3], 14L, 0xf4d50d87L);
        l1 = GG(l1, l2, l3, l, al[8], 20L, 0x455a14edL);
        l = GG(l, l1, l2, l3, al[13], 5L, 0xa9e3e905L);
        l3 = GG(l3, l, l1, l2, al[2], 9L, 0xfcefa3f8L);
        l2 = GG(l2, l3, l, l1, al[7], 14L, 0x676f02d9L);
        l1 = GG(l1, l2, l3, l, al[12], 20L, 0x8d2a4c8aL);
        l = HH(l, l1, l2, l3, al[5], 4L, 0xfffa3942L);
        l3 = HH(l3, l, l1, l2, al[8], 11L, 0x8771f681L);
        l2 = HH(l2, l3, l, l1, al[11], 16L, 0x6d9d6122L);
        l1 = HH(l1, l2, l3, l, al[14], 23L, 0xfde5380cL);
        l = HH(l, l1, l2, l3, al[1], 4L, 0xa4beea44L);
        l3 = HH(l3, l, l1, l2, al[4], 11L, 0x4bdecfa9L);
        l2 = HH(l2, l3, l, l1, al[7], 16L, 0xf6bb4b60L);
        l1 = HH(l1, l2, l3, l, al[10], 23L, 0xbebfbc70L);
        l = HH(l, l1, l2, l3, al[13], 4L, 0x289b7ec6L);
        l3 = HH(l3, l, l1, l2, al[0], 11L, 0xeaa127faL);
        l2 = HH(l2, l3, l, l1, al[3], 16L, 0xd4ef3085L);
        l1 = HH(l1, l2, l3, l, al[6], 23L, 0x4881d05L);
        l = HH(l, l1, l2, l3, al[9], 4L, 0xd9d4d039L);
        l3 = HH(l3, l, l1, l2, al[12], 11L, 0xe6db99e5L);
        l2 = HH(l2, l3, l, l1, al[15], 16L, 0x1fa27cf8L);
        l1 = HH(l1, l2, l3, l, al[2], 23L, 0xc4ac5665L);
        l = II(l, l1, l2, l3, al[0], 6L, 0xf4292244L);
        l3 = II(l3, l, l1, l2, al[7], 10L, 0x432aff97L);
        l2 = II(l2, l3, l, l1, al[14], 15L, 0xab9423a7L);
        l1 = II(l1, l2, l3, l, al[5], 21L, 0xfc93a039L);
        l = II(l, l1, l2, l3, al[12], 6L, 0x655b59c3L);
        l3 = II(l3, l, l1, l2, al[3], 10L, 0x8f0ccc92L);
        l2 = II(l2, l3, l, l1, al[10], 15L, 0xffeff47dL);
        l1 = II(l1, l2, l3, l, al[1], 21L, 0x85845dd1L);
        l = II(l, l1, l2, l3, al[8], 6L, 0x6fa87e4fL);
        l3 = II(l3, l, l1, l2, al[15], 10L, 0xfe2ce6e0L);
        l2 = II(l2, l3, l, l1, al[6], 15L, 0xa3014314L);
        l1 = II(l1, l2, l3, l, al[13], 21L, 0x4e0811a1L);
        l = II(l, l1, l2, l3, al[4], 6L, 0xf7537e82L);
        l3 = II(l3, l, l1, l2, al[11], 10L, 0xbd3af235L);
        l2 = II(l2, l3, l, l1, al[2], 15L, 0x2ad7d2bbL);
        l1 = II(l1, l2, l3, l, al[9], 21L, 0xeb86d391L);
        state[0] += l;
        state[1] += l1;
        state[2] += l2;
        state[3] += l3;
    }
    private void Encode(byte abyte0[], long al[], int i)
    {//转换函数，将al中long型的变量输出到byte型的数组abyte0中，
     //低位字节在前，高位字节在后；
        int j = 0;
        for(int k = 0; k < i; k += 4)
        {
            abyte0[k] = (byte)(int)(al[j] & 255L);
            abyte0[k + 1] = (byte)(int)(al[j] >>> 8 & 255L);
            abyte0[k + 2] = (byte)(int)(al[j] >>> 16 & 255L);
            abyte0[k + 3] = (byte)(int)(al[j] >>> 24 & 255L);
            j++;
        }
    }
    private void Decode(long al[], byte abyte0[], int i)
    {
        int j = 0;
        for(int k = 0; k < i; k += 4)
        {
            al[j] = b2iu(abyte0[k]) | b2iu(abyte0[k + 1]) << 8 | b2iu(abyte0[k + 2]) << 16 | b2iu(abyte0[k + 3]) << 24;
            j++;
        }
    }
    public static long b2iu(byte byte0)
    {
        return byte0 >= 0 ? byte0 : byte0 & 0xff;
    }
    public static String byteHEX(byte byte0)
    {//字节到十六进制的ASCII码转换
        char ac[] = {
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            'A', 'B', 'C', 'D', 'E', 'F'
        };
        char ac1[] = new char[2];
        ac1[0] = ac[byte0 >>> 4 & 0xf];
        ac1[1] = ac[byte0 & 0xf];
        String s = new String(ac1);
        return s;
    }
    public static String toMD5(String s)
    {
        MD5 md5 = new MD5();
        return md5.getMD5ofStr(s);
    }
}