/*
          md5Final整理和填寫輸出結果
        */
        private void md5Final () {
                byte[] bits = new byte[8];
                int index, padLen;

                ///* Save number of bits */
                Encode (bits, count, 8);

                ///* Pad out to 56 mod 64.
                index = (int)(count[0] >>> 3) & 0x3f;
                padLen = (index < 56) ? (56 - index) : (120 - index);
                md5Update (PADDING, padLen);

                ///* Append length (before padding) */
                md5Update(bits, 8);

                ///* Store state in digest */
                Encode (digest, state, 16);

        }
         
        /* md5Memcpy是一個內部使用的byte數組的塊拷貝函數，從input的inpos開始把len長度的
　　　　　 字節拷貝到output的outpos位置開始 
        */

        private void md5Memcpy (byte[] output, byte[] input,
                int outpos, int inpos, int len)
        {
                int i;

                for (i = 0; i < len; i++)
                        output[outpos + i] = input[inpos + i];
        }
        
        /*
           md5Transform是MD5核心變換程序，有md5Update調用，block是分塊的原始字節
        */
        private void md5Transform (byte block[]) {
                long a = state[0], b = state[1], c = state[2], d = state[3];
                long[] x = new long[16];

                Decode (x, block, 64);

                /* Round 1 */
                a = FF (a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */
                d = FF (d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */
                c = FF (c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */
                b = FF (b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */
                a = FF (a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */
                d = FF (d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */
                c = FF (c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */
                b = FF (b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */
                a = FF (a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */
                d = FF (d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */
                c = FF (c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */
                b = FF (b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */
                a = FF (a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */
                d = FF (d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */
                c = FF (c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */
                b = FF (b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */

                /* Round 2 */
                a = GG (a, b, c, d, x[1], S21, 0xf61e2562L); /* 17 */
                d = GG (d, a, b, c, x[6], S22, 0xc040b340L); /* 18 */
                c = GG (c, d, a, b, x[11], S23, 0x265e5a51L); /* 19 */
                b = GG (b, c, d, a, x[0], S24, 0xe9b6c7aaL); /* 20 */
                a = GG (a, b, c, d, x[5], S21, 0xd62f105dL); /* 21 */
                d = GG (d, a, b, c, x[10], S22, 0x2441453L); /* 22 */
                c = GG (c, d, a, b, x[15], S23, 0xd8a1e681L); /* 23 */
                b = GG (b, c, d, a, x[4], S24, 0xe7d3fbc8L); /* 24 */
                a = GG (a, b, c, d, x[9], S21, 0x21e1cde6L); /* 25 */
                d = GG (d, a, b, c, x[14], S22, 0xc33707d6L); /* 26 */
                c = GG (c, d, a, b, x[3], S23, 0xf4d50d87L); /* 27 */
                b = GG (b, c, d, a, x[8], S24, 0x455a14edL); /* 28 */
                a = GG (a, b, c, d, x[13], S21, 0xa9e3e905L); /* 29 */
                d = GG (d, a, b, c, x[2], S22, 0xfcefa3f8L); /* 30 */
                c = GG (c, d, a, b, x[7], S23, 0x676f02d9L); /* 31 */
                b = GG (b, c, d, a, x[12], S24, 0x8d2a4c8aL); /* 32 */

                /* Round 3 */
                a = HH (a, b, c, d, x[5], S31, 0xfffa3942L); /* 33 */
                d = HH (d, a, b, c, x[8], S32, 0x8771f681L); /* 34 */
                c = HH (c, d, a, b, x[11], S33, 0x6d9d6122L); /* 35 */
                b = HH (b, c, d, a, x[14], S34, 0xfde5380cL); /* 36 */
                a = HH (a, b, c, d, x[1], S31, 0xa4beea44L); /* 37 */
                d = HH (d, a, b, c, x[4], S32, 0x4bdecfa9L); /* 38 */
                c = HH (c, d, a, b, x[7], S33, 0xf6bb4b60L); /* 39 */
                b = HH (b, c, d, a, x[10], S34, 0xbebfbc70L); /* 40 */
                a = HH (a, b, c, d, x[13], S31, 0x289b7ec6L); /* 41 */
                d = HH (d, a, b, c, x[0], S32, 0xeaa127faL); /* 42 */
                c = HH (c, d, a, b, x[3], S33, 0xd4ef3085L); /* 43 */
                b = HH (b, c, d, a, x[6], S34, 0x4881d05L); /* 44 */
                a = HH (a, b, c, d, x[9], S31, 0xd9d4d039L); /* 45 */
                d = HH (d, a, b, c, x[12], S32, 0xe6db99e5L); /* 46 */
                c = HH (c, d, a, b, x[15], S33, 0x1fa27cf8L); /* 47 */
                b = HH (b, c, d, a, x[2], S34, 0xc4ac5665L); /* 48 */

                /* Round 4 */
                a = II (a, b, c, d, x[0], S41, 0xf4292244L); /* 49 */
                d = II (d, a, b, c, x[7], S42, 0x432aff97L); /* 50 */
                c = II (c, d, a, b, x[14], S43, 0xab9423a7L); /* 51 */
                b = II (b, c, d, a, x[5], S44, 0xfc93a039L); /* 52 */
                a = II (a, b, c, d, x[12], S41, 0x655b59c3L); /* 53 */
                d = II (d, a, b, c, x[3], S42, 0x8f0ccc92L); /* 54 */
                c = II (c, d, a, b, x[10], S43, 0xffeff47dL); /* 55 */
                b = II (b, c, d, a, x[1], S44, 0x85845dd1L); /* 56 */
                a = II (a, b, c, d, x[8], S41, 0x6fa87e4fL); /* 57 */
                d = II (d, a, b, c, x[15], S42, 0xfe2ce6e0L); /* 58 */
                c = II (c, d, a, b, x[6], S43, 0xa3014314L); /* 59 */
                b = II (b, c, d, a, x[13], S44, 0x4e0811a1L); /* 60 */
                a = II (a, b, c, d, x[4], S41, 0xf7537e82L); /* 61 */
                d = II (d, a, b, c, x[11], S42, 0xbd3af235L); /* 62 */
                c = II (c, d, a, b, x[2], S43, 0x2ad7d2bbL); /* 63 */
                b = II (b, c, d, a, x[9], S44, 0xeb86d391L); /* 64 */

                state[0] += a;
                state[1] += b;
                state[2] += c;
                state[3] += d;

        }
        
        /*Encode把long數組按順序拆成byte數組，因為java的long類型是64bit的，
          只拆低32bit，以適應原始C實現的用途
        */
        private void Encode (byte[] output, long[] input, int len) {
                int i, j;

                for (i = 0, j = 0; j < len; i++, j += 4) {
                        output[j] = (byte)(input[i] & 0xffL);
                        output[j + 1] = (byte)((input[i] >>> 8) & 0xffL);
                        output[j + 2] = (byte)((input[i] >>> 16) & 0xffL);
                        output[j + 3] = (byte)((input[i] >>> 24) & 0xffL);
                }
        }

        /*Decode把byte數組按順序合成成long數組，因為java的long類型是64bit的，
          只合成低32bit，高32bit清零，以適應原始C實現的用途
        */
        private void Decode (long[] output, byte[] input, int len) {
                int i, j;


                for (i = 0, j = 0; j < len; i++, j += 4)
                        output[i] = b2iu(input[j]) |
                                (b2iu(input[j + 1]) << 8) |
                                (b2iu(input[j + 2]) << 16) |
                                (b2iu(input[j + 3]) << 24);

                return;
        }
       
        /*
          b2iu是我寫的一個把byte按照不考慮正負號的原則的＂升位＂程序，因為java沒有unsigned運算
        */
        public static long b2iu(byte b) {
                return b < 0 ? b & 0x7F + 128 : b;
        }
        
 /*byteHEX()，用來把一個byte類型的數轉換成十六進制的ASCII表示，
 　因為java中的byte的toString無法實現這一點，我們又沒有C語言中的
   sprintf(outbuf,"%02X",ib)
 */
        public static String byteHEX(byte ib) {
                char[] Digit = { '0','1','2','3','4','5','6','7','8','9',
                'A','B','C','D','E','F' };
                char [] ob = new char[2];
                ob[0] = Digit[(ib >>> 4) & 0X0F];
                ob[1] = Digit[ib & 0X0F];
                String s = new String(ob);
                return s;
        }

         public static String getMD5(String str)
         {
              MD5 m = new MD5();
              return m.getMD5ofStr(str);
         }
}