package gzets.common;
import java.lang.reflect.*;
/*************************************************
md5 類實現了RSA Data Security, Inc.在提交給IETF
的RFC1321中的MD5 message-digest 算法。
*************************************************/

public class MD5 {
/* 下面這些S11-S44實際上是一個4*4的矩陣，在原始的C實現中是用#define 實現的，
這里把它們實現成為static final是表示了只讀，切能在同一個進程空間內的多個
Instance間共享*/
       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 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 };
       /* 下面的三個成員是MD5計算過程中用到的3個核心數據，在原始的C實現中
          被定義到MD5_CTX結構中

        */
       private long[] state = new long[4];  // state (ABCD)
       private long[] count = new long[2];  // number of bits, modulo 2^64 (lsb first)
       private byte[] buffer = new byte[64]; // input buffer

/* digestHexStr是MD5的唯一一個公共成員，是最新一次計算結果的
　 16進制ASCII表示.
*/
       public String digestHexStr;

       /* digest,是最新一次計算結果的2進制內部表示，表示128bit的MD5值.
*/
       private byte[] digest = new byte[16];

/*
 getMD5ofStr是類MD5最主要的公共方法，入口參數是你想要進行MD5變換的字符串
 返回的是變換完的結果，這個結果是從公共成員digestHexStr取得的．
*/
       public String getMD5ofStr(String inbuf) {
               md5Init();
               md5Update(inbuf.getBytes(), inbuf.length());
               md5Final();
               digestHexStr = "";
               for (int i = 0; i < 16; i++) {
                       digestHexStr += byteHEX(digest[i]);
               }
               return digestHexStr;

       }
       // 這是MD5這個類的標準構造函數，JavaBean要求有一個public的并且沒有參數的構造函數
       public MD5() {
               md5Init();

               return;
       }


       /* md5Init是一個初始化函數，初始化核心變量，裝入標準的幻數 */
       private void md5Init() {
               count[0] = 0L;
               count[1] = 0L;
               ///* Load magic initialization constants.

               state[0] = 0x67452301L;
               state[1] = 0xefcdab89L;
               state[2] = 0x98badcfeL;
               state[3] = 0x10325476L;

               return;
       }
       /* F, G, H ,I 是4個基本的MD5函數，在原始的MD5的C實現中，由于它們是
       簡單的位運算，可能出于效率的考慮把它們實現成了宏，在java中，我們把它們
    　　實現成了private方法，名字保持了原來C中的。 */

       private long F(long x, long y, long z) {
               return (x & y) | ((~x) & z);

       }
       private long G(long x, long y, long z) {
               return (x & z) | (y & (~z));

       }
       private long H(long x, long y, long z) {
               return x ^ y ^ z;
       }

       private long I(long x, long y, long z) {
               return y ^ (x | (~z));
       }

      /*
         FF,GG,HH和II將調用F,G,H,I進行近一步變換
         FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
         Rotation is separate from addition to prevent recomputation.
      */

       private long FF(long a, long b, long c, long d, long x, long s,
               long ac) {
               a += F (b, c, d) + x + ac;
               a = ((int) a << s) | ((int) a >>> (32 - s));
               a += b;
               return a;
       }

       private long GG(long a, long b, long c, long d, long x, long s,
               long ac) {
               a += G (b, c, d) + x + ac;
               a = ((int) a << s) | ((int) a >>> (32 - s));
               a += b;
               return a;
       }
       private long HH(long a, long b, long c, long d, long x, long s,
               long ac) {
               a += H (b, c, d) + x + ac;
               a = ((int) a << s) | ((int) a >>> (32 - s));
               a += b;
               return a;
       }
       private long II(long a, long b, long c, long d, long x, long s,
               long ac) {
               a += I (b, c, d) + x + ac;
               a = ((int) a << s) | ((int) a >>> (32 - s));
               a += b;
               return a;
       }
       /*
        md5Update是MD5的主計算過程，inbuf是要變換的字節串，inputlen是長度，這個
        函數由getMD5ofStr調用，調用之前需要調用md5init，因此把它設計成private的
       */
       private void md5Update(byte[] inbuf, int inputLen) {

               int i, index, partLen;
               byte[] block = new byte[64];
               index = (int)(count[0] >>> 3) & 0x3F;
               // /* Update number of bits */
               if ((count[0] += (inputLen << 3)) < (inputLen << 3))
                       count[1]++;
               count[1] += (inputLen >>> 29);

               partLen = 64 - index;

               // Transform as many times as possible.
               if (inputLen >= partLen) {
                       md5Memcpy(buffer, inbuf, index, 0, partLen);
                       md5Transform(buffer);

                       for (i = partLen; i + 63 < inputLen; i += 64) {

                               md5Memcpy(block, inbuf, 0, i, 64);
                               md5Transform (block);
                       }
                       index = 0;

               } else

                       i = 0;

               ///* Buffer remaining input */
               md5Memcpy(buffer, inbuf, index, i, inputLen - i);

       }

       /*
         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);