java的md5实现类

/*************************************************
md5 类实现了RSA Data Security, Inc.在提交给IETF
的RFC1321中的MD5 message-digest 算法。
*************************************************/
public class MD5 {
  /* 下面这些S11-S44实际上是一个4*4的矩阵，在原始的C实现中是用#define 实现的，
  这里把它们实现成为static final是表示了只读，切能在同一个进程空间内的多个
  Instance间共享*/
    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 };
    /* 下面的三个成员是MD5计算过程中用到的3个核心数据，在原始的C实现中
      被定义到MD5_CTX结构中
   
      */
    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的唯一一个公共成员，是最新一次计算结果的
  　 16进制ASCII表示.
  */
    public String digestHexStr;
   
    /* digest,是最新一次计算结果的2进制内部表示，表示128bit的MD5值.
  */
    private byte[] digest = new byte[16];
   
  /*
    getMD5ofStr是类MD5最主要的公共方法，入口参数是你想要进行MD5变换的字符串
    返回的是变换完的结果，这个结果是从公共成员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;

    }
    // 这是MD5这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数
    public MD5() {
          md5Init();

          return;
    }
    /* md5Init是一个初始化函数，初始化核心变量，装入标准的幻数 */
    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个基本的MD5函数，在原始的MD5的C实现中，由于它们是
    简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们
  　　实现成了private方法，名字保持了原来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将调用F,G,H,I进行近一步变换
      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的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个
      函数由getMD5ofStr调用，调用之前需要调用md5init，因此把它设计成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整理和填写输出结果
    */
    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是一个内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的
　　　　　 字节拷贝到output的outpos位置开始
    */

    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核心变换程序，有md5Update调用，block是分块的原始字节
    */
    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数组按顺序拆成byte数组，因为java的long类型是64bit的，
      只拆低32bit，以适应原始C实现的用途
    */
    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数组按顺序合成成long数组，因为java的long类型是64bit的，
      只合成低32bit，高32bit清零，以适应原始C实现的用途
    */
    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是我写的一个把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算
    */
    public static long b2iu(byte b) {
          return b < 0 ? b & 0x7F + 128 : b;
    }
   
  /*byteHEX()，用来把一个byte类型的数转换成十六进制的ASCII表示，
  　因为java中的byte的toString无法实现这一点，我们又没有C语言中的
    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 void main(String args[]){
        MD5 md5 = new MD5();
        System.out.println(md5.getMD5ofStr("admin"));
    }
}

转自：http://www.iteye.com/topic/746281