java MD5

package com.netqin.platform.util;

/**
 * 此MD5算法经过了改写，与运营系统的中MD5算法不同。
 * @author Jonas
 * @version 1.0
 */
public class MD5 {
//    ======================================================
//    MD5算法用到的变量
    private static final int S11 = 7;
    private static final int S12 = 12;
    private static final int S13 = 17;
    private static final int S14 = 22;

    private static final int S21 = 5;
    private static final int S22 = 9;
    private static final int S23 = 14;
    private static final int S24 = 20;

    private static final int S31 = 4;
    private static final int S32 = 11;
    private static final int S33 = 16;
    private static final int S34 = 23;

    private static final int S41 = 6;
    private static final int S42 = 10;
    private static final int S43 = 15;
    private static final int S44 = 21;
//    ======================================================
//    Padding
    private byte[] padding ;
//    ======================================================
//    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];
    public byte[] getDigest(){
        return digest;
    }
//    ======================================================
    private MD5_CTX context = new MD5_CTX();public MD5_CTX getContext() {
        return context;
    }

    public void setContext(MD5_CTX context) {
        this.context.count[0] = context.count[0];
        this.context.count[1] = context.count[1];
        
        this.context.state[0] = context.state[0];
        this.context.state[1] = context.state[1];
        this.context.state[2] = context.state[2];
        this.context.state[3] = context.state[3];
       
        System.arraycopy(context.buffer, 0, this.context.buffer, 0, context.buffer.length);
    }
//    ======================================================
//    构造函数
    public MD5(byte[] padding){
        this.padding = padding ;
    }
//    ======================================================
//    Init函数
    public MD5_CTX md5Init(){
        context.count[0] = 0L;
        context.count[1] = 0L;

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

        return context ;
    }
//    ======================================================
//    update函数
    public void md5Update(byte[] inbuf, int inputLen) {
        int i, index, partLen;
        byte[] block = new byte[64];
        index = (int)(context.count[0] >>> 3) & 0x3F;
        // /* Update number of bits */
        if ((context.count[0] += (inputLen << 3)) < (inputLen << 3))
            context.count[1]++;
        context.count[1] += (inputLen >>> 29);

        partLen = 64 - index;

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

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

//                        md5Memcpy(block, inbuf, 0, i, 64);
                       
                        System.arraycopy(inbuf, i, block, 0, 64);
                        md5Transform (block);
                }
                index = 0;

        } else

                i = 0;

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

}
//    ======================================================
//    final函数
     public void md5Final () {
         byte[] bits = new byte[8];
         int index, padLen;

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

         ///* Pad out to 56 mod 64.
         index = (int)(context.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, context.state, 16);
 }
//    ======================================================
    /*
    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 = context.state[0], b = context.state[1], c = context.state[2], d = context.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 */

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

 }
     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);
         }
     }

     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;
     }

     public static long b2iu(byte b) {
         return b < 0 ? b & 0x7F + 128 : b;
     }
//    ======================================================
//    基本的变换函数
    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));
    }
    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;
    }
//    ======================================================
}