package org.bouncycastle.crypto.digests;import org.bouncycastle.crypto.Digest;/** * base implementation of MD4 family style digest as outlined in * "Handbook of Applied Cryptography", pages 344 - 347. */public abstract class GeneralDigest    implements Digest{    private byte[]  xBuf;    private int     xBufOff;    private long    byteCount;    /**     * Standard constructor     */    protected GeneralDigest()    {        xBuf = new byte[4];        xBufOff = 0;    }    /**     * Copy constructor.  We are using copy constructors in place     * of the Object.clone() interface as this interface is not     * supported by J2ME.     */    protected GeneralDigest(GeneralDigest t)    {        xBuf = new byte[t.xBuf.length];        System.arraycopy(t.xBuf, 0, xBuf, 0, t.xBuf.length);        xBufOff = t.xBufOff;        byteCount = t.byteCount;    }    public void update(        byte in)    {        xBuf[xBufOff++] = in;        if (xBufOff == xBuf.length)        {            processWord(xBuf, 0);            xBufOff = 0;        }        byteCount++;    }    public void update(        byte[]  in,        int     inOff,        int     len)    {        //        // fill the current word        //        while ((xBufOff != 0) && (len > 0))        {            update(in[inOff]);            inOff++;            len--;        }        //        // process whole words.        //        while (len > xBuf.length)        {            processWord(in, inOff);            inOff += xBuf.length;            len -= xBuf.length;            byteCount += xBuf.length;        }        //        // load in the remainder.        //        while (len > 0)        {            update(in[inOff]);            inOff++;            len--;        }    }    public void finish()    {        long    bitLength = (byteCount << 3);        //        // add the pad bytes.        //        update((byte)128);        while (xBufOff != 0)        {            update((byte)0);        }        processLength(bitLength);        processBlock();    }    public void reset()    {        byteCount = 0;        xBufOff = 0;        for ( int i = 0; i < xBuf.length; i++ ) {            xBuf[i] = 0;        }    }    protected abstract void processWord(byte[] in, int inOff);    protected abstract void processLength(long bitLength);    protected abstract void processBlock();}