generaldigest.java

第三方的SQL Server and Sybase的jdbc dirver,速度更快

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 * Copyright (c) 2000 The Legion Of The Bouncy Castle (http://www.bouncycastle.org)
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
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 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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package net.sourceforge.jtds.util;

/**
 * base implementation of MD4 family style digest as outlined in
 * "Handbook of Applied Cryptography", pages 344 - 347.
 *
 * @version $Id: GeneralDigest.java,v 1.2 2004/06/27 17:00:55 bheineman Exp $
 */
public abstract class GeneralDigest
//    implements Digest - mdb: we don't care about this interface
{
    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();
}