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jTDS is an open source 100% pure Java (type 4) JDBC 3.0 driver for Microsoft SQL Server (6.5, 7, 2000, 2005, 2008, 2012) and Sybase ASE (10, 11, 12, 15). jTDS is based on FreeTDS and is currently the fastest production-ready JDBC driver for SQL Server and Sybase. jTDS is 100% JDBC 3.0 compatible, supporting forward-only and scrollable/updateable ResultSets and implementing all the DatabaseMetaData and ResultSetMetaData methods.

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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"),
 * to deal in the Software without restriction, including without limitation
 * 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,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 ******************************************************************************/

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();
}