/*-
 * Copyright (c) 2000 - 2009 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 org.bouncycastle.crypto.digests;

import org.bouncycastle.crypto.ExtendedDigest;

/**
 * base implementation of MD4 family style digest as outlined in
 * "Handbook of Applied Cryptography", pages 344 - 347.
 */
public abstract class GeneralDigest
    implements ExtendedDigest
{
    private static final int BYTE_LENGTH = 64;
    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;
        }
    }

    public int getByteLength()
    {
        return BYTE_LENGTH;
    }
    
    protected abstract void processWord(byte[] in, int inOff);

    protected abstract void processLength(long bitLength);

    protected abstract void processBlock();
}
