package org.bouncycastle.crypto.digests;import org.bouncycastle.crypto.ExtendedDigest;/** * Wrapper class that reduces the output length of a particular digest to * only the first n bytes of the digest function. */public class ShortenedDigest     implements ExtendedDigest{    private ExtendedDigest baseDigest;    private int            length;        /**     * Base constructor.     *      * @param baseDigest underlying digest to use.     * @param length length in bytes of the output of doFinal.     * @exception IllegalArgumentException if baseDigest is null, or length is greater than baseDigest.getDigestSize().     */    public ShortenedDigest(        ExtendedDigest baseDigest,        int            length)    {        if (baseDigest == null)        {            throw new IllegalArgumentException("baseDigest must not be null");        }                if (length > baseDigest.getDigestSize())        {            throw new IllegalArgumentException("baseDigest output not large enough to support length");        }                this.baseDigest = baseDigest;        this.length = length;    }        public String getAlgorithmName()    {        return baseDigest.getAlgorithmName() + "(" + length * 8 + ")";    }    public int getDigestSize()    {        return length;    }    public void update(byte in)    {        baseDigest.update(in);    }    public void update(byte[] in, int inOff, int len)    {        baseDigest.update(in, inOff, len);    }    public int doFinal(byte[] out, int outOff)    {        byte[] tmp = new byte[baseDigest.getDigestSize()];                baseDigest.doFinal(tmp, 0);                System.arraycopy(tmp, 0, out, outOff, length);                return length;    }    public void reset()    {        baseDigest.reset();    }    public int getByteLength()    {        return baseDigest.getByteLength();    }}