package org.bouncycastle.crypto;/** * a buffer wrapper for an asymmetric block cipher, allowing input * to be accumulated in a piecemeal fashion until final processing. */public class BufferedAsymmetricBlockCipher{    protected byte[]        buf;    protected int           bufOff;    private boolean                 forEncryption;    private AsymmetricBlockCipher   cipher;    /**     * base constructor.     *     * @param cipher the cipher this buffering object wraps.     */    public BufferedAsymmetricBlockCipher(        AsymmetricBlockCipher     cipher)    {        this.cipher = cipher;    }    /**     * return the underlying cipher for the buffer.     *     * @return the underlying cipher for the buffer.     */    public AsymmetricBlockCipher getUnderlyingCipher()    {        return cipher;    }    /**     * return the amount of data sitting in the buffer.     *     * @return the amount of data sitting in the buffer.     */    public int getBufferPosition()    {        return bufOff;    }    /**     * initialise the buffer and the underlying cipher.     *     * @param forEncryption if true the cipher is initialised for     *  encryption, if false for decryption.     * @param params the key and other data required by the cipher.     */    public void init(        boolean             forEncryption,        CipherParameters    params)    {        this.forEncryption = forEncryption;        reset();        cipher.init(forEncryption, params);        buf = new byte[cipher.getInputBlockSize()];        bufOff = 0;    }    /**     * returns the largest size an input block can be.     *     * @return maximum size for an input block.     */    public int getInputBlockSize()    {        return cipher.getInputBlockSize();    }    /**     * returns the maximum size of the block produced by this cipher.     *     * @return maximum size of the output block produced by the cipher.     */    public int getOutputBlockSize()    {        return cipher.getOutputBlockSize();    }    /**     * add another byte for processing.     *      * @param in the input byte.     */    public void processByte(        byte        in)    {        if (bufOff > buf.length)        {            throw new DataLengthException("attempt to process message to long for cipher");        }        buf[bufOff++] = in;    }    /**     * add len bytes to the buffer for processing.     *     * @param in the input data     * @param inOff offset into the in array where the data starts     * @param len the length of the block to be processed.     */    public void processBytes(        byte[]      in,        int         inOff,        int         len)    {        if (len == 0)        {            return;        }        if (len < 0)        {            throw new IllegalArgumentException("Can't have a negative input length!");        }        if (bufOff + len > buf.length)        {            throw new DataLengthException("attempt to process message to long for cipher");        }        System.arraycopy(in, inOff, buf, bufOff, len);        bufOff += len;    }    /**     * process the contents of the buffer using the underlying     * cipher.     *     * @return the result of the encryption/decryption process on the     * buffer.     * @exception InvalidCipherTextException if we are given a garbage block.     */    public byte[] doFinal()        throws InvalidCipherTextException    {        byte[] out = cipher.processBlock(buf, 0, bufOff);        reset();        return out;    }    /**     * Reset the buffer and the underlying cipher.     */    public void reset()    {        /*         * clean the buffer.         */        if (buf != null)        {            for (int i = 0; i < buf.length; i++)            {                buf[0] = 0;            }        }        bufOff = 0;    }}