/* * Copyright (c) 2003, 2007, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.crypto.provider; import javax.crypto.ShortBufferException; /** * This class implements padding as specified in the W3 XML ENC standard. * * @author Valerie Peng * * * @see Padding */final class ISO10126Padding implements Padding {     private int blockSize;     ISO10126Padding(int blockSize) {        this.blockSize = blockSize;    }     /**     * Adds the given number of padding bytes to the data input.     * The value of the padding bytes is determined     * by the specific padding mechanism that implements this     * interface.     *     * @param in the input buffer with the data to pad     * @param off the offset in <code>in</code> where the padding bytes     * are appended     * @param len the number of padding bytes to add     *     * @exception ShortBufferException if <code>in</code> is too small to hold     * the padding bytes     */    public void padWithLen(byte[] in, int off, int len)        throws ShortBufferException    {        if (in == null)            return;         if ((off + len) > in.length) {            throw new ShortBufferException("Buffer too small to hold padding");        }         byte paddingOctet = (byte) (len & 0xff);        byte[] padding = new byte[len];        SunJCE.RANDOM.nextBytes(padding);        padding[len-1] = paddingOctet;        System.arraycopy(padding, 0, in, off, len);        return;    }     /**     * Returns the index where the padding starts.     *     * <p>Given a buffer with padded data, this method returns the     * index where the padding starts.     *     * @param in the buffer with the padded data     * @param off the offset in <code>in</code> where the padded data starts     * @param len the length of the padded data     *     * @return the index where the padding starts, or -1 if the input is     * not properly padded     */    public int unpad(byte[] in, int off, int len) {        if ((in == null) ||            (len == 0)) { // this can happen if input is really a padded buffer            return 0;        }         byte lastByte = in[off + len - 1];        int padValue = (int)lastByte & 0x0ff;        if ((padValue < 0x01)            || (padValue > blockSize)) {            return -1;        }         int start = off + len - ((int)lastByte & 0x0ff);        if (start < off) {            return -1;        }         return start;    }     /**     * Determines how long the padding will be for a given input length.     *     * @param len the length of the data to pad     *     * @return the length of the padding     */    public int padLength(int len) {        int paddingOctet = blockSize - (len % blockSize);        return paddingOctet;    }}