/* * Copyright (c) 1996, 2006, 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 java.util.zip; import java.io.FilterInputStream;import java.io.InputStream;import java.io.IOException; /** * An input stream that also maintains a checksum of the data being read. * The checksum can then be used to verify the integrity of the input data. * * @see         Checksum * @author      David Connelly */publicclass CheckedInputStream extends FilterInputStream {    private Checksum cksum;     /**     * Creates an input stream using the specified Checksum.     * @param in the input stream     * @param cksum the Checksum     */    public CheckedInputStream(InputStream in, Checksum cksum) {        super(in);        this.cksum = cksum;    }     /**     * Reads a byte. Will block if no input is available.     * @return the byte read, or -1 if the end of the stream is reached.     * @exception IOException if an I/O error has occurred     */    public int read() throws IOException {        int b = in.read();        if (b != -1) {            cksum.update(b);        }        return b;    }     /**     * Reads into an array of bytes. If <code>len</code> is not zero, the method     * blocks until some input is available; otherwise, no     * bytes are read and <code>0</code> is returned.     * @param buf the buffer into which the data is read     * @param off the start offset in the destination array <code>b</code>     * @param len the maximum number of bytes read     * @return    the actual number of bytes read, or -1 if the end     *            of the stream is reached.     * @exception  NullPointerException If <code>buf</code> is <code>null</code>.     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,     * <code>len</code> is negative, or <code>len</code> is greater than     * <code>buf.length - off</code>     * @exception IOException if an I/O error has occurred     */    public int read(byte[] buf, int off, int len) throws IOException {        len = in.read(buf, off, len);        if (len != -1) {            cksum.update(buf, off, len);        }        return len;    }     /**     * Skips specified number of bytes of input.     * @param n the number of bytes to skip     * @return the actual number of bytes skipped     * @exception IOException if an I/O error has occurred     */    public long skip(long n) throws IOException {        byte[] buf = new byte[512];        long total = 0;        while (total < n) {            long len = n - total;            len = read(buf, 0, len < buf.length ? (int)len : buf.length);            if (len == -1) {                return total;            }            total += len;        }        return total;    }     /**     * Returns the Checksum for this input stream.     * @return the Checksum value     */    public Checksum getChecksum() {        return cksum;    }}