/*
* @(#)CheckedInputStream.java 1.23 06/10/10
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program 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.
*
* This program 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 at /legal/license.txt).
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.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
* @version 1.16, 02/02/00
* @author David Connelly
*/
public
class 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. Will block until some input
* is available.
* @param buf the buffer into which the data is read
* @param off the start offset of the data
* @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 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;
}
}