/*
* 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
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*/
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
*/
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. 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;
}
}