/*
* @(#)CheckedInputStream.java 1.22 06/04/07
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
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 1.22, 04/07/06
* @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;
}
}