/*
* @(#)CheckedInputStream.java 1.19 03/12/19
*
* Copyright 2004 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 1.19, 12/19/03
* @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;
}
}
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