/*
* Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
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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;
}
}