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	/*
	* Copyright (c) 1996, 2013, 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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.security;

	import java.io.IOException;
	import java.io.EOFException;
	import java.io.InputStream;
	import java.io.FilterInputStream;
	import java.io.PrintStream;
	import java.io.ByteArrayInputStream;

	/**
	* A transparent stream that updates the associated message digest using
	* the bits going through the stream.
	*
	* <p>To complete the message digest computation, call one of the
	* {@code digest} methods on the associated message
	* digest after your calls to one of this digest input stream's
	* {@link #read() read} methods.
	*
	* <p>It is possible to turn this stream on or off (see
	* {@link #on(boolean) on}). When it is on, a call to one of the
	* {@code read} methods
	* results in an update on the message digest. But when it is off,
	* the message digest is not updated. The default is for the stream
	* to be on.
	*
	* <p>Note that digest objects can compute only one digest (see
	* {@link MessageDigest}),
	* so that in order to compute intermediate digests, a caller should
	* retain a handle onto the digest object, and clone it for each
	* digest to be computed, leaving the original digest untouched.
	*
	* @see MessageDigest
	*
	* @see DigestOutputStream
	*
	* @author Benjamin Renaud
	* @since 1.2
	*/

	public class DigestInputStream extends FilterInputStream {

	/* NOTE: This should be made a generic UpdaterInputStream */

	/* Are we on or off? */
	private boolean on = true;

	/**
	* The message digest associated with this stream.
	*/
	protected MessageDigest digest;

	/**
	* Creates a digest input stream, using the specified input stream
	* and message digest.
	*
	* @param stream the input stream.
	*
	* @param digest the message digest to associate with this stream.
	*/
	public DigestInputStream(InputStream stream, MessageDigest digest) {
	super(stream);
	setMessageDigest(digest);
	}

	/**
	* Returns the message digest associated with this stream.
	*
	* @return the message digest associated with this stream.
	* @see #setMessageDigest(java.security.MessageDigest)
	*/
	public MessageDigest getMessageDigest() {
	return digest;
	}

	/**
	* Associates the specified message digest with this stream.
	*
	* @param digest the message digest to be associated with this stream.
	* @see #getMessageDigest()
	*/
	public void setMessageDigest(MessageDigest digest) {
	this.digest = digest;
	}

	/**
	* Reads a byte, and updates the message digest (if the digest
	* function is on). That is, this method reads a byte from the
	* input stream, blocking until the byte is actually read. If the
	* digest function is on (see {@link #on(boolean) on}), this method
	* will then call {@code update} on the message digest associated
	* with this stream, passing it the byte read.
	*
	* @return the byte read.
	*
	* @exception IOException if an I/O error occurs.
	*
	* @see MessageDigest#update(byte)
	*/
	public int read() throws IOException {
	int ch = in.read();
	if (on && ch != -1) {
	digest.update((byte)ch);
	}
	return ch;
	}

	/**
	* Reads into a byte array, and updates the message digest (if the
	* digest function is on). That is, this method reads up to
	* {@code len} bytes from the input stream into the array
	* {@code b}, starting at offset {@code off}. This method
	* blocks until the data is actually
	* read. If the digest function is on (see
	* {@link #on(boolean) on}), this method will then call {@code update}
	* on the message digest associated with this stream, passing it
	* the data.
	*
	* @param b the array into which the data is read.
	*
	* @param off the starting offset into {@code b} of where the
	* data should be placed.
	*
	* @param len the maximum number of bytes to be read from the input
	* stream into b, starting at offset {@code off}.
	*
	* @return the actual number of bytes read. This is less than
	* {@code len} if the end of the stream is reached prior to
	* reading {@code len} bytes. -1 is returned if no bytes were
	* read because the end of the stream had already been reached when
	* the call was made.
	*
	* @exception IOException if an I/O error occurs.
	*
	* @see MessageDigest#update(byte[], int, int)
	*/
	public int read(byte[] b, int off, int len) throws IOException {
	int result = in.read(b, off, len);
	if (on && result != -1) {
	digest.update(b, off, result);
	}
	return result;
	}

	/**
	* Turns the digest function on or off. The default is on. When
	* it is on, a call to one of the {@code read} methods results in an
	* update on the message digest. But when it is off, the message
	* digest is not updated.
	*
	* @param on true to turn the digest function on, false to turn
	* it off.
	*/
	public void on(boolean on) {
	this.on = on;
	}

	/**
	* Prints a string representation of this digest input stream and
	* its associated message digest object.
	*/
	public String toString() {
	return "[Digest Input Stream] " + digest.toString();
	}
	}

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