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	/*
	* Copyright (c) 1997, 2020, 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 javax.crypto;

	import java.io.*;

	/**
	* A CipherOutputStream is composed of an OutputStream and a Cipher so
	* that write() methods first process the data before writing them out
	* to the underlying OutputStream. The cipher must be fully
	* initialized before being used by a CipherOutputStream.
	*
	* <p> For example, if the cipher is initialized for encryption, the
	* CipherOutputStream will attempt to encrypt data before writing out the
	* encrypted data.
	*
	* <p> This class adheres strictly to the semantics, especially the
	* failure semantics, of its ancestor classes
	* java.io.OutputStream and java.io.FilterOutputStream. This class
	* has exactly those methods specified in its ancestor classes, and
	* overrides them all. Moreover, this class catches all exceptions
	* that are not thrown by its ancestor classes. In particular, this
	* class catches BadPaddingException and other exceptions thrown by
	* failed integrity checks during decryption. These exceptions are not
	* re-thrown, so the client will not be informed that integrity checks
	* failed. Because of this behavior, this class may not be suitable
	* for use with decryption in an authenticated mode of operation (e.g. GCM)
	* if the application requires explicit notification when authentication
	* fails. Such an application can use the Cipher API directly as an
	* alternative to using this class.
	*
	* <p> It is crucial for a programmer using this class not to use
	* methods that are not defined or overridden in this class (such as a
	* new method or constructor that is later added to one of the super
	* classes), because the design and implementation of those methods
	* are unlikely to have considered security impact with regard to
	* CipherOutputStream.
	*
	* @author Li Gong
	* @see java.io.OutputStream
	* @see java.io.FilterOutputStream
	* @see javax.crypto.Cipher
	* @see javax.crypto.CipherInputStream
	*
	* @since 1.4
	*/

	public class CipherOutputStream extends FilterOutputStream {

	// the cipher engine to use to process stream data
	private Cipher cipher;

	// the underlying output stream
	private OutputStream output;

	/* the buffer holding one byte of incoming data */
	private byte[] ibuffer = new byte[1];

	// the buffer holding data ready to be written out
	private byte[] obuffer = null;

	// stream status
	private boolean closed = false;

	/**
	* Ensure obuffer is big enough for the next update or doFinal
	* operation, given the input length <code>inLen</code> (in bytes)
	*
	* @param inLen the input length (in bytes)
	*/
	private void ensureCapacity(int inLen) {
	int minLen = cipher.getOutputSize(inLen);
	if (obuffer == null \|\| obuffer.length < minLen) {
	obuffer = new byte[minLen];
	}
	}

	/**
	*
	* Constructs a CipherOutputStream from an OutputStream and a
	* Cipher.
	* <br>Note: if the specified output stream or cipher is
	* null, a NullPointerException may be thrown later when
	* they are used.
	*
	* @param os the OutputStream object
	* @param c an initialized Cipher object
	*/
	public CipherOutputStream(OutputStream os, Cipher c) {
	super(os);
	output = os;
	cipher = c;
	};

	/**
	* Constructs a CipherOutputStream from an OutputStream without
	* specifying a Cipher. This has the effect of constructing a
	* CipherOutputStream using a NullCipher.
	* <br>Note: if the specified output stream is null, a
	* NullPointerException may be thrown later when it is used.
	*
	* @param os the OutputStream object
	*/
	protected CipherOutputStream(OutputStream os) {
	super(os);
	output = os;
	cipher = new NullCipher();
	}

	/**
	* Writes the specified byte to this output stream.
	*
	* @param b the <code>byte</code>.
	* @exception IOException if an I/O error occurs.
	*/
	@Override
	public void write(int b) throws IOException {
	ibuffer[0] = (byte) b;
	ensureCapacity(1);
	try {
	int ostored = cipher.update(ibuffer, 0, 1, obuffer);
	if (ostored > 0) {
	output.write(obuffer, 0, ostored);
	}
	} catch (ShortBufferException sbe) {
	// should never happen; re-throw just in case
	throw new IOException(sbe);
	}
	};

	/**
	* Writes <code>b.length</code> bytes from the specified byte array
	* to this output stream.
	* <p>
	* The <code>write</code> method of
	* <code>CipherOutputStream</code> calls the <code>write</code>
	* method of three arguments with the three arguments
	* <code>b</code>, <code>0</code>, and <code>b.length</code>.
	*
	* @param b the data.
	* @exception NullPointerException if <code>b</code> is null.
	* @exception IOException if an I/O error occurs.
	* @see javax.crypto.CipherOutputStream#write(byte[], int, int)
	*/
	@Override
	public void write(byte b[]) throws IOException {
	write(b, 0, b.length);
	}

	/**
	* Writes <code>len</code> bytes from the specified byte array
	* starting at offset <code>off</code> to this output stream.
	*
	* @param b the data.
	* @param off the start offset in the data.
	* @param len the number of bytes to write.
	* @exception IOException if an I/O error occurs.
	*/
	@Override
	public void write(byte b[], int off, int len) throws IOException {
	ensureCapacity(len);
	try {
	int ostored = cipher.update(b, off, len, obuffer);
	if (ostored > 0) {
	output.write(obuffer, 0, ostored);
	}
	} catch (ShortBufferException e) {
	// should never happen; re-throw just in case
	throw new IOException(e);
	}
	}

	/**
	* Flushes this output stream by forcing any buffered output bytes
	* that have already been processed by the encapsulated cipher object
	* to be written out.
	*
	* <p>Any bytes buffered by the encapsulated cipher
	* and waiting to be processed by it will not be written out. For example,
	* if the encapsulated cipher is a block cipher, and the total number of
	* bytes written using one of the <code>write</code> methods is less than
	* the cipher's block size, no bytes will be written out.
	*
	* @exception IOException if an I/O error occurs.
	*/
	@Override
	public void flush() throws IOException {
	// simply call output.flush() since 'obuffer' content is always
	// written out immediately
	output.flush();
	}

	/**
	* Closes this output stream and releases any system resources
	* associated with this stream.
	* <p>
	* This method invokes the <code>doFinal</code> method of the encapsulated
	* cipher object, which causes any bytes buffered by the encapsulated
	* cipher to be processed. The result is written out by calling the
	* <code>flush</code> method of this output stream.
	* <p>
	* This method resets the encapsulated cipher object to its initial state
	* and calls the <code>close</code> method of the underlying output
	* stream.
	*
	* @exception IOException if an I/O error occurs.
	*/
	@Override
	public void close() throws IOException {
	if (closed) {
	return;
	}

	closed = true;
	ensureCapacity(0);
	try {
	int ostored = cipher.doFinal(obuffer, 0);
	if (ostored > 0) {
	output.write(obuffer, 0, ostored);
	}
	} catch (IllegalBlockSizeException \| BadPaddingException
	\| ShortBufferException e) {
	}
	obuffer = null;
	try {
	flush();
	} catch (IOException ignored) {}
	output.close();
	}
	}

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