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	/*
	* Copyright (c) 2003, 2005, 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.
	*/

	/*
	*******************************************************************************
	* (C) Copyright IBM Corp. 1996-2005 - All Rights Reserved *
	* *
	* The original version of this source code and documentation is copyrighted *
	* and owned by IBM, These materials are provided under terms of a License *
	* Agreement between IBM and Sun. This technology is protected by multiple *
	* US and International patents. This notice and attribution to IBM may not *
	* to removed. *
	*******************************************************************************
	*/

	package sun.text.normalizer;

	import java.io.InputStream;
	import java.io.DataInputStream;
	import java.io.IOException;
	import java.util.Arrays;

	public final class ICUBinary
	{
	// public inner interface ------------------------------------------------

	/**
	* Special interface for data authentication
	*/
	public static interface Authenticate
	{
	/**
	* Method used in ICUBinary.readHeader() to provide data format
	* authentication.
	* @param version version of the current data
	* @return true if dataformat is an acceptable version, false otherwise
	*/
	public boolean isDataVersionAcceptable(byte version[]);
	}

	// public methods --------------------------------------------------------

	/**
	* <p>ICU data header reader method.
	* Takes a ICU generated big-endian input stream, parse the ICU standard
	* file header and authenticates them.</p>
	* <p>Header format:
	* <ul>
	* <li> Header size (char)
	* <li> Magic number 1 (byte)
	* <li> Magic number 2 (byte)
	* <li> Rest of the header size (char)
	* <li> Reserved word (char)
	* <li> Big endian indicator (byte)
	* <li> Character set family indicator (byte)
	* <li> Size of a char (byte) for c++ and c use
	* <li> Reserved byte (byte)
	* <li> Data format identifier (4 bytes), each ICU data has its own
	* identifier to distinguish them. [0] major [1] minor
	* [2] milli [3] micro
	* <li> Data version (4 bytes), the change version of the ICU data
	* [0] major [1] minor [2] milli [3] micro
	* <li> Unicode version (4 bytes) this ICU is based on.
	* </ul>
	* </p>
	* <p>
	* Example of use:<br>
	* <pre>
	* try {
	* FileInputStream input = new FileInputStream(filename);
	* If (Utility.readICUDataHeader(input, dataformat, dataversion,
	* unicode) {
	* System.out.println("Verified file header, this is a ICU data file");
	* }
	* } catch (IOException e) {
	* System.out.println("This is not a ICU data file");
	* }
	* </pre>
	* </p>
	* @param inputStream input stream that contains the ICU data header
	* @param dataFormatIDExpected Data format expected. An array of 4 bytes
	* information about the data format.
	* E.g. data format ID 1.2.3.4. will became an array of
	* {1, 2, 3, 4}
	* @param authenticate user defined extra data authentication. This value
	* can be null, if no extra authentication is needed.
	* @exception IOException thrown if there is a read error or
	* when header authentication fails.
	* @draft 2.1
	*/
	public static final byte[] readHeader(InputStream inputStream,
	byte dataFormatIDExpected[],
	Authenticate authenticate)
	throws IOException
	{
	DataInputStream input = new DataInputStream(inputStream);
	char headersize = input.readChar();
	int readcount = 2;
	//reading the header format
	byte magic1 = input.readByte();
	readcount ++;
	byte magic2 = input.readByte();
	readcount ++;
	if (magic1 != MAGIC1 \|\| magic2 != MAGIC2) {
	throw new IOException(MAGIC_NUMBER_AUTHENTICATION_FAILED_);
	}

	input.readChar(); // reading size
	readcount += 2;
	input.readChar(); // reading reserved word
	readcount += 2;
	byte bigendian = input.readByte();
	readcount ++;
	byte charset = input.readByte();
	readcount ++;
	byte charsize = input.readByte();
	readcount ++;
	input.readByte(); // reading reserved byte
	readcount ++;

	byte dataFormatID[] = new byte[4];
	input.readFully(dataFormatID);
	readcount += 4;
	byte dataVersion[] = new byte[4];
	input.readFully(dataVersion);
	readcount += 4;
	byte unicodeVersion[] = new byte[4];
	input.readFully(unicodeVersion);
	readcount += 4;
	if (headersize < readcount) {
	throw new IOException("Internal Error: Header size error");
	}
	input.skipBytes(headersize - readcount);

	if (bigendian != BIG_ENDIAN_ \|\| charset != CHAR_SET_
	\|\| charsize != CHAR_SIZE_
	\|\| !Arrays.equals(dataFormatIDExpected, dataFormatID)
	\|\| (authenticate != null
	&& !authenticate.isDataVersionAcceptable(dataVersion))) {
	throw new IOException(HEADER_AUTHENTICATION_FAILED_);
	}
	return unicodeVersion;
	}

	// private variables -------------------------------------------------

	/**
	* Magic numbers to authenticate the data file
	*/
	private static final byte MAGIC1 = (byte)0xda;
	private static final byte MAGIC2 = (byte)0x27;

	/**
	* File format authentication values
	*/
	private static final byte BIG_ENDIAN_ = 1;
	private static final byte CHAR_SET_ = 0;
	private static final byte CHAR_SIZE_ = 2;

	/**
	* Error messages
	*/
	private static final String MAGIC_NUMBER_AUTHENTICATION_FAILED_ =
	"ICU data file error: Not an ICU data file";
	private static final String HEADER_AUTHENTICATION_FAILED_ =
	"ICU data file error: Header authentication failed, please check if you have a valid ICU data file";
	}

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