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

	/*
	******************************************************************************
	* Copyright (C) 1996-2014, International Business Machines Corporation and
	* others. All Rights Reserved.
	******************************************************************************
	*/

	package jdk.internal.icu.impl;

	import jdk.internal.icu.lang.UCharacter;
	import jdk.internal.icu.text.UTF16;

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

	/**
	* <p>A trie is a kind of compressed, serializable table of values
	* associated with Unicode code points (0..0x10ffff).</p>
	* <p>This class defines the basic structure of a trie and provides methods
	* to <b>retrieve the offsets to the actual data</b>.</p>
	* <p>Data will be the form of an array of basic types, char or int.</p>
	* <p>The actual data format will have to be specified by the user in the
	* inner static interface com.ibm.icu.impl.Trie.DataManipulate.</p>
	* <p>This trie implementation is optimized for getting offset while walking
	* forward through a UTF-16 string.
	* Therefore, the simplest and fastest access macros are the
	* fromLead() and fromOffsetTrail() methods.
	* The fromBMP() method are a little more complicated; they get offsets even
	* for lead surrogate codepoints, while the fromLead() method get special
	* "folded" offsets for lead surrogate code units if there is relevant data
	* associated with them.
	* From such a folded offsets, an offset needs to be extracted to supply
	* to the fromOffsetTrail() methods.
	* To handle such supplementary codepoints, some offset information are kept
	* in the data.</p>
	* <p>Methods in com.ibm.icu.impl.Trie.DataManipulate are called to retrieve
	* that offset from the folded value for the lead surrogate unit.</p>
	* <p>For examples of use, see com.ibm.icu.impl.CharTrie or
	* com.ibm.icu.impl.IntTrie.</p>
	* @author synwee
	* @see com.ibm.icu.impl.CharTrie
	* @see com.ibm.icu.impl.IntTrie
	* @since release 2.1, Jan 01 2002
	*/
	public abstract class Trie
	{
	// public class declaration ----------------------------------------

	/**
	* Character data in com.ibm.impl.Trie have different user-specified format
	* for different purposes.
	* This interface specifies methods to be implemented in order for
	* com.ibm.impl.Trie, to surrogate offset information encapsulated within
	* the data.
	*/
	public static interface DataManipulate
	{
	/**
	* Called by com.ibm.icu.impl.Trie to extract from a lead surrogate's
	* data
	* the index array offset of the indexes for that lead surrogate.
	* @param value data value for a surrogate from the trie, including the
	* folding offset
	* @return data offset or 0 if there is no data for the lead surrogate
	*/
	public int getFoldingOffset(int value);
	}

	// default implementation
	private static class DefaultGetFoldingOffset implements DataManipulate {
	public int getFoldingOffset(int value) {
	return value;
	}
	}

	// protected constructor -------------------------------------------

	/**
	* Trie constructor for CharTrie use.
	* @param inputStream ICU data file input stream which contains the
	* trie
	* @param dataManipulate object containing the information to parse the
	* trie data
	* @throws IOException thrown when input stream does not have the
	* right header.
	*/
	protected Trie(InputStream inputStream,
	DataManipulate dataManipulate) throws IOException
	{
	DataInputStream input = new DataInputStream(inputStream);
	// Magic number to authenticate the data.
	int signature = input.readInt();
	m_options_ = input.readInt();

	if (!checkHeader(signature)) {
	throw new IllegalArgumentException("ICU data file error: Trie header authentication failed, please check if you have the most updated ICU data file");
	}

	if(dataManipulate != null) {
	m_dataManipulate_ = dataManipulate;
	} else {
	m_dataManipulate_ = new DefaultGetFoldingOffset();
	}
	m_isLatin1Linear_ = (m_options_ &
	HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_) != 0;
	m_dataOffset_ = input.readInt();
	m_dataLength_ = input.readInt();
	unserialize(inputStream);
	}

	// protected data members ------------------------------------------

	/**
	* Lead surrogate code points' index displacement in the index array.
	* <pre>{@code
	* 0x10000-0xd800=0x2800
	* 0x2800 >> INDEX_STAGE_1_SHIFT_
	* }</pre>
	*/
	protected static final int LEAD_INDEX_OFFSET_ = 0x2800 >> 5;
	/**
	* Shift size for shifting right the input index. 1..9
	*/
	protected static final int INDEX_STAGE_1_SHIFT_ = 5;
	/**
	* Shift size for shifting left the index array values.
	* Increases possible data size with 16-bit index values at the cost
	* of compactability.
	* This requires blocks of stage 2 data to be aligned by
	* DATA_GRANULARITY.
	* 0..INDEX_STAGE_1_SHIFT
	*/
	protected static final int INDEX_STAGE_2_SHIFT_ = 2;
	/**
	* Number of data values in a stage 2 (data array) block.
	*/
	protected static final int DATA_BLOCK_LENGTH=1<<INDEX_STAGE_1_SHIFT_;
	/**
	* Mask for getting the lower bits from the input index.
	* DATA_BLOCK_LENGTH - 1.
	*/
	protected static final int INDEX_STAGE_3_MASK_ = DATA_BLOCK_LENGTH - 1;
	/**
	* Surrogate mask to use when shifting offset to retrieve supplementary
	* values
	*/
	protected static final int SURROGATE_MASK_ = 0x3FF;
	/**
	* Index or UTF16 characters
	*/
	protected char m_index_[];
	/**
	* Internal TrieValue which handles the parsing of the data value.
	* This class is to be implemented by the user
	*/
	protected DataManipulate m_dataManipulate_;
	/**
	* Start index of the data portion of the trie. CharTrie combines
	* index and data into a char array, so this is used to indicate the
	* initial offset to the data portion.
	* Note this index always points to the initial value.
	*/
	protected int m_dataOffset_;
	/**
	* Length of the data array
	*/
	protected int m_dataLength_;

	// protected methods -----------------------------------------------

	/**
	* Gets the offset to the data which the surrogate pair points to.
	* @param lead lead surrogate
	* @param trail trailing surrogate
	* @return offset to data
	*/
	protected abstract int getSurrogateOffset(char lead, char trail);

	/**
	* Gets the offset to the data which the index ch after variable offset
	* points to.
	* Note for locating a non-supplementary character data offset, calling
	* <p>
	* getRawOffset(0, ch);
	* </p>
	* will do. Otherwise if it is a supplementary character formed by
	* surrogates lead and trail. Then we would have to call getRawOffset()
	* with getFoldingIndexOffset(). See getSurrogateOffset().
	* @param offset index offset which ch is to start from
	* @param ch index to be used after offset
	* @return offset to the data
	*/
	protected final int getRawOffset(int offset, char ch)
	{
	return (m_index_[offset + (ch >> INDEX_STAGE_1_SHIFT_)]
	<< INDEX_STAGE_2_SHIFT_)
	+ (ch & INDEX_STAGE_3_MASK_);
	}

	/**
	* Gets the offset to data which the BMP character points to
	* Treats a lead surrogate as a normal code point.
	* @param ch BMP character
	* @return offset to data
	*/
	protected final int getBMPOffset(char ch)
	{
	return (ch >= UTF16.LEAD_SURROGATE_MIN_VALUE
	&& ch <= UTF16.LEAD_SURROGATE_MAX_VALUE)
	? getRawOffset(LEAD_INDEX_OFFSET_, ch)
	: getRawOffset(0, ch);
	// using a getRawOffset(ch) makes no diff
	}

	/**
	* Gets the offset to the data which this lead surrogate character points
	* to.
	* Data at the returned offset may contain folding offset information for
	* the next trailing surrogate character.
	* @param ch lead surrogate character
	* @return offset to data
	*/
	protected final int getLeadOffset(char ch)
	{
	return getRawOffset(0, ch);
	}

	/**
	* Internal trie getter from a code point.
	* Could be faster(?) but longer with
	* {@code if((c32)<=0xd7ff) { (result)=_TRIE_GET_RAW(trie, data, 0, c32); }}
	* Gets the offset to data which the codepoint points to
	* @param ch codepoint
	* @return offset to data
	*/
	protected final int getCodePointOffset(int ch)
	{
	// if ((ch >> 16) == 0) slower
	if (ch < 0) {
	return -1;
	} else if (ch < UTF16.LEAD_SURROGATE_MIN_VALUE) {
	// fastpath for the part of the BMP below surrogates (D800) where getRawOffset() works
	return getRawOffset(0, (char)ch);
	} else if (ch < UTF16.SUPPLEMENTARY_MIN_VALUE) {
	// BMP codepoint
	return getBMPOffset((char)ch);
	} else if (ch <= UCharacter.MAX_VALUE) {
	// look at the construction of supplementary characters
	// trail forms the ends of it.
	return getSurrogateOffset(UTF16.getLeadSurrogate(ch),
	(char)(ch & SURROGATE_MASK_));
	} else {
	// return -1 if there is an error, in this case we return
	return -1;
	}
	}

	/**
	* <p>Parses the inputstream and creates the trie index with it.</p>
	* <p>This is overwritten by the child classes.
	* @param inputStream input stream containing the trie information
	* @exception IOException thrown when data reading fails.
	*/
	protected void unserialize(InputStream inputStream) throws IOException
	{
	//indexLength is a multiple of 1024 >> INDEX_STAGE_2_SHIFT_
	m_index_ = new char[m_dataOffset_];
	DataInputStream input = new DataInputStream(inputStream);
	for (int i = 0; i < m_dataOffset_; i ++) {
	m_index_[i] = input.readChar();
	}
	}

	/**
	* Determines if this is a 16 bit trie
	* @return true if this is a 16 bit trie
	*/
	protected final boolean isCharTrie()
	{
	return (m_options_ & HEADER_OPTIONS_DATA_IS_32_BIT_) == 0;
	}

	// private data members --------------------------------------------

	/**
	* Latin 1 option mask
	*/
	protected static final int HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_ = 0x200;
	/**
	* Constant number to authenticate the byte block
	*/
	protected static final int HEADER_SIGNATURE_ = 0x54726965;
	/**
	* Header option formatting
	*/
	private static final int HEADER_OPTIONS_SHIFT_MASK_ = 0xF;
	protected static final int HEADER_OPTIONS_INDEX_SHIFT_ = 4;
	protected static final int HEADER_OPTIONS_DATA_IS_32_BIT_ = 0x100;

	/**
	* Flag indicator for Latin quick access data block
	*/
	private boolean m_isLatin1Linear_;

	/**
	* <p>Trie options field.</p>
	* <p>options bit field:<br>
	* 9 1 = Latin-1 data is stored linearly at data + DATA_BLOCK_LENGTH<br>
	* 8 0 = 16-bit data, 1=32-bit data<br>
	* 7..4 INDEX_STAGE_1_SHIFT // 0..INDEX_STAGE_2_SHIFT<br>
	* 3..0 INDEX_STAGE_2_SHIFT // 1..9<br>
	*/
	private int m_options_;

	// private methods ---------------------------------------------------

	/**
	* Authenticates raw data header.
	* Checking the header information, signature and options.
	* @param signature This contains the options and type of a Trie
	* @return true if the header is authenticated valid
	*/
	private final boolean checkHeader(int signature)
	{
	// check the signature
	// Trie in big-endian US-ASCII (0x54726965).
	// Magic number to authenticate the data.
	if (signature != HEADER_SIGNATURE_) {
	return false;
	}

	if ((m_options_ & HEADER_OPTIONS_SHIFT_MASK_) !=
	INDEX_STAGE_1_SHIFT_ \|\|
	((m_options_ >> HEADER_OPTIONS_INDEX_SHIFT_) &
	HEADER_OPTIONS_SHIFT_MASK_)
	!= INDEX_STAGE_2_SHIFT_) {
	return false;
	}
	return true;
	}
	}

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