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	/*
	* Copyright (c) 2003, 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.text;

	import jdk.internal.icu.impl.CharacterIteratorWrapper;
	import jdk.internal.icu.impl.ReplaceableUCharacterIterator;
	import jdk.internal.icu.impl.UCharacterProperty;

	import java.text.CharacterIterator;

	/**
	* Abstract class that defines an API for iteration on text objects.This is an
	* interface for forward and backward iteration and random access into a text
	* object. Forward iteration is done with post-increment and backward iteration
	* is done with pre-decrement semantics, while the
	* <code>java.text.CharacterIterator</code> interface methods provided forward
	* iteration with "pre-increment" and backward iteration with pre-decrement
	* semantics. This API is more efficient for forward iteration over code points.
	* The other major difference is that this API can do both code unit and code point
	* iteration, <code>java.text.CharacterIterator</code> can only iterate over
	* code units and is limited to BMP (0 - 0xFFFF)
	* @author Ram
	* @stable ICU 2.4
	*/
	public abstract class UCharacterIterator
	implements Cloneable {

	/**
	* Protected default constructor for the subclasses
	* @stable ICU 2.4
	*/
	protected UCharacterIterator(){
	}

	/**
	* Indicator that we have reached the ends of the UTF16 text.
	* Moved from UForwardCharacterIterator.java
	* @stable ICU 2.4
	*/
	public static final int DONE = -1;

	// static final methods ----------------------------------------------------

	/**
	* Returns a <code>UCharacterIterator</code> object given a
	* source string.
	* @param source a string
	* @return UCharacterIterator object
	* @exception IllegalArgumentException if the argument is null
	* @stable ICU 2.4
	*/
	public static final UCharacterIterator getInstance(String source){
	return new ReplaceableUCharacterIterator(source);
	}

	/**
	* Returns a <code>UCharacterIterator</code> object given a
	* source StringBuffer.
	* @param source an string buffer of UTF-16 code units
	* @return UCharacterIterator object
	* @exception IllegalArgumentException if the argument is null
	* @stable ICU 2.4
	*/
	public static final UCharacterIterator getInstance(StringBuffer source){
	return new ReplaceableUCharacterIterator(source);
	}

	/**
	* Returns a <code>UCharacterIterator</code> object given a
	* CharacterIterator.
	* @param source a valid CharacterIterator object.
	* @return UCharacterIterator object
	* @exception IllegalArgumentException if the argument is null
	* @stable ICU 2.4
	*/
	public static final UCharacterIterator getInstance(CharacterIterator source){
	return new CharacterIteratorWrapper(source);
	}

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

	/**
	* Returns the length of the text
	* @return length of the text
	* @stable ICU 2.4
	*/
	public abstract int getLength();

	/**
	* Gets the current index in text.
	* @return current index in text.
	* @stable ICU 2.4
	*/
	public abstract int getIndex();

	/**
	* Returns the UTF16 code unit at index, and increments to the next
	* code unit (post-increment semantics). If index is out of
	* range, DONE is returned, and the iterator is reset to the limit
	* of the text.
	* @return the next UTF16 code unit, or DONE if the index is at the limit
	* of the text.
	* @stable ICU 2.4
	*/
	public abstract int next();

	/**
	* Returns the code point at index, and increments to the next code
	* point (post-increment semantics). If index does not point to a
	* valid surrogate pair, the behavior is the same as
	* <code>next()</code>. Otherwise the iterator is incremented past
	* the surrogate pair, and the code point represented by the pair
	* is returned.
	* @return the next codepoint in text, or DONE if the index is at
	* the limit of the text.
	* @stable ICU 2.4
	*/
	public int nextCodePoint(){
	int ch1 = next();
	if(UTF16.isLeadSurrogate((char)ch1)){
	int ch2 = next();
	if(UTF16.isTrailSurrogate((char)ch2)){
	return UCharacterProperty.getRawSupplementary((char)ch1,
	(char)ch2);
	}else if (ch2 != DONE) {
	// unmatched surrogate so back out
	previous();
	}
	}
	return ch1;
	}

	/**
	* Decrement to the position of the previous code unit in the
	* text, and return it (pre-decrement semantics). If the
	* resulting index is less than 0, the index is reset to 0 and
	* DONE is returned.
	* @return the previous code unit in the text, or DONE if the new
	* index is before the start of the text.
	* @stable ICU 2.4
	*/
	public abstract int previous();


	/**
	* Retreat to the start of the previous code point in the text,
	* and return it (pre-decrement semantics). If the index is not
	* preceeded by a valid surrogate pair, the behavior is the same
	* as <code>previous()</code>. Otherwise the iterator is
	* decremented to the start of the surrogate pair, and the code
	* point represented by the pair is returned.
	* @return the previous code point in the text, or DONE if the new
	* index is before the start of the text.
	* @stable ICU 2.4
	*/
	public int previousCodePoint(){
	int ch1 = previous();
	if(UTF16.isTrailSurrogate((char)ch1)){
	int ch2 = previous();
	if(UTF16.isLeadSurrogate((char)ch2)){
	return UCharacterProperty.getRawSupplementary((char)ch2,
	(char)ch1);
	}else if (ch2 != DONE) {
	//unmatched trail surrogate so back out
	next();
	}
	}
	return ch1;
	}

	/**
	* Sets the index to the specified index in the text.
	* @param index the index within the text.
	* @exception IndexOutOfBoundsException is thrown if an invalid index is
	* supplied
	* @stable ICU 2.4
	*/
	public abstract void setIndex(int index);

	/**
	* Sets the current index to the start.
	* @stable ICU 2.4
	*/
	public void setToStart() {
	setIndex(0);
	}

	/**
	* Fills the buffer with the underlying text storage of the iterator
	* If the buffer capacity is not enough a exception is thrown. The capacity
	* of the fill in buffer should at least be equal to length of text in the
	* iterator obtained by calling <code>getLength()</code>.
	* <b>Usage:</b>
	*
	* <pre>{@code
	* UChacterIterator iter = new UCharacterIterator.getInstance(text);
	* char[] buf = new char[iter.getLength()];
	* iter.getText(buf);
	*
	* OR
	* char[] buf= new char[1];
	* int len = 0;
	* for(;;){
	* try{
	* len = iter.getText(buf);
	* break;
	* }catch(IndexOutOfBoundsException e){
	* buf = new char[iter.getLength()];
	* }
	* }
	* }</pre>
	*
	* @param fillIn an array of chars to fill with the underlying UTF-16 code
	* units.
	* @param offset the position within the array to start putting the data.
	* @return the number of code units added to fillIn, as a convenience
	* @exception IndexOutOfBoundsException exception if there is not enough
	* room after offset in the array, or if offset < 0.
	* @stable ICU 2.4
	*/
	public abstract int getText(char[] fillIn, int offset);

	/**
	* Convenience override for <code>getText(char[], int)</code> that provides
	* an offset of 0.
	* @param fillIn an array of chars to fill with the underlying UTF-16 code
	* units.
	* @return the number of code units added to fillIn, as a convenience
	* @exception IndexOutOfBoundsException exception if there is not enough
	* room in the array.
	* @stable ICU 2.4
	*/
	public final int getText(char[] fillIn) {
	return getText(fillIn, 0);
	}

	/**
	* Convenience method for returning the underlying text storage as a string
	* @return the underlying text storage in the iterator as a string
	* @stable ICU 2.4
	*/
	public String getText() {
	char[] text = new char[getLength()];
	getText(text);
	return new String(text);
	}

	/**
	* Moves the current position by the number of code points
	* specified, either forward or backward depending on the sign of
	* delta (positive or negative respectively). If the current index
	* is at a trail surrogate then the first adjustment is by code
	* unit, and the remaining adjustments are by code points. If the
	* resulting index would be less than zero, the index is set to
	* zero, and if the resulting index would be greater than limit,
	* the index is set to limit.
	* @param delta the number of code units to move the current index.
	* @return the new index
	* @exception IndexOutOfBoundsException is thrown if an invalid delta is
	* supplied
	* @stable ICU 2.4
	*
	*/
	public int moveCodePointIndex(int delta){
	if(delta>0){
	while(delta>0 && nextCodePoint() != DONE){delta--;}
	}else{
	while(delta<0 && previousCodePoint() != DONE){delta++;}
	}
	if(delta!=0){
	throw new IndexOutOfBoundsException();
	}

	return getIndex();
	}

	/**
	* Creates a copy of this iterator, independent from other iterators.
	* If it is not possible to clone the iterator, returns null.
	* @return copy of this iterator
	* @stable ICU 2.4
	*/
	public Object clone() throws CloneNotSupportedException{
	return super.clone();
	}

	}

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