content: /*******************************************************************************
   * Copyright (c) 2000, 2008 IBM Corporation and others.
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *     IBM Corporation - initial API and implementation
   *******************************************************************************/
  package org.eclipse.wst.jsdt.internal.ui.text;
  
  import java.text.CharacterIterator;
  
  import org.eclipse.core.runtime.Assert;
  
  
  
  /**
   * A <code>CharSequence</code> based implementation of <code>CharacterIterator</code>.
   *
   * 
   */
  public class SequenceCharacterIterator implements CharacterIterator {
  
  	private int fIndex= -1;
  	private final CharSequence fSequence;
  	private final int fFirst;
  	private final int fLast;
  
  	private void invariant() {
  		Assert.isTrue(fIndex >= fFirst);
  		Assert.isTrue(fIndex <= fLast);
  	}
  
  	/**
  	 * Creates an iterator for the entire sequence.
  	 *
  	 * @param sequence the sequence backing this iterator
  	 */
  	public SequenceCharacterIterator(CharSequence sequence) {
  		this(sequence, 0);
  	}
  
  	/**
  	 * Creates an iterator.
  	 *
  	 * @param sequence the sequence backing this iterator
  	 * @param first the first character to consider
  	 * @throws IllegalArgumentException if the indices are out of bounds
  	 */
  	public SequenceCharacterIterator(CharSequence sequence, int first) throws IllegalArgumentException {
  		this(sequence, first, sequence.length());
  	}
  
  	/**
  	 * Creates an iterator.
  	 *
  	 * @param sequence the sequence backing this iterator
  	 * @param first the first character to consider
  	 * @param last the last character index to consider
  	 * @throws IllegalArgumentException if the indices are out of bounds
  	 */
  	public SequenceCharacterIterator(CharSequence sequence, int first, int last) throws IllegalArgumentException {
  		if (sequence == null)
  			throw new NullPointerException();
  		if (first < 0 || first > last)
  			throw new IllegalArgumentException();
  		if (last > sequence.length())
  			throw new IllegalArgumentException();
  		fSequence= sequence;
  		fFirst= first;
  		fLast= last;
  		fIndex= first;
  		invariant();
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#first()
  	 */
  	public char first() {
  		return setIndex(getBeginIndex());
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#last()
  	 */
  	public char last() {
  		if (fFirst == fLast)
  			return setIndex(getEndIndex());
  		else
  			return setIndex(getEndIndex() - 1);
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#current()
  	 */
  	public char current() {
  		if (fIndex >= fFirst && fIndex < fLast)
  			return fSequence.charAt(fIndex);
  		else
  			return DONE;
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#next()
  	 */
  	public char next() {
  		return setIndex(Math.min(fIndex + 1, getEndIndex()));
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#previous()
  	 */
  	public char previous() {
  		if (fIndex > getBeginIndex()) {
  			return setIndex(fIndex - 1);
  		} else {
  			return DONE;
  		}
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#setIndex(int)
  	 */
  	public char setIndex(int position) {
  		if (position >= getBeginIndex() && position <= getEndIndex())
  			fIndex= position;
  		else
  			throw new IllegalArgumentException();
  
  		invariant();
  		return current();
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#getBeginIndex()
  	 */
  	public int getBeginIndex() {
  		return fFirst;
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#getEndIndex()
  	 */
  	public int getEndIndex() {
  		return fLast;
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#getIndex()
  	 */
  	public int getIndex() {
  		return fIndex;
  	}
  
  	/*
  	 * @see java.text.CharacterIterator#clone()
  	 */
  	public Object clone() {
  		try {
  			return super.clone();
  		} catch (CloneNotSupportedException e) {
  			throw new InternalError();
  		}
  	}
  }
  