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;
  import org.eclipse.jface.text.BadLocationException;
  import org.eclipse.jface.text.IDocument;
  
  
  /**
   * An <code>IDocument</code> based implementation of
   * <code>CharacterIterator</code> and <code>CharSequence</code>. Note that
   * the supplied document is not copied; if the document is modified during the
   * lifetime of a <code>DocumentCharacterIterator</code>, the methods
   * returning document content may not always return the same values. Also, if
   * accessing the document fails with a {@link BadLocationException}, any of
   * <code>CharacterIterator</code> methods as well as <code>charAt</code>may
   * return {@link CharacterIterator#DONE}.
   *
   * 
   */
  public class DocumentCharacterIterator implements CharacterIterator, CharSequence {
  
  	private int fIndex= -1;
  	private final IDocument fDocument;
  	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 document.
  	 *
  	 * @param document the document backing this iterator
  	 */
  	public DocumentCharacterIterator(IDocument document) {
  		this(document, 0);
  	}
  
  	/**
  	 * Creates an iterator, starting at offset <code>first</code>.
  	 *
  	 * @param document the document backing this iterator
  	 * @param first the first character to consider
  	 * @throws IllegalArgumentException if the indices are out of bounds
  	 */
  	public DocumentCharacterIterator(IDocument document, int first) throws IllegalArgumentException {
  		this(document, first, document.getLength());
  	}
  
  	/**
  	 * Creates an iterator for the document contents from <code>first</code>
  	 * (inclusive) to <code>last</code> (exclusive).
  	 *
  	 * @param document the document 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 DocumentCharacterIterator(IDocument document, int first, int last) throws IllegalArgumentException {
  		if (document == null)
  			throw new NullPointerException();
  		if (first < 0 || first > last)
  			throw new IllegalArgumentException();
  		if (last > document.getLength())
  			throw new IllegalArgumentException();
  		fDocument= document;
  		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)
  			try {
  				return fDocument.getChar(fIndex);
  			} catch (BadLocationException e) {
  				// ignore
  			}
  		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();
  		}
  	}
  
  	/*
  	 * @see java.lang.CharSequence#length()
  	 */
  	public int length() {
  		return getEndIndex() - getBeginIndex();
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 * Note that, if the document is modified concurrently, this method may
  	 * return {@link CharacterIterator#DONE} if a {@link BadLocationException}
  	 * was thrown when accessing the backing document.
  	 * </p>
  	 *
  	 * @param index {@inheritDoc}
  	 * @return {@inheritDoc}
  	 */
  	public char charAt(int index) {
  		if (index >= 0 && index < length())
  			try {
  				return fDocument.getChar(getBeginIndex() + index);
  			} catch (BadLocationException e) {
  				// ignore and return DONE
  				return DONE;
  			}
  		else
  			throw new IndexOutOfBoundsException();
  	}
  
  	/*
  	 * @see java.lang.CharSequence#subSequence(int, int)
  	 */
  	public CharSequence subSequence(int start, int end) {
  		if (start < 0)
  			throw new IndexOutOfBoundsException();
  		if (end < start)
  			throw new IndexOutOfBoundsException();
  		if (end > length())
  			throw new IndexOutOfBoundsException();
  		return new DocumentCharacterIterator(fDocument, getBeginIndex() + start, getBeginIndex() + end);
  	}
  }
  