org.eclipse.jface.text/src/org/eclipse/jface/text/rules/WordPatternRule.java

/*******************************************************************************
 * Copyright (c) 2000, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.text.rules;


import org.eclipse.jface.text.Assert;



/**
 * A specific single line rule which stipulates that the start 
 * and end sequence occur within a single word, as defined by a word detector.
 *
 * @see IWordDetector
 */
public class WordPatternRule extends SingleLineRule {

	/** The word detector used by this rule */
	protected IWordDetector fDetector;
	/** The internal buffer used for pattern detection */
	private StringBuffer fBuffer= new StringBuffer();

	/**
	 * Creates a rule for the given starting and ending word
	 * pattern which, if detected, will return the specified token.
	 * A word detector is used to identify words.
	 *
	 * @param detector the word detector to be used
	 * @param startSequence the start sequence of the word pattern
	 * @param endSequence the end sequence of the word pattern
	 * @param token the token to be returned on success
	 */
	public WordPatternRule(IWordDetector detector, String startSequence, String endSequence, IToken token) {
		this(detector, startSequence, endSequence, token, (char)0);
	}

	/**
	/**
	 * Creates a rule for the given starting and ending word
	 * pattern which, if detected, will return the specified token.
	 * A word detector is used to identify words.
	 * Any character which follows the given escapeCharacter will be ignored.
	 *
	 * @param detector the word detector to be used
	 * @param startSequence the start sequence of the word pattern
	 * @param endSequence the end sequence of the word pattern
	 * @param token the token to be returned on success
	 * @param escapeCharacter the escape character
	 */
	public WordPatternRule(IWordDetector detector, String startSequence, String endSequence, IToken token, char escapeCharacter) {
		super(startSequence, endSequence, token, escapeCharacter);
		Assert.isNotNull(detector);
		fDetector= detector;
	}

	/**
	 * Returns whether the end sequence was detected.
	 * The rule acquires the rest of the word, using the
	 * provided word detector, and tests to determine if 
	 * it ends with the end sequence.
	 *
	 * @param scanner the scanner to be used
	 * @return <code>true</code> if the word ends on the given end sequence
	 */
	protected boolean endSequenceDetected(ICharacterScanner scanner) {
		fBuffer.setLength(0);
		int c= scanner.read();
		while (fDetector.isWordPart((char) c)) {
			fBuffer.append((char) c);
			c= scanner.read();
		}
		scanner.unread();
		
		if (fBuffer.length() >= fEndSequence.length) {
			for (int i=fEndSequence.length - 1, j= fBuffer.length() - 1; i >= 0; i--, j--) {
				if (fEndSequence[i] != fBuffer.charAt(j)) {
					unreadBuffer(scanner);
					return false;
				}
			}
			return true;
		}
		
		unreadBuffer(scanner);
		return false;
	}
	
	/**
	 * Returns the characters in the buffer to the scanner.
	 * Note that the rule must also return the characters
	 * read in as part of the start sequence expect the first one.
	 *
	 * @param scanner the scanner to be used
	 */
	protected void unreadBuffer(ICharacterScanner scanner) {
		fBuffer.insert(0, fStartSequence);
		for (int i= fBuffer.length() - 1; i > 0; i--)
			scanner.unread();
	}
}