SingleOperatorRule.java

/*******************************************************************************
 * Copyright (c) 2006 Oracle 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:
 *     Oracle Corporation - initial API and implementation
 *******************************************************************************/

package com.ebmwebsourcing.petals.common.xpath.internal.configuration.rules;

import org.eclipse.jface.text.rules.ICharacterScanner;
import org.eclipse.jface.text.rules.IRule;
import org.eclipse.jface.text.rules.IToken;
import org.eclipse.jface.text.rules.Token;

/**
 * Rule for a single operator. Things like +,-, *, /
 * 
 * Make sure that none of the single operators follow the single operator that
 * we specify here.
 * 
 * @author Michal Chmielewski (michal.chmielewski@oracle.com)
 * @date Oct 26, 2006
 */
public class SingleOperatorRule implements IRule {

	IToken fToken;
	String fChars;


	/**
	 * Return a brand new shiny Single Operator Rule object.
	 * @param token
	 * @param chars
	 */
	public SingleOperatorRule(IToken token, String chars) {
		assert token != null;
		this.fToken = token;
		assert chars != null;
		this.fChars = chars;
	}


	/*
	 * (non-Javadoc)
	 * @see org.eclipse.jface.text.rules.IRule
	 * #evaluate(org.eclipse.jface.text.rules.ICharacterScanner)
	 */
	public IToken evaluate(ICharacterScanner scanner) {

		int ch = scanner.read();
		if (this.fChars.indexOf(ch) >= 0) {
			// look ahead ... make sure we don't have any combination of that
			// character with the next one.
			int ch2 = scanner.read();
			scanner.unread();

			if (this.fChars.indexOf(ch2) >= 0) {
				scanner.unread();
				return Token.UNDEFINED;
			}

			return this.fToken;
		}

		scanner.unread();
		return Token.UNDEFINED;
	}
}