VdmCharRule.java

/*
 * #%~
 * org.overture.ide.ui
 * %%
 * Copyright (C) 2008 - 2014 Overture
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program 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 for more details.
 * 
 * You should have received a copy of the GNU General Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #~%
 */
package org.overture.ide.ui.editor.partitioning;

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

public class VdmCharRule implements IPredicateRule
{
	private static final char QUOTE = '\'';
	private static final char BACK_SLASH = '\\';

	@Override
	public IToken evaluate(ICharacterScanner scanner)
	{
		return evaluate(scanner, true);
	}

	@Override
	public IToken getSuccessToken()
	{
		return new Token(IVdmPartitions.STRING);
	}

	@Override
	public IToken evaluate(ICharacterScanner scanner, boolean resume)
	{
		// Examples of chars '\uffff' , '\xff', 'a'
		int r = scanner.read();
		int reads = 1;

		if (r == ICharacterScanner.EOF && r != QUOTE)
		{
			resetScanner(scanner, reads);
			return Token.UNDEFINED;
		}

		if (r == QUOTE)
		{
			r = scanner.read();
			reads++;

			// Is the char using escape characters? Could be '\uffff' or '\xff'
			if (r == BACK_SLASH)
			{
				if (isAcceptedEscapeSequence(scanner))
				{
					return getSuccessToken();
				}
			} else
			// The char is not using escape characters
			{
				if (isValdChar(r))
				{
					r = scanner.read();
					reads++;

					if (r == QUOTE)
					{
						return getSuccessToken();
					}
				}
			}
		}

		resetScanner(scanner, reads);
		return Token.UNDEFINED;
	}

	private void resetScanner(ICharacterScanner scanner, int unreads)
	{
		for (int i = 0; i < unreads; i++)
		{
			scanner.unread();
		}
	}

	private boolean isValdChar(int c)
	{
		return c != ICharacterScanner.EOF && c != '\n' && c != '\t'
				&& c != '\r';
	}

	private boolean isAcceptedEscapeSequence(ICharacterScanner scanner)
	{
		int r;
		int reads = 0;
		do
		{

			r = scanner.read();
			reads++;

			if (r == QUOTE)
			{
				return true;
			}

		}
		// Keep it simple and assume the maximum char sequence
		while (isValdChar(r) && reads <= 5);

		// Not a valid sequence so unread what has been read
		for (int i = 0; i < reads; i++)
		{
			scanner.unread();
		}

		return false;
	}
}