Literal.java

/*
 * Copyright (C) 2011 eXo Platform SAS.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.exoplatform.web.controller.regexp;

import java.io.IOException;


/**
 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a>
 */
public class Literal {
    /**
     * Return true if the char should be escaped. Note that the implementation sometime may escape the char although the context
     * in which it is used would not require its escape.
     *
     * @param c the char to test
     * @return true when the char should be escaped.
     */
    public static boolean isEscaped(char c) {
        return c >= '('
                && c <= '+' // ()*+
                || c == '?' || c == '{' || c == '}' || c == '|' || c == '$' || c == '&' || c == '^' || c == '-' || c == '.'
                || c == '[' || c == ']' || c == '\\';
    }

    /**
     * Return the char value as a string literal in a regexp. Note that the implementation does not tries to optimize the value
     * with respect to the AST context, (for instance (?) would be fine as (?) but it will rewritten as (\?).
     *
     * @param value the value
     * @return the escaped string
     */
    public String getEscape(char value) {
        switch (value) {
            case '|':
                return "\\|";
            case '&':
                return "\\&";
            case '$':
                return "\\$";
            case '^':
                return "\\^";
            case '-':
                return "\\-";
            case '.':
                return "\\.";
            case '?':
                return "\\?";
            case '+':
                return "\\+";
            case '*':
                return "\\*";
            case '[':
                return "\\[";
            case ']':
                return "\\]";
            case '(':
                return "\\(";
            case ')':
                return "\\)";
            case '{':
                return "\\{";
            case '}':
                return "\\}";
            case '\\':
                return "\\\\";
            default:
                return Character.toString(value);
        }
    }

    public static void escapeTo(char value, Appendable appendable) throws IOException, NullPointerException {
        if (appendable == null) {
            throw new NullPointerException();
        }
        if (isEscaped(value)) {
            appendable.append('\\');
        }
        appendable.append(value);
    }
}