001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020
021package org.apache.directory.api.ldap.model.subtree;
022
023
024import java.io.Reader;
025
026import antlr.CharBuffer;
027import antlr.LexerSharedInputState;
028
029
030/**
031 * A reusable lexer class extended from antlr generated lexer for an LDAP
032 * subtree specification as defined by <a
033 * href="http://www.faqs.org/rfcs/rfc3672.html"> RFC 3672</a>. This class
034 * enables the reuse of the antlr lexer without having to recreate the it every
035 * time as stated in <a
036 * href="http://www.antlr.org:8080/pipermail/antlr-interest/2003-April/003631.html">
037 * a Antlr Interest Group mail</a> .
038 * 
039 * @see <a href="http://www.faqs.org/rfcs/rfc3672.html">RFC 3672</a>
040 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
041 */
042public class ReusableAntlrSubtreeSpecificationLexer extends AntlrSubtreeSpecificationLexer
043{
044    private boolean savedCaseSensitive;
045
046    private boolean savedCaseSensitiveLiterals;
047
048
049    /**
050     * Creates a ReusableAntlrSubtreeSpecificationLexer instance.
051     * 
052     * @param in
053     *            the input to the lexer
054     */
055    public ReusableAntlrSubtreeSpecificationLexer( Reader in )
056    {
057        super( in );
058        savedCaseSensitive = getCaseSensitive();
059        savedCaseSensitiveLiterals = getCaseSensitiveLiterals();
060    }
061
062
063    /**
064     * Resets the state of an antlr lexer and initializes it with new input.
065     * 
066     * @param in
067     *            the input to the lexer
068     */
069    public void prepareNextInput( Reader in )
070    {
071        CharBuffer buf = new CharBuffer( in );
072        LexerSharedInputState state = new LexerSharedInputState( buf );
073        this.setInputState( state );
074
075        this.setCaseSensitive( savedCaseSensitive );
076
077        // no set method for this protected field.
078        this.caseSensitiveLiterals = savedCaseSensitiveLiterals;
079    }
080}