001/*
002 * Java Genetic Algorithm Library (jenetics-7.2.0).
003 * Copyright (c) 2007-2023 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020package io.jenetics.ext.internal.parser;
021
022import static java.lang.Character.isWhitespace;
023import static java.lang.String.format;
024import static java.util.Objects.requireNonNull;
025
026/**
027 * Base class for all tokenizers.
028 *
029 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
030 * @since 7.1
031 * @version 7.1
032 */
033public abstract class CharSequenceTokenizer implements Tokenizer<Token<String>> {
034
035        private static final char EOF = (char)-1;
036
037        private final CharSequence _input;
038
039        protected int pos = 0;
040        protected char c = EOF;
041
042        /**
043         * Create a new tokenizer from the given character sequence.
044         *
045         * @param input the input character sequence
046         * @throws NullPointerException if the given {@code input} is {@code null}
047         */
048        protected CharSequenceTokenizer(final CharSequence input) {
049                requireNonNull(input);
050
051                if (!input.isEmpty()) {
052                        c = input.charAt(0);
053                }
054                _input = input;
055        }
056
057        protected void match(final char ch) {
058                if (ch == c) {
059                        consume();
060                } else {
061                        throw new ParsingException(format(
062                                "Got invalid character '%s' at position '%d'; expected '%s'",
063                                c, pos, ch
064                        ));
065                }
066        }
067
068        protected void consume() {
069                if (pos + 1 >= _input.length()) {
070                        c = EOF;
071                } else {
072                        c = _input.charAt(++pos);
073                }
074        }
075
076        protected char LA(final int index) {
077                final int i = pos + index - 1;
078                return i < _input.length() && i >= 0 ? _input.charAt(i) : EOF;
079        }
080
081        public static boolean isNonEof(final char ch) {
082                return ch != EOF;
083        }
084
085        public static boolean isAlphabetic(final char c) {
086                return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z');
087        }
088
089        protected void WS() {
090                do {
091                        consume();
092                } while (isNonEof(c) && isWhitespace(c));
093        }
094
095}