io.jenetics.ext.internal.parser.CharSequenceTokenizer Maven / Gradle / Ivy

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/*
 * Java Genetic Algorithm Library (jenetics-8.1.0).
 * Copyright (c) 2007-2024 Franz Wilhelmstötter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Author:
 *    Franz Wilhelmstötter ([email protected])
 */
package io.jenetics.ext.internal.parser;

import static java.lang.Character.isWhitespace;
import static java.lang.String.format;
import static java.util.Objects.requireNonNull;

/**
 * Base class for all tokenizers.
 *
 * @author Franz Wilhelmstötter
 * @since 7.1
 * @version 7.1
 */
public abstract class CharSequenceTokenizer implements Tokenizer> {

	private static final char EOF = (char)-1;

	private final CharSequence _input;

	protected int pos = 0;
	protected char c = EOF;

	/**
	 * Create a new tokenizer from the given character sequence.
	 *
	 * @param input the input character sequence
	 * @throws NullPointerException if the given {@code input} is {@code null}
	 */
	protected CharSequenceTokenizer(final CharSequence input) {
		requireNonNull(input);

		if (!input.isEmpty()) {
			c = input.charAt(0);
		}
		_input = input;
	}

	protected void match(final char ch) {
		if (ch == c) {
			consume();
		} else {
			throw new ParsingException(format(
				"Got invalid character '%s' at position '%d'; expected '%s'",
				c, pos, ch
			));
		}
	}

	protected void consume() {
		if (pos + 1 >= _input.length()) {
			c = EOF;
		} else {
			c = _input.charAt(++pos);
		}
	}

	protected char LA(final int index) {
		final int i = pos + index - 1;
		return i < _input.length() && i >= 0 ? _input.charAt(i) : EOF;
	}

	public static boolean isNonEof(final char ch) {
		return ch != EOF;
	}

	public static boolean isAlphabetic(final char c) {
		return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z');
	}

	protected void WS() {
		do {
			consume();
		} while (isNonEof(c) && isWhitespace(c));
	}

}