ANTLR is a powerful parser generator for multiple programming languages including Java.

ANTLR contains 2 major modules:

• Runtime - For building and executing parsers/lexers generated in Java.
• Tool (The Parser Generator) - For generating parsers/lexers Java class.

ANTLR Tool Source Code files are provided in the distribution packge (antlr4-4.10.1.zip). You can download them at ANTLR Website.

You can also browse the source code below:

⏎ org/antlr/v4/codegen/model/TestSetInline.java

/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.codegen.model;

import org.antlr.v4.codegen.OutputModelFactory;
import org.antlr.v4.runtime.misc.IntervalSet;
import org.antlr.v4.tool.ast.GrammarAST;

import java.util.ArrayList;
import java.util.List;

/** */
public class TestSetInline extends SrcOp {
	public int bitsetWordSize;
	public String varName;
	public Bitset[] bitsets;

	public TestSetInline(OutputModelFactory factory, GrammarAST ast, IntervalSet set, int wordSize) {
		super(factory, ast);
		bitsetWordSize = wordSize;
		Bitset[] withZeroOffset = createBitsets(factory, set, wordSize, true);
		Bitset[] withoutZeroOffset = createBitsets(factory, set, wordSize, false);
		this.bitsets = withZeroOffset.length <= withoutZeroOffset.length ? withZeroOffset : withoutZeroOffset;
		this.varName = "_la";
	}

	private static Bitset[] createBitsets(OutputModelFactory factory,
										  IntervalSet set,
										  int wordSize,
										  boolean useZeroOffset) {
		List<Bitset> bitsetList = new ArrayList<Bitset>();
		for (int ttype : set.toArray()) {
			Bitset current = !bitsetList.isEmpty() ? bitsetList.get(bitsetList.size() - 1) : null;
			if (current == null || ttype > (current.shift + wordSize-1)) {
				current = new Bitset();
				if (useZeroOffset && ttype >= 0 && ttype < wordSize-1) {
					current.shift = 0;
				}
				else {
					current.shift = ttype;
				}

				bitsetList.add(current);
			}

			current.ttypes.add(factory.getGenerator().getTarget().getTokenTypeAsTargetLabel(factory.getGrammar(), ttype));
		}

		return bitsetList.toArray(new Bitset[0]);
	}

	public static final class Bitset {
		public int shift;
		public final List<String> ttypes = new ArrayList<String>();
	}
}

⏎ org/antlr/v4/codegen/model/TestSetInline.java

Or download all of them as a single archive file:

File name: antlr-tool-4.10.1-sources.jar
File size: 347718 bytes
Release date: 2022-04-15
Download 

⇒ Donwload antlr4-4.10.1.zip

⇐ ANTLR Runtime Source Code

⇑ Download and Review ANTLR Parser Generator

⇑⇑ FAQ for ANTLR Parser Generator