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The ANTLR 4 grammar compiler.
There is a newer version: 4.13.1.5
/*
 * Copyright (c) 2012 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.tool;

import org.antlr.v4.runtime.Token;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.runtime.misc.Nullable;
import org.antlr.v4.tool.ast.GrammarAST;

import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.Set;

/** Track the attributes within retval, arg lists etc...
 *  
 *  Each rule has potentially 3 scopes: return values,
 *  parameters, and an implicitly-named scope (i.e., a scope defined in a rule).
 *  Implicitly-defined scopes are named after the rule; rules and scopes then
 *  must live in the same name space--no collisions allowed.
 */
public class AttributeDict {
    public String name;
    public GrammarAST ast;
	public DictType type;

    /** All {@link Token} scopes (token labels) share the same fixed scope of
     *  of predefined attributes.  I keep this out of the {@link Token}
     *  interface to avoid a runtime type leakage.
     */
    public static final AttributeDict predefinedTokenDict = new AttributeDict(DictType.TOKEN);
    static {
        predefinedTokenDict.add(new Attribute("text"));
        predefinedTokenDict.add(new Attribute("type"));
        predefinedTokenDict.add(new Attribute("line"));
        predefinedTokenDict.add(new Attribute("index"));
        predefinedTokenDict.add(new Attribute("pos"));
        predefinedTokenDict.add(new Attribute("channel"));
        predefinedTokenDict.add(new Attribute("int"));
    }

    public enum DictType {
        ARG, RET, LOCAL, TOKEN,
		PREDEFINED_RULE, PREDEFINED_LEXER_RULE,
    }

    /** The list of {@link Attribute} objects. */
	@NotNull
    public final LinkedHashMap attributes =
        new LinkedHashMap();

	public AttributeDict() {}
	public AttributeDict(DictType type) { this.type = type; }

	public Attribute add(Attribute a) { a.dict = this; return attributes.put(a.name, a); }
    public Attribute get(String name) { return attributes.get(name); }

    public String getName() {
        return name;
    }

    public int size() { return attributes.size(); }

    /** Return the set of keys that collide from
     *  {@code this} and {@code other}.
     */
	@NotNull
    public Set intersection(@Nullable AttributeDict other) {
        if ( other==null || other.size()==0 || size()==0 ) {
            return Collections.emptySet();
        }

		Set result = new HashSet(attributes.keySet());
		result.retainAll(other.attributes.keySet());
		return result;
    }

    @Override
    public String toString() {
        return getName()+":"+attributes;
    }
}