antlr4-runtime/src/antlr4/state/ATNState.js

JavaScript runtime for ANTLR4

/* Copyright (c) 2012-2022 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.
 */

/**
 * The following images show the relation of states and
 * {@link ATNState//transitions} for various grammar constructs.
 *
 * <ul>
 *
 * <li>Solid edges marked with an &//0949; indicate a required
 * {@link EpsilonTransition}.</li>
 *
 * <li>Dashed edges indicate locations where any transition derived from
 * {@link Transition} might appear.</li>
 *
 * <li>Dashed nodes are place holders for either a sequence of linked
 * {@link BasicState} states or the inclusion of a block representing a nested
 * construct in one of the forms below.</li>
 *
 * <li>Nodes showing multiple outgoing alternatives with a {@code ...} support
 * any number of alternatives (one or more). Nodes without the {@code ...} only
 * support the exact number of alternatives shown in the diagram.</li>
 *
 * </ul>
 *
 * <h2>Basic Blocks</h2>
 *
 * <h3>Rule</h3>
 *
 * <embed src="images/Rule.svg" type="image/svg+xml"/>
 *
 * <h3>Block of 1 or more alternatives</h3>
 *
 * <embed src="images/Block.svg" type="image/svg+xml"/>
 *
 * <h2>Greedy Loops</h2>
 *
 * <h3>Greedy Closure: {@code (...)*}</h3>
 *
 * <embed src="images/ClosureGreedy.svg" type="image/svg+xml"/>
 *
 * <h3>Greedy Positive Closure: {@code (...)+}</h3>
 *
 * <embed src="images/PositiveClosureGreedy.svg" type="image/svg+xml"/>
 *
 * <h3>Greedy Optional: {@code (...)?}</h3>
 *
 * <embed src="images/OptionalGreedy.svg" type="image/svg+xml"/>
 *
 * <h2>Non-Greedy Loops</h2>
 *
 * <h3>Non-Greedy Closure: {@code (...)*?}</h3>
 *
 * <embed src="images/ClosureNonGreedy.svg" type="image/svg+xml"/>
 *
 * <h3>Non-Greedy Positive Closure: {@code (...)+?}</h3>
 *
 * <embed src="images/PositiveClosureNonGreedy.svg" type="image/svg+xml"/>
 *
 * <h3>Non-Greedy Optional: {@code (...)??}</h3>
 *
 * <embed src="images/OptionalNonGreedy.svg" type="image/svg+xml"/>
 */
export default class ATNState {
    constructor() {
        // Which ATN are we in?
        this.atn = null;
        this.stateNumber = ATNState.INVALID_STATE_NUMBER;
        this.stateType = null;
        this.ruleIndex = 0; // at runtime, we don't have Rule objects
        this.epsilonOnlyTransitions = false;
        // Track the transitions emanating from this ATN state.
        this.transitions = [];
        // Used to cache lookahead during parsing, not used during construction
        this.nextTokenWithinRule = null;
    }

    toString() {
        return this.stateNumber;
    }

    equals(other) {
        if (other instanceof ATNState) {
            return this.stateNumber===other.stateNumber;
        } else {
            return false;
        }
    }

    isNonGreedyExitState() {
        return false;
    }

    addTransition(trans, index) {
        if(index===undefined) {
            index = -1;
        }
        if (this.transitions.length===0) {
            this.epsilonOnlyTransitions = trans.isEpsilon;
        } else if(this.epsilonOnlyTransitions !== trans.isEpsilon) {
            this.epsilonOnlyTransitions = false;
        }
        if (index===-1) {
            this.transitions.push(trans);
        } else {
            this.transitions.splice(index, 1, trans);
        }
    }
}

// constants for serialization
ATNState.INVALID_TYPE = 0;
ATNState.BASIC = 1;
ATNState.RULE_START = 2;
ATNState.BLOCK_START = 3;
ATNState.PLUS_BLOCK_START = 4;
ATNState.STAR_BLOCK_START = 5;
ATNState.TOKEN_START = 6;
ATNState.RULE_STOP = 7;
ATNState.BLOCK_END = 8;
ATNState.STAR_LOOP_BACK = 9;
ATNState.STAR_LOOP_ENTRY = 10;
ATNState.PLUS_LOOP_BACK = 11;
ATNState.LOOP_END = 12;

ATNState.serializationNames = [
            "INVALID",
            "BASIC",
            "RULE_START",
            "BLOCK_START",
            "PLUS_BLOCK_START",
            "STAR_BLOCK_START",
            "TOKEN_START",
            "RULE_STOP",
            "BLOCK_END",
            "STAR_LOOP_BACK",
            "STAR_LOOP_ENTRY",
            "PLUS_LOOP_BACK",
            "LOOP_END" ];

ATNState.INVALID_STATE_NUMBER = -1;