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ATNState.js
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163 lines (135 loc) · 4.05 KB
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/* 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;