js.antlr4.atn.ATNSimulator.js Maven / Gradle / Ivy
//
/* 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.
*/
///
var DFAState = require('./../dfa/DFAState').DFAState;
var ATNConfigSet = require('./ATNConfigSet').ATNConfigSet;
var getCachedPredictionContext = require('./../PredictionContext').getCachedPredictionContext;
function ATNSimulator(atn, sharedContextCache) {
// The context cache maps all PredictionContext objects that are ==
// to a single cached copy. This cache is shared across all contexts
// in all ATNConfigs in all DFA states. We rebuild each ATNConfigSet
// to use only cached nodes/graphs in addDFAState(). We don't want to
// fill this during closure() since there are lots of contexts that
// pop up but are not used ever again. It also greatly slows down closure().
//
// This cache makes a huge difference in memory and a little bit in speed.
// For the Java grammar on java.*, it dropped the memory requirements
// at the end from 25M to 16M. We don't store any of the full context
// graphs in the DFA because they are limited to local context only,
// but apparently there's a lot of repetition there as well. We optimize
// the config contexts before storing the config set in the DFA states
// by literally rebuilding them with cached subgraphs only.
//
// I tried a cache for use during closure operations, that was
// whacked after each adaptivePredict(). It cost a little bit
// more time I think and doesn't save on the overall footprint
// so it's not worth the complexity.
///
this.atn = atn;
this.sharedContextCache = sharedContextCache;
return this;
}
// Must distinguish between missing edge and edge we know leads nowhere///
ATNSimulator.ERROR = new DFAState(0x7FFFFFFF, new ATNConfigSet());
ATNSimulator.prototype.getCachedContext = function(context) {
if (this.sharedContextCache ===null) {
return context;
}
var visited = {};
return getCachedPredictionContext(context, this.sharedContextCache, visited);
};
exports.ATNSimulator = ATNSimulator;