JavaScript.src.antlr4.atn.ATNSimulator.js Maven / Gradle / Ivy
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//
// [The "BSD license"]
// Copyright (c) 2013 Terence Parr
// Copyright (c) 2013 Sam Harwell
// Copyright (c) 2014 Eric Vergnaud
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// 3. The name of the author may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
///
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;