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#
# 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.
#/
from antlr4.PredictionContext import PredictionContextCache, PredictionContext, getCachedPredictionContext
from antlr4.atn.ATN import ATN
from antlr4.atn.ATNConfigSet import ATNConfigSet
from antlr4.dfa.DFAState import DFAState
class ATNSimulator(object):
__slots__ = ('atn', 'sharedContextCache', '__dict__')
# Must distinguish between missing edge and edge we know leads nowhere#/
ERROR = DFAState(configs=ATNConfigSet())
ERROR.stateNumber = 0x7FFFFFFF
# 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().
#
# <p>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.</p>
#
# <p>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.</p>
#/
def __init__(self, atn:ATN, sharedContextCache:PredictionContextCache):
self.atn = atn
self.sharedContextCache = sharedContextCache
def getCachedContext(self, context:PredictionContext):
if self.sharedContextCache is None:
return context
visited = dict()
return getCachedPredictionContext(context, self.sharedContextCache, visited)
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