def getEpsilonTarget(self, input: InputStream, config: LexerATNConfig,
t: Transition, configs: ATNConfigSet,
speculative: bool, treatEofAsEpsilon: bool):
c = None
if t.serializationType == Transition.RULE:
newContext = SingletonPredictionContext.create(
config.context, t.followState.stateNumber)
c = LexerATNConfig(state=t.target,
config=config,
context=newContext)
elif t.serializationType == Transition.PRECEDENCE:
raise UnsupportedOperationException(
"Precedence predicates are not supported in lexers.")
elif t.serializationType == Transition.PREDICATE:
# Track traversing semantic predicates. If we traverse,
# we cannot add a DFA state for this "reach" computation
# because the DFA would not test the predicate again in the
# future. Rather than creating collections of semantic predicates
# like v3 and testing them on prediction, v4 will test them on the
# fly all the time using the ATN not the DFA. This is slower but
# semantically it's not used that often. One of the key elements to
# this predicate mechanism is not adding DFA states that see
# predicates immediately afterwards in the ATN. For example,
# a : ID {p1}? | ID {p2}? ;
# should create the start state for rule 'a' (to save start state
# competition), but should not create target of ID state. The
# collection of ATN states the following ID references includes
# states reached by traversing predicates. Since this is when we
# test them, we cannot cash the DFA state target of ID.
if self.debug:
print("EVAL rule " + str(t.ruleIndex) + ":" + str(t.predIndex))
configs.hasSemanticContext = True
if self.evaluatePredicate(input, t.ruleIndex, t.predIndex,
speculative):
c = LexerATNConfig(state=t.target, config=config)
elif t.serializationType == Transition.ACTION:
if config.context is None or config.context.hasEmptyPath():
# execute actions anywhere in the start rule for a token.
#
# TODO: if the entry rule is invoked recursively, some
# actions may be executed during the recursive call. The
# problem can appear when hasEmptyPath() is true but
# isEmpty() is false. In this case, the config needs to be
# split into two contexts - one with just the empty path
# and another with everything but the empty path.
# Unfortunately, the current algorithm does not allow
# getEpsilonTarget to return two configurations, so
# additional modifications are needed before we can support
# the split operation.
lexerActionExecutor = LexerActionExecutor.append(
config.lexerActionExecutor,
self.atn.lexerActions[t.actionIndex])
c = LexerATNConfig(state=t.target,
config=config,
lexerActionExecutor=lexerActionExecutor)
else:
# ignore actions in referenced rules
c = LexerATNConfig(state=t.target, config=config)
elif t.serializationType == Transition.EPSILON:
c = LexerATNConfig(state=t.target, config=config)
elif t.serializationType in [
Transition.ATOM, Transition.RANGE, Transition.SET
]:
if treatEofAsEpsilon:
if t.matches(Token.EOF, 0, 0xFFFF):
c = LexerATNConfig(state=t.target, config=config)
return c
def _LOOK(self, s, stopState , ctx, look, lookBusy, \
calledRuleStack, seeThruPreds, addEOF):
c = ATNConfig(s, 0, ctx)
if c in lookBusy:
return
lookBusy.add(c)
if s == stopState:
if ctx is None:
look.addOne(Token.EPSILON)
return
elif ctx.isEmpty() and addEOF:
look.addOne(Token.EOF)
return
if isinstance(s, RuleStopState ):
if ctx is None:
look.addOne(Token.EPSILON)
return
elif ctx.isEmpty() and addEOF:
look.addOne(Token.EOF)
return
if ctx != PredictionContext.EMPTY:
# run thru all possible stack tops in ctx
for i in range(0, len(ctx)):
returnState = self.atn.states[ctx.getReturnState(i)]
removed = returnState.ruleIndex in calledRuleStack
try:
calledRuleStack.discard(returnState.ruleIndex)
self._LOOK(returnState, stopState, ctx.getParent(i), look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
finally:
if removed:
calledRuleStack.add(returnState.ruleIndex)
return
for t in s.transitions:
if type(t) == RuleTransition:
if t.target.ruleIndex in calledRuleStack:
continue
newContext = SingletonPredictionContext.create(ctx, t.followState.stateNumber)
try:
calledRuleStack.add(t.target.ruleIndex)
self._LOOK(t.target, stopState, newContext, look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
finally:
calledRuleStack.remove(t.target.ruleIndex)
elif isinstance(t, AbstractPredicateTransition ):
if seeThruPreds:
self._LOOK(t.target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
else:
look.addOne(self.HIT_PRED)
elif t.isEpsilon:
self._LOOK(t.target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
elif type(t) == WildcardTransition:
look.addRange( Interval(Token.MIN_USER_TOKEN_TYPE, self.atn.maxTokenType + 1) )
else:
set = t.label
if set is not None:
if isinstance(t, NotSetTransition):
set = set.complement(Token.MIN_USER_TOKEN_TYPE, self.atn.maxTokenType)
look.addSet(set)
def getEpsilonTarget(self, input:InputStream, config:LexerATNConfig, t:Transition, configs:ATNConfigSet,
speculative:bool, treatEofAsEpsilon:bool):
c = None
if t.serializationType==Transition.RULE:
newContext = SingletonPredictionContext.create(config.context, t.followState.stateNumber)
c = LexerATNConfig(state=t.target, config=config, context=newContext)
elif t.serializationType==Transition.PRECEDENCE:
raise UnsupportedOperationException("Precedence predicates are not supported in lexers.")
elif t.serializationType==Transition.PREDICATE:
# Track traversing semantic predicates. If we traverse,
# we cannot add a DFA state for this "reach" computation
# because the DFA would not test the predicate again in the
# future. Rather than creating collections of semantic predicates
# like v3 and testing them on prediction, v4 will test them on the
# fly all the time using the ATN not the DFA. This is slower but
# semantically it's not used that often. One of the key elements to
# this predicate mechanism is not adding DFA states that see
# predicates immediately afterwards in the ATN. For example,
# a : ID {p1}? | ID {p2}? ;
# should create the start state for rule 'a' (to save start state
# competition), but should not create target of ID state. The
# collection of ATN states the following ID references includes
# states reached by traversing predicates. Since this is when we
# test them, we cannot cash the DFA state target of ID.
if LexerATNSimulator.debug:
print("EVAL rule "+ str(t.ruleIndex) + ":" + str(t.predIndex))
configs.hasSemanticContext = True
if self.evaluatePredicate(input, t.ruleIndex, t.predIndex, speculative):
c = LexerATNConfig(state=t.target, config=config)
elif t.serializationType==Transition.ACTION:
if config.context is None or config.context.hasEmptyPath():
# execute actions anywhere in the start rule for a token.
#
# TODO: if the entry rule is invoked recursively, some
# actions may be executed during the recursive call. The
# problem can appear when hasEmptyPath() is true but
# isEmpty() is false. In this case, the config needs to be
# split into two contexts - one with just the empty path
# and another with everything but the empty path.
# Unfortunately, the current algorithm does not allow
# getEpsilonTarget to return two configurations, so
# additional modifications are needed before we can support
# the split operation.
lexerActionExecutor = LexerActionExecutor.append(config.lexerActionExecutor,
self.atn.lexerActions[t.actionIndex])
c = LexerATNConfig(state=t.target, config=config, lexerActionExecutor=lexerActionExecutor)
else:
# ignore actions in referenced rules
c = LexerATNConfig(state=t.target, config=config)
elif t.serializationType==Transition.EPSILON:
c = LexerATNConfig(state=t.target, config=config)
elif t.serializationType in [ Transition.ATOM, Transition.RANGE, Transition.SET ]:
if treatEofAsEpsilon:
if t.matches(Token.EOF, 0, 0xFFFF):
c = LexerATNConfig(state=t.target, config=config)
return c
