lib/python3.9/site-packages/antlr4/ParserInterpreter.py

#
# 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.
#

# A parser simulator that mimics what ANTLR's generated
#  parser code does. A ParserATNSimulator is used to make
#  predictions via adaptivePredict but this class moves a pointer through the
#  ATN to simulate parsing. ParserATNSimulator just
#  makes us efficient rather than having to backtrack, for example.
#
#  This properly creates parse trees even for left recursive rules.
#
#  We rely on the left recursive rule invocation and special predicate
#  transitions to make left recursive rules work.
#
#  See TestParserInterpreter for examples.
#
from antlr4.dfa.DFA import DFA
from antlr4.BufferedTokenStream import TokenStream
from antlr4.Lexer import Lexer
from antlr4.Parser import Parser
from antlr4.ParserRuleContext import InterpreterRuleContext, ParserRuleContext
from antlr4.Token import Token
from antlr4.atn.ATN import ATN
from antlr4.atn.ATNState import StarLoopEntryState, ATNState, LoopEndState
from antlr4.atn.ParserATNSimulator import ParserATNSimulator
from antlr4.PredictionContext import PredictionContextCache
from antlr4.atn.Transition import Transition
from antlr4.error.Errors import RecognitionException, UnsupportedOperationException, FailedPredicateException


class ParserInterpreter(Parser):
    __slots__ = (
        'grammarFileName', 'atn', 'tokenNames', 'ruleNames', 'decisionToDFA',
        'sharedContextCache', '_parentContextStack',
        'pushRecursionContextStates'
    )

    def __init__(self, grammarFileName:str, tokenNames:list, ruleNames:list, atn:ATN, input:TokenStream):
        super().__init__(input)
        self.grammarFileName = grammarFileName
        self.atn = atn
        self.tokenNames = tokenNames
        self.ruleNames = ruleNames
        self.decisionToDFA = [ DFA(state) for state in atn.decisionToState ]
        self.sharedContextCache = PredictionContextCache()
        self._parentContextStack = list()
        # identify the ATN states where pushNewRecursionContext must be called
        self.pushRecursionContextStates = set()
        for state in atn.states:
            if not isinstance(state, StarLoopEntryState):
                continue
            if state.isPrecedenceDecision:
                self.pushRecursionContextStates.add(state.stateNumber)
        # get atn simulator that knows how to do predictions
        self._interp = ParserATNSimulator(self, atn, self.decisionToDFA, self.sharedContextCache)

    # Begin parsing at startRuleIndex#
    def parse(self, startRuleIndex:int):
        startRuleStartState = self.atn.ruleToStartState[startRuleIndex]
        rootContext = InterpreterRuleContext(None, ATNState.INVALID_STATE_NUMBER, startRuleIndex)
        if startRuleStartState.isPrecedenceRule:
            self.enterRecursionRule(rootContext, startRuleStartState.stateNumber, startRuleIndex, 0)
        else:
            self.enterRule(rootContext, startRuleStartState.stateNumber, startRuleIndex)
        while True:
            p = self.getATNState()
            if p.stateType==ATNState.RULE_STOP :
                # pop; return from rule
                if len(self._ctx)==0:
                    if startRuleStartState.isPrecedenceRule:
                        result = self._ctx
                        parentContext = self._parentContextStack.pop()
                        self.unrollRecursionContexts(parentContext.a)
                        return result
                    else:
                        self.exitRule()
                        return rootContext
                self.visitRuleStopState(p)

            else:
                try:
                    self.visitState(p)
                except RecognitionException as e:
                    self.state = self.atn.ruleToStopState[p.ruleIndex].stateNumber
                    self._ctx.exception = e
                    self._errHandler.reportError(self, e)
                    self._errHandler.recover(self, e)

    def enterRecursionRule(self, localctx:ParserRuleContext, state:int, ruleIndex:int, precedence:int):
        self._parentContextStack.append((self._ctx, localctx.invokingState))
        super().enterRecursionRule(localctx, state, ruleIndex, precedence)

    def getATNState(self):
        return self.atn.states[self.state]

    def visitState(self, p:ATNState):
        edge = 0
        if len(p.transitions) > 1:
            self._errHandler.sync(self)
            edge = self._interp.adaptivePredict(self._input, p.decision, self._ctx)
        else:
            edge = 1

        transition = p.transitions[edge - 1]
        tt = transition.serializationType
        if tt==Transition.EPSILON:

            if self.pushRecursionContextStates[p.stateNumber] and not isinstance(transition.target, LoopEndState):
                t = self._parentContextStack[-1]
                ctx = InterpreterRuleContext(t[0], t[1], self._ctx.ruleIndex)
                self.pushNewRecursionContext(ctx, self.atn.ruleToStartState[p.ruleIndex].stateNumber, self._ctx.ruleIndex)

        elif tt==Transition.ATOM:

            self.match(transition.label)

        elif tt in [ Transition.RANGE, Transition.SET, Transition.NOT_SET]:

            if not transition.matches(self._input.LA(1), Token.MIN_USER_TOKEN_TYPE, Lexer.MAX_CHAR_VALUE):
                self._errHandler.recoverInline(self)
            self.matchWildcard()

        elif tt==Transition.WILDCARD:

            self.matchWildcard()

        elif tt==Transition.RULE:

            ruleStartState = transition.target
            ruleIndex = ruleStartState.ruleIndex
            ctx = InterpreterRuleContext(self._ctx, p.stateNumber, ruleIndex)
            if ruleStartState.isPrecedenceRule:
                self.enterRecursionRule(ctx, ruleStartState.stateNumber, ruleIndex, transition.precedence)
            else:
                self.enterRule(ctx, transition.target.stateNumber, ruleIndex)

        elif tt==Transition.PREDICATE:

            if not self.sempred(self._ctx, transition.ruleIndex, transition.predIndex):
                raise FailedPredicateException(self)

        elif tt==Transition.ACTION:

            self.action(self._ctx, transition.ruleIndex, transition.actionIndex)

        elif tt==Transition.PRECEDENCE:

            if not self.precpred(self._ctx, transition.precedence):
                msg = "precpred(_ctx, " + str(transition.precedence) + ")"
                raise FailedPredicateException(self, msg)

        else:
            raise UnsupportedOperationException("Unrecognized ATN transition type.")

        self.state = transition.target.stateNumber

    def visitRuleStopState(self, p:ATNState):
        ruleStartState = self.atn.ruleToStartState[p.ruleIndex]
        if ruleStartState.isPrecedenceRule:
            parentContext = self._parentContextStack.pop()
            self.unrollRecursionContexts(parentContext.a)
            self.state = parentContext[1]
        else:
            self.exitRule()

        ruleTransition = self.atn.states[self.state].transitions[0]
        self.state = ruleTransition.followState.stateNumber