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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.
*/
#include "atn/RuleStopState.h"
#include "atn/Transition.h"
#include "atn/RuleTransition.h"
#include "atn/SingletonPredictionContext.h"
#include "atn/AbstractPredicateTransition.h"
#include "atn/WildcardTransition.h"
#include "atn/NotSetTransition.h"
#include "misc/IntervalSet.h"
#include "atn/ATNConfig.h"
#include "atn/EmptyPredictionContext.h"
#include "support/CPPUtils.h"
#include "atn/LL1Analyzer.h"
using namespace antlr4;
using namespace antlr4::atn;
using namespace antlrcpp;
LL1Analyzer::LL1Analyzer(const ATN &atn) : _atn(atn) {
}
LL1Analyzer::~LL1Analyzer() {
}
std::vector<misc::IntervalSet> LL1Analyzer::getDecisionLookahead(ATNState *s) const {
std::vector<misc::IntervalSet> look;
if (s == nullptr) {
return look;
}
look.resize(s->transitions.size()); // Fills all interval sets with defaults.
for (size_t alt = 0; alt < s->transitions.size(); alt++) {
bool seeThruPreds = false; // fail to get lookahead upon pred
ATNConfig::Set lookBusy;
antlrcpp::BitSet callRuleStack;
_LOOK(s->transitions[alt]->target, nullptr, PredictionContext::EMPTY,
look[alt], lookBusy, callRuleStack, seeThruPreds, false);
// Wipe out lookahead for this alternative if we found nothing
// or we had a predicate when we !seeThruPreds
if (look[alt].size() == 0 || look[alt].contains(HIT_PRED)) {
look[alt].clear();
}
}
return look;
}
misc::IntervalSet LL1Analyzer::LOOK(ATNState *s, RuleContext *ctx) const {
return LOOK(s, nullptr, ctx);
}
misc::IntervalSet LL1Analyzer::LOOK(ATNState *s, ATNState *stopState, RuleContext *ctx) const {
misc::IntervalSet r;
bool seeThruPreds = true; // ignore preds; get all lookahead
Ref<PredictionContext> lookContext = ctx != nullptr ? PredictionContext::fromRuleContext(_atn, ctx) : nullptr;
ATNConfig::Set lookBusy;
antlrcpp::BitSet callRuleStack;
_LOOK(s, stopState, lookContext, r, lookBusy, callRuleStack, seeThruPreds, true);
return r;
}
void LL1Analyzer::_LOOK(ATNState *s, ATNState *stopState, Ref<PredictionContext> const& ctx, misc::IntervalSet &look,
ATNConfig::Set &lookBusy, antlrcpp::BitSet &calledRuleStack, bool seeThruPreds, bool addEOF) const {
Ref<ATNConfig> c = std::make_shared<ATNConfig>(s, 0, ctx);
if (lookBusy.count(c) > 0) // Keep in mind comparison is based on members of the class, not the actual instance.
return;
lookBusy.insert(c);
// ml: s can never be null, hence no need to check if stopState is != null.
if (s == stopState) {
if (ctx == nullptr) {
look.add(Token::EPSILON);
return;
} else if (ctx->isEmpty() && addEOF) {
look.add(Token::EOF);
return;
}
}
if (s->getStateType() == ATNState::RULE_STOP) {
if (ctx == nullptr) {
look.add(Token::EPSILON);
return;
} else if (ctx->isEmpty() && addEOF) {
look.add(Token::EOF);
return;
}
if (ctx != PredictionContext::EMPTY) {
bool removed = calledRuleStack.test(s->ruleIndex);
calledRuleStack[s->ruleIndex] = false;
auto onExit = finally([removed, &calledRuleStack, s] {
if (removed) {
calledRuleStack.set(s->ruleIndex);
}
});
// run thru all possible stack tops in ctx
for (size_t i = 0; i < ctx->size(); i++) {
ATNState *returnState = _atn.states[ctx->getReturnState(i)];
_LOOK(returnState, stopState, ctx->getParent(i), look, lookBusy, calledRuleStack, seeThruPreds, addEOF);
}
return;
}
}
size_t n = s->transitions.size();
for (size_t i = 0; i < n; i++) {
Transition *t = s->transitions[i];
if (t->getSerializationType() == Transition::RULE) {
if (calledRuleStack[(static_cast<RuleTransition*>(t))->target->ruleIndex]) {
continue;
}
Ref<PredictionContext> newContext = SingletonPredictionContext::create(ctx, (static_cast<RuleTransition*>(t))->followState->stateNumber);
auto onExit = finally([t, &calledRuleStack] {
calledRuleStack[(static_cast<RuleTransition*>(t))->target->ruleIndex] = false;
});
calledRuleStack.set((static_cast<RuleTransition*>(t))->target->ruleIndex);
_LOOK(t->target, stopState, newContext, look, lookBusy, calledRuleStack, seeThruPreds, addEOF);
} else if (is<AbstractPredicateTransition *>(t)) {
if (seeThruPreds) {
_LOOK(t->target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF);
} else {
look.add(HIT_PRED);
}
} else if (t->isEpsilon()) {
_LOOK(t->target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF);
} else if (t->getSerializationType() == Transition::WILDCARD) {
look.addAll(misc::IntervalSet::of(Token::MIN_USER_TOKEN_TYPE, static_cast<ssize_t>(_atn.maxTokenType)));
} else {
misc::IntervalSet set = t->label();
if (!set.isEmpty()) {
if (is<NotSetTransition*>(t)) {
set = set.complement(misc::IntervalSet::of(Token::MIN_USER_TOKEN_TYPE, static_cast<ssize_t>(_atn.maxTokenType)));
}
look.addAll(set);
}
}
}
}
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