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/*
* [The "BSD license"]
* Copyright (c) 2010 Terence Parr
* 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.
*/
package org.antlr.analysis;
import org.antlr.grammar.v3.ANTLRParser;
import org.antlr.misc.MultiMap;
import org.antlr.misc.Utils;
import org.antlr.runtime.Token;
import org.antlr.tool.ErrorManager;
import org.antlr.tool.Grammar;
import org.antlr.tool.GrammarAST;
import java.util.*;
/** Collection of information about what is wrong with a decision as
* discovered while building the DFA predictor.
*
* The information is collected during NFA→DFA conversion and, while
* some of this is available elsewhere, it is nice to have it all tracked
* in one spot so a great error message can be easily had. I also like
* the fact that this object tracks it all for later perusing to make an
* excellent error message instead of lots of imprecise on-the-fly warnings
* (during conversion).
*
* A decision normally only has one problem; e.g., some input sequence
* can be matched by multiple alternatives. Unfortunately, some decisions
* such as
*
* a : ( A | B ) | ( A | B ) | A ;
*
* have multiple problems. So in general, you should approach a decision
* as having multiple flaws each one uniquely identified by a DFAState.
* For example, statesWithSyntacticallyAmbiguousAltsSet tracks the set of
* all DFAStates where ANTLR has discovered a problem. Recall that a decision
* is represented internall with a DFA comprised of multiple states, each of
* which could potentially have problems.
*
* Because of this, you need to iterate over this list of DFA states. You'll
* note that most of the informational methods like
* getSampleNonDeterministicInputSequence() require a DFAState. This state
* will be one of the iterated states from stateToSyntacticallyAmbiguousAltsSet.
*
* This class is not thread safe due to shared use of visited maps etc...
* Only one thread should really need to access one DecisionProbe anyway.
*/
public class DecisionProbe {
public DFA dfa;
/** Track all DFA states with nondeterministic alternatives.
* By reaching the same DFA state, a path through the NFA for some input
* is able to reach the same NFA state by starting at more than one
* alternative's left edge. Though, later, we may find that predicates
* resolve the issue, but track info anyway.
* Note that from the DFA state, you can ask for
* which alts are nondeterministic.
*/
protected Set statesWithSyntacticallyAmbiguousAltsSet = new HashSet();
/** Track just like stateToSyntacticallyAmbiguousAltsMap, but only
* for nondeterminisms that arise in the Tokens rule such as keyword vs
* ID rule. The state maps to the list of Tokens rule alts that are
* in conflict.
*/
protected Map> stateToSyntacticallyAmbiguousTokensRuleAltsMap =
new HashMap>();
/** Was a syntactic ambiguity resolved with predicates? Any DFA
* state that predicts more than one alternative, must be resolved
* with predicates or it should be reported to the user.
*/
protected Set statesResolvedWithSemanticPredicatesSet = new HashSet();
/** Track the predicates for each alt per DFA state;
* more than one DFA state might have syntactically ambig alt prediction.
* Maps DFA state to another map, mapping alt number to a
* SemanticContext (pred(s) to execute to resolve syntactic ambiguity).
*/
protected Map> stateToAltSetWithSemanticPredicatesMap =
new HashMap>();
/** Tracks alts insufficiently covered.
* For example, p1||true gets reduced to true and so leaves
* whole alt uncovered. This maps DFA state to the set of alts
*/
protected Map>> stateToIncompletelyCoveredAltsMap =
new HashMap>>();
/** The set of states w/o emanating edges and w/o resolving sem preds. */
protected Set danglingStates = new HashSet();
/** The overall list of alts within the decision that have at least one
* conflicting input sequence.
*/
protected Set altsWithProblem = new HashSet();
/** If decision with > 1 alt has recursion in > 1 alt, it's (likely) nonregular
* lookahead. The decision cannot be made with a DFA.
* the alts are stored in altsWithProblem.
*/
public boolean nonLLStarDecision = false;
/** Recursion is limited to a particular depth. If that limit is exceeded
* the proposed new NFAConfiguration is recorded for the associated DFA state.
*/
protected MultiMap stateToRecursionOverflowConfigurationsMap =
new MultiMap();
/*
protected Map> stateToRecursionOverflowConfigurationsMap =
new HashMap>();
*/
/** Left recursion discovered. The proposed new NFAConfiguration
* is recorded for the associated DFA state.
protected Map> stateToLeftRecursiveConfigurationsMap =
new HashMap>();
*/
/** Did ANTLR have to terminate early on the analysis of this decision? */
protected boolean timedOut = false;
/** Used to find paths through syntactically ambiguous DFA. If we've
* seen statement number before, what did we learn?
*/
protected Map stateReachable;
public static final Integer REACHABLE_BUSY = Utils.integer(-1);
public static final Integer REACHABLE_NO = Utils.integer(0);
public static final Integer REACHABLE_YES = Utils.integer(1);
/** Used while finding a path through an NFA whose edge labels match
* an input sequence. Tracks the input position
* we were at the last time at this node. If same input position, then
* we'd have reached same state without consuming input...probably an
* infinite loop. Stop. Set<String>. The strings look like
* stateNumber_labelIndex.
*/
protected Set statesVisitedAtInputDepth;
protected Set statesVisitedDuringSampleSequence;
public static boolean verbose = false;
public DecisionProbe(DFA dfa) {
this.dfa = dfa;
}
// I N F O R M A T I O N A B O U T D E C I S I O N
/** Return a string like "3:22: ( A {;} | B )" that describes this
* decision.
*/
public String getDescription() {
return dfa.getNFADecisionStartState().getDescription();
}
public boolean isReduced() {
return dfa.isReduced();
}
public boolean isCyclic() {
return dfa.isCyclic();
}
/** If no states are dead-ends, no alts are unreachable, there are
* no nondeterminisms unresolved by syn preds, all is ok with decision.
*/
public boolean isDeterministic() {
if ( danglingStates.isEmpty() &&
statesWithSyntacticallyAmbiguousAltsSet.isEmpty() &&
dfa.getUnreachableAlts().isEmpty() )
{
return true;
}
if ( statesWithSyntacticallyAmbiguousAltsSet.size()>0 ) {
for (DFAState d : statesWithSyntacticallyAmbiguousAltsSet) {
if ( !statesResolvedWithSemanticPredicatesSet.contains(d) ) {
return false;
}
}
// no syntactically ambig alts were left unresolved by predicates
return true;
}
return false;
}
/** Did the analysis complete it's work? */
// public boolean analysisTimedOut() {
// return timedOut;
// }
/** Took too long to analyze a DFA */
public boolean analysisOverflowed() {
return stateToRecursionOverflowConfigurationsMap.size()>0;
}
/** Found recursion in > 1 alt */
public boolean isNonLLStarDecision() {
return nonLLStarDecision;
}
/** How many states does the DFA predictor have? */
public int getNumberOfStates() {
return dfa.getNumberOfStates();
}
/** Get a list of all unreachable alternatives for this decision. There
* may be multiple alternatives with ambiguous input sequences, but this
* is the overall list of unreachable alternatives (either due to
* conflict resolution or alts w/o accept states).
*/
public List getUnreachableAlts() {
return dfa.getUnreachableAlts();
}
/** return set of states w/o emanating edges and w/o resolving sem preds.
* These states come about because the analysis algorithm had to
* terminate early to avoid infinite recursion for example (due to
* left recursion perhaps).
*/
public Set getDanglingStates() {
return danglingStates;
}
public Set getNonDeterministicAlts() {
return altsWithProblem;
}
/** Return the sorted list of alts that conflict within a single state.
* Note that predicates may resolve the conflict.
*/
public List getNonDeterministicAltsForState(DFAState targetState) {
Set nondetAlts = targetState.getNonDeterministicAlts();
if ( nondetAlts==null ) {
return null;
}
List sorted = new LinkedList();
sorted.addAll(nondetAlts);
Collections.sort(sorted); // make sure it's 1, 2, ...
return sorted;
}
/** Return all DFA states in this DFA that have NFA configurations that
* conflict. You must report a problem for each state in this set
* because each state represents a different input sequence.
*/
public Set getDFAStatesWithSyntacticallyAmbiguousAlts() {
return statesWithSyntacticallyAmbiguousAltsSet;
}
/** Which alts were specifically turned off to resolve nondeterminisms?
* This is different than the unreachable alts. Disabled doesn't mean that
* the alternative is totally unreachable necessarily, it just means
* that for this DFA state, that alt is disabled. There may be other
* accept states for that alt that make an alt reachable.
*/
public Set getDisabledAlternatives(DFAState d) {
return d.getDisabledAlternatives();
}
/** If a recursion overflow is resolve with predicates, then we need
* to shut off the warning that would be generated.
*/
public void removeRecursiveOverflowState(DFAState d) {
Integer stateI = Utils.integer(d.stateNumber);
stateToRecursionOverflowConfigurationsMap.remove(stateI);
}
/** Return a List<Label> indicating an input sequence that can be matched
* from the start state of the DFA to the targetState (which is known
* to have a problem).
*/
public List
