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777 lines
30 KiB
Java
777 lines
30 KiB
Java
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/*
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[The "BSD licence"]
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Copyright (c) 2005-2006 Terence Parr
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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3. The name of the author may not be used to endorse or promote products
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derived from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package org.antlr.analysis;
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import org.antlr.misc.IntSet;
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import org.antlr.misc.MultiMap;
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import org.antlr.misc.OrderedHashSet;
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import org.antlr.misc.Utils;
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import org.antlr.tool.Grammar;
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import java.util.*;
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/** A DFA state represents a set of possible NFA configurations.
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* As Aho, Sethi, Ullman p. 117 says "The DFA uses its state
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* to keep track of all possible states the NFA can be in after
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* reading each input symbol. That is to say, after reading
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* input a1a2..an, the DFA is in a state that represents the
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* subset T of the states of the NFA that are reachable from the
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* NFA's start state along some path labeled a1a2..an."
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* In conventional NFA->DFA conversion, therefore, the subset T
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* would be a bitset representing the set of states the
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* NFA could be in. We need to track the alt predicted by each
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* state as well, however. More importantly, we need to maintain
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* a stack of states, tracking the closure operations as they
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* jump from rule to rule, emulating rule invocations (method calls).
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* Recall that NFAs do not normally have a stack like a pushdown-machine
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* so I have to add one to simulate the proper lookahead sequences for
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* the underlying LL grammar from which the NFA was derived.
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*
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* I use a list of NFAConfiguration objects. An NFAConfiguration
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* is both a state (ala normal conversion) and an NFAContext describing
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* the chain of rules (if any) followed to arrive at that state. There
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* is also the semantic context, which is the "set" of predicates found
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* on the path to this configuration.
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*
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* A DFA state may have multiple references to a particular state,
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* but with different NFAContexts (with same or different alts)
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* meaning that state was reached via a different set of rule invocations.
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*/
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public class DFAState extends State {
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public static final int INITIAL_NUM_TRANSITIONS = 4;
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public static final int PREDICTED_ALT_UNSET = NFA.INVALID_ALT_NUMBER-1;
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/** We are part of what DFA? Use this ref to get access to the
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* context trees for an alt.
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*/
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public DFA dfa;
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/** Track the transitions emanating from this DFA state. The List
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* elements are Transition objects.
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*/
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protected List<Transition> transitions =
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new ArrayList<Transition>(INITIAL_NUM_TRANSITIONS);
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/** When doing an acyclic DFA, this is the number of lookahead symbols
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* consumed to reach this state. This value may be nonzero for most
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* dfa states, but it is only a valid value if the user has specified
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* a max fixed lookahead.
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*/
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protected int k;
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/** The NFA->DFA algorithm may terminate leaving some states
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* without a path to an accept state, implying that upon certain
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* input, the decision is not deterministic--no decision about
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* predicting a unique alternative can be made. Recall that an
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* accept state is one in which a unique alternative is predicted.
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*/
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protected int acceptStateReachable = DFA.REACHABLE_UNKNOWN;
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/** Rather than recheck every NFA configuration in a DFA state (after
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* resolving) in findNewDFAStatesAndAddDFATransitions just check
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* this boolean. Saves a linear walk perhaps DFA state creation.
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* Every little bit helps.
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*/
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protected boolean resolvedWithPredicates = false;
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/** If a closure operation finds that we tried to invoke the same
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* rule too many times (stack would grow beyond a threshold), it
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* marks the state has aborted and notifies the DecisionProbe.
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*/
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public boolean abortedDueToRecursionOverflow = false;
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/** If we detect recursion on more than one alt, decision is non-LL(*),
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* but try to isolate it to only those states whose closure operations
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* detect recursion. There may be other alts that are cool:
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*
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* a : recur '.'
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* | recur ';'
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* | X Y // LL(2) decision; don't abort and use k=1 plus backtracking
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* | X Z
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* ;
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*
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* 12/13/2007: Actually this has caused problems. If k=*, must terminate
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* and throw out entire DFA; retry with k=1. Since recursive, do not
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* attempt more closure ops as it may take forever. Exception thrown
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* now and we simply report the problem. If synpreds exist, I'll retry
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* with k=1.
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*/
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protected boolean abortedDueToMultipleRecursiveAlts = false;
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/** Build up the hash code for this state as NFA configurations
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* are added as it's monotonically increasing list of configurations.
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*/
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protected int cachedHashCode;
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protected int cachedUniquelyPredicatedAlt = PREDICTED_ALT_UNSET;
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public int minAltInConfigurations=Integer.MAX_VALUE;
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public boolean atLeastOneConfigurationHasAPredicate = false;
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/** The set of NFA configurations (state,alt,context) for this DFA state */
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public OrderedHashSet<NFAConfiguration> nfaConfigurations =
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new OrderedHashSet<NFAConfiguration>();
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public List<NFAConfiguration> configurationsWithLabeledEdges =
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new ArrayList<NFAConfiguration>();
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/** Used to prevent the closure operation from looping to itself and
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* hence looping forever. Sensitive to the NFA state, the alt, and
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* the stack context. This just the nfa config set because we want to
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* prevent closures only on states contributed by closure not reach
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* operations.
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*
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* Two configurations identical including semantic context are
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* considered the same closure computation. @see NFAToDFAConverter.closureBusy().
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*/
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protected Set<NFAConfiguration> closureBusy = new HashSet<NFAConfiguration>();
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/** As this state is constructed (i.e., as NFA states are added), we
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* can easily check for non-epsilon transitions because the only
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* transition that could be a valid label is transition(0). When we
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* process this node eventually, we'll have to walk all states looking
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* for all possible transitions. That is of the order: size(label space)
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* times size(nfa states), which can be pretty damn big. It's better
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* to simply track possible labels.
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*/
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protected OrderedHashSet<Label> reachableLabels;
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public DFAState(DFA dfa) {
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this.dfa = dfa;
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}
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public void reset() {
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//nfaConfigurations = null; // getGatedPredicatesInNFAConfigurations needs
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configurationsWithLabeledEdges = null;
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closureBusy = null;
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reachableLabels = null;
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}
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public Transition transition(int i) {
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return (Transition)transitions.get(i);
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}
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public int getNumberOfTransitions() {
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return transitions.size();
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}
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public void addTransition(Transition t) {
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transitions.add(t);
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}
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/** Add a transition from this state to target with label. Return
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* the transition number from 0..n-1.
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*/
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public int addTransition(DFAState target, Label label) {
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transitions.add( new Transition(label, target) );
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return transitions.size()-1;
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}
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public Transition getTransition(int trans) {
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return transitions.get(trans);
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}
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public void removeTransition(int trans) {
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transitions.remove(trans);
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}
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/** Add an NFA configuration to this DFA node. Add uniquely
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* an NFA state/alt/syntactic&semantic context (chain of invoking state(s)
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* and semantic predicate contexts).
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*
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* I don't see how there could be two configurations with same
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* state|alt|synCtx and different semantic contexts because the
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* semantic contexts are computed along the path to a particular state
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* so those two configurations would have to have the same predicate.
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* Nonetheless, the addition of configurations is unique on all
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* configuration info. I guess I'm saying that syntactic context
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* implies semantic context as the latter is computed according to the
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* former.
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*
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* As we add configurations to this DFA state, track the set of all possible
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* transition labels so we can simply walk it later rather than doing a
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* loop over all possible labels in the NFA.
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*/
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public void addNFAConfiguration(NFAState state, NFAConfiguration c) {
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if ( nfaConfigurations.contains(c) ) {
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return;
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}
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nfaConfigurations.add(c);
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// track min alt rather than compute later
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if ( c.alt < minAltInConfigurations ) {
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minAltInConfigurations = c.alt;
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}
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if ( c.semanticContext!=SemanticContext.EMPTY_SEMANTIC_CONTEXT ) {
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atLeastOneConfigurationHasAPredicate = true;
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}
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// update hashCode; for some reason using context.hashCode() also
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// makes the GC take like 70% of the CPU and is slow!
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cachedHashCode += c.state + c.alt;
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// update reachableLabels
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// We're adding an NFA state; check to see if it has a non-epsilon edge
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if ( state.transition[0] != null ) {
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Label label = state.transition[0].label;
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if ( !(label.isEpsilon()||label.isSemanticPredicate()) ) {
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// this NFA state has a non-epsilon edge, track for fast
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// walking later when we do reach on this DFA state we're
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// building.
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configurationsWithLabeledEdges.add(c);
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if ( state.transition[1] ==null ) {
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// later we can check this to ignore o-A->o states in closure
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c.singleAtomTransitionEmanating = true;
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}
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addReachableLabel(label);
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}
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}
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}
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public NFAConfiguration addNFAConfiguration(NFAState state,
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int alt,
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NFAContext context,
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SemanticContext semanticContext)
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{
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NFAConfiguration c = new NFAConfiguration(state.stateNumber,
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alt,
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context,
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semanticContext);
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addNFAConfiguration(state, c);
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return c;
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}
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/** Add label uniquely and disjointly; intersection with
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* another set or int/char forces breaking up the set(s).
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*
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* Example, if reachable list of labels is [a..z, {k,9}, 0..9],
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* the disjoint list will be [{a..j,l..z}, k, 9, 0..8].
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*
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* As we add NFA configurations to a DFA state, we might as well track
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* the set of all possible transition labels to make the DFA conversion
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* more efficient. W/o the reachable labels, we'd need to check the
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* whole vocabulary space (could be 0..\uFFFF)! The problem is that
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* labels can be sets, which may overlap with int labels or other sets.
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* As we need a deterministic set of transitions from any
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* state in the DFA, we must make the reachable labels set disjoint.
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* This operation amounts to finding the character classes for this
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* DFA state whereas with tools like flex, that need to generate a
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* homogeneous DFA, must compute char classes across all states.
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* We are going to generate DFAs with heterogeneous states so we
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* only care that the set of transitions out of a single state are
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* unique. :)
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*
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* The idea for adding a new set, t, is to look for overlap with the
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* elements of existing list s. Upon overlap, replace
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* existing set s[i] with two new disjoint sets, s[i]-t and s[i]&t.
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* (if s[i]-t is nil, don't add). The remainder is t-s[i], which is
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* what you want to add to the set minus what was already there. The
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* remainder must then be compared against the i+1..n elements in s
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* looking for another collision. Each collision results in a smaller
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* and smaller remainder. Stop when you run out of s elements or
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* remainder goes to nil. If remainder is non nil when you run out of
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* s elements, then add remainder to the end.
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*
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* Single element labels are treated as sets to make the code uniform.
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*/
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protected void addReachableLabel(Label label) {
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if ( reachableLabels==null ) {
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reachableLabels = new OrderedHashSet<Label>();
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}
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/*
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System.out.println("addReachableLabel to state "+dfa.decisionNumber+"."+stateNumber+": "+label.getSet().toString(dfa.nfa.grammar));
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System.out.println("start of add to state "+dfa.decisionNumber+"."+stateNumber+": " +
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"reachableLabels="+reachableLabels.toString());
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*/
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if ( reachableLabels.contains(label) ) { // exact label present
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return;
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}
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IntSet t = label.getSet();
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IntSet remainder = t; // remainder starts out as whole set to add
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int n = reachableLabels.size(); // only look at initial elements
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// walk the existing list looking for the collision
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for (int i=0; i<n; i++) {
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Label rl = reachableLabels.get(i);
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/*
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System.out.println("comparing ["+i+"]: "+label.toString(dfa.nfa.grammar)+" & "+
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rl.toString(dfa.nfa.grammar)+"="+
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intersection.toString(dfa.nfa.grammar));
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*/
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if ( !Label.intersect(label, rl) ) {
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continue;
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}
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//System.out.println(label+" collides with "+rl);
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// For any (s_i, t) with s_i&t!=nil replace with (s_i-t, s_i&t)
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// (ignoring s_i-t if nil; don't put in list)
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// Replace existing s_i with intersection since we
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// know that will always be a non nil character class
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IntSet s_i = rl.getSet();
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IntSet intersection = s_i.and(t);
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reachableLabels.set(i, new Label(intersection));
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// Compute s_i-t to see what is in current set and not in incoming
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IntSet existingMinusNewElements = s_i.subtract(t);
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//System.out.println(s_i+"-"+t+"="+existingMinusNewElements);
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if ( !existingMinusNewElements.isNil() ) {
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// found a new character class, add to the end (doesn't affect
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// outer loop duration due to n computation a priori.
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Label newLabel = new Label(existingMinusNewElements);
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reachableLabels.add(newLabel);
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}
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/*
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System.out.println("after collision, " +
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"reachableLabels="+reachableLabels.toString());
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*/
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// anything left to add to the reachableLabels?
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remainder = t.subtract(s_i);
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if ( remainder.isNil() ) {
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break; // nothing left to add to set. done!
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}
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t = remainder;
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}
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if ( !remainder.isNil() ) {
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/*
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System.out.println("before add remainder to state "+dfa.decisionNumber+"."+stateNumber+": " +
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"reachableLabels="+reachableLabels.toString());
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System.out.println("remainder state "+dfa.decisionNumber+"."+stateNumber+": "+remainder.toString(dfa.nfa.grammar));
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*/
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Label newLabel = new Label(remainder);
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reachableLabels.add(newLabel);
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}
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/*
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System.out.println("#END of add to state "+dfa.decisionNumber+"."+stateNumber+": " +
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"reachableLabels="+reachableLabels.toString());
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*/
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}
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public OrderedHashSet getReachableLabels() {
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return reachableLabels;
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}
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public void setNFAConfigurations(OrderedHashSet<NFAConfiguration> configs) {
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this.nfaConfigurations = configs;
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}
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/** A decent hash for a DFA state is the sum of the NFA state/alt pairs.
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* This is used when we add DFAState objects to the DFA.states Map and
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* when we compare DFA states. Computed in addNFAConfiguration()
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*/
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public int hashCode() {
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if ( cachedHashCode==0 ) {
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// LL(1) algorithm doesn't use NFA configurations, which
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// dynamically compute hashcode; must have something; use super
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return super.hashCode();
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}
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return cachedHashCode;
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}
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||
|
/** Two DFAStates are equal if their NFA configuration sets are the
|
||
|
* same. This method is used to see if a DFA state already exists.
|
||
|
*
|
||
|
* Because the number of alternatives and number of NFA configurations are
|
||
|
* finite, there is a finite number of DFA states that can be processed.
|
||
|
* This is necessary to show that the algorithm terminates.
|
||
|
*
|
||
|
* Cannot test the DFA state numbers here because in DFA.addState we need
|
||
|
* to know if any other state exists that has this exact set of NFA
|
||
|
* configurations. The DFAState state number is irrelevant.
|
||
|
*/
|
||
|
public boolean equals(Object o) {
|
||
|
// compare set of NFA configurations in this set with other
|
||
|
DFAState other = (DFAState)o;
|
||
|
return this.nfaConfigurations.equals(other.nfaConfigurations);
|
||
|
}
|
||
|
|
||
|
/** Walk each configuration and if they are all the same alt, return
|
||
|
* that alt else return NFA.INVALID_ALT_NUMBER. Ignore resolved
|
||
|
* configurations, but don't ignore resolveWithPredicate configs
|
||
|
* because this state should not be an accept state. We need to add
|
||
|
* this to the work list and then have semantic predicate edges
|
||
|
* emanating from it.
|
||
|
*/
|
||
|
public int getUniquelyPredictedAlt() {
|
||
|
if ( cachedUniquelyPredicatedAlt!=PREDICTED_ALT_UNSET ) {
|
||
|
return cachedUniquelyPredicatedAlt;
|
||
|
}
|
||
|
int alt = NFA.INVALID_ALT_NUMBER;
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
// ignore anything we resolved; predicates will still result
|
||
|
// in transitions out of this state, so must count those
|
||
|
// configurations; i.e., don't ignore resolveWithPredicate configs
|
||
|
if ( configuration.resolved ) {
|
||
|
continue;
|
||
|
}
|
||
|
if ( alt==NFA.INVALID_ALT_NUMBER ) {
|
||
|
alt = configuration.alt; // found first nonresolved alt
|
||
|
}
|
||
|
else if ( configuration.alt!=alt ) {
|
||
|
return NFA.INVALID_ALT_NUMBER;
|
||
|
}
|
||
|
}
|
||
|
this.cachedUniquelyPredicatedAlt = alt;
|
||
|
return alt;
|
||
|
}
|
||
|
|
||
|
/** Return the uniquely mentioned alt from the NFA configurations;
|
||
|
* Ignore the resolved bit etc... Return INVALID_ALT_NUMBER
|
||
|
* if there is more than one alt mentioned.
|
||
|
*/
|
||
|
public int getUniqueAlt() {
|
||
|
int alt = NFA.INVALID_ALT_NUMBER;
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
if ( alt==NFA.INVALID_ALT_NUMBER ) {
|
||
|
alt = configuration.alt; // found first alt
|
||
|
}
|
||
|
else if ( configuration.alt!=alt ) {
|
||
|
return NFA.INVALID_ALT_NUMBER;
|
||
|
}
|
||
|
}
|
||
|
return alt;
|
||
|
}
|
||
|
|
||
|
/** When more than one alternative can match the same input, the first
|
||
|
* alternative is chosen to resolve the conflict. The other alts
|
||
|
* are "turned off" by setting the "resolved" flag in the NFA
|
||
|
* configurations. Return the set of disabled alternatives. For
|
||
|
*
|
||
|
* a : A | A | A ;
|
||
|
*
|
||
|
* this method returns {2,3} as disabled. This does not mean that
|
||
|
* the alternative is totally unreachable, it just means that for this
|
||
|
* DFA state, that alt is disabled. There may be other accept states
|
||
|
* for that alt.
|
||
|
*/
|
||
|
public Set getDisabledAlternatives() {
|
||
|
Set disabled = new LinkedHashSet();
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
if ( configuration.resolved ) {
|
||
|
disabled.add(Utils.integer(configuration.alt));
|
||
|
}
|
||
|
}
|
||
|
return disabled;
|
||
|
}
|
||
|
|
||
|
protected Set getNonDeterministicAlts() {
|
||
|
int user_k = dfa.getUserMaxLookahead();
|
||
|
if ( user_k>0 && user_k==k ) {
|
||
|
// if fixed lookahead, then more than 1 alt is a nondeterminism
|
||
|
// if we have hit the max lookahead
|
||
|
return getAltSet();
|
||
|
}
|
||
|
else if ( abortedDueToMultipleRecursiveAlts || abortedDueToRecursionOverflow ) {
|
||
|
// if we had to abort for non-LL(*) state assume all alts are a problem
|
||
|
return getAltSet();
|
||
|
}
|
||
|
else {
|
||
|
return getConflictingAlts();
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/** Walk each NFA configuration in this DFA state looking for a conflict
|
||
|
* where (s|i|ctx) and (s|j|ctx) exist, indicating that state s with
|
||
|
* context conflicting ctx predicts alts i and j. Return an Integer set
|
||
|
* of the alternative numbers that conflict. Two contexts conflict if
|
||
|
* they are equal or one is a stack suffix of the other or one is
|
||
|
* the empty context.
|
||
|
*
|
||
|
* Use a hash table to record the lists of configs for each state
|
||
|
* as they are encountered. We need only consider states for which
|
||
|
* there is more than one configuration. The configurations' predicted
|
||
|
* alt must be different or must have different contexts to avoid a
|
||
|
* conflict.
|
||
|
*
|
||
|
* Don't report conflicts for DFA states that have conflicting Tokens
|
||
|
* rule NFA states; they will be resolved in favor of the first rule.
|
||
|
*/
|
||
|
protected Set<Integer> getConflictingAlts() {
|
||
|
// TODO this is called multiple times: cache result?
|
||
|
//System.out.println("getNondetAlts for DFA state "+stateNumber);
|
||
|
Set<Integer> nondeterministicAlts = new HashSet<Integer>();
|
||
|
|
||
|
// If only 1 NFA conf then no way it can be nondeterministic;
|
||
|
// save the overhead. There are many o-a->o NFA transitions
|
||
|
// and so we save a hash map and iterator creation for each
|
||
|
// state.
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
if ( numConfigs <=1 ) {
|
||
|
return null;
|
||
|
}
|
||
|
|
||
|
// First get a list of configurations for each state.
|
||
|
// Most of the time, each state will have one associated configuration.
|
||
|
MultiMap<Integer, NFAConfiguration> stateToConfigListMap =
|
||
|
new MultiMap<Integer, NFAConfiguration>();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
Integer stateI = Utils.integer(configuration.state);
|
||
|
stateToConfigListMap.map(stateI, configuration);
|
||
|
}
|
||
|
// potential conflicts are states with > 1 configuration and diff alts
|
||
|
Set states = stateToConfigListMap.keySet();
|
||
|
int numPotentialConflicts = 0;
|
||
|
for (Iterator it = states.iterator(); it.hasNext();) {
|
||
|
Integer stateI = (Integer) it.next();
|
||
|
boolean thisStateHasPotentialProblem = false;
|
||
|
List configsForState = (List)stateToConfigListMap.get(stateI);
|
||
|
int alt=0;
|
||
|
int numConfigsForState = configsForState.size();
|
||
|
for (int i = 0; i < numConfigsForState && numConfigsForState>1 ; i++) {
|
||
|
NFAConfiguration c = (NFAConfiguration) configsForState.get(i);
|
||
|
if ( alt==0 ) {
|
||
|
alt = c.alt;
|
||
|
}
|
||
|
else if ( c.alt!=alt ) {
|
||
|
/*
|
||
|
System.out.println("potential conflict in state "+stateI+
|
||
|
" configs: "+configsForState);
|
||
|
*/
|
||
|
// 11/28/2005: don't report closures that pinch back
|
||
|
// together in Tokens rule. We want to silently resolve
|
||
|
// to the first token definition ala lex/flex by ignoring
|
||
|
// these conflicts.
|
||
|
// Also this ensures that lexers look for more and more
|
||
|
// characters (longest match) before resorting to predicates.
|
||
|
// TestSemanticPredicates.testLexerMatchesLongestThenTestPred()
|
||
|
// for example would terminate at state s1 and test predicate
|
||
|
// meaning input "ab" would test preds to decide what to
|
||
|
// do but it should match rule C w/o testing preds.
|
||
|
if ( dfa.nfa.grammar.type!=Grammar.LEXER ||
|
||
|
!dfa.decisionNFAStartState.enclosingRule.name.equals(Grammar.ARTIFICIAL_TOKENS_RULENAME) )
|
||
|
{
|
||
|
numPotentialConflicts++;
|
||
|
thisStateHasPotentialProblem = true;
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
if ( !thisStateHasPotentialProblem ) {
|
||
|
// remove NFA state's configurations from
|
||
|
// further checking; no issues with it
|
||
|
// (can't remove as it's concurrent modification; set to null)
|
||
|
stateToConfigListMap.put(stateI, null);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// a fast check for potential issues; most states have none
|
||
|
if ( numPotentialConflicts==0 ) {
|
||
|
return null;
|
||
|
}
|
||
|
|
||
|
// we have a potential problem, so now go through config lists again
|
||
|
// looking for different alts (only states with potential issues
|
||
|
// are left in the states set). Now we will check context.
|
||
|
// For example, the list of configs for NFA state 3 in some DFA
|
||
|
// state might be:
|
||
|
// [3|2|[28 18 $], 3|1|[28 $], 3|1, 3|2]
|
||
|
// I want to create a map from context to alts looking for overlap:
|
||
|
// [28 18 $] -> 2
|
||
|
// [28 $] -> 1
|
||
|
// [$] -> 1,2
|
||
|
// Indeed a conflict exists as same state 3, same context [$], predicts
|
||
|
// alts 1 and 2.
|
||
|
// walk each state with potential conflicting configurations
|
||
|
for (Iterator it = states.iterator(); it.hasNext();) {
|
||
|
Integer stateI = (Integer) it.next();
|
||
|
List configsForState = (List)stateToConfigListMap.get(stateI);
|
||
|
// compare each configuration pair s, t to ensure:
|
||
|
// s.ctx different than t.ctx if s.alt != t.alt
|
||
|
int numConfigsForState = 0;
|
||
|
if ( configsForState!=null ) {
|
||
|
numConfigsForState = configsForState.size();
|
||
|
}
|
||
|
for (int i = 0; i < numConfigsForState; i++) {
|
||
|
NFAConfiguration s = (NFAConfiguration) configsForState.get(i);
|
||
|
for (int j = i+1; j < numConfigsForState; j++) {
|
||
|
NFAConfiguration t = (NFAConfiguration)configsForState.get(j);
|
||
|
// conflicts means s.ctx==t.ctx or s.ctx is a stack
|
||
|
// suffix of t.ctx or vice versa (if alts differ).
|
||
|
// Also a conflict if s.ctx or t.ctx is empty
|
||
|
if ( s.alt != t.alt && s.context.conflictsWith(t.context) ) {
|
||
|
nondeterministicAlts.add(Utils.integer(s.alt));
|
||
|
nondeterministicAlts.add(Utils.integer(t.alt));
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if ( nondeterministicAlts.size()==0 ) {
|
||
|
return null;
|
||
|
}
|
||
|
return nondeterministicAlts;
|
||
|
}
|
||
|
|
||
|
/** Get the set of all alts mentioned by all NFA configurations in this
|
||
|
* DFA state.
|
||
|
*/
|
||
|
public Set getAltSet() {
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
Set alts = new HashSet();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
alts.add(Utils.integer(configuration.alt));
|
||
|
}
|
||
|
if ( alts.size()==0 ) {
|
||
|
return null;
|
||
|
}
|
||
|
return alts;
|
||
|
}
|
||
|
|
||
|
public Set getGatedSyntacticPredicatesInNFAConfigurations() {
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
Set<SemanticContext> synpreds = new HashSet<SemanticContext>();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
SemanticContext gatedPredExpr =
|
||
|
configuration.semanticContext.getGatedPredicateContext();
|
||
|
// if this is a manual syn pred (gated and syn pred), add
|
||
|
if ( gatedPredExpr!=null &&
|
||
|
configuration.semanticContext.isSyntacticPredicate() )
|
||
|
{
|
||
|
synpreds.add(configuration.semanticContext);
|
||
|
}
|
||
|
}
|
||
|
if ( synpreds.size()==0 ) {
|
||
|
return null;
|
||
|
}
|
||
|
return synpreds;
|
||
|
}
|
||
|
|
||
|
/** For gated productions, we need an OR'd list of all predicates for the
|
||
|
* target of an edge so we can gate the edge based upon the predicates
|
||
|
* associated with taking that path (if any).
|
||
|
*
|
||
|
* For syntactic predicates, we only want to generate predicate
|
||
|
* evaluations as it transitions to an accept state; waste to
|
||
|
* do it earlier. So, only add gated preds derived from manually-
|
||
|
* specified syntactic predicates if this is an accept state.
|
||
|
*
|
||
|
* Also, since configurations w/o gated predicates are like true
|
||
|
* gated predicates, finding a configuration whose alt has no gated
|
||
|
* predicate implies we should evaluate the predicate to true. This
|
||
|
* means the whole edge has to be ungated. Consider:
|
||
|
*
|
||
|
* X : ('a' | {p}?=> 'a')
|
||
|
* | 'a' 'b'
|
||
|
* ;
|
||
|
*
|
||
|
* Here, you 'a' gets you from s0 to s1 but you can't test p because
|
||
|
* plain 'a' is ok. It's also ok for starting alt 2. Hence, you can't
|
||
|
* test p. Even on the edge going to accept state for alt 1 of X, you
|
||
|
* can't test p. You can get to the same place with and w/o the context.
|
||
|
* Therefore, it is never ok to test p in this situation.
|
||
|
*
|
||
|
* TODO: cache this as it's called a lot; or at least set bit if >1 present in state
|
||
|
*/
|
||
|
public SemanticContext getGatedPredicatesInNFAConfigurations() {
|
||
|
SemanticContext unionOfPredicatesFromAllAlts = null;
|
||
|
int numConfigs = nfaConfigurations.size();
|
||
|
for (int i = 0; i < numConfigs; i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
SemanticContext gatedPredExpr =
|
||
|
configuration.semanticContext.getGatedPredicateContext();
|
||
|
if ( gatedPredExpr==null ) {
|
||
|
// if we ever find a configuration w/o a gated predicate
|
||
|
// (even if it's a nongated predicate), we cannot gate
|
||
|
// the indident edges.
|
||
|
return null;
|
||
|
}
|
||
|
else if ( acceptState || !configuration.semanticContext.isSyntacticPredicate() ) {
|
||
|
// at this point we have a gated predicate and, due to elseif,
|
||
|
// we know it's an accept and not a syn pred. In this case,
|
||
|
// it's safe to add the gated predicate to the union. We
|
||
|
// only want to add syn preds if it's an accept state. Other
|
||
|
// gated preds can be used with edges leading to accept states.
|
||
|
if ( unionOfPredicatesFromAllAlts==null ) {
|
||
|
unionOfPredicatesFromAllAlts = gatedPredExpr;
|
||
|
}
|
||
|
else {
|
||
|
unionOfPredicatesFromAllAlts =
|
||
|
SemanticContext.or(unionOfPredicatesFromAllAlts,gatedPredExpr);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
if ( unionOfPredicatesFromAllAlts instanceof SemanticContext.TruePredicate ) {
|
||
|
return null;
|
||
|
}
|
||
|
return unionOfPredicatesFromAllAlts;
|
||
|
}
|
||
|
|
||
|
/** Is an accept state reachable from this state? */
|
||
|
public int getAcceptStateReachable() {
|
||
|
return acceptStateReachable;
|
||
|
}
|
||
|
|
||
|
public void setAcceptStateReachable(int acceptStateReachable) {
|
||
|
this.acceptStateReachable = acceptStateReachable;
|
||
|
}
|
||
|
|
||
|
public boolean isResolvedWithPredicates() {
|
||
|
return resolvedWithPredicates;
|
||
|
}
|
||
|
|
||
|
/** Print all NFA states plus what alts they predict */
|
||
|
public String toString() {
|
||
|
StringBuffer buf = new StringBuffer();
|
||
|
buf.append(stateNumber+":{");
|
||
|
for (int i = 0; i < nfaConfigurations.size(); i++) {
|
||
|
NFAConfiguration configuration = (NFAConfiguration) nfaConfigurations.get(i);
|
||
|
if ( i>0 ) {
|
||
|
buf.append(", ");
|
||
|
}
|
||
|
buf.append(configuration);
|
||
|
}
|
||
|
buf.append("}");
|
||
|
return buf.toString();
|
||
|
}
|
||
|
|
||
|
public int getLookaheadDepth() {
|
||
|
return k;
|
||
|
}
|
||
|
|
||
|
public void setLookaheadDepth(int k) {
|
||
|
this.k = k;
|
||
|
if ( k > dfa.max_k ) { // track max k for entire DFA
|
||
|
dfa.max_k = k;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
}
|