Examples with DFAState org.antlr.v4.runtime.dfa.DFAState used on opensource projects

Example 16 with DFAState

use of org.antlr.v4.runtime.dfa.DFAState in project antlr4 by antlr.

the class LexerATNSimulator method execATN.

protected int execATN(CharStream input, DFAState ds0) {
    // System.out.println("enter exec index "+input.index()+" from "+ds0.configs);
    if (debug) {
        System.out.format(Locale.getDefault(), "start state closure=%s\n", ds0.configs);
    }
    if (ds0.isAcceptState) {
        // allow zero-length tokens
        captureSimState(prevAccept, input, ds0);
    }
    int t = input.LA(1);
    // s is current/from DFA state
    DFAState s = ds0;
    while (true) {
        // while more work
        if (debug) {
            System.out.format(Locale.getDefault(), "execATN loop starting closure: %s\n", s.configs);
        }
        // As we move src->trg, src->trg, we keep track of the previous trg to
        // avoid looking up the DFA state again, which is expensive.
        // If the previous target was already part of the DFA, we might
        // be able to avoid doing a reach operation upon t. If s!=null,
        // it means that semantic predicates didn't prevent us from
        // creating a DFA state. Once we know s!=null, we check to see if
        // the DFA state has an edge already for t. If so, we can just reuse
        // it's configuration set; there's no point in re-computing it.
        // This is kind of like doing DFA simulation within the ATN
        // simulation because DFA simulation is really just a way to avoid
        // computing reach/closure sets. Technically, once we know that
        // we have a previously added DFA state, we could jump over to
        // the DFA simulator. But, that would mean popping back and forth
        // a lot and making things more complicated algorithmically.
        // This optimization makes a lot of sense for loops within DFA.
        // A character will take us back to an existing DFA state
        // that already has lots of edges out of it. e.g., .* in comments.
        DFAState target = getExistingTargetState(s, t);
        if (target == null) {
            target = computeTargetState(input, s, t);
        }
        if (target == ERROR) {
            break;
        }
        // end of the token.
        if (t != IntStream.EOF) {
            consume(input);
        }
        if (target.isAcceptState) {
            captureSimState(prevAccept, input, target);
            if (t == IntStream.EOF) {
                break;
            }
        }
        t = input.LA(1);
        // flip; current DFA target becomes new src/from state
        s = target;
    }
    return failOrAccept(prevAccept, input, s.configs, t);
}

Example 17 with DFAState

use of org.antlr.v4.runtime.dfa.DFAState in project antlr4 by antlr.

the class LexerATNSimulator method addDFAEdge.

protected DFAState addDFAEdge(DFAState from, int t, ATNConfigSet q) {
    /* leading to this call, ATNConfigSet.hasSemanticContext is used as a
		 * marker indicating dynamic predicate evaluation makes this edge
		 * dependent on the specific input sequence, so the static edge in the
		 * DFA should be omitted. The target DFAState is still created since
		 * execATN has the ability to resynchronize with the DFA state cache
		 * following the predicate evaluation step.
		 *
		 * TJP notes: next time through the DFA, we see a pred again and eval.
		 * If that gets us to a previously created (but dangling) DFA
		 * state, we can continue in pure DFA mode from there.
		 */
    boolean suppressEdge = q.hasSemanticContext;
    q.hasSemanticContext = false;
    DFAState to = addDFAState(q);
    if (suppressEdge) {
        return to;
    }
    addDFAEdge(from, t, to);
    return to;
}

Example 18 with DFAState

use of org.antlr.v4.runtime.dfa.DFAState in project antlr4 by antlr.

the class LexerATNSimulator method addDFAState.

/**
 * Add a new DFA state if there isn't one with this set of
 *		configurations already. This method also detects the first
 *		configuration containing an ATN rule stop state. Later, when
 *		traversing the DFA, we will know which rule to accept.
 */
protected DFAState addDFAState(ATNConfigSet configs) {
    /* the lexer evaluates predicates on-the-fly; by this point configs
		 * should not contain any configurations with unevaluated predicates.
		 */
    assert !configs.hasSemanticContext;
    DFAState proposed = new DFAState(configs);
    ATNConfig firstConfigWithRuleStopState = null;
    for (ATNConfig c : configs) {
        if (c.state instanceof RuleStopState) {
            firstConfigWithRuleStopState = c;
            break;
        }
    }
    if (firstConfigWithRuleStopState != null) {
        proposed.isAcceptState = true;
        proposed.lexerActionExecutor = ((LexerATNConfig) firstConfigWithRuleStopState).getLexerActionExecutor();
        proposed.prediction = atn.ruleToTokenType[firstConfigWithRuleStopState.state.ruleIndex];
    }
    DFA dfa = decisionToDFA[mode];
    synchronized (dfa.states) {
        DFAState existing = dfa.states.get(proposed);
        if (existing != null)
            return existing;
        DFAState newState = proposed;
        newState.stateNumber = dfa.states.size();
        configs.setReadonly(true);
        newState.configs = configs;
        dfa.states.put(newState, newState);
        return newState;
    }
}

Example 19 with DFAState

use of org.antlr.v4.runtime.dfa.DFAState in project antlr4 by antlr.

the class LexerATNSimulator method matchATN.

protected int matchATN(CharStream input) {
    ATNState startState = atn.modeToStartState.get(mode);
    if (debug) {
        System.out.format(Locale.getDefault(), "matchATN mode %d start: %s\n", mode, startState);
    }
    int old_mode = mode;
    ATNConfigSet s0_closure = computeStartState(input, startState);
    boolean suppressEdge = s0_closure.hasSemanticContext;
    s0_closure.hasSemanticContext = false;
    DFAState next = addDFAState(s0_closure);
    if (!suppressEdge) {
        decisionToDFA[mode].s0 = next;
    }
    int predict = execATN(input, next);
    if (debug) {
        System.out.format(Locale.getDefault(), "DFA after matchATN: %s\n", decisionToDFA[old_mode].toLexerString());
    }
    return predict;
}

Example 20 with DFAState

use of org.antlr.v4.runtime.dfa.DFAState in project antlr4 by antlr.

the class ProfilingATNSimulator method computeTargetState.

@Override
protected DFAState computeTargetState(DFA dfa, DFAState previousD, int t) {
    DFAState state = super.computeTargetState(dfa, previousD, t);
    currentState = state;
    return state;
}