getReachableConfigSet method

void getReachableConfigSet(CharStream input, ATNConfigSet configs, ATNConfigSet reach, int t,)

Given a starting configuration set, figure out all ATN configurations we can reach upon input t. Parameter reach is a return parameter.

Implementation

void getReachableConfigSet(
  CharStream input,
  ATNConfigSet configs,
  ATNConfigSet reach,
  int t,
) {
  // this is used to skip processing for configs which have a lower priority
  // than a config that already reached an accept state for the same rule
  var skipAlt = ATN.INVALID_ALT_NUMBER;
  for (var c in configs) {
    final currentAltReachedAcceptState = c.alt == skipAlt;
    if (currentAltReachedAcceptState &&
        (c as LexerATNConfig).hasPassedThroughNonGreedyDecision()) {
      continue;
    }

    if (debug) {
      log('testing ${getTokenName(t)} at ${c.toString(recog, true)}\n',
          level: Level.FINE.value);
    }

    final n = c.state.numberOfTransitions;
    for (var ti = 0; ti < n; ti++) {
      // for each transition
      final trans = c.state.transition(ti);
      final target = getReachableTarget(trans, t);
      if (target != null) {
        var lexerActionExecutor = (c as LexerATNConfig).lexerActionExecutor;
        if (lexerActionExecutor != null) {
          lexerActionExecutor = lexerActionExecutor
              .fixOffsetBeforeMatch(input.index - startIndex);
        }

        final treatEofAsEpsilon = t == IntStream.EOF;
        if (closure(
            input,
            LexerATNConfig.dup(c, target,
                lexerActionExecutor: lexerActionExecutor),
            reach,
            currentAltReachedAcceptState,
            true,
            treatEofAsEpsilon)) {
          // any remaining configs for this alt have a lower priority than
          // the one that just reached an accept state.
          skipAlt = c.alt;
          break;
        }
      }
    }
  }
}