backtrackParseInternal method

int backtrackParseInternal(IntSegmentedTuple action, int initial_token)

Implementation

int backtrackParseInternal(IntSegmentedTuple action, int initial_token) {
  //
  // Allocate configuration stack.
  //
  var configuration_stack = ConfigurationStack(prs);

  //
  // Keep parsing until we successfully reach the end of file or
  // an error is encountered. The list of actions executed will
  // be stored in the "action" tuple.
  //
  var error_token = 0,
      maxStackTop = stateStackTop,
      start_token = tokStream.peek(),
      curtok = (initial_token > 0 ? initial_token : tokStream.getToken()),
      current_kind = tokStream.getKind(curtok),
      act = tAction(stateStack[stateStackTop], current_kind);

  //
  // The main driver loop
  //
  for (;;) {
    //
    // if the parser needs to stop processing,
    // it may do so here.
    //
    if (monitor != null && monitor!.isCancelled()) return 0;

    if (act <= NUM_RULES) {
      action.add(act); // save this reduce action
      stateStackTop--;
      act = process_backtrack_reductions(act);
    } else if (act > ERROR_ACTION) {
      action.add(act); // save this shift-reduce action
      curtok = tokStream.getToken();
      current_kind = tokStream.getKind(curtok);
      act = process_backtrack_reductions(act - ERROR_ACTION);
    } else if (act < ACCEPT_ACTION) {
      action.add(act); // save this shift action
      curtok = tokStream.getToken();
      current_kind = tokStream.getKind(curtok);
    } else if (act == ERROR_ACTION) {
      error_token = (error_token > curtok ? error_token : curtok);

      var configuration = configuration_stack.pop();
      if (configuration == null) {
        act = ERROR_ACTION;
      } else {
        action.reset(configuration.action_length);
        act = configuration.act;
        curtok = configuration.curtok;
        current_kind = tokStream.getKind(curtok);
        tokStream.reset(curtok == initial_token
            ? start_token
            : tokStream.getNext(curtok));
        stateStackTop = configuration.stack_top;
        configuration.retrieveStack(stateStack);
        continue;
      }
      break;
    } else if (act > ACCEPT_ACTION) {
      if (configuration_stack.findConfiguration(
          stateStack, stateStackTop, curtok)) {
        act = ERROR_ACTION;
      } else {
        configuration_stack.push(
            stateStack, stateStackTop, act + 1, curtok, action.size());
        act = prs.baseAction(act);
        maxStackTop =
            stateStackTop > maxStackTop ? stateStackTop : maxStackTop;
      }
      continue;
    } else {
      break;
    } // assert(act == ACCEPT_ACTION);
    try {
      stateStack[++stateStackTop] = act;
    } on RangeError {
      reallocateStateStack();
      stateStack[stateStackTop] = act;
    }

    act = tAction(act, current_kind);
  }

  return (act == ERROR_ACTION ? error_token : 0);
}