getNtermIndex method

int getNtermIndex(int start, int sym, int buffer_position)

Implementation

int getNtermIndex(int start, int sym, int buffer_position) {
  var highest_symbol = sym - NT_OFFSET,
      tok = tokStream.getKind(buffer[buffer_position]);
  tokStream.reset(buffer[buffer_position + 1]);

  //
  // Initialize stack index of temp_stack and initialize maximum
  // position of state stack that is still useful.
  //
  tempStackTop = 0;
  tempStack[tempStackTop] = start;

  var act = ntAction(start, highest_symbol);
  if (act > NUM_RULES) // goto action?
  {
    tempStack[tempStackTop + 1] = act;
    act = tAction(act, tok);
  }

  while (act <= NUM_RULES) {
    //
    // Process all goto-reduce actions following reduction,
    // until a goto action is computed ...
    //
    do {
      tempStackTop -= (rhs(act) - 1);
      if (tempStackTop < 0) return nonterminalIndex(highest_symbol);
      if (tempStackTop == 0) highest_symbol = lhs(act);
      act = ntAction(tempStack[tempStackTop], lhs(act));
    } while (act <= NUM_RULES);
    tempStack[tempStackTop + 1] = act;
    act = tAction(act, tok);
  }

  return nonterminalIndex(highest_symbol);
}