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JavaCC is a parser/scanner generator for Java.
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// Bit vector to track possible kinds. maxLongs = MAX(kind) / 64 + 1;
private ${STATIC?static :}final long[] jjcurActive = new long[${maxLongs}];
private ${STATIC?static :}final long[] jjnewActive = new long[${maxLongs}];
private ${STATIC?static :}final int jjRunDfa() {
  int curPos = 0;
  for (int i = 0; i < ${maxLongs}; i++) jjcurActive[i] = 0xffffffffffffffffL;
  do {
    // Algorithm: Keep trying to match a DFA as long as there is one
    // possible and in the end, start the NFA if the string literal token
    // match can also be a prefix of non-string literal token.

    if (finalStates[curPos].containsKey((char)curChar)) {
      // The current input character at the current position marks the end
      // of a literal token match e.g., pos == 2 and curChar == 'r' can
      // potentially mark the token "for" in Java grammar.
      final int[] kindAndNext= finalStates[curPos].get((char)curChar);
      for (int i = 0; i < kindAndNext.length; i += 2) {
        int kind = kindAndNext[i];
        // See if this kind is feasible based on the prefix. So for examaple,
        // in Java grammar, pos == 3 and curChar == 'e' can indicate the match
        // of one the 4 tokens - "byte", "case", "else", "true".
        // The jjcurActive bit mask tracks the feasible ones as we go through
        // input. So if the kind is one of the currently active kinds to 
        // be matched, we match it.
        if ((jjcurActive[kind >> 6] & (1L << (kind % 64))) != 0L) {
          // Store the kind matched so far.
          jjmatchedPos = curPos;
          jjmatchedKind = kind;
          int nfaState = kindAndNext[i + 1];
          if (nfaState != -1) {
            return jjStartNfaWithStates_0(curPos, kind, nfaState);
          }
        }
      }
    }

    // curChar at curPos is a prefix of another string literal token.
    // So for example in Java grammar, curChar == 't' and and
    // curPos == '2', then this could end up begin the "interface" token.
    boolean continueDfa = false;
    if (validKinds[curPos].containsKey((char)curChar)) {
      int[] validKind = validKinds[curPos].get((char)curChar);
      for (final int kind : validKind) {
        if ((jjcurActive[kind >> 6] & (1L << (kind % 64))) != 0L) {
          continueDfa = true;
          break;
        }
      }

      if (continueDfa) {
        for (int i = 0; i < ${maxLongs}; i++) jjnewActive[i] = 0L;
        for (final int kind : validKind) {
          jjnewActive[kind >> 6] |= 1L << (kind % 64);
        }
        for (int i = 0; i < ${maxLongs}; i++) jjcurActive[i] &= jjnewActive[i];
      }
    }

    if (!continueDfa) {
      if (curPos == 0) return jjMoveNfa(0, 0);
      return jjStartNfa_0(curPos - 1, jjcurActive);
    }

    int i = 0;
    for (; i < ${maxLongs}; i++) {
      if (jjcurActive[i] != 0L) break;
    }
    if (i == ${maxLongs}) {
      // No more NFA or DFS possible so just return. For example, in Java
      // grammar, when curPos == 1 and curChar == "|" it will return a
      // "||" token as it is not a prefix of any other token.
      return curPos + 1;
    }

    // Move to the next character.
    try {
      // We cannot update curChar unless we can actually advance the stream.
      curChar = input_stream.readChar();
    } catch(java.io.IOException e) {
      // No more input so curPos and curChar are used to start the NFA.
      return jjStopStringLiteralDfa_0(curPos, jjcurActive);
    }
    curPos++;
  } while(true);
}

private ${STATIC?static :}final int jjMoveNfa(int startState, int curPos) {
  if (startState<0) {
    return curPos + 1;
  }

  java.util.Stack stateSet = new java.util.Stack();
  java.util.Stack newStateSet = new java.util.Stack();
  final java.util.BitSet added = new java.util.BitSet(67);
  final java.util.BitSet done = new java.util.BitSet(67);
  int kind = 0x7fffffff;
  stateSet.push(startState);
  done.set(startState);
  for (int s : jjcompositeState[state]) { 
    if (!done.get(s)) stateSet.push(s);
    done.set(s);
  }
  do {
    added.clear();
    done.clear();
    do {
      final int state = stateSet.pop();
      done.set(state);
      if (jjChars[state].get(curChar)) {
        for (int newState : jjnextStateSet[state]) {
          if (added.get(newState)) continue;
          added.set(newState);
          newStateSet.push(newState);
        }
        final int newKind = jjmatchKinds[state];
        if (kind > newKind) kind = newKind;
      }
    } while (!stateSet.empty());

    if (kind != 0x7fffffff) {
       if (jjmatchedPos != curPos || jjmatchedKind > kind) {
         jjmatchedKind = kind;
       }
       jjmatchedPos = curPos;
       kind = 0x7fffffff;
    }
    ++curPos;
    if (newStateSet.empty()) {
      return curPos;
    }

    java.util.Stack tmp = stateSet;
    stateSet = newStateSet;
    newStateSet = tmp;
    try {
      curChar = input_stream.readChar();
    } catch(java.io.IOException e) {
      return curPos;
    }
  } while (!stateSet.empty());

  assert(false) :
      "Internal error. Please submit a bug at: https://github.com/javacc/javacc/issues";
  return curPos;
}
#fi