// If block is true, Read and Write will block when there is no data to read or no space to write.
// If block is false, Read and Write will return ErrIsEmpty or ErrIsFull immediately.
// By default, the ring buffer is not blocking.
// This setting should be called before any Read or Write operation or after a Reset.
func (r *RingBuffer) SetBlocking(block bool) *RingBuffer {
	r.block = block
	if block {

     * always under a lock.
     */
    private static final class SupplantableFuture implements Cancellable {
      private final ReentrantLock lock;

      @GuardedBy("lock")
      private Future<@Nullable Void> currentFuture;

      SupplantableFuture(ReentrantLock lock, Future<@Nullable Void> currentFuture) {
        this.lock = lock;
        this.currentFuture = currentFuture;
      }

type NetLocker interface {
	// Do read lock for given LockArgs.  It should return
	// * a boolean to indicate success/failure of the operation
	// * an error on failure of lock request operation.
	RLock(ctx context.Context, args LockArgs) (bool, error)

	// Do write lock for given LockArgs. It should return
	// * a boolean to indicate success/failure of the operation
	// * an error on failure of lock request operation.

  internal inline fun Any.assertThreadHoldsLock() {
    if (assertionsEnabled && !taskRunner.lock.isHeldByCurrentThread) {
      throw AssertionError("Thread ${Thread.currentThread().name} MUST hold lock on $this")
    }
  }

  @Suppress("NOTHING_TO_INLINE")
  internal inline fun Any.assertThreadDoesntHoldLock() {
    if (assertionsEnabled && taskRunner.lock.isHeldByCurrentThread) {

   */
  @GuardedBy("lock")
  private int runningTasks = 0;

  @GuardedBy("lock")
  private boolean shutdown = false;

  @Override
  public void execute(Runnable command) {
    startTask();
    try {
      command.run();
    } finally {
      endTask();
    }
  }

  @Override
  public boolean isShutdown() {
    synchronized (lock) {
      return shutdown;
    }
  }

  outFinished: Boolean,
  inFinished: Boolean,
  headers: Headers?,
) {
  internal val lock: ReentrantLock = ReentrantLock()
  val condition: Condition = lock.newCondition()

  // Internal state is guarded by [lock]. No long-running or potentially blocking operations are
  // performed while the lock is held.

  /** The bytes consumed and acknowledged by the stream. */
  val readBytes: WindowCounter = WindowCounter(id)

			Op:   "open",
			Path: path,
			Err:  syscall.EINVAL,
		}
	}

	lock := syscall.Flock_t{
		Start:  0,
		Len:    0,
		Pid:    0,
		Type:   lockType,
		Whence: 0,
	}

	f, err := os.OpenFile(path, flag, perm)
	if err != nil {
		return nil, err
	}

	if err = syscall.FcntlFlock(f.Fd(), rlockType, &lock); err != nil {
		f.Close()
		if err == syscall.EAGAIN {
			err = ErrAlreadyLocked
		}

	}
}

// Test lock race
func TestNSLockRace(t *testing.T) {
	t.Skip("long test skip it")

	ctx := context.Background()

	for i := 0; i < 10000; i++ {
		nsLk := newNSLock(false)

		// lk1; ref=1
		if !nsLk.lock(ctx, "volume", "path", "source", "opsID", false, time.Second) {
			t.Fatal("failed to acquire lock")
		}

		// lk2
		lk2ch := make(chan struct{})

		dm2nd.Lock(id, source)

		// Release lock after 10 seconds
		go func() {
			time.Sleep(2 * testDrwMutexAcquireTimeout)
			// fmt.Println("Unlocking dm2")

			dm2nd.Unlock(context.Background())
		}()

		dm3rd.Lock(id, source)

		// fmt.Printf("3rd lock obtained after 1st & 2nd locks are released\n")
		time.Sleep(testDrwMutexRefreshCallTimeout)

		dm3rd.Unlock(context.Background())
	}()

    lockAndUnlockNested(detectingLocks, reps);
  }

  private static void lockAndUnlockNested(Lock[] locks, int reps) {
    for (int i = 0; i < reps; i++) {
      for (int j = 0; j < locks.length; j++) {
        locks[j].lock();
      }
      for (int j = locks.length - 1; j >= 0; j--) {
        locks[j].unlock();
      }
    }
  }