*
   * @throws IOException if the trailers cannot be loaded, such as if the network connection is
   *     dropped.
   */
  @Throws(IOException::class)
  fun peekTrailers(): Headers? = trailersSource.peek()

  /**
   * Peeks up to [byteCount] bytes from the response body and returns them as a new response
   * body. If fewer than [byteCount] bytes are in the response body, the full response body is

     * This stream class is unbuffered. Therefore this method will always
     * return 0 for streams connected to regular files. However, a
     * stream created from a Named Pipe this method will query the server using a
     * "peek named pipe" operation and return the number of available bytes
     * on the server.
     */
    @Override
    public int available() throws IOException {
        SmbNamedPipe pipe;
        TransPeekNamedPipe req;

     * This stream class is unbuffered. Therefore this method will always
     * return 0 for streams connected to regular files. However, a
     * stream created from a Named Pipe this method will query the server using a
     * "peek named pipe" operation and return the number of available bytes
     * on the server.
     */
    @Override
    public int available() throws IOException {
        return 0;
    }

    /**

   *     Iterators.peekingIterator(Iterators.forArray("a", "b"));
   * String a1 = peekingIterator.peek(); // returns "a"
   * String a2 = peekingIterator.peek(); // also returns "a"
   * String a3 = peekingIterator.next(); // also returns "a"
   * }
   *
   * <p>Any structural changes to the underlying iteration (aside from those performed by the
   * iterator's own {@link PeekingIterator#remove()} method) will leave the iterator in an undefined

   *     Iterators.peekingIterator(Iterators.forArray("a", "b"));
   * String a1 = peekingIterator.peek(); // returns "a"
   * String a2 = peekingIterator.peek(); // also returns "a"
   * String a3 = peekingIterator.next(); // also returns "a"
   * }
   *
   * <p>Any structural changes to the underlying iteration (aside from those performed by the
   * iterator's own {@link PeekingIterator#remove()} method) will leave the iterator in an undefined

                  } catch (ExecutionException expected) {
                  }
                  try {
                    peeker.getDone(nonInput);
                    fail("Peeker should not be able to peek into non-input ClosingFuture.");
                  } catch (IllegalArgumentException expected) {
                  }
                  capturedPeeker.set(peeker);
                  return closeable2;
                },

                  } catch (ExecutionException expected) {
                  }
                  try {
                    peeker.getDone(nonInput);
                    fail("Peeker should not be able to peek into non-input ClosingFuture.");
                  } catch (IllegalArgumentException expected) {
                  }
                  capturedPeeker.set(peeker);
                  return closeable2;
                },

    Deque<NodeAndRemainingSuccessors<N>> stack = new ArrayDeque<>();
    stack.addLast(new NodeAndRemainingSuccessors<>(startNode));

    while (!stack.isEmpty()) {
      // To peek at the top two items, we need to temporarily remove one.
      NodeAndRemainingSuccessors<N> top = stack.removeLast();
      NodeAndRemainingSuccessors<N> prev = stack.peekLast();
      stack.addLast(top);

      drainRecencyQueue();

      ReferenceEntry<K, V> e;
      while ((e = writeQueue.peek()) != null && map.isExpired(e, now)) {
        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
          throw new AssertionError();
        }
      }
      while ((e = accessQueue.peek()) != null && map.isExpired(e, now)) {
        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {

    monitor.enterWhen(notEmpty);
    try {
      return extract();
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable E peek() {
    Monitor monitor = this.monitor;
    if (monitor.enterIf(notEmpty)) {
      try {
        return items[takeIndex];
      } finally {
        monitor.leave();
      }
    } else {