*     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**

 *
 * Each derivation can capture the next value or any intermediate objects for later closing.
 *
 * <p>A step can be the input to at most one derived step. Once you transform its value, catch its
 * exception, or combine it with others, you cannot do anything else with it, including declare it
 * to be the last step of the pipeline.
 *
 * <h4>Transforming</h4>
 *

                    Iterator<Item> right = ((ListItem) item).iterator();

                    while (left.hasNext() || right.hasNext()) {
                        Item l = left.hasNext() ? left.next() : null;
                        Item r = right.hasNext() ? right.next() : null;

                        // if this is shorter, then invert the compare and mul with -1

        }

        if (buf[0] != 5 && buf[1] != 0) {
            throw new IOException("Unexpected DCERPC PDU header");
        }

        flags = buf[3] & 0xFF;
        // next read is start of new frag
        isStart = (flags & DCERPC_LAST_FRAG) == DCERPC_LAST_FRAG;

        length = Encdec.dec_uint16le(buf, 8);
        if (length > max_recv) {

   */
  public HashingInputStream(HashFunction hashFunction, InputStream in) {
    super(checkNotNull(in));
    this.hasher = checkNotNull(hashFunction.newHasher());
  }

  /**
   * Reads the next byte of data from the underlying input stream and updates the hasher with the
   * byte read.
   */
  @Override
  @CanIgnoreReturnValue
  public int read() throws IOException {
    int b = in.read();
    if (b != -1) {

    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();
      }

      @Override
      public K next() {
        return entryIterator.next().getKey();
      }
    };
  }

  Spliterator<K> keySpliterator() {
    return CollectSpliterators.map(entrySet().spliterator(), Entry::getKey);
  }

    assertThrows(
        ConcurrentModificationException.class,
        () -> {
          Iterator<E> iterator = collection.iterator();
          assertTrue(collection.add(e3()));
          iterator.next();
        });
  }

  /**
   * Returns the {@link Method} instance for {@link #testAdd_nullSupported()} so that tests of
   * {@link java.util.Collections#checkedCollection(java.util.Collection, Class)} can suppress it

    assertThrows(
        ConcurrentModificationException.class,
        () -> {
          Iterator<E> iterator = collection.iterator();
          assertTrue(collection.add(e3()));
          iterator.next();
        });
  }

  /**
   * Returns the {@link Method} instance for {@link #testAdd_nullSupported()} so that tests of
   * {@link java.util.Collections#checkedCollection(java.util.Collection, Class)} can suppress it

             * or to the start of the entry containing the
             * filename(e.g. NT). Ahhrg! In either case the
             * lastNameOffset falls between the start of the
             * entry and the next entry.
             */

            if (lastNameBufferIndex >= bufferIndex
                    && (e.getNextEntryOffset() == 0 || lastNameBufferIndex < bufferIndex + e.getNextEntryOffset())) {

        // Verify the size field (first 4 bytes)
        assertEquals(48, (value[0] & 0xFF) | ((value[1] & 0xFF) << 8) | ((value[2] & 0xFF) << 16) | ((value[3] & 0xFF) << 24));
        // Verify the zero field (next 4 bytes)
        assertEquals(0, (value[4] & 0xFF) | ((value[5] & 0xFF) << 8) | ((value[6] & 0xFF) << 16) | ((value[7] & 0xFF) << 24));

        // Verify customData part
        byte[] actualCustomData = new byte[8];