*   <li>If the first character was a high surrogate value, then an attempt is made to read the
   *       next character.
   *       <ol>
   *         <li><b>If the end of the sequence was reached, the negated value of the trailing high
   *             surrogate is returned.</b>
   *         <li><b>If the next character was a valid low surrogate, the code point value of the
   *             high/low surrogate pair is returned.</b>

   *   <li>If the first character was a high surrogate value, then an attempt is made to read the
   *       next character.
   *       <ol>
   *         <li><b>If the end of the sequence was reached, the negated value of the trailing high
   *             surrogate is returned.</b>
   *         <li><b>If the next character was a valid low surrogate, the code point value of the
   *             high/low surrogate pair is returned.</b>

    assertThat(UnsignedLongs.compare(0xffffffffffffffffL, 0)).isGreaterThan(0);

    // both with high bit set
    assertThat(UnsignedLongs.compare(0xff1a618b7f65ea12L, 0xffffffffffffffffL)).isLessThan(0);
    assertThat(UnsignedLongs.compare(0xffffffffffffffffL, 0xff1a618b7f65ea12L)).isGreaterThan(0);

    // one with high bit set
    assertThat(UnsignedLongs.compare(0x5a4316b8c153ac4dL, 0xff1a618b7f65ea12L)).isLessThan(0);

    return fmix(h1, Ints.BYTES);
  }

  @Override
  public HashCode hashLong(long input) {
    int low = (int) input;
    int high = (int) (input >>> 32);

    int k1 = mixK1(low);
    int h1 = mixH1(seed, k1);

    k1 = mixK1(high);
    h1 = mixH1(h1, k1);

    return fmix(h1, Longs.BYTES);
  }

  @Override
  public HashCode hashUnencodedChars(CharSequence input) {

    // center will be at either low or high.
    int low = requiredFrom;
    int high = requiredTo;
    while (high > low + 1) {
      int mid = (low + high) >>> 1;
      if (allRequired[mid] > centerFloor) {
        high = mid;
      } else if (allRequired[mid] < centerFloor) {
        low = mid;
      } else {

    // Two differing invalid pairs.
    assertEquals("abc\uD8AB", Strings.commonPrefix("abc\uD8AB\uD8ABdef", "abc\uD8AB\uD8ACxyz"));
    // One orphan high surrogate.
    assertEquals("", Strings.commonPrefix("\uD8AB\uDCAB", "\uD8AB"));
    // Two orphan high surrogates.
    assertEquals("\uD8AB", Strings.commonPrefix("\uD8AB", "\uD8AB"));
  }

    return fmix(h1, Ints.BYTES);
  }

  @Override
  public HashCode hashLong(long input) {
    int low = (int) input;
    int high = (int) (input >>> 32);

    int k1 = mixK1(low);
    int h1 = mixH1(seed, k1);

    k1 = mixK1(high);
    h1 = mixH1(h1, k1);

    return fmix(h1, Longs.BYTES);
  }

  @Override
  public HashCode hashUnencodedChars(CharSequence input) {

    CompactHashSet<E> set = createWithExpectedSize(elements.length);
    Collections.addAll(set, elements);
    return set;
  }

  /**
   * Creates a {@code CompactHashSet} instance, with a high enough "initial capacity" that it
   * <i>should</i> hold {@code expectedSize} elements without growth.
   *
   * @param expectedSize the number of elements you expect to add to the returned set

   * Returns a hash function implementing FarmHash's Fingerprint64, an open-source algorithm.
   *
   * <p>This is designed for generating persistent fingerprints of strings. It isn't
   * cryptographically secure, but it produces a high-quality hash with fewer collisions than some
   * alternatives we've used in the past.
   *
   * <p>FarmHash fingerprints are encoded by {@link HashCode#asBytes} in little-endian order. This

        .withFeatures(features)
        .suppressing(parentBuilder.getSuppressedTests())
        .createTestSuite();
  }

  /**
   * Returns an array of four bogus elements that will always be too high or too low for the
   * display. This includes two values for each extreme.
   *
   * <p>This method (dangerously) assume that the strings {@code "!! a"} and {@code "~~ z"} will