return fmix(h1, length);
    }
  }

  private static long codePointToFourUtf8Bytes(int codePoint) {
    // codePoint has at most 21 bits
    return ((0xFL << 4) | (codePoint >>> 18))
        | ((0x80L | (0x3F & (codePoint >>> 12))) << 8)
        | ((0x80L | (0x3F & (codePoint >>> 6))) << 16)
        | ((0x80L | (0x3F & codePoint)) << 24);
  }

  private static long charToThreeUtf8Bytes(char c) {

    return y - lessThanBranchFree(x, powersOf10[y]);
  }

  // maxLog10ForLeadingZeros[i] == floor(log10(2^(Long.SIZE - i)))
  @VisibleForTesting
  static final byte[] maxLog10ForLeadingZeros = {
    19, 18, 18, 18, 18, 17, 17, 17, 16, 16, 16, 15, 15, 15, 15, 14, 14, 14, 13, 13, 13, 12, 12, 12,
    12, 11, 11, 11, 10, 10, 10, 9, 9, 9, 9, 8, 8, 8, 7, 7, 7, 6, 6, 6, 6, 5, 5, 5, 4, 4, 4, 3, 3, 3,
    3, 2, 2, 2, 1, 1, 1, 0, 0, 0
  };

                newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20))
            .size());
    assertEquals(
        Integer.MAX_VALUE,
        Collections2.orderedPermutations(
                newArrayList(
                    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21))
            .size());
  }

  public void testPermutationSetContains() {

                newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20))
            .size());
    assertEquals(
        Integer.MAX_VALUE,
        Collections2.orderedPermutations(
                newArrayList(
                    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21))
            .size());
  }

  public void testPermutationSetContains() {

    long z = hashLength16(y, a + rotateRight(b + K2, 18) + c, mul);
    long e = load64(bytes, offset + 16) * mul;
    long f = load64(bytes, offset + 24);
    long g = (y + load64(bytes, offset + length - 32)) * mul;
    long h = (z + load64(bytes, offset + length - 24)) * mul;
    return hashLength16(
        rotateRight(e + f, 43) + rotateRight(g, 30) + h, e + rotateRight(f + a, 18) + g, mul);
  }

  /*

      ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS;

  // 1920 [chars 0x0080 to 0x07FF]
  private static final long TWO_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x07FF - 0x0080 + 1;

  // 18,304
  private static final long EXPECTED_TWO_BYTE_ROUNDTRIPPABLE_COUNT =
      // Both bytes are one byte characters
      (long) Math.pow(EXPECTED_ONE_BYTE_ROUNDTRIPPABLE_COUNT, 2)
          +

    rangeMap.put(Range.closedOpen(1, 3), 1);
    rangeMap.put(Range.closedOpen(3, 5), 1);
    rangeMap.put(Range.closedOpen(7, 10), 2);
    rangeMap.put(Range.closedOpen(12, 15), 2);
    rangeMap.put(Range.closedOpen(18, 19), 3);

    rangeMap.putCoalescing(Range.closedOpen(-5, -4), 0); // disconnected
    rangeMap.putCoalescing(Range.closedOpen(-6, -5), 0); // lower than minimum

   * single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the
   * preferred assignment.)
   *
   * @since 8.0
   */
  public static final byte DC2 = 18;

  /**
   * Device Control 3. Characters for the control of ancillary devices associated with data
   * processing or telecommunication systems, more especially switching devices "on" or "off." (If a

    <profile>
      <id>javac-for-jvm18plus</id>
      <activation>
        <!--
            In order to build and run the tests against JDK 18+, we need to pass java.security.manager=allow, to make
            the deprecated 'java.lang.SecurityManager' available for use.
         -->
        <jdk>[18,]</jdk>
      </activation>
      <properties>
        <test.add.args>-Djava.security.manager=allow</test.add.args>
      </properties>

      int i = off;
      for (int remaining = len; remaining >= 3; remaining -= 3) {
        int chunk = (bytes[i++] & 0xFF) << 16 | (bytes[i++] & 0xFF) << 8 | bytes[i++] & 0xFF;
        target.append(alphabet.encode(chunk >>> 18));
        target.append(alphabet.encode((chunk >>> 12) & 0x3F));
        target.append(alphabet.encode((chunk >>> 6) & 0x3F));
        target.append(alphabet.encode(chunk & 0x3F));
      }
      if (i < off + len) {