/**
 * An abstract composition of multiple hash functions. {@linkplain #newHasher()} delegates to the
 * {@code Hasher} objects of the delegate hash functions, and in the end, they are used by
 * {@linkplain #makeHash(Hasher[])} that constructs the final {@code HashCode}.
 *
 * @author Dimitris Andreou
 */
@Immutable
abstract class AbstractCompositeHashFunction extends AbstractHashFunction {

  }

  private static void assertNullsThrowException(Funnel<?> funnel) {
    PrimitiveSink primitiveSink =
        new AbstractStreamingHasher(4, 4) {
          @Override
          protected HashCode makeHash() {
            throw new UnsupportedOperationException();
          }

          @Override
          protected void process(ByteBuffer bb) {
            while (bb.hasRemaining()) {
              bb.get();

    }
    return makeHash();
  }

  /**
   * Computes a hash code based on the data that have been provided to this hasher. This is called
   * after all chunks are handled with {@link #process} and any leftover bytes that did not make a
   * complete chunk are handled with {@link #processRemaining}.
   */
  protected abstract HashCode makeHash();

  // Process pent-up data in chunks

      b += buffer.remaining();
      for (int i = 0; buffer.hasRemaining(); i += 8) {
        finalM ^= (buffer.get() & 0xFFL) << i;
      }
    }

    @Override
    protected HashCode makeHash() {
      // End with a byte encoding the positive integer b mod 256.
      finalM ^= b << 56;
      processM(finalM);

      // Finalization
      v2 ^= 0xFFL;
      sipRound(d);

    @Override
    public Hasher newHasher() {
      return new AbstractStreamingHasher(4, 4) {
        final ByteArrayOutputStream out = new ByteArrayOutputStream();

        @Override
        protected HashCode makeHash() {
          return HashCode.fromBytes(out.toByteArray());
        }

        @Override
        protected void process(ByteBuffer bb) {
          while (bb.hasRemaining()) {
            out.write(bb.get());

          break;
        default:
          throw new AssertionError("Should never get here.");
      }
      h1 ^= mixK1(k1);
      h2 ^= mixK2(k2);
    }

    @Override
    protected HashCode makeHash() {
      h1 ^= length;
      h2 ^= length;

      h1 += h2;
      h2 += h1;

      h1 = fmix64(h1);
      h2 = fmix64(h2);

      h1 += h2;
      h2 += h1;

      b += buffer.remaining();
      for (int i = 0; buffer.hasRemaining(); i += 8) {
        finalM ^= (buffer.get() & 0xFFL) << i;
      }
    }

    @Override
    protected HashCode makeHash() {
      // End with a byte encoding the positive integer b mod 256.
      finalM ^= b << 56;
      processM(finalM);

      // Finalization
      v2 ^= 0xFFL;
      sipRound(d);

    }

    Sink(int chunkSize) {
      super(chunkSize);
      this.chunkSize = chunkSize;
      this.bufferSize = chunkSize;
    }

    @Override
    protected HashCode makeHash() {
      return HashCode.fromBytes(out.toByteArray());
    }

    @Override
    protected void process(ByteBuffer bb) {
      processCalled++;
      assertEquals(ByteOrder.LITTLE_ENDIAN, bb.order());

      while (bb.hasRemaining()) {
        crc0 = (crc0 >>> 8) ^ byteTable[(bb.get() ^ crc0) & 0xFF];
      }
      finished = true;
    }

    @Override
    protected HashCode makeHash() {
      if (!finished) {
        // processRemaining does teardown we always want to do -- the folding together of the four
        // rolling CRCs.  So we call it on an empty ByteBuffer if we didn't already.

            "the number of bits (%s) in hashFunction (%s) must be divisible by 8",
            function.bits(),
            function);
      }
    }

    @Override
    HashCode makeHash(Hasher[] hashers) {
      byte[] bytes = new byte[bits() / 8];
      int i = 0;
      for (Hasher hasher : hashers) {
        HashCode newHash = hasher.hash();