}
    HashCode[] codes = new HashCode[hashers.size()];
    for (int i = 0; i < hashers.size(); i++) {
      codes[i] = hashers.get(i).hash();
    }
    for (int i = 1; i < codes.length; i++) {
      assertEquals(codes[i - 1], codes[i]);
    }
  }

  public void testPutStringWithLowSurrogate() {

}

// HashBorrower keeps track of borrowed hashers and allows to return them all.
type HashBorrower struct {
	pool     *bpool.Pool[hash.Hash]
	borrowed []hash.Hash
}

// Borrow a single hasher.
func (h *HashBorrower) Borrow() hash.Hash {
	hasher := h.pool.Get()
	h.borrowed = append(h.borrowed, hasher)
	hasher.Reset()
	return hasher
}

      checkNotDone();
      checkNotNull(bytes);
      mac.update(bytes);
    }

    private void checkNotDone() {
      checkState(!done, "Cannot re-use a Hasher after calling hash() on it");
    }

    @Override
    public HashCode hash() {
      checkNotDone();
      done = true;
      return HashCode.fromBytesNoCopy(mac.doFinal());
    }
  }

    super(checkNotNull(out));
    this.hasher = checkNotNull(hashFunction.newHasher());
  }

  @Override
  public void write(int b) throws IOException {
    hasher.putByte((byte) b);
    out.write(b);
  }

  @Override
  public void write(byte[] bytes, int off, int len) throws IOException {
    hasher.putBytes(bytes, off, len);
    out.write(bytes, off, len);
  }

  /**

    Hasher hasher = hmacMd5(MD5_KEY).newHasher();

    assertThat(
            hasher
                .putString("The quick brown fox jumps over the lazy dog", UTF_8)
                .hash()
                .toString())
        .isEqualTo("9753980fe94daa8ecaa82216519393a9");
    assertThrows(IllegalStateException.class, hasher::hash);
  }

  public void testToString() {
    byte[] keyData = "secret key".getBytes(UTF_8);

    // https://github.com/aappleby/smhasher/blob/master/src/main.cpp
    HashTestUtils.verifyHashFunction(hf, 32, 0xB0F57EE3);
  }

  public void testParanoid() {
    HashFn hf =
        new HashFn() {
          @Override
          public byte[] hash(byte[] input, int seed) {
            Hasher hasher = murmur3_32(seed).newHasher();
            byteArrayFunnel().funnel(input, hasher);

    @CanIgnoreReturnValue
    @Override
    public Hasher putInt(int i) {
      update(4, i);
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    public Hasher putLong(long l) {
      update(4, (int) l);
      update(4, l >>> 32);
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    public Hasher putChar(char c) {
      update(2, c);
      return this;

    }
    return HashCode.fromBytes(bb.array());
  }

  public void testParanoid() {
    HashFn hf =
        new HashFn() {
          @Override
          public byte[] hash(byte[] input, int seed) {
            Hasher hasher = murmur3_128(seed).newHasher();
            byteArrayFunnel().funnel(input, hasher);
            return hasher.hash().asBytes();
          }
        };

      checkNotDone();
      digest.update(bytes);
    }

    private void checkNotDone() {
      checkState(!done, "Cannot re-use a Hasher after calling hash() on it");
    }

    @Override
    public HashCode hash() {
      checkNotDone();
      done = true;
      return (bytes == digest.getDigestLength())
          ? HashCode.fromBytesNoCopy(digest.digest())

  }

  @Override
  public int bits() {
    return bits;
  }

  @Override
  public Hasher newHasher() {
    return new ChecksumHasher(checksumSupplier.get());
  }

  @Override
  public String toString() {
    return toString;
  }

  /** Hasher that updates a checksum. */
  private final class ChecksumHasher extends AbstractByteHasher {
    private final Checksum checksum;