* @author Dimitris Andreou
 */
@Immutable
final class MessageDigestHashFunction extends AbstractHashFunction implements Serializable {

  @SuppressWarnings("Immutable") // cloned before each use
  private final MessageDigest prototype;

  private final int bytes;
  private final boolean supportsClone;
  private final String toString;

  MessageDigestHashFunction(String algorithmName, String toString) {

      assertEquals(
          HashCode.fromBytes(Arrays.copyOf(digest.digest(input), bytes)),
          new MessageDigestHashFunction(algorithmName, bytes, algorithmName).hashBytes(input));
    }
    int maxSize = digest.getDigestLength();
    assertThrows(
        IllegalArgumentException.class,
        () -> new MessageDigestHashFunction(algorithmName, maxSize + 1, algorithmName));
  }

      assertEquals(
          HashCode.fromBytes(Arrays.copyOf(digest.digest(input), bytes)),
          new MessageDigestHashFunction(algorithmName, bytes, algorithmName).hashBytes(input));
    }
    int maxSize = digest.getDigestLength();
    assertThrows(
        IllegalArgumentException.class,
        () -> new MessageDigestHashFunction(algorithmName, maxSize + 1, algorithmName));
  }

    static final HashFunction SHA_1 = new MessageDigestHashFunction("SHA-1", "Hashing.sha1()");
  }

  /** Returns a hash function implementing the SHA-256 algorithm (256 hash bits). */
  public static HashFunction sha256() {
    return Sha256Holder.SHA_256;
  }

  private static final class Sha256Holder {
    static final HashFunction SHA_256 =
        new MessageDigestHashFunction("SHA-256", "Hashing.sha256()");
  }