}

  /** Returns a hash function implementing the SHA-512 algorithm (512 hash bits). */
  public static HashFunction sha512() {
    return Sha512Holder.SHA_512;
  }

  private static class Sha512Holder {
    static final HashFunction SHA_512 =
        new MessageDigestHashFunction("SHA-512", "Hashing.sha512()");
  }

  /**

    assertThat(actual)
        .containsExactly(
            1,
            2,
            4,
            8,
            16,
            32,
            64,
            128,
            256,
            512,
            1024,
            2048,
            4096,
            8192,
            16384,
            32768,
            65536,
            131072,
            262144,
            524288,

    assertThat(actual)
        .containsExactly(
            1,
            2,
            4,
            8,
            16,
            32,
            64,
            128,
            256,
            512,
            1024,
            2048,
            4096,
            8192,
            16384,
            32768,
            65536,
            131072,
            262144,
            524288,

   * without being so large that it causes problems for systems with atypical memory management if
   * approaches 2 or 3 are used.
   */
  private static final int ZERO_COPY_CHUNK_SIZE = 512 * 1024;

  private ByteStreams() {}

  /**
   * Copies all bytes from the input stream to the output stream. Does not close or flush either
   * stream.
   *

    public int hashCode() {
      return alphabet.hashCode() ^ Objects.hashCode(paddingChar);
    }
  }

  private static final class Base16Encoding extends StandardBaseEncoding {
    final char[] encoding = new char[512];

    Base16Encoding(String name, String alphabetChars) {
      this(new Alphabet(name, alphabetChars.toCharArray()));
    }

    private Base16Encoding(Alphabet alphabet) {
      super(alphabet, null);