* Reads a {@code long} as specified by {@link DataInputStream#readLong()}, except using
   * little-endian byte order.
   *
   * @return the next eight bytes of the input stream, interpreted as a {@code long} in
   *     little-endian byte order
   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue // to skip some bytes
  @Override
  public long readLong() throws IOException {
    byte b1 = readAndCheckByte();

    metadata: ByteString?,
  ) {
    val source = file.source().buffer()
    assertThat(source.readByteString(prefix.size.toLong())).isEqualTo(prefix)
    assertThat(source.readLong()).isEqualTo(upstreamSize)
    assertThat(source.readLong()).isEqualTo(metadataSize.toLong())
    if (upstream != null) {
      assertThat(source.readUtf8(upstreamSize)).isEqualTo(upstream)
    }
    if (metadata != null) {

  @Override
  char readChar();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  int readInt();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  long readLong();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  float readFloat();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  double readDouble();

    assertEquals('\u6100', in.readChar());
    assertEquals(-12150, in.readShort());
    assertEquals(20675, in.readUnsignedShort());
    assertEquals(0xBEBAFECA, in.readInt());
    assertEquals(0xBEBAFECAEFBEADDEL, in.readLong());
    assertEquals("Herby Derby", in.readUTF());
    assertEquals(0xBEBAFECA, Float.floatToIntBits(in.readFloat()));
    assertEquals(0xBEBAFECAEFBEADDEL, Double.doubleToLongBits(in.readDouble()));
  }

    assertEquals('\u6100', in.readChar());
    assertEquals(-12150, in.readShort());
    assertEquals(20675, in.readUnsignedShort());
    assertEquals(0xBEBAFECA, in.readInt());
    assertEquals(0xBEBAFECAEFBEADDEL, in.readLong());
    assertEquals("Herby Derby", in.readUTF());
    assertEquals(0xBEBAFECA, Float.floatToIntBits(in.readFloat()));
    assertEquals(0xBEBAFECAEFBEADDEL, Double.doubleToLongBits(in.readDouble()));
  }

  @Override
  char readChar();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  int readInt();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  long readLong();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  float readFloat();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  double readDouble();

      val prefix = header.readByteString(PREFIX_CLEAN.size.toLong())
      if (prefix != PREFIX_CLEAN) throw IOException("unreadable cache file")
      val upstreamSize = header.readLong()
      val metadataSize = header.readLong()

      // Read the metadata.
      val metadataBuffer = Buffer()
      fileOperator.read(FILE_HEADER_SIZE + upstreamSize, metadataBuffer, metadataSize)

    assertEquals('\u6100', in.readChar());
    assertEquals(-12150, in.readShort());
    assertEquals(20675, in.readUnsignedShort());
    assertEquals(0xBEBAFECA, in.readInt());
    assertEquals(0xBEBAFECAEFBEADDEL, in.readLong());
    assertEquals("Herby Derby", in.readUTF());
    assertEquals(0xBEBAFECA, Float.floatToIntBits(in.readFloat()));
    assertEquals(0xBEBAFECAEFBEADDEL, Double.doubleToLongBits(in.readDouble()));
  }

    assertEquals('\u6100', in.readChar());
    assertEquals(-12150, in.readShort());
    assertEquals(20675, in.readUnsignedShort());
    assertEquals(0xBEBAFECA, in.readInt());
    assertEquals(0xBEBAFECAEFBEADDEL, in.readLong());
    assertEquals("Herby Derby", in.readUTF());
    assertEquals(0xBEBAFECA, Float.floatToIntBits(in.readFloat()));
    assertEquals(0xBEBAFECAEFBEADDEL, Double.doubleToLongBits(in.readDouble()));
  }

    if (bytesLeft == 0L) throw ProtocolException("unexpected length: $bytesLeft at $this")
    val byteArray = source.readByteArray(bytesLeft)
    return BigInteger(byteArray)
  }

  fun readLong(): Long {
    if (bytesLeft !in 1..8) throw ProtocolException("unexpected length: $bytesLeft at $this")

    var result = source.readByte().toLong() // No "and 0xff" because this is a signed value!