/**
   * A trust manager for Android applications that customize the trust manager.
   *
   * This class exploits knowledge of Android implementation details. This class is potentially
   * much faster to initialize than [BasicTrustRootIndex] because it doesn't need to load and
   * index trusted CA certificates.
   */
  internal data class CustomTrustRootIndex(
    private val trustManager: X509TrustManager,

    opcode: Int,
    payload: ByteString,
  ) {
    if (writerClosed) throw IOException("closed")

    val length = payload.size
    require(length <= PAYLOAD_BYTE_MAX) {
      "Payload size must be less than or equal to $PAYLOAD_BYTE_MAX"
    }

    val b0 = B0_FLAG_FIN or opcode
    sinkBuffer.writeByte(b0)

    var b1 = length
    if (isClient) {
      b1 = b1 or B1_FLAG_MASK

   *
   * @param code Status code as defined by
   *     [Section 7.4 of RFC 6455](http://tools.ietf.org/html/rfc6455#section-7.4).
   * @param reason Reason for shutting down, no longer than 123 bytes of UTF-8 encoded data (**not** characters) or null.
   * @throws IllegalArgumentException if [code] is invalid or [reason] is too long.
   */
  fun close(
    code: Int,
    reason: String?,
  ): Boolean