apply {
        require(tls) { "no cipher suites for cleartext connections" }
        require(cipherSuites.isNotEmpty()) { "At least one cipher suite is required" }

        this.cipherSuites = cipherSuites.copyOf() as Array<String> // Defensive copy.
      }

    fun allEnabledTlsVersions() =
      apply {
        require(tls) { "no TLS versions for cleartext connections" }

        when {
          it.sourceCodePoint1 < codePoint -> -1
          it.sourceCodePoint0 > codePoint -> 1
          else -> 0
        }
      }

    // Code points must be in 0..0x10ffff.
    require(index in mappings.indices) { "unexpected code point: $codePoint" }

    val mapping = mappings[index]
    var result = true

    when (mapping.type) {
      TYPE_IGNORED -> Unit

   * explicitly closed.
   */
  fun truncateLastFrame(length: Int): Http2Writer {
    val lastFrame = outFrames.removeAt(outFrames.size - 1)
    require(length < bytesOut.size - lastFrame.start)

    // Move everything from bytesOut into a new buffer.
    val fullBuffer = Buffer()
    bytesOut.read(fullBuffer, bytesOut.size)

  }

  fun writeObjectIdentifier(s: String) {
    val utf8 = Buffer().writeUtf8(s)
    val v1 = utf8.readDecimalLong()
    require(utf8.readByte() == '.'.code.toByte())
    val v2 = utf8.readDecimalLong()
    writeVariableLengthLong(v1 * 40 + v2)

    while (!utf8.exhausted()) {
      require(utf8.readByte() == '.'.code.toByte())
      val vN = utf8.readDecimalLong()
      writeVariableLengthLong(vN)
    }
  }

  open fun getSelectedProtocol(sslSocket: SSLSocket): String? = null

  /** For MockWebServer. This returns the inbound SNI names. */
  @SuppressLint("NewApi")
  @IgnoreJRERequirement // This function is overridden to require API >= 24.
  open fun getHandshakeServerNames(sslSocket: SSLSocket): List<String> {
    val session = sslSocket.session as? ExtendedSSLSession ?: return listOf()

    upstreamSize: Long,
    metadataSize: Long,
  ) {
    val header =
      Buffer().apply {
        write(prefix)
        writeLong(upstreamSize)
        writeLong(metadataSize)
        require(size == FILE_HEADER_SIZE)
      }

    val fileOperator = FileOperator(file!!.channel)
    fileOperator.write(0, header, FILE_HEADER_SIZE)
  }

  @Throws(IOException::class)

  if (address[11] != 255.toByte()) return false

  return true
}

/** Encodes an IPv4 address in canonical form according to RFC 4001. */
internal fun inet4AddressToAscii(address: ByteArray): String {
  require(address.size == 4)
  return Buffer()
    .writeDecimalLong((address[0] and 0xff).toLong())
    .writeByte('.'.code)
    .writeDecimalLong((address[1] and 0xff).toLong())
    .writeByte('.'.code)

  method: String,
  body: RequestBody?,
): Request.Builder =
  apply {
    require(method.isNotEmpty()) {
      "method.isEmpty() == true"
    }
    if (body == null) {
      require(!HttpMethod.requiresRequestBody(method)) {
        "method $method must have a request body."
      }
    } else {
      require(HttpMethod.permitsRequestBody(method)) {
        "method $method must not have a request body."

        when (val label = match.groups[1]!!.value) {
          "CERTIFICATE" -> {
            require(certificatePem == null) { "string includes multiple certificates" }
            certificatePem = match.groups[0]!!.value // Keep --BEGIN-- and --END-- for certificates.
          }
          "PRIVATE KEY" -> {
            require(pkcs8Base64 == null) { "string includes multiple private keys" }

  @Throws(IOException::class)
  private fun writeControlFrame(
    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