val headers =
      Headers.Builder()
        .add("WWW-Authenticate: Basic realm=\"protected area\", charset=\"US-ASCII\"")
        .build()
    val expectedAuthParams = mutableMapOf<String?, String>()
    expectedAuthParams["realm"] = "protected area"
    expectedAuthParams["charset"] = "US-ASCII"
    assertThat(headers.parseChallenges("WWW-Authenticate"))
      .isEqualTo(listOf(Challenge("Basic", expectedAuthParams)))
  }

    )
    assertEquals(
      "US-ASCII",
      noCharset.charset(Charsets.US_ASCII)!!.name(),
    )
    val charset = parse("text/plain; charset=iso-8859-1")
    assertEquals(
      "ISO-8859-1",
      charset.charset(Charsets.UTF_8)!!.name(),
    )
    assertEquals(
      "ISO-8859-1",
      charset.charset(Charsets.US_ASCII)!!.name(),
    )
  }

  @Test fun testTurkishDotlessIWithEnUs() {

   * This is like [toLowerCase] except that it does nothing if this contains any non-ASCII
   * characters. We want to avoid lower casing special chars like U+212A (Kelvin symbol) because
   * they can return ASCII characters that match real hostnames.
   */
  private fun String.asciiToLowercase(): String {
    return when {
      isAscii() -> lowercase(Locale.US) // This is an ASCII string.
      else -> this
    }
  }

 * limitations under the License.
 */
package okhttp3.internal.idn

import okio.Buffer
import okio.ByteString.Companion.encodeUtf8

/**
 * An [RFC 3492] punycode decoder for converting ASCII to Unicode domain name labels. This is
 * intended for use in Internationalized Domain Names (IDNs).
 *
 * This class contains a Kotlin implementation of the pseudocode specified by RFC 3492. It includes

 * example this converts `☃.net` to `xn--n3h.net`, and `WwW.GoOgLe.cOm` to `www.google.com`.
 * `null` will be returned if the host cannot be ToASCII encoded or if the result contains
 * unsupported ASCII characters.
 */
internal fun String.toCanonicalHost(): String? {
  val host: String = this

  // If the input contains a :, it’s an IPv6 address.
  if (":" in host) {

 */
package okhttp3.internal.http2

import okio.ByteString
import okio.ByteString.Companion.encodeUtf8

/** HTTP header: the name is an ASCII string, but the value can be UTF-8. */
data class Header(
  /** Name in case-insensitive ASCII encoding. */
  @JvmField val name: ByteString,
  /** Value in UTF-8 encoding. */
  @JvmField val value: ByteString,
) {

    "output": null
  },
  {
    "input": "xn--a.ß",
    "output": null
  },
  {
    "input": "xn--ls8h=",
    "output": null
  },
  {
    "comment": "Invalid Punycode (contains non-ASCII character)",
    "input": "xn--tešla",
    "output": null
  },
  {
    "comment": "Valid Punycode",
    "input": "xn--zca.xn--zca",
    "output": "xn--zca.xn--zca"
  },
  {
    "comment": "Mixed",

internal object DnsRecordCodec {
  private const val SERVFAIL = 2
  private const val NXDOMAIN = 3
  const val TYPE_A = 0x0001
  const val TYPE_AAAA = 0x001c
  private const val TYPE_PTR = 0x000c
  private val ASCII = Charsets.US_ASCII

  fun encodeQuery(
    host: String,
    type: Int,
  ): ByteString =
    Buffer().apply {
      writeShort(0) // query id
      writeShort(256) // flags with recursion

internal fun Array<String>.concat(value: String): Array<String> {
  val result = copyOf(size + 1)
  result[result.lastIndex] = value
  return result as Array<String>
}

/** Increments [startIndex] until this string is not ASCII whitespace. Stops at [endIndex]. */
internal fun String.indexOfFirstNonAsciiWhitespace(
  startIndex: Int = 0,
  endIndex: Int = length,
): Int {
  for (i in startIndex until endIndex) {
    when (this[i]) {

    encapsulation enabled.
 *  Fix: Strictly verify hostnames used with OkHttp's `HostnameVerifier`. Programs that make direct
    manual calls to `HostnameVerifier` could be defeated if the hostnames they pass in are not
    strictly ASCII. This issue is tracked as [CVE-2021-0341].


## Version 4.9.1

_2021-01-30_

 *  Fix: Work around a crash in Android 10 and 11 that may be triggered when two threads