* 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

    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

   * 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
    }
  }

    executeSynchronously(Request(server.url("/")))
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(0)
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(1)
  }

  /** We forbid non-ASCII characters in outgoing request headers, but accept UTF-8.  */
  @Test
  fun responseHeaderParsingIsLenient() {
    val headersBuilder = Headers.Builder()
    headersBuilder.add("Content-Length", "0")

 *  Fix: Fail fast when the cache is corrupted.
 *  Fix: Fail fast when a private key cannot be encoded.
 *  Fix: Fail fast when attempting to verify a non-ASCII hostname.
 *  Upgrade: [GraalVM 21][graalvm_21].
 *  Upgrade: [Kotlin 1.4.20][kotlin_1_4_20].


## Version 5.0.0-alpha.1

_2021-01-30_

**This release adds initial support for [GraalVM][graalvm].**

 *
 * Mappings may overlap.
 *
 * ASCII-Only
 * ==========
 *
 * Neither the section index nor the ranges data use bit 0x80 anywhere. That means the data is
 * strictly ASCII. This is intended to make it efficient to encode this data as a string, and to
 * index into it as a string.
 *
 * The mappings data contains non-ASCII characters.
 */
internal class IdnaMappingTable internal constructor(