}

  init {
    FLAGS[FLAG_NONE] = ""
    FLAGS[FLAG_END_STREAM] = "END_STREAM"

    val prefixFlags = intArrayOf(FLAG_END_STREAM)

    FLAGS[FLAG_PADDED] = "PADDED"
    for (prefixFlag in prefixFlags) {
      FLAGS[prefixFlag or FLAG_PADDED] = FLAGS[prefixFlag] + "|PADDED"
    }

    FLAGS[FLAG_END_HEADERS] = "END_HEADERS" // Same as END_PUSH_PROMISE.
    FLAGS[FLAG_PRIORITY] = "PRIORITY" // Same as FLAG_COMPRESSED.

* **REMOVED:** ~~TLSv1~~

##### COMPATIBLE_TLS versions

* **NEW:** TLSv1.3
* **NEW:** TLSv1.2
* **NEW:** TLSv1.1
* TLSv1

[OkHttp 3.12][OkHttp312]
------------------------

_2018-11-16_

Added support for TLSv1.3.

##### RESTRICTED_TLS cipher suites

 * **NEW:** TLS_AES_128_GCM_SHA256[¹][tlsv13_only]
 * **NEW:** TLS_AES_256_GCM_SHA384[¹][tlsv13_only]
 * **NEW:** TLS_CHACHA20_POLY1305_SHA256[¹][tlsv13_only]

      object : Task("$okHttpName ConnectionPool connection opener") {
        override fun runOnce(): Long = openConnections(this@scheduleOpener)
      },
    )
  }

  /**
   * Holding the lock of the connection being added or removed when mutating this, and check its
   * [RealConnection.noNewExchanges] property. This defends against races where a connection is
   * simultaneously adopted and removed.
   */

  }

  /**
   * Returns an iterator over the cache's current entries. This iterator doesn't throw
   * `ConcurrentModificationException`, but if new entries are added while iterating, those new
   * entries will not be returned by the iterator. If existing entries are removed during iteration,
   * they will be absent (unless they were already returned).
   *

      ),
    )

    // The original 'A' header is retained because the network response doesn't have one.
    // The original 'B' headers are replaced by the network response.
    // The network's 'C' header is added.
    val response2 = get(server.url("/"))
    assertThat(response2.body.string()).isEqualTo("abcd")
    assertThat(response2.headers).isEqualTo(
      headersOf(
        "Etag", "a", "Cache-Control", "max-age=0",

      "00000010",
      "00000011",
      "END_HEADERS",
      "END_STREAM|END_HEADERS",
      "00000110",
      "00000111",
      "PADDED",
      "END_STREAM|PADDED",
      "00001010",
      "00001011",
      "00001100",
      "END_STREAM|END_HEADERS|PADDED",
      "00001110",
      "00001111",
      "00010000",
      "00010001",
      "00010010",
      "00010011",
      "00010100",

import okhttp3.internal.http2.Http2.FLAG_END_HEADERS
import okhttp3.internal.http2.Http2.FLAG_END_STREAM
import okhttp3.internal.http2.Http2.FLAG_NONE
import okhttp3.internal.http2.Http2.FLAG_PADDED
import okhttp3.internal.http2.Http2.FLAG_PRIORITY
import okhttp3.internal.http2.Http2.TYPE_GOAWAY
import okio.Buffer
import okio.BufferedSink
import okio.BufferedSource
import okio.ByteString

      } else {
        sslSocket.enabledProtocols
      }

    // In accordance with https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00 the SCSV
    // cipher is added to signal that a protocol fallback has taken place.
    val supportedCipherSuites = sslSocket.supportedCipherSuites
    val indexOfFallbackScsv =
      supportedCipherSuites.indexOf(
        "TLS_FALLBACK_SCSV",

When writing request headers, use `header(name, value)` to set the only occurrence of `name` to `value`. If there are existing values, they will be removed before the new value is added. Use `addHeader(name, value)` to add a header without removing the headers already present.

/**
 * Read and write HPACK v10.
 *
 * http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-12
 *
 * This implementation uses an array for the dynamic table and a list for indexed entries. Dynamic
 * entries are added to the array, starting in the last position moving forward. When the array
 * fills, it is doubled.
 */
@Suppress("NAME_SHADOWING")
object Hpack {
  private const val PREFIX_4_BITS = 0x0f