* limitations under the License.
 */

package okhttp3.internal.connection

import java.net.Inet6Address
import java.net.InetAddress
import okhttp3.internal.interleave

/**
 * Implementation of HappyEyeballs Sorting Addresses.
 *
 * The current implementation does not address any of:
 *  - Async DNS split by IP class
 *  - Stateful handling of connectivity results

   *
   * ### Duplex Transmission
   *
   * With regular HTTP calls the request always completes sending before the response may begin
   * receiving. With duplex the request and response may be interleaved! That is, request body bytes
   * may be sent after response headers or body bytes have been received.
   *
   * Though any call may be initiated as a duplex call, only web servers that are specially

     * Cache#invalidate invalidations}.
     */
    void recordEviction();

    /**
     * Returns a snapshot of this counter's values. Note that this may be an inconsistent view, as
     * it may be interleaved with update operations.
     */
    CacheStats snapshot();
  }

  /**
   * A thread-safe {@link StatsCounter} implementation for use by {@link Cache} implementors.
   *
   * @since 10.0
   */

     * Cache#invalidate invalidations}.
     */
    void recordEviction();

    /**
     * Returns a snapshot of this counter's values. Note that this may be an inconsistent view, as
     * it may be interleaved with update operations.
     */
    CacheStats snapshot();
  }

  /**
   * A thread-safe {@link StatsCounter} implementation for use by {@link Cache} implementors.
   *
   * @since 10.0
   */

    // a multithreaded environment for a couple of reasons:
    //
    // 1. Subscribers to events posted on different threads can be interleaved with each other
    //    freely. (A event on one thread, B event on another could yield any of
    //    [a1, a2, a3, b1, b2], [a1, b2, a2, a3, b2], [a1, b2, b3, a2, a3], etc.)

#### Http2Writer

Socket writes are guarded by the Http2Writer. Only one stream can write at a time so that messages are not interleaved. Writes are either made by application-layer threads or the do-stuff-later pool.

### Holding multiple locks