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   /*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
    * "License"); you may not use this file except in compliance with the License. You may obtain a
    * copy of the License at:
    *
    * https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software distributed under the License
   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   * or implied. See the License for the specific language governing permissions and limitations under
   * the License.
   */
  package io.netty.example.http2.helloworld.client;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.codec.http2.Http2Settings;
  
  import java.util.concurrent.TimeUnit;
  
  /**
   * Reads the first {@link Http2Settings} object and notifies a {@link io.netty.channel.ChannelPromise}
   */
  public class Http2SettingsHandler extends SimpleChannelInboundHandler<Http2Settings> {
      private final ChannelPromise promise;
  
      /**
       * Create new instance
       *
       * @param promise Promise object used to notify when first settings are received
       */
      public Http2SettingsHandler(ChannelPromise promise) {
          this.promise = promise;
      }
  
      /**
       * Wait for this handler to be added after the upgrade to HTTP/2, and for initial preface
       * handshake to complete.
       *
       * @param timeout Time to wait
       * @param unit {@link java.util.concurrent.TimeUnit} for {@code timeout}
       * @throws Exception if timeout or other failure occurs
       */
      public void awaitSettings(long timeout, TimeUnit unit) throws Exception {
          if (!promise.awaitUninterruptibly(timeout, unit)) {
              throw new IllegalStateException("Timed out waiting for settings");
          }
          if (!promise.isSuccess()) {
              throw new RuntimeException(promise.cause());
          }
      }
  
      @Override
      protected void channelRead0(ChannelHandlerContext ctx, Http2Settings msg) throws Exception {
          promise.setSuccess();
  
          // Only care about the first settings message
          ctx.pipeline().remove(this);
      }
  }