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   /*
    * Copyright 2013 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.util.internal;
  
  import io.netty.util.ReferenceCountUtil;
  import io.netty.util.concurrent.Promise;
  import io.netty.util.internal.ObjectPool.Handle;
  import io.netty.util.internal.ObjectPool.ObjectCreator;
  
  /**
   * Some pending write which should be picked up later.
   */
  public final class PendingWrite {
      private static final ObjectPool<PendingWrite> RECYCLER = ObjectPool.newPool(new ObjectCreator<PendingWrite>() {
          @Override
          public PendingWrite newObject(Handle<PendingWrite> handle) {
              return new PendingWrite(handle);
          }
      });
  
      /**
       * Create a new empty {@link RecyclableArrayList} instance
       */
      public static PendingWrite newInstance(Object msg, Promise<Void> promise) {
          PendingWrite pending = RECYCLER.get();
          pending.msg = msg;
          pending.promise = promise;
          return pending;
      }
  
      private final Handle<PendingWrite> handle;
      private Object msg;
      private Promise<Void> promise;
  
      private PendingWrite(Handle<PendingWrite> handle) {
          this.handle = handle;
      }
  
      /**
       * Clear and recycle this instance.
       */
      public boolean recycle() {
          msg = null;
          promise = null;
          handle.recycle(this);
          return true;
      }
  
      /**
       * Fails the underlying {@link Promise} with the given cause and recycle this instance.
       */
      public boolean failAndRecycle(Throwable cause) {
          ReferenceCountUtil.release(msg);
          if (promise != null) {
              promise.setFailure(cause);
          }
          return recycle();
      }
  
      /**
       * Mark the underlying {@link Promise} successfully and recycle this instance.
       */
      public boolean successAndRecycle() {
          if (promise != null) {
              promise.setSuccess(null);
          }
          return recycle();
      }
  
      public Object msg() {
          return msg;
      }
  
      public Promise<Void> promise() {
          return promise;
      }
  
      /**
       * Recycle this instance and return the {@link Promise}.
       */
      public Promise<Void> recycleAndGet() {
          Promise<Void> promise = this.promise;
          recycle();
          return promise;
      }
  }