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1   /*
2    * Copyright 2016 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.util.concurrent;
17  
18  import io.netty.util.internal.ObjectUtil;
19  
20  public final class PromiseCombiner {
21      private int expectedCount;
22      private int doneCount;
23      private boolean doneAdding;
24      private Promise<Void> aggregatePromise;
25      private Throwable cause;
26      private final GenericFutureListener<Future<?>> listener = new GenericFutureListener<Future<?>>() {
27          @Override
28          public void operationComplete(Future<?> future) throws Exception {
29              ++doneCount;
30              if (!future.isSuccess() && cause == null) {
31                  cause = future.cause();
32              }
33              if (doneCount == expectedCount && doneAdding) {
34                  tryPromise();
35              }
36          }
37      };
38  
39      @SuppressWarnings({ "unchecked", "rawtypes" })
40      public void add(Promise promise) {
41          checkAddAllowed();
42          ++expectedCount;
43          promise.addListener(listener);
44      }
45  
46      @SuppressWarnings({ "unchecked", "rawtypes" })
47      public void addAll(Promise... promises) {
48          checkAddAllowed();
49          expectedCount += promises.length;
50          for (Promise promise : promises) {
51              promise.addListener(listener);
52          }
53      }
54  
55      public void finish(Promise<Void> aggregatePromise) {
56          if (doneAdding) {
57              throw new IllegalStateException("Already finished");
58          }
59          doneAdding = true;
60          this.aggregatePromise = ObjectUtil.checkNotNull(aggregatePromise, "aggregatePromise");
61          if (doneCount == expectedCount) {
62              tryPromise();
63          }
64      }
65  
66      private boolean tryPromise() {
67          return (cause == null) ? aggregatePromise.trySuccess(null) : aggregatePromise.tryFailure(cause);
68      }
69  
70      private void checkAddAllowed() {
71          if (doneAdding) {
72              throw new IllegalStateException("Adding promises is not allowed after finished adding");
73          }
74      }
75  }