1 /*
2  * Copyright (C) 2013 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * 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,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.inputmethod.latin.utils;
18 
19 import android.util.Log;
20 
21 import java.util.concurrent.CountDownLatch;
22 import java.util.concurrent.TimeUnit;
23 
24 /**
25  * This class is a holder of the result of an asynchronous computation.
26  *
27  * @param <E> the type of the result.
28  */
29 public class AsyncResultHolder<E> {
30 
31     private final Object mLock = new Object();
32 
33     private E mResult;
34     private final String mTag;
35     private final CountDownLatch mLatch;
36 
AsyncResultHolder(final String tag)37     public AsyncResultHolder(final String tag) {
38         mTag = tag;
39         mLatch = new CountDownLatch(1);
40     }
41 
42     /**
43      * Sets the result value of this holder.
44      *
45      * @param result the value to set.
46      */
set(final E result)47     public void set(final E result) {
48         synchronized(mLock) {
49             if (mLatch.getCount() > 0) {
50                 mResult = result;
51                 mLatch.countDown();
52             }
53         }
54     }
55 
56     /**
57      * Gets the result value held in this holder.
58      * Causes the current thread to wait unless the value is set or the specified time is elapsed.
59      *
60      * @param defaultValue the default value.
61      * @param timeOut the maximum time to wait.
62      * @return if the result is set before the time limit then the result, otherwise defaultValue.
63      */
get(final E defaultValue, final long timeOut)64     public E get(final E defaultValue, final long timeOut) {
65         try {
66             return mLatch.await(timeOut, TimeUnit.MILLISECONDS) ? mResult : defaultValue;
67         } catch (InterruptedException e) {
68             Log.w(mTag, "get() : Interrupted after " + timeOut + " ms");
69             return defaultValue;
70         }
71     }
72 }
73