1 /*
2  * Copyright (C) 2010 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.quicksearchbox.util;
18 
19 
20 import android.util.Log;
21 
22 import java.util.ArrayList;
23 import java.util.List;
24 
25 /**
26  * Executes NamedTasks in batches of a given size.  Tasks are queued until
27  * executeNextBatch is called.
28  */
29 public class BatchingNamedTaskExecutor implements NamedTaskExecutor {
30 
31     private static final boolean DBG = false;
32     private static final String TAG = "QSB.BatchingNamedTaskExecutor";
33 
34     private final NamedTaskExecutor mExecutor;
35 
36     /** Queue of tasks waiting to be dispatched to mExecutor **/
37     private final ArrayList<NamedTask> mQueuedTasks = new ArrayList<NamedTask>();
38 
39     /**
40      * Creates a new BatchingSourceTaskExecutor.
41      *
42      * @param executor A SourceTaskExecutor for actually executing the tasks.
43      */
BatchingNamedTaskExecutor(NamedTaskExecutor executor)44     public BatchingNamedTaskExecutor(NamedTaskExecutor executor) {
45         mExecutor = executor;
46     }
47 
execute(NamedTask task)48     public void execute(NamedTask task) {
49         synchronized (mQueuedTasks) {
50             if (DBG) Log.d(TAG, "Queuing " + task);
51             mQueuedTasks.add(task);
52         }
53     }
54 
dispatch(NamedTask task)55     private void dispatch(NamedTask task) {
56         if (DBG) Log.d(TAG, "Dispatching " + task);
57         mExecutor.execute(task);
58     }
59 
60     /**
61      * Instructs the executor to submit the next batch of results.
62      * @param batchSize the maximum number of entries to execute.
63      */
executeNextBatch(int batchSize)64     public void executeNextBatch(int batchSize) {
65         NamedTask[] batch = new NamedTask[0];
66         synchronized (mQueuedTasks) {
67             int count = Math.min(mQueuedTasks.size(), batchSize);
68             List<NamedTask> nextTasks = mQueuedTasks.subList(0, count);
69             batch = nextTasks.toArray(batch);
70             nextTasks.clear();
71             if (DBG) Log.d(TAG, "Dispatching batch of " + count);
72         }
73 
74         for (NamedTask task : batch) {
75             dispatch(task);
76         }
77     }
78 
79     /**
80      * Cancel any unstarted tasks running in this executor.  This instance
81      * should not be re-used after calling this method.
82      */
cancelPendingTasks()83     public void cancelPendingTasks() {
84         synchronized (mQueuedTasks) {
85             mQueuedTasks.clear();
86         }
87     }
88 
close()89     public void close() {
90         cancelPendingTasks();
91         mExecutor.close();
92     }
93 }
94