BatchingNamedTaskExecutor.java revision b5fc08b7f16a32d3865f44b7f26d8aaa5304a2ad 
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
17package com.android.quicksearchbox.util;
18
19
20import android.util.Log;
21
22import java.util.ArrayList;
23import java.util.List;
24
25/**
26 * Executes NamedTasks in batches of a given size.  Tasks are queued until
27 * executeNextBatch is called.
28 */
29public 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     */
44    public BatchingNamedTaskExecutor(NamedTaskExecutor executor) {
45        mExecutor = executor;
46    }
47
48    public void execute(NamedTask task) {
49        synchronized (mQueuedTasks) {
50            if (DBG) Log.d(TAG, "Queuing " + task);
51            mQueuedTasks.add(task);
52        }
53    }
54
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     */
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     */
83    public void cancelPendingTasks() {
84        synchronized (mQueuedTasks) {
85            mQueuedTasks.clear();
86        }
87        mExecutor.cancelPendingTasks();
88    }
89
90    public void close() {
91        cancelPendingTasks();
92        mExecutor.close();
93    }
94}
95