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      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      */
     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     }
     88 
     89     public void close() {
     90         cancelPendingTasks();
     91         mExecutor.close();
     92     }
     93 }
     94