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      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.bitmap;
     18 
     19 import android.util.Log;
     20 import android.util.LruCache;
     21 
     22 import com.android.bitmap.ReusableBitmap.NullReusableBitmap;
     23 import com.android.bitmap.util.Trace;
     24 
     25 /**
     26  * This subclass provides custom pool behavior. The pool can be set to block on {@link #poll()} if
     27  * nothing can be returned. This is useful if you know you will incur high costs upon receiving
     28  * nothing from the pool, and you do not want to incur those costs at the critical moment when the
     29  * UI is animating.
     30  *
     31  * This subclass provides custom cache behavior. Null values can be cached. Later,
     32  * when the same key is used to retrieve the value, a {@link NullReusableBitmap} singleton will
     33  * be returned.
     34  */
     35 public class UnrefedBitmapCache extends UnrefedPooledCache<RequestKey, ReusableBitmap>
     36         implements BitmapCache {
     37     private boolean mBlocking = false;
     38     private final Object mLock = new Object();
     39 
     40     private LruCache<RequestKey, NullReusableBitmap> mNullRequests;
     41 
     42     private final static boolean DEBUG = DecodeTask.DEBUG;
     43     private final static String TAG = UnrefedBitmapCache.class.getSimpleName();
     44 
     45     public UnrefedBitmapCache(final int targetSizeBytes, final float nonPooledFraction,
     46             final int nullCapacity) {
     47         super(targetSizeBytes, nonPooledFraction);
     48 
     49         if (nullCapacity > 0) {
     50             mNullRequests = new LruCache<RequestKey, NullReusableBitmap>(nullCapacity);
     51         }
     52     }
     53 
     54     /**
     55      * Declare that {@link #poll()} should now block until it can return something.
     56      */
     57     @Override
     58     public void setBlocking(final boolean blocking) {
     59         synchronized (mLock) {
     60             if (DEBUG) {
     61                 Log.d(TAG, String.format("AltBitmapCache: block %b", blocking));
     62             }
     63             mBlocking = blocking;
     64             if (!mBlocking) {
     65                 // no longer blocking. Notify every thread.
     66                 mLock.notifyAll();
     67             }
     68         }
     69     }
     70 
     71     @Override
     72     protected int sizeOf(final ReusableBitmap value) {
     73         return value.getByteCount();
     74     }
     75 
     76     /**
     77      * If {@link #setBlocking(boolean)} has been called with true, this method will block until a
     78      * resource is available.
     79      * @return an available resource, or null if none are available. Null will never be returned
     80      * until blocking is set to false.
     81      */
     82     @Override
     83     public ReusableBitmap poll() {
     84         ReusableBitmap bitmap;
     85         synchronized (mLock) {
     86             while ((bitmap = super.poll()) == null && mBlocking) {
     87                 if (DEBUG) {
     88                     Log.d(TAG, String.format(
     89                             "AltBitmapCache: %s waiting", Thread.currentThread().getName()));
     90                 }
     91                 Trace.beginSection("sleep");
     92                 try {
     93                     // block
     94                     mLock.wait();
     95                     if (DEBUG) {
     96                         Log.d(TAG, String.format("AltBitmapCache: %s notified",
     97                                 Thread.currentThread().getName()));
     98                     }
     99                 } catch (InterruptedException ignored) {
    100                 }
    101                 Trace.endSection();
    102             }
    103         }
    104         return bitmap;
    105     }
    106 
    107     @Override
    108     public void offer(final ReusableBitmap value) {
    109         synchronized (mLock) {
    110             super.offer(value);
    111             if (DEBUG) {
    112                 Log.d(TAG, "AltBitmapCache: offer +1");
    113             }
    114             // new resource gained. Notify one thread.
    115             mLock.notify();
    116         }
    117     }
    118 
    119     @Override
    120     public ReusableBitmap get(final RequestKey key, final boolean incrementRefCount) {
    121         if (mNullRequests != null && mNullRequests.get(key) != null) {
    122             return NullReusableBitmap.getInstance();
    123         }
    124         return super.get(key, incrementRefCount);
    125     }
    126 
    127     /**
    128      * Note: The cache only supports same-sized bitmaps.
    129      */
    130     @Override
    131     public ReusableBitmap put(final RequestKey key, final ReusableBitmap value) {
    132         if (mNullRequests != null && (value == null || value == NullReusableBitmap.getInstance())) {
    133             mNullRequests.put(key, NullReusableBitmap.getInstance());
    134             return null;
    135         }
    136 
    137         return super.put(key, value);
    138     }
    139 }
    140