AltBitmapCache.java revision 1aba32575a08da6cbad80af8446201d73c59783d 
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
17package com.android.bitmap;
18
19import com.android.mail.utils.LogTag;
20import com.android.mail.utils.LogUtils;
21
22/**
23 * This subclass provides custom pool behavior. The pool can be set to block on {@link #poll()} if
24 * nothing can be returned. This is useful if you know you will incur high costs upon receiving
25 * nothing from the pool, and you do not want to incur those costs at the critical moment when the
26 * UI is animating.
27 */
28public class AltBitmapCache extends AltPooledCache<DecodeTask.Request, ReusableBitmap>
29        implements BitmapCache {
30    private boolean mBlocking = false;
31    private final Object mLock = new Object();
32
33    private final static boolean DEBUG = false;
34    private final static String TAG = LogTag.getLogTag();
35
36    public AltBitmapCache(final int targetSizeBytes, final float nonPooledFraction) {
37        super(targetSizeBytes, nonPooledFraction);
38    }
39
40    /**
41     * Declare that {@link #poll()} should now block until it can return something.
42     */
43    public void setBlocking(final boolean blocking) {
44        synchronized (mLock) {
45            if (DEBUG) LogUtils.d(TAG, "AltBitmapCache: block %b", blocking);
46            mBlocking = blocking;
47            if (!mBlocking) {
48                // no longer blocking. Notify every thread.
49                mLock.notifyAll();
50            }
51        }
52    }
53
54    @Override
55    protected int sizeOf(final ReusableBitmap value) {
56        return value.getByteCount();
57    }
58
59    /**
60     * If {@link #setBlocking(boolean)} has been called with true, this method will block until a
61     * resource is available.
62     * @return an available resource, or null if none are available. Null will never be returned
63     * until blocking is set to false.
64     */
65    @Override
66    public ReusableBitmap poll() {
67        ReusableBitmap bitmap;
68        synchronized (mLock) {
69            while ((bitmap = super.poll()) == null && mBlocking) {
70                if (DEBUG) {
71                    LogUtils.d(TAG, "AltBitmapCache: %s waiting", Thread.currentThread().getName());
72                }
73                Trace.beginSection("sleep");
74                try {
75                    // block
76                    mLock.wait();
77                    if (DEBUG) {
78                        LogUtils.d(TAG, "AltBitmapCache: %s notified",
79                                Thread.currentThread().getName());
80                    }
81                } catch (InterruptedException e) {
82                }
83                Trace.endSection();
84            }
85        }
86        return bitmap;
87    }
88
89    @Override
90    public void offer(final ReusableBitmap value) {
91        synchronized (mLock) {
92            super.offer(value);
93            if (DEBUG) LogUtils.d(TAG, "AltBitmapCache: offer +1");
94            // new resource gained. Notify one thread.
95            mLock.notify();
96        }
97    }
98}
99