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/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.camera;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import java.io.FileDescriptor;
import java.util.Iterator;
import java.util.WeakHashMap;
/**
* This class provides several utilities to cancel bitmap decoding.
*
* The function decodeFileDescriptor() is used to decode a bitmap. During
* decoding if another thread wants to cancel it, it calls the function
* cancelThreadDecoding() specifying the Thread which is in decoding.
*
* cancelThreadDecoding() is sticky until allowThreadDecoding() is called.
*
* You can also cancel decoding for a set of threads using ThreadSet as
* the parameter for cancelThreadDecoding. To put a thread into a ThreadSet,
* use the add() method. A ThreadSet holds (weak) references to the threads,
* so you don't need to remove Thread from it if some thread dies.
*/
public class BitmapManager {
private static final String TAG = "BitmapManager";
private static enum State {CANCEL, ALLOW}
private static class ThreadStatus {
public State mState = State.ALLOW;
public BitmapFactory.Options mOptions;
@Override
public String toString() {
String s;
if (mState == State.CANCEL) {
s = "Cancel";
} else if (mState == State.ALLOW) {
s = "Allow";
} else {
s = "?";
}
s = "thread state = " + s + ", options = " + mOptions;
return s;
}
}
public static class ThreadSet implements Iterable<Thread> {
private final WeakHashMap<Thread, Object> mWeakCollection =
new WeakHashMap<Thread, Object>();
public void add(Thread t) {
mWeakCollection.put(t, null);
}
public void remove(Thread t) {
mWeakCollection.remove(t);
}
public Iterator<Thread> iterator() {
return mWeakCollection.keySet().iterator();
}
}
private final WeakHashMap<Thread, ThreadStatus> mThreadStatus =
new WeakHashMap<Thread, ThreadStatus>();
private static BitmapManager sManager = null;
private BitmapManager() {
}
/**
* Get thread status and create one if specified.
*/
private synchronized ThreadStatus getOrCreateThreadStatus(Thread t) {
ThreadStatus status = mThreadStatus.get(t);
if (status == null) {
status = new ThreadStatus();
mThreadStatus.put(t, status);
}
return status;
}
/**
* The following three methods are used to keep track of
* BitmapFaction.Options used for decoding and cancelling.
*/
private synchronized void setDecodingOptions(Thread t,
BitmapFactory.Options options) {
getOrCreateThreadStatus(t).mOptions = options;
}
synchronized void removeDecodingOptions(Thread t) {
ThreadStatus status = mThreadStatus.get(t);
status.mOptions = null;
}
/**
* The following two methods are used to allow/cancel a set of threads
* for bitmap decoding.
*/
public synchronized void allowThreadDecoding(ThreadSet threads) {
for (Thread t : threads) {
allowThreadDecoding(t);
}
}
public synchronized void cancelThreadDecoding(ThreadSet threads) {
for (Thread t : threads) {
cancelThreadDecoding(t);
}
}
/**
* The following three methods are used to keep track of which thread
* is being disabled for bitmap decoding.
*/
public synchronized boolean canThreadDecoding(Thread t) {
ThreadStatus status = mThreadStatus.get(t);
if (status == null) {
// allow decoding by default
return true;
}
boolean result = (status.mState != State.CANCEL);
return result;
}
public synchronized void allowThreadDecoding(Thread t) {
getOrCreateThreadStatus(t).mState = State.ALLOW;
}
public synchronized void cancelThreadDecoding(Thread t) {
ThreadStatus status = getOrCreateThreadStatus(t);
status.mState = State.CANCEL;
if (status.mOptions != null) {
status.mOptions.requestCancelDecode();
}
// Wake up threads in waiting list
notifyAll();
}
public static synchronized BitmapManager instance() {
if (sManager == null) {
sManager = new BitmapManager();
}
return sManager;
}
/**
* The real place to delegate bitmap decoding to BitmapFactory.
*/
public Bitmap decodeFileDescriptor(FileDescriptor fd,
BitmapFactory.Options options) {
if (options.mCancel) {
return null;
}
Thread thread = Thread.currentThread();
if (!canThreadDecoding(thread)) {
Log.d(TAG, "Thread " + thread + " is not allowed to decode.");
return null;
}
setDecodingOptions(thread, options);
Bitmap b = BitmapFactory.decodeFileDescriptor(fd, null, options);
removeDecodingOptions(thread);
return b;
}
}
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