/*
* Copyright (C) 2011 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 android.content.pm;
import android.os.Binder;
import android.os.IBinder;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.RemoteException;
import android.util.Log;
import java.util.ArrayList;
import java.util.List;
/**
* Transfer a large list of Parcelable objects across an IPC. Splits into
* multiple transactions if needed.
*
* Caveat: for efficiency and security, all elements must be the same concrete type.
* In order to avoid writing the class name of each object, we must ensure that
* each object is the same type, or else unparceling then reparceling the data may yield
* a different result if the class name encoded in the Parcelable is a Base type.
* See b/17671747.
*
* @hide
*/
public class ParceledListSlice<T extends Parcelable> implements Parcelable {
private static String TAG = "ParceledListSlice";
private static boolean DEBUG = false;
/*
* TODO get this number from somewhere else. For now set it to a quarter of
* the 1MB limit.
*/
private static final int MAX_IPC_SIZE = 256 * 1024;
private static final int MAX_FIRST_IPC_SIZE = MAX_IPC_SIZE / 2;
private final List<T> mList;
public ParceledListSlice(List<T> list) {
mList = list;
}
private ParceledListSlice(Parcel p, ClassLoader loader) {
final int N = p.readInt();
mList = new ArrayList<T>(N);
if (DEBUG) Log.d(TAG, "Retrieving " + N + " items");
if (N <= 0) {
return;
}
Parcelable.Creator<T> creator = p.readParcelableCreator(loader);
Class<?> listElementClass = null;
int i = 0;
while (i < N) {
if (p.readInt() == 0) {
break;
}
final T parcelable = p.readCreator(creator, loader);
if (listElementClass == null) {
listElementClass = parcelable.getClass();
} else {
verifySameType(listElementClass, parcelable.getClass());
}
mList.add(parcelable);
if (DEBUG) Log.d(TAG, "Read inline #" + i + ": " + mList.get(mList.size()-1));
i++;
}
if (i >= N) {
return;
}
final IBinder retriever = p.readStrongBinder();
while (i < N) {
if (DEBUG) Log.d(TAG, "Reading more @" + i + " of " + N + ": retriever=" + retriever);
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInt(i);
try {
retriever.transact(IBinder.FIRST_CALL_TRANSACTION, data, reply, 0);
} catch (RemoteException e) {
Log.w(TAG, "Failure retrieving array; only received " + i + " of " + N, e);
return;
}
while (i < N && reply.readInt() != 0) {
final T parcelable = reply.readCreator(creator, loader);
verifySameType(listElementClass, parcelable.getClass());
mList.add(parcelable);
if (DEBUG) Log.d(TAG, "Read extra #" + i + ": " + mList.get(mList.size()-1));
i++;
}
reply.recycle();
data.recycle();
}
}
private static void verifySameType(final Class<?> expected, final Class<?> actual) {
if (!actual.equals(expected)) {
throw new IllegalArgumentException("Can't unparcel type "
+ actual.getName() + " in list of type "
+ expected.getName());
}
}
public List<T> getList() {
return mList;
}
@Override
public int describeContents() {
int contents = 0;
for (int i=0; i<mList.size(); i++) {
contents |= mList.get(i).describeContents();
}
return contents;
}
/**
* Write this to another Parcel. Note that this discards the internal Parcel
* and should not be used anymore. This is so we can pass this to a Binder
* where we won't have a chance to call recycle on this.
*/
@Override
public void writeToParcel(Parcel dest, int flags) {
final int N = mList.size();
final int callFlags = flags;
dest.writeInt(N);
if (DEBUG) Log.d(TAG, "Writing " + N + " items");
if (N > 0) {
final Class<?> listElementClass = mList.get(0).getClass();
dest.writeParcelableCreator(mList.get(0));
int i = 0;
while (i < N && dest.dataSize() < MAX_FIRST_IPC_SIZE) {
dest.writeInt(1);
final T parcelable = mList.get(i);
verifySameType(listElementClass, parcelable.getClass());
parcelable.writeToParcel(dest, callFlags);
if (DEBUG) Log.d(TAG, "Wrote inline #" + i + ": " + mList.get(i));
i++;
}
if (i < N) {
dest.writeInt(0);
Binder retriever = new Binder() {
@Override
protected boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
if (code != FIRST_CALL_TRANSACTION) {
return super.onTransact(code, data, reply, flags);
}
int i = data.readInt();
if (DEBUG) Log.d(TAG, "Writing more @" + i + " of " + N);
while (i < N && reply.dataSize() < MAX_IPC_SIZE) {
reply.writeInt(1);
final T parcelable = mList.get(i);
verifySameType(listElementClass, parcelable.getClass());
parcelable.writeToParcel(reply, callFlags);
if (DEBUG) Log.d(TAG, "Wrote extra #" + i + ": " + mList.get(i));
i++;
}
if (i < N) {
if (DEBUG) Log.d(TAG, "Breaking @" + i + " of " + N);
reply.writeInt(0);
}
return true;
}
};
if (DEBUG) Log.d(TAG, "Breaking @" + i + " of " + N + ": retriever=" + retriever);
dest.writeStrongBinder(retriever);
}
}
}
@SuppressWarnings("unchecked")
public static final Parcelable.ClassLoaderCreator<ParceledListSlice> CREATOR =
new Parcelable.ClassLoaderCreator<ParceledListSlice>() {
public ParceledListSlice createFromParcel(Parcel in) {
return new ParceledListSlice(in, null);
}
@Override
public ParceledListSlice createFromParcel(Parcel in, ClassLoader loader) {
return new ParceledListSlice(in, loader);
}
public ParceledListSlice[] newArray(int size) {
return new ParceledListSlice[size];
}
};
}
|
