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/*
* Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.sufficientlysecure.keychain.util;
import android.os.Parcel;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
/**
* If Parcelables are above 1 MB, Android OS fails to send them via the Binder IPC:
* JavaBinder E !!! FAILED BINDER TRANSACTION !!!
* To overcome this issue this class allows to cache Parcelables, mapped by unique UUIDs,
* which are written to the parcel instead of the whole Parcelable.
*/
public class ParcelableCache<E> {
private static final UUID NULL_UUID = new UUID(0, 0);
/**
* A HashMap of UUID:Object
* This is used such that when we become parceled, we are
* well below the 1 MB boundary that is specified.
*/
private ConcurrentHashMap<UUID, E> objectCache = new ConcurrentHashMap<>();
/**
* Dehydrate a Parcelable (such that it is available after deparcelization)
* Returns the NULL uuid (0) if you hand it null.
*
* @param parcelable A Parcelable to dehydrate
* @return a UUID, the ticket for your dehydrated Parcelable
*/
private UUID dehydrateParcelable(E parcelable) {
if (parcelable == null) {
return NULL_UUID;
} else {
UUID uuid = UUID.randomUUID();
objectCache.put(uuid, parcelable);
return uuid;
}
}
/**
* Rehydrate a Parcelable after going through parcelization,
* invalidating its place in the dehydration pool.
* This is used such that when parcelized, the Parcelable is no larger than 1 MB.
*
* @param uuid A UUID ticket that identifies the log in question.
* @return An OperationLog.
*/
private E rehydrateParcelable(UUID uuid) {
// UUID.equals isn't well documented; we use compareTo instead.
if (NULL_UUID.compareTo(uuid) == 0) {
return null;
} else {
E parcelable = objectCache.get(uuid);
objectCache.remove(uuid);
return parcelable;
}
}
public E readFromParcelAndGetFromCache(Parcel source) {
long mostSig = source.readLong();
long leastSig = source.readLong();
UUID mTicket = new UUID(mostSig, leastSig);
// fetch the dehydrated parcelable out of storage (this removes it from the dehydration pool)
return rehydrateParcelable(mTicket);
}
public void cacheAndWriteToParcel(E parcelable, Parcel dest) {
// Get a ticket for our parcelable.
UUID mTicket = dehydrateParcelable(parcelable);
// And write out the UUID most and least significant bits.
dest.writeLong(mTicket.getMostSignificantBits());
dest.writeLong(mTicket.getLeastSignificantBits());
}
}
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