CollectionFuture.java
/*
* Copyright 2019 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 androidx.camera.core.impl.utils.futures;
import androidx.annotation.Nullable;
import androidx.camera.core.impl.utils.Optional;
import androidx.concurrent.ListenableFuture;
import androidx.core.util.Preconditions;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
/**
* Aggregate future that collects (stores) results of each future.
*
* <p>Copied and adapted from Guava.
*/
abstract class CollectionFuture<V, C> extends AggregateFuture<V, C> {
abstract class CollectionFutureRunningState extends RunningState {
private List<Optional<V>> mValues;
CollectionFutureRunningState(
Collection<? extends ListenableFuture<? extends V>> futures,
boolean allMustSucceed) {
super(futures, allMustSucceed, true);
this.mValues =
futures.isEmpty()
? new ArrayList<Optional<V>>()
: new ArrayList<Optional<V>>(futures.size());
// Populate the results list with null initially.
for (int i = 0; i < futures.size(); ++i) {
mValues.add(null);
}
}
@Override
final void collectOneValue(boolean allMustSucceed, int index, @Nullable V returnValue) {
List<Optional<V>> localValues = mValues;
if (localValues != null) {
localValues.set(index, Optional.fromNullable(returnValue));
} else {
// Some other future failed or has been cancelled, causing this one to also be
// cancelled or have an exception set. This should only happen if allMustSucceed
// is true or if the output itself has been cancelled.
Preconditions.checkState(
allMustSucceed || isCancelled(),
"Future was done before all dependencies completed");
}
}
@Override
final void handleAllCompleted() {
List<Optional<V>> localValues = mValues;
if (localValues != null) {
set(combine(localValues));
} else {
Preconditions.checkState(isDone());
}
}
@Override
void releaseResourcesAfterFailure() {
super.releaseResourcesAfterFailure();
this.mValues = null;
}
abstract C combine(List<Optional<V>> values);
}
/** Used for {@link Futures#successfulAsList}. */
static final class ListFuture<V> extends CollectionFuture<V, List<V>> {
ListFuture(
Collection<? extends ListenableFuture<? extends V>> futures,
boolean allMustSucceed) {
init(new ListFutureRunningState(futures, allMustSucceed));
}
private final class ListFutureRunningState extends CollectionFutureRunningState {
ListFutureRunningState(
Collection<? extends ListenableFuture<? extends V>> futures,
boolean allMustSucceed) {
super(futures, allMustSucceed);
}
@Override
public List<V> combine(List<Optional<V>> values) {
List<V> result = new ArrayList<>(values.size());
for (Optional<V> element : values) {
result.add(element != null ? element.orNull() : null);
}
return result;
}
}
}
}