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// Copyright 2015 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.query2.engine;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.MapMaker;
import com.google.devtools.build.lib.collect.CompactHashSet;
import java.util.Collections;
import java.util.Set;
/** Several query utilities to make easier to work with query callbacks and uniquifiers. */
public final class QueryUtil {
private QueryUtil() { }
/** A {@link Callback} that can aggregate all the partial results into one set. */
public interface AggregateAllCallback<T> extends Callback<T> {
Set<T> getResult();
}
/** A {@link OutputFormatterCallback} that can aggregate all the partial results into one set. */
public abstract static class AggregateAllOutputFormatterCallback<T>
extends OutputFormatterCallback<T> implements AggregateAllCallback<T> {
}
private static class AggregateAllOutputFormatterCallbackImpl<T>
extends AggregateAllOutputFormatterCallback<T> {
private final Set<T> result = CompactHashSet.create();
@Override
public final void processOutput(Iterable<T> partialResult) {
Iterables.addAll(result, partialResult);
}
@Override
public Set<T> getResult() {
return result;
}
}
/**
* Returns a fresh {@link AggregateAllOutputFormatterCallback} that can aggregate all the partial
* results into one set.
*
* <p>Intended to be used by top-level evaluation of {@link QueryExpression}s; contrast with
* {@link #newAggregateAllCallback}.
*/
public static <T> AggregateAllOutputFormatterCallback<T>
newAggregateAllOutputFormatterCallback() {
return new AggregateAllOutputFormatterCallbackImpl<>();
}
/**
* Returns a fresh {@link AggregateAllCallback}.
*
* <p>Intended to be used by {@link QueryExpression} implementations; contrast with
* {@link #newAggregateAllOutputFormatterCallback}.
*/
public static <T> AggregateAllCallback<T> newAggregateAllCallback() {
return new AggregateAllOutputFormatterCallbackImpl<>();
}
/**
* Fully evaluate a {@code QueryExpression} and return a set with all the results.
*
* <p>Should only be used by QueryExpressions when it is the only way of achieving correctness.
*/
public static <T> Set<T> evalAll(
QueryEnvironment<T> env, VariableContext<T> context, QueryExpression expr)
throws QueryException, InterruptedException {
AggregateAllCallback<T> callback = newAggregateAllCallback();
env.eval(expr, context, callback);
return callback.getResult();
}
/** A trivial {@link Uniquifier} base class. */
public abstract static class AbstractUniquifier<T, K>
extends AbstractUniquifierBase<T, K> {
private final CompactHashSet<K> alreadySeen = CompactHashSet.create();
@Override
public final boolean unique(T element) {
return alreadySeen.add(extractKey(element));
}
/**
* Extracts an unique key that can be used to dedupe the given {@code element}.
*
* <p>Depending on the choice of {@code K}, this enables potential memory optimizations.
*/
protected abstract K extractKey(T element);
}
/** A trivial {@link ThreadSafeUniquifier} base class. */
public abstract static class AbstractThreadSafeUniquifier<T, K>
extends AbstractUniquifierBase<T, K> implements ThreadSafeUniquifier<T> {
private final Set<K> alreadySeen;
protected AbstractThreadSafeUniquifier(int concurrencyLevel) {
this.alreadySeen = Collections.newSetFromMap(
new MapMaker().concurrencyLevel(concurrencyLevel).<K, Boolean>makeMap());
}
@Override
public final boolean unique(T element) {
return alreadySeen.add(extractKey(element));
}
/**
* Extracts an unique key that can be used to dedupe the given {@code element}.
*
* <p>Depending on the choice of {@code K}, this enables potential memory optimizations.
*/
protected abstract K extractKey(T element);
}
private abstract static class AbstractUniquifierBase<T, K> implements Uniquifier<T> {
@Override
public final ImmutableList<T> unique(Iterable<T> newElements) {
ImmutableList.Builder<T> result = ImmutableList.builder();
for (T element : newElements) {
if (unique(element)) {
result.add(element);
}
}
return result.build();
}
}
}
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