com.google.devtools.build.lib.collect.nestedset.MemoizedUniquefierNestedSet.java Source code

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Here is the source code for com.google.devtools.build.lib.collect.nestedset.MemoizedUniquefierNestedSet.java

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// Copyright 2014 Google Inc. 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.collect.nestedset;

import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;

import java.util.List;
import java.util.Set;

/**
 * A NestedSet that keeps a memoized uniquifier so that it is faster to fill a set.
 *
 * <p>This class does not keep the memoized object itself so that we can take advantage of the
 * memory field alignment (Memory alignment does not put in the same structure the fields of a
 * class and its extensions).
 */
public abstract class MemoizedUniquefierNestedSet<E> extends NestedSet<E> {

    @Override
    public List<E> toList() {
        ImmutableList.Builder<E> builder = new ImmutableList.Builder<>();
        memoizedFill(builder);
        return builder.build();
    }

    @Override
    public Set<E> toSet() {
        ImmutableSet.Builder<E> builder = new ImmutableSet.Builder<>();
        memoizedFill(builder);
        return builder.build();
    }

    /**
     * It does not make sense to have a {@code MemoizedUniquefierNestedSet} if it is empty.
     */
    @Override
    public boolean isEmpty() {
        return false;
    }

    abstract Object getMemo();

    abstract void setMemo(Object object);

    /**
     * Fill a collection builder by using a memoized {@code Uniqueifier} for faster uniqueness check.
     */
    final void memoizedFill(ImmutableCollection.Builder<E> builder) {
        Uniqueifier memoed;
        synchronized (this) {
            Object memo = getMemo();
            if (memo == null) {
                RecordingUniqueifier uniqueifier = new RecordingUniqueifier();
                getOrder().<E>expander().expandInto(this, uniqueifier, builder);
                setMemo(uniqueifier.getMemo());
                return;
            } else {
                memoed = RecordingUniqueifier.createReplayUniqueifier(memo);
            }
        }
        getOrder().<E>expander().expandInto(this, memoed, builder);
    }
}