com.google.devtools.build.lib.actions.ArtifactIdRegistry.java Source code

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Here is the source code for com.google.devtools.build.lib.actions.ArtifactIdRegistry.java

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// Copyright 2014 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.actions;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.MapMaker;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * A registry that keeps a map of artifacts to unique integer ids.
 */
class ArtifactIdRegistry implements ArtifactSerializer, ArtifactDeserializer {

    /**
     * A sequence of registered artifacts. The position in the list is the artifact's id.
     *
     * <p>Synchronized using {@link #artifactIdsLock}.
     */
    private final List<Artifact> serializedArtifactList = new ArrayList<>();

    /**
     * A map of artifacts to unique integer ids.
     *
     * <p>Writes to this map must be synchronized using {@link #artifactIdsLock}, in order to
     * maintain consistency with {@link #serializedArtifactList}.
     */
    private final ConcurrentMap<Artifact, Integer> serializedArtifactIds = new MapMaker().concurrencyLevel(1)
            .makeMap();

    /**
     * A lock for keeping {@code serializedArtifactList} and {@code serializedArtifactIds} in sync.
     */
    private ReadWriteLock artifactIdsLock = new ReentrantReadWriteLock();

    ArtifactIdRegistry() {
    }

    @Override
    public int getArtifactId(Artifact artifact) {
        Integer artifactId = serializedArtifactIds.get(artifact);
        if (artifactId == null) {
            artifactId = assignArtifactId(artifact);
        }
        return artifactId;
    }

    private Integer assignArtifactId(Artifact artifact) {
        artifactIdsLock.writeLock().lock();
        try {
            Integer artifactId = serializedArtifactIds.get(artifact);
            if (artifactId == null) {
                artifactId = serializedArtifactList.size();
                serializedArtifactList.add(artifact);
                serializedArtifactIds.put(artifact, artifactId);
            }
            return artifactId;
        } finally {
            artifactIdsLock.writeLock().unlock();
        }
    }

    @Override
    public Artifact lookupArtifactById(int artifactId) {
        artifactIdsLock.readLock().lock();
        try {
            return serializedArtifactList.get(artifactId);
        } finally {
            artifactIdsLock.readLock().unlock();
        }
    }

    @Override
    public ImmutableList<Artifact> lookupArtifactsByIds(Iterable<Integer> artifactIds) {
        int size = Iterables.size(artifactIds);
        Artifact[] result = new Artifact[size];

        int i = 0;

        artifactIdsLock.readLock().lock();
        try {
            for (int artifactId : artifactIds) {
                result[i] = serializedArtifactList.get(artifactId);
                i++;
            }
        } finally {
            artifactIdsLock.readLock().unlock();
        }

        return ImmutableList.copyOf(result);
    }
}