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// Copyright 2019 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.runtime;
import com.google.common.util.concurrent.Uninterruptibles;
import com.google.devtools.build.lib.buildeventstream.ArtifactGroupNamer;
import com.google.devtools.build.lib.buildeventstream.BuildEventStreamProtos.BuildEventId.NamedSetOfFilesId;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CountDownLatch;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;
/** Conversion of paths to URIs. */
@ThreadSafe
public class CountingArtifactGroupNamer implements ArtifactGroupNamer {
private final ConcurrentMap<NestedSet.Node, LatchedGroupName> nodeNames =
new ConcurrentHashMap<>();
@Override
@Nullable
public NamedSetOfFilesId apply(NestedSet.Node id) {
LatchedGroupName name = nodeNames.get(id);
if (name == null) {
return null;
}
return NamedSetOfFilesId.newBuilder().setId(name.getName()).build();
}
/**
* If the {@link NestedSet} has no name already, return a new name for it. Return null otherwise.
*/
@Nullable
public LatchedGroupName maybeName(NestedSet<?> set) {
NestedSet.Node id = set.toNode();
LatchedGroupName existingGroupName;
LatchedGroupName newGroupName;
// synchronized necessary only to ensure node names are chosen uniquely and compactly.
// TODO(adgar): consider dropping compactness and unconditionally increment an AtomicLong to
// pick unique node names.
synchronized (this) {
newGroupName = new LatchedGroupName(nodeNames.size());
existingGroupName = nodeNames.putIfAbsent(id, newGroupName);
}
if (existingGroupName != null) {
existingGroupName.waitUntilWritten();
return null;
}
return newGroupName;
}
/**
* A name for a {@code NestedSet<?>} that the constructor must {@link #close()} after the set is
* written, allowing all other consumers to {@link #waitUntilWritten()}.
*/
public static class LatchedGroupName implements AutoCloseable {
private final CountDownLatch latch;
private final int name;
public LatchedGroupName(int name) {
this.latch = new CountDownLatch(1);
this.name = name;
}
@Override
public void close() {
latch.countDown();
}
String getName() {
return Integer.toString(name);
}
private void waitUntilWritten() {
Uninterruptibles.awaitUninterruptibly(latch);
}
}
}