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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.skyframe;
import com.google.devtools.build.lib.bugreport.BugReport;
import com.google.devtools.build.lib.concurrent.PooledInterner;
import com.google.devtools.build.lib.concurrent.ThreadSafety;
import com.google.devtools.build.lib.util.TestType;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import javax.annotation.Nullable;
/**
* A {@link SkyKey} is effectively a pair (type, name) that identifies a Skyframe value.
*
* <p>SkyKey implementations are heavily used as map keys. Thus, they should have fast {@link
* #hashCode} implementations (cached if necessary). The same SkyKey may be created multiple times
* by different {@code SkyFunction}s requesting it, and so it should have effective interning. There
* will likely be more SkyKeys on the JVM heap than any other non-native type, so be mindful of
* memory usage (in particular object wrapper size and memory alignment)! Typically the
* implementation should have a fixed {@link #functionName} implementation and return itself as the
* {@link #argument} in order to reduce the cost of wrapper objects.
*/
public interface SkyKey extends Serializable {
SkyFunctionName functionName();
default Object argument() {
return this;
}
/**
* Returns {@code true} if this key produces a {@link SkyValue} that can be reused across builds.
*
* <p>Values may be unshareable because they are just not serializable, or because they contain
* data that cannot safely be reused as-is by another invocation, such as stamping information or
* "flaky" values like test statuses.
*
* <p>Unshareable data should not be serialized, since it will never be reused. Attempts to fetch
* a key's serialized data will call this method and only perform the fetch if it returns {@code
* true}.
*
* <p>The result of this method only applies to non-error values. In case of an error, {@link
* ErrorInfo#isTransitivelyTransient()} can be used to determine shareability.
*/
default boolean valueIsShareable() {
return true;
}
/**
* Returns {@code true} if this key's {@link SkyFunction} would like Skyframe to schedule its
* reevaluation when any of its previously requested unfinished deps completes. Otherwise,
* Skyframe will schedule reevaluation only when all previously requested unfinished deps
* complete.
*/
default boolean supportsPartialReevaluation() {
return false;
}
@Nullable
default SkyKeyInterner<?> getSkyKeyInterner() {
return null;
}
static <T extends SkyKey> SkyKeyInterner<T> newInterner() {
return new SkyKeyInterner<>();
}
/** {@link PooledInterner} for {@link SkyKey}s. */
final class SkyKeyInterner<T extends SkyKey> extends PooledInterner<T> {
@Nullable static Pool<? extends SkyKey> globalPool = null;
/**
* Sets the {@link Pool} to be used for interning.
*
* <p>The pool is strongly retained until it is cleared, which can be accomplished by passing
* {@code null} to this method.
*/
@ThreadSafety.ThreadCompatible
static void setGlobalPool(@Nullable Pool<SkyKey> pool) {
// No synchronization is needed. Setting global pool is guaranteed to happen sequentially
// since only one build can happen at the same time.
if (pool != null
&& globalPool != null
&& (!TestType.isInTest() || TestType.getTestType() == TestType.SHELL_INTEGRATION)) {
BugReport.sendNonFatalBugReport(
new IllegalStateException("Global SkyKey pool not cleared before setting another"));
}
globalPool = pool;
}
@Override
@SuppressWarnings("unchecked")
protected Pool<T> getPool() {
return (Pool<T>) globalPool;
}
/**
* Call {@link #weakInternUnchecked(SkyKey)} on {@link SkyKeyInterner} returned by {@code
* key.getSkyKeyInterner}. This method is created to remove casts and
* {@code @SuppressWarnings("unchecked")} in callers and put them in one place.
*/
@CanIgnoreReturnValue
@SuppressWarnings("unchecked")
T weakInternUnchecked(SkyKey sample) {
return weakIntern((T) sample);
}
}
}