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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.skyframe;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import javax.annotation.Nullable;
/**
* A node in the graph without the means to access its value. All operations on this class are
* thread-safe.
*
* <p>This interface is public only for the benefit of alternative graph implementations outside of
* the package.
*/
public interface ThinNodeEntry {
/** Returns whether the entry has been built and is finished evaluating. */
@ThreadSafe
boolean isDone();
/**
* Returns an immutable iterable of the direct deps of this node. This method may only be called
* after the evaluation of this node is complete.
*
* <p>This method is not very efficient, but is only be called in limited circumstances --
* when the node is about to be deleted, or when the node is expected to have no direct deps (in
* which case the overhead is not so bad). It should not be called repeatedly for the same node,
* since each call takes time proportional to the number of direct deps of the node.
*/
@ThreadSafe
Iterable<SkyKey> getDirectDeps();
/**
* Removes a reverse dependency.
*/
@ThreadSafe
void removeReverseDep(SkyKey reverseDep);
/**
* Removes a reverse dependency.
*
* <p>May only be called if this entry is not done (i.e. {@link #isDone} is false) and
* {@param reverseDep} is present in {@link #getReverseDeps}
*/
@ThreadSafe
void removeInProgressReverseDep(SkyKey reverseDep);
/**
* Returns a copy of the set of reverse dependencies. Note that this introduces a potential
* check-then-act race; {@link #removeReverseDep} may fail for a key that is returned here.
*/
@ThreadSafe
Iterable<SkyKey> getReverseDeps();
/**
* Returns true if the entry is marked dirty, meaning that at least one of its transitive
* dependencies is marked changed.
*/
@ThreadSafe
boolean isDirty();
/**
* Returns true if the entry is marked changed, meaning that it must be re-evaluated even if its
* dependencies' values have not changed.
*/
@ThreadSafe
boolean isChanged();
/**
* Marks this node dirty, or changed if {@code isChanged} is true. The node is put in the
* just-created state. It will be re-evaluated if necessary during the evaluation phase,
* but if it has not changed, it will not force a re-evaluation of its parents.
*
* <p>{@code markDirty(b)} must not be called on an undone node if {@code isChanged() == b}.
* It is the caller's responsibility to ensure that this does not happen. Calling
* {@code markDirty(false)} when {@code isChanged() == true} has no effect. The idea here is that
* the caller will only ever want to call {@code markDirty()} a second time if a transition from a
* dirty-unchanged state to a dirty-changed state is required.
*
* @return A {@link ThinNodeEntry.MarkedDirtyResult} if the node was previously clean, and
* {@code null} if it was already dirty. If it was already dirty, the caller should abort its
* handling of this node, since another thread is already dealing with it.
*/
@Nullable
@ThreadSafe
MarkedDirtyResult markDirty(boolean isChanged);
/**
* Returned by {@link #markDirty} if that call changed the node from clean to dirty. Contains an
* iterable of the node's reverse deps for efficiency, because the single use case for {@link
* #markDirty} is during invalidation, and if such an invalidation call wins, the invalidator
* must immediately afterwards schedule the invalidation of the node's reverse deps.
*/
class MarkedDirtyResult {
private final Iterable<SkyKey> reverseDepsUnsafe;
public MarkedDirtyResult(Iterable<SkyKey> reverseDepsUnsafe) {
this.reverseDepsUnsafe = reverseDepsUnsafe;
}
public Iterable<SkyKey> getReverseDepsUnsafe() {
return reverseDepsUnsafe;
}
}
}
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