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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 com.google.devtools.build.lib.events.ExtendedEventHandler;
import com.google.devtools.build.skyframe.QueryableGraph.Reason;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
/**
* Read-only graph that exposes the dependents, dependencies (reverse dependents), and value and
* exception (if any) of a given node.
*
* <p>Certain graph implementations can throw {@link InterruptedException} when trying to retrieve
* node entries. Such exceptions should not be caught locally -- they should be allowed to propagate
* up.
*/
@ThreadSafe
public interface WalkableGraph {
/**
* Returns the value of the given key, or {@code null} if it has no value due to an error during
* its computation or it is not done in the graph.
*
* <p>A node that is done in the graph must have either a non-null getValue, a non-null {@link
* #getException}, or a true {@link #isCycle}.
*
* <p>These three methods should all be reading the same {@link
* NodeEntry#getValueMaybeWithMetadata} value internally, so once that value is indirectly
* retrieved via one of these methods, the others can read it for free. This is relevant for graph
* implementations that may throw an {@link InterruptedException} on retrieving entries and value.
*/
@Nullable
SkyValue getValue(SkyKey key) throws InterruptedException;
/**
* Returns a map giving the values of the given keys for done keys that were successfully
* computed. Or in other words, it filters out non-existent nodes, pending nodes and nodes that
* produced an exception.
*/
Map<SkyKey, SkyValue> getSuccessfulValues(Iterable<SkyKey> keys) throws InterruptedException;
/**
* Returns a map giving exceptions associated to the given keys for done keys. Keys not present in
* the graph or whose nodes are not done will be present in the returned map, with null value. In
* other words, if {@code key} is in {@param keys}, then the returned map will contain an entry
* for {@code key} if and only if the node for {@code key} did <i>not</i> evaluate successfully
* without error.
*/
Map<SkyKey, Exception> getMissingAndExceptions(Iterable<SkyKey> keys) throws InterruptedException;
/**
* Returns the exception thrown when computing the node with the given key, if any. If the node
* was computed successfully, depends on a cycle without any other error, or is not done in the
* graph, returns null.
*/
@Nullable
Exception getException(SkyKey key) throws InterruptedException;
/**
* Returns true if the node with the given {@code key} depends on a cycle. Returns false if the
* node does not depend on a cycle, or is not done in the graph.
*/
boolean isCycle(SkyKey key) throws InterruptedException;
/**
* Returns a map giving the direct dependencies of the nodes with the given keys. A node for each
* given key must be done in the graph if it exists.
*/
Map<SkyKey, Iterable<SkyKey>> getDirectDeps(Iterable<SkyKey> keys) throws InterruptedException;
/**
* Returns a map giving the reverse dependencies of the nodes with the given keys. A node for each
* given key must be done in the graph if it exists.
*/
Map<SkyKey, Iterable<SkyKey>> getReverseDeps(Iterable<SkyKey> keys) throws InterruptedException;
/**
* Examines all the given keys. Returns an iterable of keys whose corresponding nodes are
* currently available to be fetched.
*
* <p>Note: An unavailable node does not mean it is not in the graph. It only means it's not ready
* to be fetched immediately.
*/
Iterable<SkyKey> getCurrentlyAvailableNodes(Iterable<SkyKey> keys, Reason reason);
/** Provides a WalkableGraph on demand after preparing it. */
interface WalkableGraphFactory {
EvaluationResult<SkyValue> prepareAndGet(
Set<SkyKey> roots, int numThreads, ExtendedEventHandler eventHandler)
throws InterruptedException;
/** Returns the {@link SkyKey} that defines this universe. */
SkyKey getUniverseKey(Collection<String> roots, String offset);
}
}
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