| // 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 java.io.Serializable; |
| |
| /** |
| * 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; |
| } |
| } |