// 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();
Object argument();
}