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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.lib.actions.cache;
import com.google.devtools.build.lib.actions.FileStateType;
import javax.annotation.Nullable;
/**
* An interface to represent the state of a file system object for the execution phase. This is not
* used by Skyframe for invalidation, it is primarily used by the action cache and the various
* {@link com.google.devtools.build.lib.exec.SpawnRunner} implementations.
*/
public interface Metadata {
/**
* Marker interface for singleton implementations of the Metadata interface. This is only needed
* for a correct implementation of {@code equals}.
*/
public interface Singleton {
}
/**
* The type of the underlying file system object. If it is a regular file, then it is
* guaranteed to have a digest. Otherwise it does not have a digest.
*/
FileStateType getType();
/**
* Returns a digest of the content of the underlying file system object; must always return a
* non-null value for instances of type {@link FileStateType#REGULAR_FILE}. Otherwise may return
* null.
*
* <p>All instances of this interface must either have a digest or return a last-modified time.
* Clients should prefer using the digest for content identification (e.g., for caching), and only
* fall back to the last-modified time if no digest is available.
*
* <p>The return value is owned by this object and must not be modified.
*/
@Nullable
byte[] getDigest();
/** Returns the file's size, or 0 if the underlying file system object is not a file. */
// TODO(ulfjack): Throw an exception if it's not a file.
long getSize();
/**
* Returns the last modified time; see the documentation of {@link #getDigest} for when this can
* and should be called.
*/
long getModifiedTime();
/**
* Index used to resolve remote files.
*
* <p>0 indicates that no such information is available which can mean that it's either a local
* file or empty.
*/
default int getLocationIndex() {
return 0;
}
}
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