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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.skyframe;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.lib.vfs.FileStatus;
import java.io.IOException;
import java.io.Serializable;
import java.util.Objects;
/**
* In case we can't get a fast digest from the filesystem, we store this metadata as a proxy to the
* file contents. Currently it is a pair of a relevant timestamp and a "node id". On Linux the
* former is the ctime and the latter is the inode number. We might want to add the device number in
* the future.
*
* <p>For a Linux example of why mtime alone is insufficient, note that 'mv' preserves timestamps.
* So if files 'a' and 'b' initially have the same timestamp, then we would think 'b' is unchanged
* after the user executes `mv a b` between two builds.
*/
@AutoCodec
public final class FileContentsProxy implements Serializable {
private final long ctime;
private final long nodeId;
/**
* Visible for serialization / deserialization. Do not use this method, but call {@link #create}
* instead.
*/
public FileContentsProxy(long ctime, long nodeId) {
this.ctime = ctime;
this.nodeId = nodeId;
}
public static FileContentsProxy create(FileStatus stat) throws IOException {
// Note: there are file systems that return mtime for this call instead of ctime, such as the
// WindowsFileSystem.
return new FileContentsProxy(stat.getLastChangeTime(), stat.getNodeId());
}
/** Visible for serialization / deserialization. Do not use this method; use {@link #equals}. */
public long getCTime() {
return ctime;
}
/** Visible for serialization / deserialization. Do not use this method; use {@link #equals}. */
public long getNodeId() {
return nodeId;
}
@Override
public boolean equals(Object other) {
if (other == this) {
return true;
}
if (!(other instanceof FileContentsProxy)) {
return false;
}
FileContentsProxy that = (FileContentsProxy) other;
return ctime == that.ctime && nodeId == that.nodeId;
}
@Override
public int hashCode() {
return Objects.hash(ctime, nodeId);
}
@Override
public String toString() {
return prettyPrint();
}
public String prettyPrint() {
return String.format("ctime of %d and nodeId of %d", ctime, nodeId);
}
}
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