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// Copyright 2017 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.android.junctions;
import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.windows.jni.WindowsFileOperations;
import java.io.IOException;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;
import javax.annotation.Nullable;
/**
* Junction creator implementation for Windows.
*
* <p>Creates a junction (or uses a cached one) for a path. If the path is a directory, the junction
* points to it, and the returned path is the junction's path. If the path is a file, the junction
* points to its parent, and the returned path is the file's path through the junction.
*
* <p>The `close` method deletes all junctions that this object created, along with the `dir`
* directory where the junctions are created. The purpose of this is to avoid other methods (such as
* ScopedTemporaryDirectory.close) to traverse these junctions believing they are regular
* directories and deleting files in them that are actually outside of the directory tree.
*/
public final class WindowsJunctionCreator implements JunctionCreator {
private final Path dir;
private Map<Path, Path> paths; // allocated lazily, but semantically final
private int junctionIndex = 0;
public WindowsJunctionCreator(Path dir) {
this.dir = Preconditions.checkNotNull(dir);
}
@Nullable
public Path create(@Nullable Path path) throws IOException {
if (path == null) {
return null;
}
if (paths == null) {
paths = new HashMap<>();
}
path = path.toAbsolutePath();
if (path.toFile().isDirectory()) {
Path link = paths.get(path);
if (link == null) {
link = dir.resolve(Integer.toString(junctionIndex++));
WindowsFileOperations.createJunction(link.toString(), path.toString());
paths.put(path, link);
}
return link;
}
Path parent = path.getParent();
return (parent == null) ? path : create(parent).resolve(path.getFileName());
}
@Override
public void close() throws IOException {
// Delete all junctions, otherwise the temp directory deleter would follow them and delete files
// from directories they point to.
if (paths != null) {
for (Path link : paths.values()) {
link.toFile().delete();
}
}
dir.toFile().delete();
}
}
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