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/*
* Copyright 2022 Google LLC
*
* 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.android.libraries.mobiledatadownload.file.openers;
import android.net.Uri;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.system.Os;
import android.system.OsConstants;
import android.system.StructStat;
import com.google.android.libraries.mobiledatadownload.file.OpenContext;
import com.google.android.libraries.mobiledatadownload.file.Opener;
import com.google.android.libraries.mobiledatadownload.file.SynchronousFileStorage;
import com.google.android.libraries.mobiledatadownload.file.common.internal.Exceptions;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
* Deletes the file or directory at the given URI recursively. This behaves similarly to {@link
* SynchronousFileStorage#deleteRecursively} except as described in the following paragraph.
*
* <p>If an IO exception occurs attempting to read, open, or delete any file under the given
* directory, this method skips that file and continues. All such exceptions are collected and,
* after attempting to delete all files, an {@code IOException} is thrown containing those
* exceptions as {@linkplain Throwable#getSuppressed() suppressed exceptions}.
*
* <p>WARNING: this opener suffers from the following caveats and should be used with caution:
*
* <ul>
* <li>Directory tree traversal is not an atomic operation
* </ul>
*
* <p>Usage: <code>
* storage.open(uri, RecursiveDeleteOpener.create());
* </code>
*/
public final class RecursiveDeleteOpener implements Opener<Void> {
private boolean noFollowLinks;
public static RecursiveDeleteOpener create() {
return new RecursiveDeleteOpener();
}
@CanIgnoreReturnValue
public RecursiveDeleteOpener withNoFollowLinks() {
this.noFollowLinks = true;
return this;
}
@Override
public Void open(OpenContext openContext) throws IOException {
List<IOException> exceptions = new ArrayList<>();
deleteRecursively(openContext.storage(), openContext.encodedUri(), exceptions);
if (!exceptions.isEmpty()) {
throw Exceptions.combinedIOException("Failed to delete one or more files", exceptions);
}
return null; // for Void return type
}
private void deleteRecursively(
SynchronousFileStorage storage, Uri uri, List<IOException> exceptions) {
ReadFileOpener readFileOpener = ReadFileOpener.create().withShortCircuit();
try {
if (storage.isDirectory(uri)) {
if (!noFollowLinks || !isSymlink(uri, storage, readFileOpener)) {
for (Uri child : storage.children(uri)) {
deleteRecursively(storage, child, exceptions);
}
}
storage.deleteDirectory(uri);
} else {
storage.deleteFile(uri);
}
} catch (IOException e) {
exceptions.add(e);
}
}
private static boolean isSymlink(
Uri uri, SynchronousFileStorage storage, ReadFileOpener readFileOpener) {
if (VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) {
try {
File file = storage.open(uri, readFileOpener);
if (file == null || !file.exists()) {
return false;
}
StructStat stat = Os.lstat(file.getAbsolutePath());
return (stat.st_mode & OsConstants.S_IFLNK) != 0;
} catch (Exception e) {
// NOTE: this should be ErrnoException, but we're forced to catch Exception to avoid
// breaking lower sdk levels (exceptions aren't stripped from dead code blocks).
return false;
}
}
return false;
}
}
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