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/*
* Copyright (C) 2021 The Android Open Source Project
*
* 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.
*/
#include "restorable_file.h"
#include <string>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
namespace {
constexpr char kTmpFileSuffix[] = ".tmp";
constexpr char kBackupFileSuffix[] = ".backup";
std::string GetTmpFilePath(const std::string& path) {
return android::base::StringPrintf("%s%s", path.c_str(), kTmpFileSuffix);
}
std::string GetBackupFilePath(const std::string& path) {
return android::base::StringPrintf("%s%s", path.c_str(), kBackupFileSuffix);
}
void UnlinkPossiblyNonExistingFile(const std::string& path) {
if (unlink(path.c_str()) < 0) {
if (errno != ENOENT && errno != EROFS) { // EROFS reported even if it does not exist.
PLOG(ERROR) << "Cannot unlink: " << path;
}
}
}
// Check if file for the given path exists
bool FileExists(const std::string& path) {
struct stat st;
return ::stat(path.c_str(), &st) == 0;
}
} // namespace
namespace android {
namespace installd {
RestorableFile::RestorableFile() : RestorableFile(-1, "") {}
RestorableFile::RestorableFile(int value, const std::string& path) : unique_file_(value, path) {
// As cleanup is null, this does not make much difference but use unique_file_ only for closing
// tmp file.
unique_file_.DisableCleanup();
}
RestorableFile::~RestorableFile() {
reset();
}
void RestorableFile::reset() {
// need to copy before reset clears it.
std::string path(unique_file_.path());
unique_file_.reset();
if (!path.empty()) {
UnlinkPossiblyNonExistingFile(GetTmpFilePath(path));
}
}
bool RestorableFile::CreateBackupFile() {
if (path().empty() || !FileExists(path())) {
return true;
}
std::string backup = GetBackupFilePath(path());
UnlinkPossiblyNonExistingFile(backup);
if (rename(path().c_str(), backup.c_str()) < 0) {
PLOG(ERROR) << "Cannot rename " << path() << " to " << backup;
return false;
}
return true;
}
bool RestorableFile::CommitWorkFile() {
std::string path(unique_file_.path());
// Keep the path with Commit for debugging purpose.
unique_file_.reset(-1, path);
if (!path.empty()) {
if (rename(GetTmpFilePath(path).c_str(), path.c_str()) < 0) {
PLOG(ERROR) << "Cannot rename " << GetTmpFilePath(path) << " to " << path;
// Remove both files as renaming can fail due to the original file as well.
UnlinkPossiblyNonExistingFile(path);
UnlinkPossiblyNonExistingFile(GetTmpFilePath(path));
return false;
}
}
return true;
}
bool RestorableFile::RestoreBackupFile() {
std::string backup = GetBackupFilePath(path());
if (path().empty() || !FileExists(backup)) {
return true;
}
UnlinkPossiblyNonExistingFile(path());
if (rename(backup.c_str(), path().c_str()) < 0) {
PLOG(ERROR) << "Cannot rename " << backup << " to " << path();
return false;
}
return true;
}
void RestorableFile::RemoveBackupFile() {
UnlinkPossiblyNonExistingFile(GetBackupFilePath(path()));
}
const UniqueFile& RestorableFile::GetUniqueFile() const {
return unique_file_;
}
void RestorableFile::ResetAndRemoveAllFiles() {
std::string path(unique_file_.path());
reset();
RemoveAllFiles(path);
}
RestorableFile RestorableFile::CreateWritableFile(const std::string& path, int permissions) {
std::string tmp_file_path = GetTmpFilePath(path);
// If old tmp file exists, delete it.
UnlinkPossiblyNonExistingFile(tmp_file_path);
int fd = -1;
if (!path.empty()) {
fd = open(tmp_file_path.c_str(), O_RDWR | O_CREAT, permissions);
if (fd < 0) {
PLOG(ERROR) << "Cannot create file: " << tmp_file_path;
}
}
RestorableFile rf(fd, path);
return rf;
}
void RestorableFile::RemoveAllFiles(const std::string& path) {
UnlinkPossiblyNonExistingFile(GetTmpFilePath(path));
UnlinkPossiblyNonExistingFile(GetBackupFilePath(path));
UnlinkPossiblyNonExistingFile(path);
}
} // namespace installd
} // namespace android
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