platform_system_core/fastboot/storage.cpp

/*
 * Copyright (C) 2023 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 <android-base/file.h>
#include <android-base/logging.h>

#include <fstream>
#include <iterator>

#include "storage.h"
#include "util.h"

ConnectedDevicesStorage::ConnectedDevicesStorage() {
    home_fastboot_path_ = GetHomeDirPath() + kPathSeparator + ".fastboot";
    devices_path_ = home_fastboot_path_ + kPathSeparator + "devices";

    // We're using a separate file for locking because the Windows LockFileEx does not
    // permit opening a file stream for the locked file, even within the same process. So,
    // we have to use fd or handle API to manipulate the storage files, which makes it
    // nearly impossible to fully rewrite a file content without having to recreate it.
    // Unfortunately, this is not an option during holding a lock.
    devices_lock_path_ = home_fastboot_path_ + kPathSeparator + "devices.lock";
}

bool ConnectedDevicesStorage::Exists() const {
    return FileExists(devices_path_);
}

void ConnectedDevicesStorage::WriteDevices(const FileLock&, const std::set<std::string>& devices) {
    std::ofstream devices_stream(devices_path_);
    std::copy(devices.begin(), devices.end(),
              std::ostream_iterator<std::string>(devices_stream, "\n"));
}

std::set<std::string> ConnectedDevicesStorage::ReadDevices(const FileLock&) {
    std::ifstream devices_stream(devices_path_);
    std::istream_iterator<std::string> start(devices_stream), end;
    std::set<std::string> devices(start, end);
    return devices;
}

void ConnectedDevicesStorage::Clear(const FileLock&) {
    if (!android::base::RemoveFileIfExists(devices_path_)) {
        LOG(FATAL) << "Failed to clear connected device list: " << devices_path_;
    }
}

FileLock ConnectedDevicesStorage::Lock() const {
    if (!EnsureDirectoryExists(home_fastboot_path_)) {
        LOG(FATAL) << "Cannot create directory: " << home_fastboot_path_;
    }
    return FileLock(devices_lock_path_);
}