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// Copyright 2015 The Cobalt 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.
#ifndef COBALT_STORAGE_STORE_UPGRADE_VIRTUAL_FILE_SYSTEM_H_
#define COBALT_STORAGE_STORE_UPGRADE_VIRTUAL_FILE_SYSTEM_H_
#include <map>
#include <string>
#include <vector>
#include "base/basictypes.h"
#include "base/synchronization/lock.h"
#include "base/threading/thread_checker.h"
namespace cobalt {
namespace storage {
namespace store_upgrade {
class VirtualFile;
// Implements a simple virtual filesystem, primarily intended to
// be used for providing an in-memory filesystem that SQLite can write to,
// and allowing that filesystem to be saved out into a single memory buffer.
// Contains a mapping from paths to their corresponding memory blocks.
// VirtualFileSystem must be serialized, deserialized, and destroyed on the
// same thread it was created on.
// Open/Delete are thread-safe so that SQL can run on any thread.
class VirtualFileSystem {
public:
struct SerializedHeader {
int32 version;
int32 file_size;
int32 file_count;
};
// Returns the version of the VirtualFileSystem header in buffer.
// -1 if buffer is invalid.
static int GetHeaderVersion(const SerializedHeader& header);
static int GetCurrentVersion();
VirtualFileSystem();
~VirtualFileSystem();
// Serializes the file system out to a single contiguous buffer.
// A dry run only calculates the number of bytes needed.
// Returns the number of bytes written.
int Serialize(uint8* buffer, bool dry_run);
// Deserializes a file system from a memory buffer.
// Returns false on failure.
bool Deserialize(const uint8* buffer, int buffer_size);
// Simple file open. Will create a file if it does not exist, and files are
// always readable and writable.
VirtualFile* Open(const std::string& filename);
std::vector<std::string> ListFiles();
void Delete(const std::string& filename);
private:
void ClearFileTable();
void SQLRegister();
void SQLUnregister();
typedef std::map<std::string, VirtualFile*> FileTable;
FileTable table_;
// Certain operations (serialize, deserialize) must run on the same thread.
THREAD_CHECKER(thread_checker_);
// Lock to protect the file table. We want to support SQL queries on any
// thread.
base::Lock file_table_lock_;
};
} // namespace store_upgrade
} // namespace storage
} // namespace cobalt
#endif // COBALT_STORAGE_STORE_UPGRADE_VIRTUAL_FILE_SYSTEM_H_