sandboxed_vfs_file.h | Explore in Territory

// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SQL_SANDBOXED_VFS_FILE_H_
#define SQL_SANDBOXED_VFS_FILE_H_

#include "base/dcheck_is_on.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ptr_exclusion.h"
#include "third_party/sqlite/sqlite3.h"

namespace sql {

// The file types associated with a SQLite database.
enum class SandboxedVfsFileType { … };

class SandboxedVfs;

// SQLite VFS file implementation that works in a sandboxed process.
//
// An instance is created when SQLite calls into SandboxedVfs::Open(). The
// instance is deleted by a call to SandboxedVfsFile::Close().
//
// The SQLite VFS API includes a complex locking strategy documented in
// https://www.sqlite.org/lockingv3.html
//
// This implementation uses a simplified locking strategy, where we grab an
// exclusive lock when entering any of the modes that prepare for a transition
// to EXCLUSIVE. (These modes are RESERVED and PENDING). This approach is easy
// to implement on top of base::File's locking primitives, at the cost of some
// false contention, which makes us slower under high concurrency.
//
// SQLite's built-in VFSes use the OS support for locking a range of bytes in
// the file, rather locking than the whole file.
class SandboxedVfsFile { … };

// sqlite3_file "subclass" that bridges to a SandboxedVfsFile instance.
struct SandboxedVfsFileSqliteBridge { … };

}  // namespace sql

#endif  // SQL_SANDBOXED_VFS_FILE_H_
chromium/sql/sandboxed_vfs_file.h
