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// Copyright 2025 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_IMPL_H_
#define SQL_SANDBOXED_VFS_FILE_IMPL_H_
#include "base/component_export.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "sql/sandboxed_vfs.h"
#include "sql/sandboxed_vfs_file.h"
namespace sql {
// 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 SandboxedVfsFileImpl::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 COMPONENT_EXPORT(SQL) SandboxedVfsFileImpl : public SandboxedVfsFile {
public:
SandboxedVfsFileImpl(base::File file,
base::FilePath file_path,
sql::SandboxedVfsFileType file_type,
SandboxedVfs* vfs);
~SandboxedVfsFileImpl() override;
// sqlite3_file implementation.
int Close() override;
int Read(void* buffer, int size, sqlite3_int64 offset) override;
int Write(const void* buffer, int size, sqlite3_int64 offset) override;
int Truncate(sqlite3_int64 size) override;
int Sync(int flags) override;
int FileSize(sqlite3_int64* result_size) override;
int Lock(int mode) override;
int Unlock(int mode) override;
int CheckReservedLock(int* has_reserved_lock) override;
int FileControl(int opcode, void* data) override;
int SectorSize() override;
int DeviceCharacteristics() override;
int ShmMap(int page_index,
int page_size,
int extend_file_if_needed,
void volatile** result) override;
int ShmLock(int offset, int size, int flags) override;
void ShmBarrier() override;
int ShmUnmap(int also_delete_file) override;
int Fetch(sqlite3_int64 offset, int size, void** result) override;
int Unfetch(sqlite3_int64 offset, void* fetch_result) override;
private:
// Constructed from a file handle passed from the browser process.
base::File file_;
// One of the SQLite locking mode constants.
int sqlite_lock_mode_;
// The SandboxedVfs that created this instance.
const raw_ptr<SandboxedVfs> vfs_;
// Tracked to check assumptions about SQLite's locking protocol.
const SandboxedVfsFileType file_type_;
// Used to identify the file in IPCs to the browser process.
const base::FilePath file_path_;
};
} // namespace sql
#endif // SQL_SANDBOXED_VFS_FILE_IMPL_H_
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