system/lib/wasmfs/backend.h

// Copyright 2021 The Emscripten Authors.  All rights reserved.
// Emscripten is available under two separate licenses, the MIT license and the
// University of Illinois/NCSA Open Source License.  Both these licenses can be
// found in the LICENSE file.

// This file defines the modular backend abstract class.
// Other file system backends can use this to interface with the new file
// system. Current Status: Work in Progress. See
// https://github.com/emscripten-core/emscripten/issues/15041.

#pragma once

#include "file.h"

namespace wasmfs {
// A backend (or modular backend) provides a base for the new file system to
// extend its storage capabilities. Files and directories will be represented in
// the file system structure, but their underlying backing could exist in
// persistent storage, another thread, etc.
class Backend {

public:
  virtual std::shared_ptr<DataFile> createFile(mode_t mode) = 0;
  virtual std::shared_ptr<Directory> createDirectory(mode_t mode) = 0;
  virtual ~Backend() = default;
};

// This will return an instance of a MemoryFileBackend.
// Note: Backends will be defined in cpp files, but functions to instantiate
// them will be defined in a header file. This is so that any unused backends
// are not linked in if they are not called.
// TODO: In the next PR, a user-visible header is introduced. Update this
// comment then.
backend_t createMemoryFileBackend();
} // namespace wasmfs