chromium/third_party/perfetto/src/trace_processor/sqlite/module_lifecycle_manager.h

/*
 * Copyright (C) 2024 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.
 */

#ifndef SRC_TRACE_PROCESSOR_SQLITE_MODULE_LIFECYCLE_MANAGER_H_
#define SRC_TRACE_PROCESSOR_SQLITE_MODULE_LIFECYCLE_MANAGER_H_

#include <memory>
#include <string>
#include <string_view>

#include "perfetto/base/logging.h"
#include "perfetto/ext/base/flat_hash_map.h"

namespace perfetto::trace_processor::sqlite {

// Helper class which abstracts away management of per-vtab state of an SQLite
// virtual table module.
//
// SQLite has some subtle semantics around lifecycle of vtabs which makes state
// management complex. This class attempts to encapsulate some of that
// complexity as a central place where we can document the quirks.
//
// Usage of this class:
// struct MyModule : sqlite::Module<MyModule> {
//   struct Context {
//     // Store the manager in the context object.
//     ModuleStateManager<MyModule> manager.
//     ... (other fields)
//   }
//   struct Vtab : sqlite::Module<MyModule>::Vtab {
//     // Store the per-vtab-state pointer in the vtab object.
//     ModuleStateManager<MyModule>::PerVtabState* state;
//     ... (other fields)
//   }
//   static void OnCreate(...) {
//     ...
//     // Call OnCreate on the manager object and store the returned pointer.
//     tab->state = ctx->manager.OnCreate(argv);
//     ...
//   }
//   static void OnDestroy(...) {
//     ...
//     // Call OnDestroy with the stored state pointer.
//     sqlite::ModuleStateManager<MyModule>::OnDestroy(tab->state);
//     ...
//   }
//   // Do the same in OnConnect and OnDisconnect as in OnCreate and OnDestroy
//   // respectively.
//   static void OnConnect(...)
//   static void OnDisconnect(...)
// }
template <typename Module>
class ModuleStateManager { … };

}  // namespace perfetto::trace_processor::sqlite

#endif  // SRC_TRACE_PROCESSOR_SQLITE_MODULE_LIFECYCLE_MANAGER_H_