chromium/components/history/core/browser/in_memory_history_backend.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// The InMemoryHistoryBackend is a wrapper around the in-memory URL database.
// It maintains an in-memory cache of a subset of history that is required for
// low-latency operations, such as in-line autocomplete.
//
// The in-memory cache provides the following guarantees:
//  (1.) It will always contain URLRows that either have a `typed_count` > 0; or
//       that have a corresponding search term, in which case information about
//       the search term is also stored.
//  (2.) It will be an actual subset, i.e., it will contain verbatim data, and
//       will never contain more data that can be found in the main database.
//
// The InMemoryHistoryBackend is created on the history thread and passed to the
// main thread where operations can be completed synchronously. It listens for
// notifications from the "regular" history backend and keeps itself in sync.

#ifndef COMPONENTS_HISTORY_CORE_BROWSER_IN_MEMORY_HISTORY_BACKEND_H_
#define COMPONENTS_HISTORY_CORE_BROWSER_IN_MEMORY_HISTORY_BACKEND_H_

#include <memory>
#include <string>

#include "base/gtest_prod_util.h"
#include "base/scoped_observation.h"
#include "components/history/core/browser/history_service.h"
#include "components/history/core/browser/history_service_observer.h"
#include "components/history/core/browser/keyword_id.h"

namespace base {
class FilePath;
}

namespace history {

class HistoryBackendTestBase;
class InMemoryDatabase;
class InMemoryHistoryBackendTest;
class URLRow;

class InMemoryHistoryBackend : public HistoryServiceObserver { … };

}  // namespace history

#endif  // COMPONENTS_HISTORY_CORE_BROWSER_IN_MEMORY_HISTORY_BACKEND_H_