chromium/chrome/renderer/instant_restricted_id_cache.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_RENDERER_INSTANT_RESTRICTED_ID_CACHE_H_
#define CHROME_RENDERER_INSTANT_RESTRICTED_ID_CACHE_H_

#include <stddef.h>

#include <set>
#include <utility>
#include <vector>

#include "base/check_op.h"
#include "base/containers/lru_cache.h"
#include "base/gtest_prod_util.h"
#include "base/numerics/wrapping_math.h"
#include "chrome/common/search/instant_types.h"

// In InstantExtended, iframes are used to display objects which can only be
// referenced by the Instant page using an ID (restricted ID). These IDs need to
// be unique and cached for a while so that the SearchBox API can fetch the
// object info based on the ID when required by the Instant page. The reason to
// use a cache of N items as against just the last set of results is that there
// may be race conditions - e.g. the user clicks on a result being shown but the
// result set has internally changed but not yet been displayed.
//
// The cache can be used in two modes:
//
// 1. To store items and assign restricted IDs to them. The cache will store
//    a max of |max_cache_size_| items and assign them unique IDs.
//
// 2. To store items that already have restricted IDs assigned to them (e.g.
//    from another instance of the cache). The cache will then not generate IDs
//    and does not make any guarantees of the uniqueness of the IDs. If multiple
//    items are inserted with the same ID, the cache will return the last
//    inserted item in GetItemWithRestrictedID() call.

// T needs to be copyable.
template <typename T>
class InstantRestrictedIDCache { … };

template <typename T>
InstantRestrictedIDCache<T>::InstantRestrictedIDCache(size_t max_cache_size)
    : … { … }

template <typename T>
InstantRestrictedIDCache<T>::~InstantRestrictedIDCache() { … }

template <typename T>
void InstantRestrictedIDCache<T>::AddItems(const ItemVector& items) { … }

template <typename T>
void InstantRestrictedIDCache<T>::AddItemsWithRestrictedID(
    const ItemIDVector& items) { … }

template <typename T>
void InstantRestrictedIDCache<T>::GetCurrentItems(ItemIDVector* items) const { … }

template <typename T>
bool InstantRestrictedIDCache<T>::GetItemWithRestrictedID(
    InstantRestrictedID restricted_id,
    T* item) const { … }

#endif  // CHROME_RENDERER_INSTANT_RESTRICTED_ID_CACHE_H_