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- // Copyright 2016 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "net/nqe/network_quality_store.h"
- #include "base/bind.h"
- #include "base/location.h"
- #include "base/observer_list.h"
- #include "base/threading/thread_task_runner_handle.h"
- #include "net/base/network_change_notifier.h"
- namespace net::nqe::internal {
- NetworkQualityStore::NetworkQualityStore() {
- static_assert(kMaximumNetworkQualityCacheSize > 0,
- "Size of the network quality cache must be > 0");
- // This limit should not be increased unless the logic for removing the
- // oldest cache entry is rewritten to use a doubly-linked-list LRU queue.
- static_assert(kMaximumNetworkQualityCacheSize <= 20,
- "Size of the network quality cache must <= 20");
- }
- NetworkQualityStore::~NetworkQualityStore() {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- }
- void NetworkQualityStore::Add(
- const nqe::internal::NetworkID& network_id,
- const nqe::internal::CachedNetworkQuality& cached_network_quality) {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- DCHECK_LE(cached_network_qualities_.size(),
- static_cast<size_t>(kMaximumNetworkQualityCacheSize));
- if (cached_network_quality.effective_connection_type() ==
- EFFECTIVE_CONNECTION_TYPE_UNKNOWN) {
- return;
- }
- // Remove the entry from the map, if it is already present.
- cached_network_qualities_.erase(network_id);
- if (cached_network_qualities_.size() == kMaximumNetworkQualityCacheSize) {
- // Remove the oldest entry.
- auto oldest_entry_iterator = cached_network_qualities_.begin();
- for (auto it = cached_network_qualities_.begin();
- it != cached_network_qualities_.end(); ++it) {
- if ((it->second).OlderThan(oldest_entry_iterator->second))
- oldest_entry_iterator = it;
- }
- cached_network_qualities_.erase(oldest_entry_iterator);
- }
- cached_network_qualities_.insert(
- std::make_pair(network_id, cached_network_quality));
- DCHECK_LE(cached_network_qualities_.size(),
- static_cast<size_t>(kMaximumNetworkQualityCacheSize));
- for (auto& observer : network_qualities_cache_observer_list_)
- observer.OnChangeInCachedNetworkQuality(network_id, cached_network_quality);
- }
- bool NetworkQualityStore::GetById(
- const nqe::internal::NetworkID& network_id,
- nqe::internal::CachedNetworkQuality* cached_network_quality) const {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- // First check if an exact match can be found.
- for (const auto& cached_quality : cached_network_qualities_) {
- if (network_id.type != cached_quality.first.type ||
- network_id.id != cached_quality.first.id) {
- // The |type| and |id| must match.
- continue;
- }
- // Check for an exact match, and return immediately if one is found.
- // It's possible that the current network does not have signal strength
- // available. In that case, return the cached network quality when the
- // signal strength was unavailable.
- if (network_id.signal_strength == cached_quality.first.signal_strength) {
- *cached_network_quality = cached_quality.second;
- return true;
- }
- }
- // Handle the case when current network does not have signal strength
- // available. Return the cached network quality that corresponds to the
- // highest signal strength. This ensures that the method returns the fastest
- // network quality possible for the current network, and serves as a
- // conservative estimate.
- if (network_id.signal_strength == INT32_MIN) {
- auto matching_it = cached_network_qualities_.end();
- for (auto it = cached_network_qualities_.begin();
- it != cached_network_qualities_.end(); ++it) {
- if (network_id.type != it->first.type || network_id.id != it->first.id) {
- // The |type| and |id| must match.
- continue;
- }
- // The cached network must have signal strength available. If the cached
- // signal strength is unavailable, then this case would have been handled
- // above.
- DCHECK_NE(INT32_MIN, it->first.signal_strength);
- if (matching_it == cached_network_qualities_.end() ||
- it->first.signal_strength > matching_it->first.signal_strength) {
- matching_it = it;
- }
- }
- if (matching_it == cached_network_qualities_.end())
- return false;
- *cached_network_quality = matching_it->second;
- return true;
- }
- // Finally, handle the case where the current network has a valid signal
- // strength, but there is no exact match.
- // |matching_it| points to the entry that has the same connection type and
- // id as |network_id|, and has the signal strength closest to the signal
- // stength of |network_id|.
- auto matching_it = cached_network_qualities_.end();
- int matching_it_diff_signal_strength = INT32_MAX;
- // Find the closest estimate.
- for (auto it = cached_network_qualities_.begin();
- it != cached_network_qualities_.end(); ++it) {
- if (network_id.type != it->first.type || network_id.id != it->first.id) {
- // The |type| and |id| must match.
- continue;
- }
- DCHECK_LE(0, network_id.signal_strength);
- // Determine if the signal strength of |network_id| is closer to the
- // signal strength of the network at |it| then that of the network at
- // |matching_it|.
- int diff_signal_strength =
- std::abs(network_id.signal_strength - it->first.signal_strength);
- if (it->first.signal_strength == INT32_MIN) {
- // Current network has signal strength available. However, the persisted
- // network does not. Set the |diff_signal_strength| to INT32_MAX. This
- // ensures that if an entry with a valid signal strength is found later
- // during iteration, then that entry will be used. If no entry with valid
- // signal strength is found, then this entry will be used.
- diff_signal_strength = INT32_MAX;
- }
- if (matching_it == cached_network_qualities_.end() ||
- diff_signal_strength < matching_it_diff_signal_strength) {
- matching_it = it;
- matching_it_diff_signal_strength = diff_signal_strength;
- }
- }
- if (matching_it == cached_network_qualities_.end())
- return false;
- *cached_network_quality = matching_it->second;
- return true;
- }
- void NetworkQualityStore::AddNetworkQualitiesCacheObserver(
- NetworkQualitiesCacheObserver* observer) {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- network_qualities_cache_observer_list_.AddObserver(observer);
- // Notify the |observer| on the next message pump since |observer| may not
- // be completely set up for receiving the callbacks.
- base::ThreadTaskRunnerHandle::Get()->PostTask(
- FROM_HERE,
- base::BindOnce(&NetworkQualityStore::NotifyCacheObserverIfPresent,
- weak_ptr_factory_.GetWeakPtr(), observer));
- }
- void NetworkQualityStore::RemoveNetworkQualitiesCacheObserver(
- NetworkQualitiesCacheObserver* observer) {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- network_qualities_cache_observer_list_.RemoveObserver(observer);
- }
- void NetworkQualityStore::NotifyCacheObserverIfPresent(
- NetworkQualitiesCacheObserver* observer) const {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- if (!network_qualities_cache_observer_list_.HasObserver(observer))
- return;
- for (const auto& it : cached_network_qualities_)
- observer->OnChangeInCachedNetworkQuality(it.first, it.second);
- }
- } // namespace net::nqe::internal
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