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/*
* Copyright (C) 2023 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 LOCATION_LBS_CONTEXTHUB_NANOAPPS_NEARBY_ADV_REPORT_CACHE_H_
#define LOCATION_LBS_CONTEXTHUB_NANOAPPS_NEARBY_ADV_REPORT_CACHE_H_
#include "third_party/contexthub/chre/util/include/chre/util/time.h"
#ifdef NEARBY_PROFILE
#include <ash/profile.h>
#endif
#include <limits>
#include <utility>
#include "third_party/contexthub/chre/util/include/chre/util/dynamic_vector.h"
namespace nearby {
class AdvReportCache {
public:
// Constructs advertise report cache.
#ifdef NEARBY_PROFILE
AdvReportCache() {
ashProfileInit(
&profile_data_, "[NEARBY_ADV_CACHE_PERF]", 1000 /* print_interval_ms */,
false /* report_total_thread_cycles */, true /* printCsvFormat */);
}
#else
AdvReportCache() = default;
#endif
// Deconstructs advertise report cache and releases all resources.
~AdvReportCache() {
Clear();
}
// Move assignment operator
AdvReportCache &operator=(AdvReportCache &&other) {
if (&other == this) {
return *this;
}
Clear();
cache_reports_ = std::move(other.cache_reports_);
cache_expire_nanosec_ = other.cache_expire_nanosec_;
return *this;
}
// Releases all resources {cache element, heap memory} in cache.
void Clear();
// Adds advertise report to cache with deduplicating by
// unique key which is {advertiser address and data}.
// Among advertise report with the same key, latest one will be placed at the
// same index of existing report in advertise reports cache.
void Push(const chreBleAdvertisingReport &report);
// Return advertise reports in cache after refreshing the cache elements.
chre::DynamicVector<chreBleAdvertisingReport> &GetAdvReports() {
Refresh();
return cache_reports_;
}
// Computes moving average with previous average (previous) and a current data
// point (current). Returns the computed average.
int8_t ComputeMovingAverage(int8_t previous, int8_t current) const {
return static_cast<int8_t>(current * kMovingAverageWeight +
previous * (1 - kMovingAverageWeight));
}
// Sets current cache timeout value.
void SetCacheTimeout(uint64_t cache_expire_millisec) {
cache_expire_nanosec_ =
cache_expire_millisec * chre::kOneMillisecondInNanoseconds;
}
// Removes cached elements older than the cache timeout.
void Refresh();
// Removes cached elements older than the cache timeout if cache count is
// larger than threshold.
void RefreshIfNeeded();
private:
// Weight for a current data point in moving average.
static constexpr float kMovingAverageWeight = 0.3f;
// Default value for advertise report cache to expire.
// Uses large enough value that it won't end soon.
static constexpr uint64_t kMaxExpireTimeNanoSec =
std::numeric_limits<uint64_t>::max();
// Default value for threshold cache count to trigger refresh.
// At the worst case, roughly 2KB ( = 255 byte * 8) could be allocated for the
// cache elements exired.
static constexpr size_t kRefreshCacheCountThreshold = 8;
chre::DynamicVector<chreBleAdvertisingReport> cache_reports_;
// Current cache timeout value.
uint64_t cache_expire_nanosec_ = kMaxExpireTimeNanoSec;
#ifdef NEARBY_PROFILE
ashProfileData profile_data_;
#endif
};
} // namespace nearby
#endif // LOCATION_LBS_CONTEXTHUB_NANOAPPS_NEARBY_ADV_REPORT_CACHE_H_
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