| // 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. |
| |
| #ifndef NET_NQE_OBSERVATION_BUFFER_H_ |
| #define NET_NQE_OBSERVATION_BUFFER_H_ |
| |
| #include <stdint.h> |
| |
| #include <map> |
| #include <memory> |
| #include <set> |
| #include <vector> |
| |
| #include "base/containers/circular_deque.h" |
| #include "base/optional.h" |
| #include "base/time/tick_clock.h" |
| #include "net/base/net_export.h" |
| #include "net/nqe/network_quality_estimator_util.h" |
| #include "net/nqe/network_quality_observation.h" |
| #include "net/nqe/network_quality_observation_source.h" |
| |
| namespace base { |
| |
| class TimeTicks; |
| |
| } // namespace base |
| |
| namespace net { |
| |
| class NetworkQualityEstimatorParams; |
| |
| namespace nqe { |
| |
| namespace internal { |
| |
| struct WeightedObservation; |
| |
| // Stores observations sorted by time and provides utility functions for |
| // computing weighted and non-weighted summary statistics. |
| class NET_EXPORT_PRIVATE ObservationBuffer { |
| public: |
| ObservationBuffer(const NetworkQualityEstimatorParams* params, |
| const base::TickClock* tick_clock, |
| double weight_multiplier_per_second, |
| double weight_multiplier_per_signal_level); |
| |
| // This constructor does not copy the |observations_| from |other| to |this|. |
| // As such, this constructor should only be called before adding any |
| // observations to |other|. |
| ObservationBuffer(const ObservationBuffer& other); |
| |
| ~ObservationBuffer(); |
| |
| // Adds |observation| to the buffer. The oldest observation in the buffer |
| // will be evicted to make room if the buffer is already full. |
| void AddObservation(const Observation& observation); |
| |
| // Returns the number of observations in this buffer. |
| size_t Size() const { return static_cast<size_t>(observations_.size()); } |
| |
| // Returns the capacity of this buffer. |
| size_t Capacity() const; |
| |
| // Clears the observations stored in this buffer. |
| void Clear() { observations_.clear(); } |
| |
| // Returns true iff the |percentile| value of the observations in this |
| // buffer is available. Sets |result| to the computed |percentile| |
| // value of all observations made on or after |begin_timestamp|. If the |
| // value is unavailable, false is returned and |result| is not modified. |
| // Percentile value is unavailable if all the values in observation buffer are |
| // older than |begin_timestamp|. |current_signal_strength| is the current |
| // signal strength. |result| must not be null. If |observations_count| is not |
| // null, then it is set to the number of observations that were available |
| // in the observation buffer for computing the percentile. |
| base::Optional<int32_t> GetPercentile(base::TimeTicks begin_timestamp, |
| int32_t current_signal_strength, |
| int percentile, |
| size_t* observations_count) const; |
| |
| void SetTickClockForTesting(const base::TickClock* tick_clock) { |
| tick_clock_ = tick_clock; |
| } |
| |
| // Removes all observations from the buffer whose corresponding entry in |
| // |deleted_observation_sources| is set to true. For example, if index 1 and |
| // 3 in |deleted_observation_sources| are set to true, then all observations |
| // in the buffer that have source set to either 1 or 3 would be removed. |
| void RemoveObservationsWithSource( |
| bool deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_MAX]); |
| |
| private: |
| // Computes the weighted observations and stores them in |
| // |weighted_observations| sorted by ascending |WeightedObservation.value|. |
| // Only the observations with timestamp later than |begin_timestamp| are |
| // considered. |current_signal_strength| is the current signal strength |
| // when the observation was taken. This method also sets |total_weight| to |
| // the total weight of all observations. Should be called only when there is |
| // at least one observation in the buffer. |
| void ComputeWeightedObservations( |
| const base::TimeTicks& begin_timestamp, |
| int32_t current_signal_strength, |
| std::vector<WeightedObservation>* weighted_observations, |
| double* total_weight) const; |
| |
| const NetworkQualityEstimatorParams* params_; |
| |
| // Holds observations sorted by time, with the oldest observation at the |
| // front of the queue. |
| base::circular_deque<Observation> observations_; |
| |
| // The factor by which the weight of an observation reduces every second. |
| // For example, if an observation is 6 seconds old, its weight would be: |
| // weight_multiplier_per_second_ ^ 6 |
| // Calculated from |kHalfLifeSeconds| by solving the following equation: |
| // weight_multiplier_per_second_ ^ kHalfLifeSeconds = 0.5 |
| const double weight_multiplier_per_second_; |
| |
| // The factor by which the weight of an observation reduces for every unit |
| // difference in the current signal strength, and the signal strength at |
| // which the observation was taken. |
| // For example, if the observation was taken at 1 unit, and current signal |
| // strength is 4 units, the weight of the observation would be: |
| // |weight_multiplier_per_signal_level_| ^ 3. |
| const double weight_multiplier_per_signal_level_; |
| |
| const base::TickClock* tick_clock_; |
| |
| DISALLOW_ASSIGN(ObservationBuffer); |
| }; |
| |
| } // namespace internal |
| |
| } // namespace nqe |
| |
| } // namespace net |
| |
| #endif // NET_NQE_OBSERVATION_BUFFER_H_ |