| // 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_BASE_PERCENTILE_ESTIMATOR_H_ |
| #define NET_BASE_PERCENTILE_ESTIMATOR_H_ |
| |
| #include "base/callback.h" |
| #include "base/macros.h" |
| #include "net/base/net_export.h" |
| |
| namespace net { |
| |
| // This class estimates statistical percentiles (e.g. 10%l, 50%l) for |
| // integer distributions presented in stream form. These estimates |
| // adjust automatically when the stream distribution changes. |
| // TODO(rdsmith): Expand the class to maintain floating point |
| // estimates rather than integer estimates, when there's a use case |
| // for that that deserves the extra complexity and pitfalls of |
| // floating point arithmetic. |
| class NET_EXPORT PercentileEstimator { |
| public: |
| using RandomNumberCallback = base::Callback<int(void)>; |
| |
| static const int kMedianPercentile = 50; |
| |
| // |percentile| is a number between 0 and 100 indicating what percentile |
| // should be estimated (e.g. 50 would be a median estimate). |
| // |initial_estimate| is the value the class is seeded with; in other |
| // words, if AddSample() is never called, |
| // |CurrentEstimate() == initial_estimate|. |
| PercentileEstimator(int percentile, int initial_estimate); |
| |
| ~PercentileEstimator(); |
| |
| int current_estimate() const { return current_estimate_; } |
| void AddSample(int sample); |
| |
| // Specify a callback that will generate a "random" number |
| // in the range [0,99] on each call. Used so that tests can |
| // rely on reproducible behavior. |
| void SetRandomNumberGeneratorForTesting( |
| RandomNumberCallback generator_callback); |
| |
| private: |
| const int percentile_; |
| |
| bool sign_positive_; |
| int current_estimate_; |
| int current_step_; |
| |
| RandomNumberCallback generator_callback_; |
| |
| DISALLOW_COPY_AND_ASSIGN(PercentileEstimator); |
| }; |
| |
| } // namespace net |
| |
| #endif // NET_BASE_PERCENTILE_ESTIMATOR_H_ |