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| -rw-r--r-- | src/log_accel.hh | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/src/log_accel.hh b/src/log_accel.hh new file mode 100644 index 0000000..0090946 --- /dev/null +++ b/src/log_accel.hh @@ -0,0 +1,101 @@ +/** + * Copyright (c) 2014, Timothy Stack + * + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or otherlist materials provided with the distribution. + * * Neither the name of Timothy Stack nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * @file log_accel.hh + */ + +#ifndef log_accel_h +#define log_accel_h + +#include <cmath> + +#include <stdint.h> + +#include "base/lnav_log.hh" + +/** + * Helper class for figuring out changes in the log message rate. + */ +class log_accel { +public: + /*< The direction of the message rate: steady, accelerating, or decelerating + */ + enum direction_t { + A_STEADY, + A_DECEL, + A_ACCEL, + }; + + /** + * Add a time point that will be used to compute velocity and then + * acceleration. Points should be added in reverse order, from most + * recent to oldest. + * + * @param point The point in time. + * @return True if more points can be added. + */ + bool add_point(int64_t point); + + /** + * Get the average acceleration based on the time points we've received. + * + * @return The average message acceleration. + */ + double get_avg_accel() const; + + /** + * Compute the message rate direction. If the average acceleration is less + * than a certain threshold, then we consider the rate to be steady. + * Otherwise, the message rate is increasing or decreasing. + * + * @return The direction of the message rate. + */ + direction_t get_direction() const; + +private: + /** + * The amount of historical data to include in the average acceleration + * computation. + */ + static const int HISTORY_SIZE = 8; + /** + * The minimum range of velocities seen. This value should limit false- + * positives for small millisecond level fluctuations. + */ + static const double MIN_RANGE; + static const double THRESHOLD; + + int64_t la_last_point{0}; + bool la_last_point_set{false}; + int64_t la_min_velocity{INT64_MAX}; + int64_t la_max_velocity{INT64_MIN}; + int64_t la_velocity[HISTORY_SIZE]; + int la_velocity_size{0}; +}; + +#endif |