filters.hpp

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#pragma once
 
#include <cstddef>
 
namespace bst {
 
template <class T>
class ConsecutiveValuesFilter {
public:
  ConsecutiveValuesFilter(T initial_value, size_t filter_threshold = 0)
      : filter_threshold_{filter_threshold}, current_value_{initial_value},
        new_value_{initial_value} {
  }
 
  ~ConsecutiveValuesFilter() = default;
 
  void reset(T value) {
    current_count_ = 0;
    current_value_ = value;
  }
 
  void setFilterThreshold(size_t filter_threshold) {
    filter_threshold_ = filter_threshold;
  }
 
  bool addValue(T value) {
    // If the value is the same as the current value, decrement the count until
    // it's back to zero.
    if (value == current_value_) {
      if (current_count_ != 0) {
        current_count_--;
      }
      return false;
    }
 
    // If the value is the same as the currently being counted value, increment
    // the count.
    if (value == new_value_) {
      current_count_++;
    } else {
      // If the value is different from the current or the new value, reset the
      // count and set the new, new value.
      new_value_ = value;
      current_count_ = 1;
    }
 
    // If the count is greater than the filter threshold, set the current value
    // to the new value and reset the count.
    if (current_count_ >= filter_threshold_) {
      current_value_ = new_value_;
      current_count_ = 0;
      return true;
    }
 
    return false;
  }
 
  T getCurrentValue() const {
    return current_value_;
  }
 
private:
  size_t filter_threshold_;
 
  size_t current_count_{0};
 
  T current_value_{};
 
  T new_value_{};
};
 
} // namespace bst