throughput_counter.rb

class ThroughputCounter
  WINDOW_SIZE = 256
  Measurement = Struct.new(:n, :at)

  def initialize(window_size: WINDOW_SIZE)
    @wsize = window_size
    @total_sent = 0
    @measurements = [Measurement.new(0, now_monotonic)]
  end

  # Adds a new measurement
  def <<(n)
    @measurements << Measurement.new(n, now_monotonic)
    @measurements.shift if @measurements.length > @wsize
    @total_sent += n
    self
  end

  def total
    @total_sent
  end

  def avg_speed_per_second
    delta_t = now_monotonic - @measurements.first.at
    return 0 if delta_t < 0.001

    delta_transfer = @measurements.map(&:n).inject(0.0, &:+)
    delta_transfer / delta_t
  end

  def last_sample_at_monotonic
    @measurements.last.at
  end

  def now_monotonic
    Process.clock_gettime(Process::CLOCK_MONOTONIC)
  end
end