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use super::RateCounter;
use std::collections::VecDeque;
use std::time::Instant;
#[derive(Clone)]
pub struct RollingRateCounter {
updates: VecDeque<Instant>,
rate: f64,
samples: u64,
}
impl RollingRateCounter {
pub fn new(samples: u64) -> Self {
if samples == 0 {
panic!("Tried to build a RollingRateCounter with a sample_rate of 0")
}
RollingRateCounter {
updates: VecDeque::with_capacity(samples as usize),
rate: 0.0,
samples: samples,
}
}
}
impl RateCounter for RollingRateCounter {
fn samples(&self) -> u64 {
self.samples
}
fn set_samples(&mut self, samples: u64) {
if samples == 0 {
panic!("Tried to set sample_rate of a RollingRateCounter to 0");
}
self.samples = samples;
while self.updates.len() > self.samples as usize {
self.updates.remove(0);
}
}
fn update(&mut self) {
while self.updates.len() >= self.samples as usize {
self.updates.pop_front();
}
self.updates.push_back(Instant::now());
self.rate = 0.0;
for (index, _) in self.updates.iter().enumerate() {
if index == 0 {
continue;
}
let delta_t = self.updates[index].duration_since(self.updates[index - 1]);
let delta_t = delta_t.as_secs() as f64 + delta_t.subsec_nanos() as f64 * 1e-9;
let avg_delta_t = (self.rate + delta_t) / 2.0;
self.rate = self.samples as f64 / avg_delta_t;
}
}
fn rate(&self) -> f64 {
self.rate
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_rolling_rate_counter() {
let mut c = RollingRateCounter::new(10);
assert!(
c.rate() == 0.0,
"Counter should have no data before it gets enough samples (has {}).",
c.rate()
);
let sample_period = ::std::time::Duration::from_millis(10);
for _ in 1..11 {
let start = Instant::now();
while start.elapsed() < sample_period {}
c.update();
}
let difference = 100.0 - c.rate();
assert!(
difference < 10.0,
"Counter rate {} should be closer to actual rate 100.0.",
c.rate()
);
}
}