[refactor] Simplifying and enhancing update method

* Also keeping `value_at` simpler

limitador/src/storage/atomic_expiring_value.rs

@@ -21,13 +21,12 @@ impl AtomicExpiringValue {
  }
 
  pub fn value_at(&self, when: SystemTime) -> i64 {
- let expiry = self.expiry.load(Ordering::SeqCst);
  let when = when
  .duration_since(UNIX_EPOCH)
  .expect("SystemTime before UNIX EPOCH!")
  .as_micros() as u64;
+ let expiry = self.expiry.load(Ordering::SeqCst);
  if expiry <= when {
- self.value.swap(0, Ordering::SeqCst);
  return 0;
  }
  self.value.load(Ordering::SeqCst)
@@ -44,33 +43,19 @@ impl AtomicExpiringValue {
  .expect("SystemTime before UNIX EPOCH!")
  .as_micros() as u64;
 
- let mut expiry = self.expiry.load(Ordering::SeqCst);
- let mut current = self.value_at(when);
-
- loop {
- let new_value = current + delta;
- let value_result =
- self.value
- .compare_exchange(current, new_value, Ordering::SeqCst, Ordering::SeqCst);
- let expiry_result: Result<u64, u64> = if expiry <= when_micros {
- self.expiry.compare_exchange(
- expiry,
- when_micros + ttl_micros,
- Ordering::SeqCst,
- Ordering::SeqCst,
- )
- } else {
- Ok(expiry)
- };
- match (value_result, expiry_result) {
- (Ok(_), Ok(_)) => break,
- (Err(_), Err(e)) => {
- current = self.value_at(when);
- expiry = e;
- }
- _ => {}
+ let expiry = self.expiry.load(Ordering::SeqCst);
+ if expiry <= when_micros {
+ let new_expiry = when_micros + ttl_micros;
+ if self
+ .expiry
+ .compare_exchange(expiry, new_expiry, Ordering::SeqCst, Ordering::SeqCst)
+ .is_ok()
+ {
+ self.value.store(delta, Ordering::SeqCst);
  }
+ return;
  }
+ self.value.fetch_add(delta, Ordering::SeqCst);
  }
 
  pub fn ttl(&self) -> Duration {