1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

//! A module providing the `HitCount` metric.

use crate::{
    atomic::AtomicInt,
    clear::Clear,
    metric::{Counter, Metric},
};
use aspect::{Enter, OnResult};
use serde::Serialize;
use std::ops::Deref;

/// A metric counting how many times an expression as been hit, before it
/// returns.
///
/// This is a light-weight metric.
///
/// By default, `HitCount` uses a lock-free `u64` `Counter`, which makes sense
/// in multithread scenarios. Non-threaded applications can gain performance by
/// using a `std::cell:Cell<u64>` instead.
#[derive(Clone, Default, Debug, Serialize)]
pub struct HitCount<C: Counter = AtomicInt<u64>>(pub C);

impl<C: Counter, R> Metric<R> for HitCount<C> {}

impl<C: Counter> Enter for HitCount<C> {
    type E = ();
    fn enter(&self) -> Self::E {
        self.0.incr();
    }
}

impl<C: Counter, R> OnResult<R> for HitCount<C> {}

impl<C: Counter> Clear for HitCount<C> {
    fn clear(&self) {
        self.0.clear()
    }
}

impl<C: Counter> Deref for HitCount<C> {
    type Target = C;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}