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
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
use libc;
use ops::Sub;
use time::Duration;
use sync::Once;
const NANOS_PER_SEC: u64 = 1_000_000_000;
pub struct SteadyTime {
t: libc::LARGE_INTEGER,
}
impl SteadyTime {
pub fn now() -> SteadyTime {
let mut t = SteadyTime { t: 0 };
unsafe { libc::QueryPerformanceCounter(&mut t.t); }
t
}
}
fn frequency() -> libc::LARGE_INTEGER {
static mut FREQUENCY: libc::LARGE_INTEGER = 0;
static ONCE: Once = Once::new();
unsafe {
ONCE.call_once(|| {
libc::QueryPerformanceFrequency(&mut FREQUENCY);
});
FREQUENCY
}
}
impl<'a> Sub for &'a SteadyTime {
type Output = Duration;
fn sub(self, other: &SteadyTime) -> Duration {
let diff = self.t as u64 - other.t as u64;
let nanos = mul_div_u64(diff, NANOS_PER_SEC, frequency() as u64);
Duration::new(nanos / NANOS_PER_SEC, (nanos % NANOS_PER_SEC) as u32)
}
}
fn mul_div_u64(value: u64, numer: u64, denom: u64) -> u64 {
let q = value / denom;
let r = value % denom;
q * numer + r * numer / denom
}
#[test]
fn test_muldiv() {
assert_eq!(mul_div_u64( 1_000_000_000_001, 1_000_000_000, 1_000_000),
1_000_000_000_001_000);
}