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use std::time::Duration;
use muldiv::MulDiv;
const NANOS_PER_SEC: u64 = 1_000_000_000;
const MILLIS_PER_SEC: u64 = 1_000;
const NANOS_PER_MILLI: u64 = NANOS_PER_SEC / MILLIS_PER_SEC;
pub trait DurationExt {
fn as_millis(&self) -> Option<u64>;
fn mul_u64(&self, rhs: u64) -> Self;
fn div_u64(&self, rhs: u64) -> Self;
}
impl DurationExt for Duration {
fn as_millis(&self) -> Option<u64> {
self.as_secs()
.checked_mul(MILLIS_PER_SEC)
.and_then(|m| m.checked_add(self.subsec_nanos() as u64 / NANOS_PER_MILLI))
}
fn mul_u64(&self, rhs: u64) -> Duration {
let a = rhs / NANOS_PER_SEC;
let b = rhs % NANOS_PER_SEC;
let total_nanos = self.subsec_nanos() as u64 * b;
let nanos = (total_nanos % NANOS_PER_SEC as u64) as u32;
let secs = self.as_secs()
.checked_mul(rhs)
.and_then(|s| s.checked_add(total_nanos / NANOS_PER_SEC))
.and_then(|s| s.checked_add(self.subsec_nanos() as u64 * a))
.expect("overflow when multiplying duration");
debug_assert!(nanos < NANOS_PER_SEC as u32);
Duration::new(secs, nanos)
}
fn div_u64(&self, rhs: u64) -> Duration {
let secs = self.as_secs() / rhs;
let carry = self.as_secs() - secs * rhs;
let extra_nanos = carry.mul_div_floor(NANOS_PER_SEC, rhs)
.expect("overflow when dividing duration");
let nanos = (self.subsec_nanos() as u64 / rhs + extra_nanos) as u32;
debug_assert!(nanos < NANOS_PER_SEC as u32);
Duration::new(secs, nanos)
}
}
#[cfg(test)]
mod test {
use std::time::Duration;
use super::*;
#[test]
fn as_millis() {
assert_eq!(Some(1100), Duration::new(1, 100_000_999).as_millis());
assert_eq!(None, Duration::from_secs(1 << 60).as_millis());
}
#[test]
fn mul_u64() {
assert_eq!(Duration::new(0, 1).mul_u64(2), Duration::new(0, 2));
assert_eq!(Duration::new(1, 1).mul_u64(3), Duration::new(3, 3));
assert_eq!(Duration::new(0, 500_000_001).mul_u64(4), Duration::new(2, 4));
assert_eq!(Duration::new(0, 500_000_001).mul_u64(4000),
Duration::new(2000, 4000));
assert_eq!(Duration::new(0, 500_000_000).mul_u64(1 << 63),
Duration::new(1 << 62, 0));
}
#[test]
fn div_u64() {
assert_eq!(Duration::new(0, 1).div_u64(2), Duration::new(0, 0));
assert_eq!(Duration::new(1, 1).div_u64(3), Duration::new(0, 333_333_333));
assert_eq!(Duration::new(99, 999_999_000).div_u64(100),
Duration::new(0, 999_999_990));
assert_eq!(Duration::new(1 << 62, 0).div_u64(1 << 63),
Duration::new(0, 500_000_000));
}
}