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use std::io::{self, Write};
use std::time::{Duration, Instant};
/// RAII timer to measure how long phases take.
#[derive(Debug)]
pub struct Timer<'a> {
output: bool,
name: &'a str,
start: Instant,
}
impl<'a> Timer<'a> {
/// Creates a Timer with the given name, and starts it. By default,
/// will print to stderr when it is `drop`'d
pub fn new(name: &'a str) -> Self {
Timer {
output: true,
name,
start: Instant::now(),
}
}
/// Sets whether or not the Timer will print a message
/// when it is dropped.
pub fn with_output(mut self, output: bool) -> Self {
self.output = output;
self
}
/// Returns the time elapsed since the timer's creation
pub fn elapsed(&self) -> Duration {
Instant::now() - self.start
}
fn print_elapsed(&mut self) {
if self.output {
let elapsed = self.elapsed();
let time = (elapsed.as_secs() as f64) * 1e3 +
(elapsed.subsec_nanos() as f64) / 1e6;
let stderr = io::stderr();
// Arbitrary output format, subject to change.
writeln!(stderr.lock(), " time: {:>9.3} ms.\t{}", time, self.name)
.expect("timer write should not fail");
}
}
}
impl<'a> Drop for Timer<'a> {
fn drop(&mut self) {
self.print_elapsed();
}
}