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Capture elapsed duration in Thread::park_timeout example #42597

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Jun 14, 2017
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Capture elapsed duration in Thread::park_timeout example #42597

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14 changes: 9 additions & 5 deletions src/libstd/thread/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -787,12 +787,16 @@ pub fn park_timeout_ms(ms: u32) {
///
/// let timeout = Duration::from_secs(2);
/// let beginning_park = Instant::now();
/// park_timeout(timeout);
///
/// while beginning_park.elapsed() < timeout {
/// println!("restarting park_timeout after {:?}", beginning_park.elapsed());
/// let timeout = timeout - beginning_park.elapsed();
/// park_timeout(timeout);
/// let mut timeout_remaining = timeout;
/// loop {
/// park_timeout(timeout_remaining);
/// let elapsed = beginning_park.elapsed();
/// if elapsed >= timeout {
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I think this should compare against timeout_remaining, right?

Similarly, below the subtraction should be against timeout_remaining instead of timeout?

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Nah, I think it is right as-is.

In the loop, elapsed is the total duration since creation of beginning_park (created outside of the loop). It is a rough measure of the total duration we've parked for thus far.
timeout is the total desired park duration.
Thus, comparing the two seems okay (we're comparing two "totals").
If we need to park some more, we calculate the difference between the total desired park duration and the total elapsed park duration, and use that value in yet-another-park.

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Ah right yes sorry got mixed up!

/// break;
/// }
/// println!("restarting park_timeout after {:?}", elapsed);
/// timeout_remaining = timeout - elapsed;
/// }
/// ```
///
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