51 lines
1.8 KiB
Rust
51 lines
1.8 KiB
Rust
use std::time::{Duration, SystemTime, UNIX_EPOCH};
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/// Temporary trait for `checked operations` on SystemTime until these are available in standard library
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pub trait CheckedSystemTime {
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/// Returns `Some<SystemTime>` when the result less or equal to `i32::max_value` to prevent `SystemTime` to panic because
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/// it is platform specific, possible representations are i32, i64, u64 and Duration. `None` otherwise
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fn checked_add(self, _d: Duration) -> Option<SystemTime>;
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/// Returns `Some<SystemTime>` when the result is successful and `None` when it is not
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fn checked_sub(self, _d: Duration) -> Option<SystemTime>;
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}
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impl CheckedSystemTime for SystemTime {
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fn checked_add(self, dur: Duration) -> Option<SystemTime> {
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let this_dur = self.duration_since(UNIX_EPOCH).ok()?;
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let total_time = this_dur.checked_add(dur)?;
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if total_time.as_secs() <= i32::max_value() as u64 {
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Some(self + dur)
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} else {
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None
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}
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}
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fn checked_sub(self, dur: Duration) -> Option<SystemTime> {
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let this_dur = self.duration_since(UNIX_EPOCH).ok()?;
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let total_time = this_dur.checked_sub(dur)?;
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if total_time.as_secs() <= i32::max_value() as u64 {
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Some(self - dur)
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} else {
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None
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}
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}
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}
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#[cfg(test)]
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mod tests {
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#[test]
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fn it_works() {
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use super::CheckedSystemTime;
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use std::time::{Duration, SystemTime, UNIX_EPOCH};
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assert!(CheckedSystemTime::checked_add(UNIX_EPOCH, Duration::new(i32::max_value() as u64 + 1, 0)).is_none());
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assert!(CheckedSystemTime::checked_add(UNIX_EPOCH, Duration::new(i32::max_value() as u64, 0)).is_some());
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assert!(CheckedSystemTime::checked_add(UNIX_EPOCH, Duration::new(i32::max_value() as u64 - 1, 1_000_000_000)).is_some());
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assert!(CheckedSystemTime::checked_sub(UNIX_EPOCH, Duration::from_secs(120)).is_none());
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assert!(CheckedSystemTime::checked_sub(SystemTime::now(), Duration::from_secs(1000)).is_some());
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}
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}
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