openethereum/util/time-utils/src/lib.rs

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// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.
// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity Ethereum. If not, see <http://www.gnu.org/licenses/>.
use std::time::{Duration, SystemTime, UNIX_EPOCH};
/// Temporary trait for `checked operations` on SystemTime until these are available in the standard library
pub trait CheckedSystemTime {
/// Returns `Some<SystemTime>` when the result less or equal to `i32::max_value` to prevent `SystemTime` to panic because
/// it is platform specific, possible representations are i32, i64, u64 or Duration. `None` otherwise
fn checked_add(self, _d: Duration) -> Option<SystemTime>;
/// Returns `Some<SystemTime>` when the result is successful and `None` when it is not
fn checked_sub(self, _d: Duration) -> Option<SystemTime>;
}
impl CheckedSystemTime for SystemTime {
fn checked_add(self, dur: Duration) -> Option<SystemTime> {
let this_dur = self.duration_since(UNIX_EPOCH).ok()?;
let total_time = this_dur.checked_add(dur)?;
if total_time.as_secs() <= i32::max_value() as u64 {
Some(self + dur)
} else {
None
}
}
fn checked_sub(self, dur: Duration) -> Option<SystemTime> {
let this_dur = self.duration_since(UNIX_EPOCH).ok()?;
let total_time = this_dur.checked_sub(dur)?;
if total_time.as_secs() <= i32::max_value() as u64 {
Some(self - dur)
} else {
None
}
}
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
use super::CheckedSystemTime;
use std::time::{Duration, SystemTime, UNIX_EPOCH};
assert!(CheckedSystemTime::checked_add(UNIX_EPOCH, Duration::new(i32::max_value() as u64 + 1, 0)).is_none());
assert!(CheckedSystemTime::checked_add(UNIX_EPOCH, Duration::new(i32::max_value() as u64, 0)).is_some());
assert!(CheckedSystemTime::checked_add(UNIX_EPOCH, Duration::new(i32::max_value() as u64 - 1, 1_000_000_000)).is_some());
assert!(CheckedSystemTime::checked_sub(UNIX_EPOCH, Duration::from_secs(120)).is_none());
assert!(CheckedSystemTime::checked_sub(SystemTime::now(), Duration::from_secs(1000)).is_some());
}
}