atomic-time 0.2.1

Lock-free, thread-safe atomic versions of Duration, SystemTime, Instant and their Option variants
Documentation 
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<div align="center">
<h1>Atomic Time</h1>
</div>
<div align="center">

Lock-free, thread-safe atomic versions of Duration, SystemTime, Instant and their Option variants

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English | [简体中文][zh-cn-url]

</div>

## Introduction

`atomic-time` provides lock-free, thread-safe atomic versions of Rust's standard time types. All types use `AtomicU128` (via [`portable-atomic`](https://crates.io/crates/portable-atomic)) under the hood and expose the same API patterns as the standard `std::sync::atomic` types (`load`, `store`, `swap`, `compare_exchange`, `compare_exchange_weak`, `fetch_update`).

### Types

| Type | Wraps | `no_std` |
|------|-------|----------|
| `AtomicDuration` | `Duration` | Yes |
| `AtomicOptionDuration` | `Option<Duration>` | Yes |
| `AtomicSystemTime` | `SystemTime` | No |
| `AtomicOptionSystemTime` | `Option<SystemTime>` | No |
| `AtomicInstant` | `Instant` | No |
| `AtomicOptionInstant` | `Option<Instant>` | No |

## Installation

```toml
[dependencies]
atomic-time = "0.2"
```

### Feature Flags

| Feature | Default | Description |
|---------|---------|-------------|
| `std` | Yes | Enables `SystemTime` and `Instant` types |
| `serde` | No | Enables `Serialize`/`Deserialize` for all types |

For `no_std` environments (only `AtomicDuration` and `AtomicOptionDuration` are available):

```toml
[dependencies]
atomic-time = { version = "0.2", default-features = false }
```

## Example

```rust
use std::sync::Arc;
use std::sync::atomic::Ordering;
use std::time::Duration;
use atomic_time::AtomicDuration;

let timeout = Arc::new(AtomicDuration::new(Duration::from_secs(30)));

// Update from another thread
let timeout_clone = timeout.clone();
std::thread::spawn(move || {
    timeout_clone.store(Duration::from_secs(60), Ordering::Release);
});
```

```rust
use std::sync::atomic::Ordering;
use std::time::Instant;
use atomic_time::AtomicOptionInstant;

// Track the last time an event occurred
let last_event = AtomicOptionInstant::none();
assert_eq!(last_event.load(Ordering::Relaxed), None);

last_event.store(Some(Instant::now()), Ordering::Release);
assert!(last_event.load(Ordering::Acquire).is_some());
```

## Benchmarks

Run with `cargo bench` in the `benchmark/` directory. Apple M4 Pro.

### Duration (`cargo bench --bench duration`)

| Implementation | Single-thread load | Single-thread store | Contended read | Load under write contention | Contended store |
|---|---|---|---|---|---|
| `AtomicDuration` | 1.04 ns | 0.72 ns | 1.08 ns | 4.44 ns | 10.7 ns |
| `AtomicOptionDuration` | 1.16 ns | 0.74 ns | 1.20 ns | 4.73 ns | 14.5 ns |
| `ArcSwap<Duration>` | 2.30 ns | 86.5 ns | 2.38 ns | 15.5 ns | 1,400 ns |
| `parking_lot::RwLock` | 3.40 ns | 2.09 ns | 9.3 ns | 241.8 ns | 37.7 ns |
| `std::sync::RwLock` | 4.44 ns | 2.26 ns | 411.2 ns | 89.0 ns | 36.8 ns |

### Instant (`cargo bench --bench instant`)

| Implementation | Single-thread load | Single-thread store | Contended read | Load under write contention | Contended store |
|---|---|---|---|---|---|
| `AtomicInstant` | 2.16 ns | 3.52 ns | 2.17 ns | 14.97 ns | 22.7 ns |
| `AtomicOptionInstant` | 2.36 ns | 3.51 ns | 2.40 ns | 17.63 ns | 21.2 ns |
| `ArcSwap<Instant>` | 2.95 ns | 74.9 ns | 2.92 ns | 17.53 ns | 972 ns |
| `parking_lot::RwLock` | 3.43 ns | 2.10 ns | 81.3 ns | 213.9 ns | 26.9 ns |
| `std::sync::RwLock` | 4.48 ns | 2.28 ns | 422.3 ns | 87.7 ns | 76.9 ns |

### SystemTime (`cargo bench --bench system_time`)

| Implementation | Single-thread load | Single-thread store | Contended read | Load under write contention | Contended store |
|---|---|---|---|---|---|
| `AtomicSystemTime` | 1.26 ns | 3.41 ns | 1.28 ns | 8.89 ns | 27.1 ns |
| `AtomicOptionSystemTime` | 1.25 ns | 3.47 ns | 1.30 ns | 9.17 ns | 25.2 ns |
| `ArcSwap<SystemTime>` | 2.29 ns | 83.7 ns | 2.39 ns | 16.4 ns | 1,227 ns |
| `parking_lot::RwLock` | 3.50 ns | 2.13 ns | 22.0 ns | 204.5 ns | 31.0 ns |
| `std::sync::RwLock` | 4.69 ns | 2.31 ns | 554.2 ns | 84.4 ns | 38.7 ns |

> **Contended read** = 4 background threads also reading; **Load under write contention** = 4 background threads writing, load measured on main thread; **Contended store** = 4 background threads writing, store measured on main thread. All numbers from Apple M4 Pro.

## MSRV

The minimum supported Rust version is **1.70.0**.

## License

`atomic-time` is under the terms of both the MIT license and the
Apache License (Version 2.0).

See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT) for details.

Copyright (c) 2026 Al Liu.

[Github-url]: https://github.com/al8n/atomic-time/
[CI-url]: https://github.com/al8n/atomic-time/actions/workflows/ci.yml
[doc-url]: https://docs.rs/atomic-time
[crates-url]: https://crates.io/crates/atomic-time
[codecov-url]: https://app.codecov.io/gh/al8n/atomic-time/
[zh-cn-url]: https://github.com/al8n/atomic-time/tree/main/README-zh_CN.md