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#browser #instant #rust #systemtime #time #wasm #wasm-bindgen #web

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README

web-time

Description

Complete drop-in replacement for [std::time] that works in browsers.

Currently [Instant::now()] and [SystemTime::now()] will simply panic when using the wasm32-unknown-unknown target. This implementation uses [Performance.now()] for [Instant] and [Date.now()] for [SystemTime] to offer a drop-in replacement that works in browsers.

At the same time the library will simply re-export [std::time] when not using the wasm32-unknown-unknown or wasm32v1-none target and will not pull in any dependencies.

Additionally, if compiled with target-feature = "atomics" it will synchronize the timestamps to account for different context's, like web workers. See [Performance.timeOrigin] for more information.

Target

This library specifically targets browsers, that support [Performance.now()], with the wasm32-unknown-unknown or wasm32v1-none target. Emscripten is not supported. WASI doesn't require support as it has it's own native API to deal with [std::time].

Furthermore it depends on [wasm-bindgen], which is required. This library will continue to depend on it until a viable alternative presents itself, in which case multiple ecosystems could be supported.

Note

Ticking during sleep

Currently a known bug is affecting browsers on operating system other then Windows. This bug prevents [Instant] from continuing to tick when the context is asleep. While this doesn't conflict with Rusts requirements of [Instant], by chance Rust's Std has the same problem.

See the MDN documentation on this for more information.

Context support

The implementation of [Instant::now()] relies on the availability of the [Performance object], a lack thereof will cause a panic. This can happen if called from a [worklet].

Usage

You can simply import the types you need:

use web_time::{Instant, SystemTime};
let now = Instant::now(); let time = SystemTime::now();

Using -Ctarget-feature=+nontrapping-fptoint will improve the performance of [Instant::now()] and [SystemTime::now()], but the vast majority of the time is still spent going through JS.

Features

`std` (enabled by default)

Enables the corresponding crate feature in all dependencies and allows for some optimized instruction output.

Without this crate feature compilation the standard library is not included. Has no effect on targets other then wasm32-unknown-unknown or wasm32v1-none.

`msrv` (enabled by default)

Allows web-time to make use of features only available in higher MSRVs. This offers compile-time detection and does not break compilation when enabled with the crates MSRV.

Rust v1.77 + std: Enables the use of the [f64.nearest] instruction. Which will significantly

reduce the instruction count for [Instant::now()].

Rust Nightly: Enables the use of the [f64.trunc] and [f64.nearest] instruction. Which will

significantly reduce the instruction count for [Instant::now()].

`serde`

Implements [serde::Deserialize] and [serde::Serialize] for [SystemTime].

Conditional Configurations

`docsrs`

This requires Rust nightly and enhances the documentation. It must only be used with RUSTDOCFLAGS, not with RUSTFLAGS.

MSRV Policy

The MSRV is v1.60. Changes to the MSRV will be accompanied by a minor version bump.

Changelog

See the [CHANGELOG] file for details.

Contributing

See the [CONTRIBUTING] file for details.

Attribution

Inspiration was taken from the instant project.

Additional insight was taken from the time project.

License

Licensed under either of

Apache License, Version 2.0 ([LICENSE-APACHE] or )
MIT license ([LICENSE-MIT] or )

at your option.

Copyright

A majority of the code and documentation was taken from [std::time]. For license information see #License.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

[CHANGELOG]: https://github.com/daxpedda/web-time/blob/v1.1.0/CHANGELOG.md [CONTRIBUTING]: https://github.com/daxpedda/web-time/blob/v1.1.0/CONTRIBUTING.md [LICENSE-MIT]: https://github.com/daxpedda/web-time/blob/v1.1.0/LICENSE-MIT [LICENSE-APACHE]: https://github.com/daxpedda/web-time/blob/v1.1.0/LICENSE-APACHE [worklet]: https://developer.mozilla.org/en-US/docs/Web/API/Worklet [Date.now()]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/now [Instant]: https://doc.rust-lang.org/std/time/struct.Instant.html [Instant::now()]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.now [SystemTime]: https://doc.rust-lang.org/std/time/struct.SystemTime.html [SystemTime::now()]: https://doc.rust-lang.org/std/time/struct.SystemTime.html#method.now [std::time]: https://doc.rust-lang.org/std/time/ [performance.now()]: https://developer.mozilla.org/en-US/docs/Web/API/Performance/now [Performance.timeOrigin]: https://developer.mozilla.org/en-US/docs/Web/API/Performance/timeOrigin [Performance object]: https://developer.mozilla.org/en-US/docs/Web/API/performance_property [serde::Deserialize]: https://docs.rs/serde/1/serde/trait.Deserialize.html [serde::Serialize]: https://docs.rs/serde/1/serde/trait.Serialize.html [wasm-bindgen]: https://crates.io/crates/wasm-bindgen [f64.nearest]: https://webassembly.github.io/spec/core/syntax/instructions.html#syntax-instr-numeric [f64.trunc]: https://webassembly.github.io/spec/core/syntax/instructions.html#syntax-instr-numeric