commit	ec7f2af74a3f95b80b0cfc6a33aff7c86482a244	[log] [tgz]
author	Chih-Hung Hsieh <chh@google.com>	Mon Oct 26 23:18:21 2020 +0000
committer	Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>	Mon Oct 26 23:18:21 2020 +0000
tree	2f2e247d971d04be02491ca39a4bc29b7fc55224
parent	67c670ce1f952884dc5f417de6d23a240f22cced [diff]
parent	26041ccd7a20d18c463d52a3f6ccd723cef1ca70 [diff]

tree: 2f2e247d971d04be02491ca39a4bc29b7fc55224

README.md

Instant

If you call std::time::Instant::now() on a WASM platform, it will panic. This crate provides a partial replacement for std::time::Instant that works on WASM too. This defines the type instant::Instant which is:

A struct emulating the behavior of std::time::Instant if you are targeting wasm32-unknown-unknown or wasm32-unknown-asmjs and you enabled either the stdweb or the wasm-bindgen feature. This emulation is based on the javascript performance.now() function.
A type alias for std::time::Instant otherwise.

Note that even if the stdweb or wasm-bindgen feature is enabled, this crate will continue to rely on std::time::Instant as long as you are not targeting wasm32. This allows for portable code that will work on both native and WASM platforms.

The feature `now`.

By enabling the feature now the function instant::now() will be exported and will either:

Call performance.now() when compiling for a WASM platform with the features stdweb or wasm-bindgen enabled, or using a custom javascript function.
Call time::precise_time_s() * 1000.0 otherwise.

The result is expressed in milliseconds.

Examples

Using `instant` for a native platform.

Cargo.toml:

[dependencies]
instant = "0.1"

main.rs:

fn main() {
    // Will be the same as `std::time::Instant`.
    let now = instant::Instant::new();
}

Using `instant` for a WASM platform.

This example shows the use of the stdweb feature. It would be similar with wasm-bindgen.

Cargo.toml:

[dependencies]
instant = { version = "0.1", features = [ "stdweb" ] }

main.rs:

fn main() {
    // Will emulate `std::time::Instant` based on `performance.now()`.
    let now = instant::Instant::new();
}

Using `instant` for any platform enabling a feature transitively.

Cargo.toml:

[features]
stdweb = [ "instant/stdweb" ]
wasm-bindgen = [ "instant/wasm-bindgen" ]

[dependencies]
instant = "0.1"

lib.rs:

fn my_function() {
    // Will select the proper implementation depending on the
    // feature selected by the user.
    let now = instant::Instant::new();
}

Using the feature `now`.

Cargo.toml:

[features]
stdweb = [ "instant/stdweb" ]
wasm-bindgen = [ "instant/wasm-bindgen" ]

[dependencies]
instant = { version = "0.1", features = [ "now" ] }

lib.rs:

fn my_function() {
    // Will select the proper implementation depending on the
    // feature selected by the user.
    let now_instant = instant::Instant::new();
    let now_milliseconds = instant::now(); // In milliseconds.
}

Using the feature `now` without `stdweb` or `wasm-bindgen`.

Cargo.toml:

[dependencies]
instant = { version = "0.", features = [ "now" ] }

lib.rs:

fn my_function() {
    // Will use the 'now' javascript implementation.
    let now_instant = instant::Instant::new();
    let now_milliseconds = instant::now(); // In milliseconds.
}

javascript WASM bindings file:

function now() {
	return Date.now() / 1000.0;
}

Instant

The feature now.

Examples

Using instant for a native platform.

Using instant for a WASM platform.

Using instant for any platform enabling a feature transitively.

Using the feature now.

Using the feature now without stdweb or wasm-bindgen.

The feature `now`.

Using `instant` for a native platform.

Using `instant` for a WASM platform.

Using `instant` for any platform enabling a feature transitively.

Using the feature `now`.

Using the feature `now` without `stdweb` or `wasm-bindgen`.