commit	c368efd594425abb1b71656c323abb5f3e693c53	[log] [tgz]
author	Xin Li <delphij@google.com>	Tue Mar 08 11:03:43 2022 +0000
committer	Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>	Tue Mar 08 11:03:43 2022 +0000
tree	4a79f8bd26d95e83102eaa2bd02e03a49b61a4cb
parent	b753132403ede7933e83400971c712807b75068b [diff]
parent	dd4b72848ce0aa5da40d9e6db324ebabe29bc352 [diff]

tree: 4a79f8bd26d95e83102eaa2bd02e03a49b61a4cb

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.

This crate also exports the function instant::now() which returns a representation of the current time as an f64, expressed in milliseconds, in a platform-agnostic way. instant::now() 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.
Return the time elapsed since the Unix Epoch on native, non-WASM platforms.

Note: The old feature, now, has been deprecated. instant::now() is always exported and the now feature flag no longer has any effect. It remains listed in Cargo.toml to avoid introducing breaking changes and may be removed in future versions.

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::now();
}

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::now();
}

Using `instant` for a WASM platform where `performance.now()` is not available.

This example shows the use of the inaccurate feature.

Cargo.toml:

[dependencies]
instant = { version = "0.1", features = [ "wasm-bindgen", "inaccurate" ] }

main.rs:

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

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::now();
}

Using `instant::now()`

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::Instant::now();
    let now_milliseconds = instant::now(); // In milliseconds.
}

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

Cargo.toml:

[dependencies]
instant = "0.1"

lib.rs:

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

javascript WASM bindings file:

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

Instant

Examples

Using instant for a native platform.

Using instant for a WASM platform.

Using instant for a WASM platform where performance.now() is not available.

Using instant for any platform enabling a feature transitively.

Using instant::now()

Using the feature now without stdweb or wasm-bindgen.

Using `instant` for a native platform.

Using `instant` for a WASM platform.

Using `instant` for a WASM platform where `performance.now()` is not available.

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

Using `instant::now()`

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