mirror of
https://github.com/fluencelabs/wasm-bindgen
synced 2025-06-08 10:31:21 +00:00
a2aa28e4d3
This commit adds a new attribute to `#[wasm_bindgen]`: `start`. The `start` attribute can be used to indicate that a function should be executed when the module is loaded, configuring the `start` function of the wasm executable. While this doesn't necessarily literally configure the `start` section, it does its best! Only one crate in a crate graph may indicate `#[wasm_bindgen(start)]`, so it's not recommended to be used in libraries but only end-user applications. Currently this still must be used with the `crate-type = ["cdylib"]` annotation in `Cargo.toml`. The implementation here is somewhat tricky because of the circular dependency between our generated JS and the wasm file that we emit. This circular dependency makes running initialization routines (like the `start` shim) particularly fraught with complications because one may need to run before the other but bundlers may not necessarily respect it. Workarounds have been implemented for various emission strategies, for example calling the start function directly after exports are wired up with `--no-modules` and otherwise working around what appears to be a Webpack bug with initializers running in a different order than we'd like. In any case, this in theory doesn't show up to the end user! Closes #74
41 lines
1.1 KiB
Rust
41 lines
1.1 KiB
Rust
extern crate humantime;
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extern crate wasm_bindgen;
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extern crate web_sys;
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use std::time::{Duration, SystemTime, UNIX_EPOCH};
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use wasm_bindgen::prelude::*;
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// lifted from the `console_log` example
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#[wasm_bindgen]
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extern "C" {
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#[wasm_bindgen(js_namespace = console)]
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fn log(a: &str);
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}
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macro_rules! console_log {
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($($t:tt)*) => (log(&format_args!($($t)*).to_string()))
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}
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#[wasm_bindgen(start)]
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pub fn run() {
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let window = web_sys::window().expect("should have a window in this context");
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let performance = window
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.performance()
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.expect("performance should be available");
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console_log!("the current time (in ms) is {}", performance.now());
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let start = perf_to_system(performance.timing().request_start());
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let end = perf_to_system(performance.timing().response_end());
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console_log!("request started at {}", humantime::format_rfc3339(start));
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console_log!("request ended at {}", humantime::format_rfc3339(end));
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}
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fn perf_to_system(amt: f64) -> SystemTime {
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let secs = (amt as u64) / 1_000;
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let nanos = ((amt as u32) % 1_000) * 1_000_000;
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UNIX_EPOCH + Duration::new(secs, nanos)
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}
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