This library provides a WASI implementation for Node.js and browsers in a tree-shaking friendly way. The system calls provided by this library are configurable.
With minimal configuration, it provides WASI system calls which just return WASI_ENOSYS.
- No dependencies
- Tree-shaking friendly
- 3 KB when minimal configuration
- 6 KB when all features enabled
- Almost compatible interface with Node.js WASI implementation
- Well tested, thanks to wasi-test-suite by Casper Beyer
npm install uwasiimport { WASI, useAll } from "uwasi";
import fs from "node:fs/promises";
async function main() {
const wasi = new WASI({
args: process.argv.slice(2),
features: [useAll()],
});
const bytes = await fs.readFile(process.argv[2]);
const { instance } = await WebAssembly.instantiate(bytes, {
wasi_snapshot_preview1: wasi.wasiImport,
});
const exitCode = wasi.start(instance);
console.log("exit code:", exitCode);
/* With Reactor model
wasi.initialize(instance);
*/
}
main()import { WASI, useAll } from "uwasi";
const wasi = new WASI({
features: [],
});import { WASI, useArgs, useClock } from "uwasi";
const wasi = new WASI({
args: ["./a.out", "hello", "world"],
features: [useEnviron, useArgs, useClock, useProc, useRandom()],
});By default, stdin behaves like /dev/null, stdout and stderr print to the console.
import { WASI, useStdio } from "uwasi";
const wasi = new WASI({
features: [useStdio()],
});You can use custom backends for stdio by passing handlers to useStdio.
import { WASI, useStdio } from "uwasi";
const inputs = ["Y", "N", "Y", "Y"];
const wasi = new WASI({
features: [useStdio({
stdin: () => inputs.shift() || "",
stdout: (str) => document.body.innerHTML += str,
stderr: (str) => document.body.innerHTML += str,
})],
});Some of WASI system calls are not implemented yet. Contributions are welcome!
| Syscall | Status | Notes |
|---|---|---|
args_XXX |
✅ | |
clock_XXX |
✅ | Monotonic clock is unavailable due to JS API limitation |
environ_XXX |
✅ | |
fd_XXX |
🚧 | stdin/stdout/stderr are supported |
path_XXX |
❌ | |
poll_oneoff |
❌ | |
proc_XXX |
✅ | |
random_get |
✅ | |
sched_yield |
❌ | |
sock_XXX |
❌ |