Skip to main content
Deno 2 is finally here 🎉️
Learn more
Module

std/wasi/README.md

Deno standard library
Go to Latest
The Standard Library has been moved to JSR. See the blog post for details.
File

wasi

This module provides an implementation of the WebAssembly System Interface

Supported Syscalls

wasi_snapshot_preview1

  • args_get
  • args_sizes_get
  • environ_get
  • environ_sizes_get
  • clock_res_get
  • clock_time_get
  • fd_advise
  • fd_allocate
  • fd_close
  • fd_datasync
  • fd_fdstat_get
  • fd_fdstat_set_flags
  • fd_fdstat_set_rights
  • fd_filestat_get
  • fd_filestat_set_size
  • fd_filestat_set_times
  • fd_pread
  • fd_prestat_get
  • fd_prestat_dir_name
  • fd_pwrite
  • fd_read
  • fd_readdir
  • fd_renumber
  • fd_seek
  • fd_sync
  • fd_tell
  • fd_write
  • path_create_directory
  • path_filestat_get
  • path_filestat_set_times
  • path_link
  • path_open
  • path_readlink
  • path_remove_directory
  • path_rename
  • path_symlink
  • path_unlink_file
  • poll_oneoff
  • proc_exit
  • proc_raise
  • sched_yield
  • random_get
  • sock_recv
  • sock_send
  • sock_shutdown

Usage

import WASI from "https://deno.land/std/wasi/snapshot_preview1.ts";

const wasi = new WASI({
  args: Deno.args,
  env: Deno.env,
});

const binary = await Deno.readFile("path/to/your/module.wasm");
const module = await WebAssembly.compile(binary);
const instance = await WebAssembly.instantiate(module, {
  wasi_snapshot_preview1: wasi.exports,
});

wasi.memory = module.exports.memory;

if (module.exports._start) {
  instance.exports._start();
} else if (module.exports._initialize) {
  instance.exports._initialize();
} else {
  throw new Error("No entry point found");
}

Testing

The test suite for this module spawns rustc processes to compile various example Rust programs. You must have wasm targets enabled:

rustup target add wasm32-wasi
rustup target add wasm32-unknown-unknown