@wasmer/wasi

The Package for using WASI easily from Node and the Browser

WASI

import { WASI } from "@wasmer/wasi"

Constructor

new WASI(wasiConfigObject): WASI

Constructs a new WASI instance.

The wasiConfigObject is is as follows:

const browserBindings = require("@wasmer/wasi/lib/bindings/browser");
// for Node:
// const nodeBindings = require("@wasmer/wasi/lib/bindings/node");

let myWASIInstance = new WASI({
  // OPTIONAL: The pre-opened dirctories
  preopenDirectories: {},

  // OPTIONAL: The environment vars
  env: {},

  // OPTIONAL: The arguments provided
  args: [],

  // OPTIONAL: The environment bindings (fs, path),
  // useful for using WASI in diferent environments
  // such as Node.js, Browsers, ...
  bindings: {
    // hrtime: (time?: [number, number]) -> number
    // exit: (code?: number) -> void
    // kill: (pid: number, signal?: string | number) -> void
    // randomFillSync: (buffer: Buffer, offset?: number, size?: number) -> Buffer
    // isTTY: () -> bool
    // fs: Filesystem (with similar API interface as Node 'fs' module)
    // path: Path  (with similar API Interface as Node 'path' module)
    ...browserBindings // Use `nodeBindings` for Node
  }
});

This returns a WASI instance. Please see the Instance properties section to learn about the WASI instance.

Class Properties

Instance Properties

memory

wasiInstance.memory: WebAssembly.Memory

WebAssembly.memory object, that is a view into the Wasm Module's linear memory.

view

wasiInstance.view: DataView

DataView object, that is a view into the Wasm Module's linear memory.

FD_MAP

wasiInstance.FD_MAP: Map<number, File>

Javascript Map, where the key is the file descriptor, and the value is a Javascript File.

exports

wasiInstance.exports: Exports

WASI API to be imported in the importObject on instantiation.

bindings

wasiInstance.bindings: WASIBindings

The bindings for common node like objects, such as fs for filesystem, these should work by default, but are applied depending on the platform. You can view the source code for your respective platform's bindings here.

start

wasiInstance.start(wasmInstance: WebAssembly.Instance): void

Function that takes in a WASI WebAssembly Instance and starts it.

getImports

wasiInstance.getImports(wasmModule: WebAssembly.Module): Exports

Function that returns the map of corresponding imports for the WASI module. It will throw an error in case the wasmModule is not a WASI Module, or it have an incompatible version.