wasm

@rollup/plugin-wasm

🍣 A Rollup which allows importing and bundling WebAssembly modules.

WebAssembly Modules are imported asynchronous as base64 strings. Small modules can be imported synchronously.

Requirements

This plugin requires an LTS Node version (v14.0.0+) and Rollup v1.20.0+.

Install

Using npm:

npm install @rollup/plugin-wasm --save-dev

Usage

Create a rollup.config.js configuration file and import the plugin:

import { wasm } from '@rollup/plugin-wasm';

export default {
  input: 'src/index.js',
  output: {
    dir: 'output',
    format: 'cjs'
  },
  plugins: [wasm()]
};

Then call rollup either via the CLI or the API.

Options

sync

Type: Array[...String]
Default: null

Specifies an array of strings that each represent a WebAssembly file to load synchronously. See Synchronous Modules for a functional example.

maxFileSize

Type: Number
Default: 14336 (14kb)

The maximum file size for inline files. If a file exceeds this limit, it will be copied to the destination folder and loaded from a separate file at runtime. If maxFileSize is set to 0 all files will be copied.

Files specified in sync to load synchronously are always inlined, regardless of size.

publicPath

Type: String
Default: (empty string)

A string which will be added in front of filenames when they are not inlined but are copied.

targetEnv

Type: "auto" | "browser" | "node"
Default: "auto"

Configures what code is emitted to instantiate the Wasm (both inline and separate):

• "auto" will determine the environment at runtime and invoke the correct methods accordingly
• "auto-inline" always inlines the Wasm and will decode it according to the environment
• "browser" omits emitting code that requires node.js builtin modules that may play havoc on downstream bundlers
• "node" omits emitting code that requires fetch

WebAssembly Example

Given the following simple C file:

int main() {
  return 42;
}

Compile the file using emscripten, or the online WasmFiddle tool. Then import and instantiate the resulting file:

import sample from './sample.wasm';

sample({ ...imports }).then(({ instance }) => {
  console.log(instance.exports.main());
});

The WebAssembly is inlined as a base64 encoded string. At runtime the string is decoded and a module is returned.

Note: The base64 string that represents the WebAssembly within the bundle will be ~33% larger than the original file.

Synchronous Modules

Small modules (< 4KB) can be compiled synchronously by specifying them in the configuration.

wasm({
  sync: ['web/sample.wasm', 'web/foobar.wasm']
});

This means that the exports can be accessed immediately.

import sample from './sample.wasm';

const instance = sample({ ...imports });

console.log(instance.exports.main());

Meta

CONTRIBUTING

LICENSE (MIT)