emwrap

Node.js CLI tool for wrapping emscripten glue code to module.

Support module type:

• umd (default, support browser <script>, Node.js and bundler)
• cjs (support Node.js and CommonJS bundler)
• esm (support browser <script type="module"> and ES module bundler, if using pthread, bundle umd instead)
• mjs (support Node.js runtime only, all js emitted by emscripten need to rename .mjs suffix via --output)

npm install -g @tybys/emwrap

emwrap [--name=myWasmLib]
       [--module=<umd | esm | cjs | mjs>]
       [--minify]
       [--weixin]
       [--worker]
       [--output=/path/to/output.js]
       [--script=/path/to/script.js]
       [--initscript=/path/to/script.js]
       [--exports=UTF8ToString,stringToUTF8]
       /path/to/emscripten/glue.js

--weixin: Support WXWebAssembly in WeChat miniprogram environment, pthread and workers are not supported.

Usage

Note: you should avoid passing -sMODULARIZE=1 or -o mjs extension to emcc / em++.

UMD

You can use --js-transform option:

emcc -o glue.js -O3 --js-transform "emwrap --name=myWasmLib" main.c

Windows:

emcc -o glue.js -O3 --js-transform "emwrap.cmd --name=myWasmLib" main.c

or in two steps:

emcc -o glue.js -O3 main.c
emwrap --name=myWasmLib --minify glue.js

Browser <script>:

<script src="glue.js"></script>
<script>
  myWasmLib.default().then(function (ctx) {
    var Module = ctx.Module;
    Module.myfunction();
  });
</script>

Webpack:

import init from './glue.js'
// const init = require('./glue.js').default
init().then(({ Module }) => { Module.myfunction() })

Make sure to set node.__dirname: false or node: false in your webpack configuration.

module.exports = {
  node: {
    __dirname: false,
    __filename: false
  }
  // or
  // node: false
}

ES Module

emcc -o glue.js -O3 main.c
emwrap --module=esm --minify glue.js

<script type="module">
  import init from './glue.js'
  init().then(({ Module }) => { Module.myfunction() })
</script>

Webpack is ok as well.

Override Emscripten Module options

Pass options to the default exported init function:

init({
  locateFile (path, dir) {
    if (/\.worker\.m?js$/.test(path)) {
      return 'your/custom/worker/js/path'
    } else {
      return 'your/custom/wasm/path'
    }
  },
  mainScriptUrlOrBlob: 'import/main/js/path/from/worker'
}).then(({ Module }) => {
  // ...
})

CMake

npm install -D @tybys/emwrap

add_custom_command(TARGET yourtarget POST_BUILD
  COMMAND npx emwrap "--name=umdname" "$<TARGET_FILE:yourtarget>"
  # COMMAND node "./other-script.js"
)