@emnapi/wasi-threads

This package makes wasi-threads proposal based WASI modules work in Node.js and browser.

Quick Start

index.html

1<script src="./node_modules/@tybys/wasm-util/dist/wasm-util.js"></script>
2<script src="./node_modules/@emnapi/wasi-threads/dist/wasi-threads.js"></script>
3<script src="./index.js"></script>

If your application will block browser main thread (for example pthread_join), please run it in worker instead.

1<script>
2  // pthread_join (Atomics.wait) cannot be called in browser main thread
3  new Worker('./index.js')
4</script>

index.js

1const ENVIRONMENT_IS_NODE =
2  typeof process === 'object' && process !== null &&
3  typeof process.versions === 'object' && process.versions !== null &&
4  typeof process.versions.node === 'string';
5
6(function (main) {
7  if (ENVIRONMENT_IS_NODE) {
8    main(require)
9  } else {
10    if (typeof importScripts === 'function') {
11      importScripts('./node_modules/@tybys/wasm-util/dist/wasm-util.js')
12      importScripts('./node_modules/@emnapi/wasi-threads/dist/wasi-threads.js')
13    }
14    const nodeWasi = { WASI: globalThis.wasmUtil.WASI }
15    const nodeWorkerThreads = {
16      Worker: globalThis.Worker
17    }
18    const _require = function (request) {
19      if (request === 'node:wasi' || request === 'wasi') return nodeWasi
20      if (request === 'node:worker_threads' || request === 'worker_threads') return nodeWorkerThreads
21      if (request === '@emnapi/wasi-threads') return globalThis.wasiThreads
22      throw new Error('Can not find module: ' + request)
23    }
24    main(_require)
25  }
26})(async function (require) {
27  const { WASI } = require('wasi')
28  const { Worker } = require('worker_threads')
29  const { WASIThreads } = require('@emnapi/wasi-threads')
30
31  const wasi = new WASI({
32    version: 'preview1'
33  })
34  const wasiThreads = new WASIThreads({
35    wasi,
36
37    /**
38     * avoid Atomics.wait() deadlock during thread creation in browser
39     * see https://emscripten.org/docs/tools_reference/settings_reference.html#pthread-pool-size
40     */
41    reuseWorker: ENVIRONMENT_IS_NODE
42      ? false
43      : {
44          size: 4 /** greater than actual needs (2) */,
45          strict: true
46        },
47
48    /**
49     * Synchronous thread creation
50     * pthread_create will not return until thread worker actually starts
51     */
52    waitThreadStart: typeof window === 'undefined' ? 1000 : false,
53
54    onCreateWorker: () => {
55      return new Worker('./worker.js', {
56        execArgv: ['--experimental-wasi-unstable-preview1']
57      })
58    }
59  })
60  const memory = new WebAssembly.Memory({
61    initial: 16777216 / 65536,
62    maximum: 2147483648 / 65536,
63    shared: true
64  })
65  let input
66  const file = 'path/to/your/wasi-module.wasm'
67  try {
68    input = require('fs').readFileSync(require('path').join(__dirname, file))
69  } catch (err) {
70    const response = await fetch(file)
71    input = await response.arrayBuffer()
72  }
73  let { module, instance } = await WebAssembly.instantiate(input, {
74    env: { memory },
75    wasi_snapshot_preview1: wasi.wasiImport,
76    ...wasiThreads.getImportObject()
77  })
78
79  wasiThreads.setup(instance, module, memory)
80  await wasiThreads.preloadWorkers()
81
82  if (typeof instance.exports._start === 'function') {
83    return wasi.start(instance)
84  } else {
85    wasi.initialize(instance)
86    // instance.exports.exported_wasm_function()
87  }
88})

worker.js

1(function (main) {
2  const ENVIRONMENT_IS_NODE =
3    typeof process === 'object' && process !== null &&
4    typeof process.versions === 'object' && process.versions !== null &&
5    typeof process.versions.node === 'string'
6
7  if (ENVIRONMENT_IS_NODE) {
8    const _require = function (request) {
9      return require(request)
10    }
11
12    const _init = function () {
13      const nodeWorkerThreads = require('worker_threads')
14      const parentPort = nodeWorkerThreads.parentPort
15
16      parentPort.on('message', (data) => {
17        globalThis.onmessage({ data })
18      })
19
20      Object.assign(globalThis, {
21        self: globalThis,
22        require,
23        Worker: nodeWorkerThreads.Worker,
24        importScripts: function (f) {
25          (0, eval)(require('fs').readFileSync(f, 'utf8') + '//# sourceURL=' + f)
26        },
27        postMessage: function (msg) {
28          parentPort.postMessage(msg)
29        }
30      })
31    }
32
33    main(_require, _init)
34  } else {
35    importScripts('./node_modules/@tybys/wasm-util/dist/wasm-util.js')
36    importScripts('./node_modules/@emnapi/wasi-threads/dist/wasi-threads.js')
37
38    const nodeWasi = { WASI: globalThis.wasmUtil.WASI }
39    const _require = function (request) {
40      if (request === '@emnapi/wasi-threads') return globalThis.wasiThreads
41      if (request === 'node:wasi' || request === 'wasi') return nodeWasi
42      throw new Error('Can not find module: ' + request)
43    }
44    const _init = function () {}
45    main(_require, _init)
46  }
47})(function main (require, init) {
48  init()
49
50  const { WASI } = require('wasi')
51  const { ThreadMessageHandler, WASIThreads } = require('@emnapi/wasi-threads')
52
53  const handler = new ThreadMessageHandler({
54    async onLoad ({ wasmModule, wasmMemory }) {
55      const wasi = new WASI({
56        version: 'preview1'
57      })
58
59      const wasiThreads = new WASIThreads({
60        wasi,
61        childThread: true
62      })
63
64      const originalInstance = await WebAssembly.instantiate(wasmModule, {
65        env: {
66          memory: wasmMemory,
67        },
68        wasi_snapshot_preview1: wasi.wasiImport,
69        ...wasiThreads.getImportObject()
70      })
71
72      // must call `initialize` instead of `start` in child thread
73      const instance = wasiThreads.initialize(originalInstance, wasmModule, wasmMemory)
74
75      return { module: wasmModule, instance }
76    }
77  })
78
79  globalThis.onmessage = function (e) {
80    handler.handle(e)
81    // handle other messages
82  }
83})