emnapi

This is 2.x branch, go stable 1.x branch here

Node-API implementation for Emscripten, wasi-sdk and clang with wasm support.

This project aims to

Help users port their or existing Node-API native addons to wasm with code change as less as possible.
Make runtime behavior matches native Node.js as much as possible.

This project also powers the WebAssembly feature for napi-rs, and enables many Node.js native addons to run on StackBlitz's WebContainer.

Node-API changes will be synchronized into this repo.

See documentation for more details:

中文文档：

Full API List

How to build Node-API official examples

If you want to deep dive into WebAssembly, highly recommend you to visit learn-wasm.dev.

Prerequests

You will need to install:

Node.js >= v22.12.0
npm >= v8

Tool chain choices:

Emscripten >= v4.1.7 with EMSDK environment variable set
wasi-sdk >= v26 with WASI_SDK_PATH environment variable set

Build system choices:

CMake >= v3.13
node-gyp >= v10.2.0
make / ninja

Optional:

node-addon-api >= 6.1.0

There are several choices to get make for Windows user

Install mingw-w64, then use mingw32-make
Download MSVC prebuilt binary of GNU make, add to %Path% then rename it to mingw32-make
Install Visual Studio 2022 C++ desktop workload, use nmake in Visual Studio Developer Command Prompt
Install Visual C++ Build Tools, use nmake in Visual Studio Developer Command Prompt

Build from source

git clone https://github.com/toyobayashi/emnapi.git
cd ./emnapi
npm install -g node-gyp
npm install
npm run build             # output ./packages/*/dist
node ./script/release.js  # output ./out

# test for emscripten
npm run rebuild -w packages/test
npm run test -w packages/test

# test for wasi-sdk
npm run rebuild:wt -w packages/test
npm run test:wt -w packages/test

See CONTRIBUTING for more details.

Quick Start

See full example

NPM Install

npm install -D emnapi
npm install @emnapi/runtime

# additionally, for wasi-sdk, install @emnapi/core
npm install @emnapi/core

# if you need node-addon-api
npm install node-addon-api

Each package should match the same version.

Using C

Create binding.c:

#include <node_api.h>

// ...

NAPI_MODULE_INIT() {
  napi_value fn;
  napi_create_function(env, "run", NAPI_AUTO_LENGTH, run, NULL, &fn);
  napi_set_named_property(env, exports, "run", fn);
  return exports;
}

Build with Emscripten:

emcc -O3 -pthread \
    -DBUILDING_NODE_EXTENSION \
    "-DNAPI_EXTERN=__attribute__((__import_module__(\"env\")))" \
    -I./node_modules/emnapi/include/node \
    -L./node_modules/emnapi/lib/wasm32-emscripten \
    --js-library=./node_modules/emnapi/dist/library_napi.js \
    -sWASM_BIGINT=1 \
    -sALLOW_MEMORY_GROWTH=1 \
    -sALLOW_TABLE_GROWTH=1 \
    -sEXPORTED_FUNCTIONS=$(node -p "JSON.stringify(require('emnapi').requiredConfig.emscripten.settings.EXPORTED_FUNCTIONS)") \
    -sEXPORTED_RUNTIME_METHODS=$(node -p "JSON.stringify(require('emnapi').requiredConfig.emscripten.settings.EXPORTED_RUNTIME_METHODS)") \
    -sEXPORT_ES6=1 \
    -sPTHREAD_POOL_SIZE=4 \
    -o out/binding.js \
    binding.c \
    -lemnapi-mt

Build with wasi-sdk:

"$WASI_SDK_PATH/bin/clang" --target=wasm32-wasip1-threads -O3 \
    -pthread -matomics -mbulk-memory \
    -DBUILDING_NODE_EXTENSION \
    -I./node_modules/emnapi/include/node \
    -L./node_modules/emnapi/lib/wasm32-wasip1-threads \
    --sysroot="$WASI_SDK_PATH/share/wasi-sysroot" \
    -mexec-model=reactor \
    -Wl,--import-memory -Wl,--shared-memory -Wl,--export-memory \
    -Wl,--export-table -Wl,--growable-table \
    -Wl,--export=malloc,--export=free \
    -Wl,--export=napi_register_wasm_v1 \
    -Wl,--export=emnapi_create_env,--export=emnapi_delete_env \
    -Wl,--export-if-defined=node_api_module_get_api_version_v1 \
    -Wl,--export-if-defined=uv_library_shutdown \
    -Wl,--import-undefined \
    -o out/binding.wasm \
    binding.c \
    -lemnapi-mt

Use in JavaScript (Emscripten):

import init from './out/binding.js'
import { createContext } from '@emnapi/runtime'

const emnapiCtx = createContext()
const Module = await init()
const binding = Module.emnapiInit({
  context: emnapiCtx,
  asyncWorkPoolSize: 4 // the same effect to UV_THREADPOOL_SIZE, must less than PTHREAD_POOL_SIZE
})
binding.run(/* ... */)

// cleanup
Module._uv_library_shutdown()
emnapiCtx.destroy()

For non-emscripten please reference full JavaScript example

Using C++ and node-addon-api

Note: C++ wrapper can only be used to target Node.js v14.6.0+ and modern browsers those support FinalizationRegistry and WeakRef (v8 engine v8.4+)!

Create binding.cpp:

#include <napi.h>

// ...

Napi::Object Init(Napi::Env env, Napi::Object exports) {
  exports.Set("run", Napi::Function::New(env, Run));
  return exports;
}

NODE_API_MODULE(binding, Init)

Build with Emscripten:

em++ -O3 -pthread \
    -DBUILDING_NODE_EXTENSION \
    -DNAPI_DISABLE_CPP_EXCEPTIONS \
    "-DNAPI_EXTERN=__attribute__((__import_module__(\"env\")))" \
    -I./node_modules/emnapi/include/node \
    -I$(node -p "require('node-addon-api').include_dir") \
    -L./node_modules/emnapi/lib/wasm32-emscripten \
    --js-library=./node_modules/emnapi/dist/library_napi.js \
    -sWASM_BIGINT=1 \
    -sALLOW_MEMORY_GROWTH=1 \
    -sALLOW_TABLE_GROWTH=1 \
    -sEXPORTED_FUNCTIONS=$(node -p "JSON.stringify(require('emnapi').requiredConfig.emscripten.settings.EXPORTED_FUNCTIONS)") \
    -sEXPORTED_RUNTIME_METHODS=$(node -p "JSON.stringify(require('emnapi').requiredConfig.emscripten.settings.EXPORTED_RUNTIME_METHODS)") \
    -sEXPORT_ES6=1 \
    -sPTHREAD_POOL_SIZE=4 \
    -o out/binding-naa.js \
    binding.cpp \
    -lemnapi-mt

Build with wasi-sdk:

"$WASI_SDK_PATH/bin/clang++" --target=wasm32-wasip1-threads -O3 \
    -pthread -matomics -mbulk-memory -fno-exceptions \
    -DBUILDING_NODE_EXTENSION \
    -DNAPI_DISABLE_CPP_EXCEPTIONS \
    -I./node_modules/emnapi/include/node \
    -I$(node -p "require('node-addon-api').include_dir") \
    -L./node_modules/emnapi/lib/wasm32-wasip1-threads \
    --sysroot="$WASI_SDK_PATH/share/wasi-sysroot" \
    -mexec-model=reactor \
    -Wl,--import-memory -Wl,--shared-memory -Wl,--export-memory \
    -Wl,--export-table -Wl,--growable-table \
    -Wl,--export=malloc,--export=free \
    -Wl,--export=napi_register_wasm_v1 \
    -Wl,--export=emnapi_create_env,--export=emnapi_delete_env \
    -Wl,--export-if-defined=node_api_module_get_api_version_v1 \
    -Wl,--export-if-defined=uv_library_shutdown \
    -Wl,--import-undefined \
    -o out/binding-naa.wasm \
    binding.cpp \
    -lemnapi-mt

Using CMake

Create CMakeLists.txt:

cmake_minimum_required(VERSION 3.13)
project(myproject)

# optional: enable node-addon-api
# set(EMNAPI_FIND_NODE_ADDON_API ON)

add_subdirectory("node_modules/emnapi")

add_executable(binding binding.c)

target_link_libraries(binding PRIVATE emnapi-mt)

if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten")
  # ...
elseif((CMAKE_SYSTEM_NAME STREQUAL "WASI") AND (CMAKE_C_COMPILER_TARGET STREQUAL "wasm32-wasi-threads"))
  # ...
endif()

Build with Emscripten:

mkdir build && cd build
emcmake cmake .. -DCMAKE_BUILD_TYPE=Release
cmake --build .

Build with wasi-sdk:

mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_TOOLCHAIN_FILE="$WASI_SDK_PATH/share/cmake/wasi-sdk-pthread.cmake"
cmake --build .

Using node-gyp

Require node-gyp >= 10.2.0

See emnapi-node-gyp-test for examples.

Variables

Arch: node-gyp configure --arch=<wasm32 | wasm64>

// node-gyp configure -- -Dvariable_name=value

declare var OS: 'emscripten' | 'wasi' | 'unknown' | 'wasm' | ''

/**
 * Enable async work and threadsafe-functions
 * @default 0
 */
declare var wasm_threads: 0 | 1

/** @default 1048576 */
declare var stack_size: number

/** @default 16777216 */
declare var initial_memory: number

/** @default 2147483648 */
declare var max_memory: number

/** @default path.join(path.dirname(commonGypiPath,'./dist/library_napi.js')) */
declare var emnapi_js_library: string

/** @default 0 */
declare var emnapi_manual_linking: 0 | 1

Create binding.gyp

{
  "targets": [
    {
      "target_name": "hello",
      "sources": [
        "hello.c"
      ],
      "conditions": [
        ["OS == 'emscripten'", {
          "product_extension": "js", # required

          "cflags": [],
          "cflags_c": [],
          "cflags_cc": [],
          "ldflags": []
        }],
        ["OS == 'wasi'", {
          # ...
        }],
        ["OS in ' wasm unknown'", {
          # ...
        }]
      ]
    }
  ]
}

Add the following environment variables.

# Linux or macOS
export GYP_CROSSCOMPILE=1

# emscripten
export AR_target="$EMSDK/upstream/emscripten/emar"
export CC_target="$EMSDK/upstream/emscripten/emcc"
export CXX_target="$EMSDK/upstream/emscripten/em++"

# wasi-sdk
export AR_target="$WASI_SDK_PATH/bin/ar"
export CC_target="$WASI_SDK_PATH/bin/clang"
export CXX_target="$WASI_SDK_PATH/bin/clang++"

@REM Windows

set GYP_CROSSCOMPILE=1

@REM emscripten
call set AR_target=%%EMSDK:\=/%%/upstream/emscripten/emar.bat
call set CC_target=%%EMSDK:\=/%%/upstream/emscripten/emcc.bat
call set CXX_target=%%EMSDK:\=/%%/upstream/emscripten/em++.bat

@REM wasi-sdk
call set AR_target=%%WASI_SDK_PATH:\=/%%/bin/ar.exe
call set CC_target=%%WASI_SDK_PATH:\=/%%/bin/clang.exe
call set CXX_target=%%WASI_SDK_PATH:\=/%%/bin/clang++.exe

Build

# Linux or macOS

# emscripten
emmake node-gyp rebuild \
  --arch=wasm32 \
  --nodedir=./node_modules/emnapi \
  -- -f make-emscripten # -Dwasm_threads=1

# wasi
node-gyp rebuild \
  --arch=wasm32 \
  --nodedir=./node_modules/emnapi \
  -- -f make-wasi # -Dwasm_threads=1

# bare wasm32
node-gyp rebuild \
  --arch=wasm32 \
  --nodedir=./node_modules/emnapi \
  -- -f make-wasm # -Dwasm_threads=1

@REM Use make generator on Windows
@REM Run the bat file in POSIX-like environment (e.g. Cygwin)

@REM emscripten
call npx.cmd node-gyp configure --arch=wasm32 --nodedir=./node_modules/emnapi -- -f make-emscripten
call emmake.bat make -C %~dp0build

@REM wasi
call npx.cmd node-gyp configure --arch=wasm32 --nodedir=./node_modules/emnapi -- -f make-wasi
make -C %~dp0build

@REM bare wasm32
call npx.cmd node-gyp configure --arch=wasm32 --nodedir=./node_modules/emnapi -- -f make-wasm
make -C %~dp0build

Using Rust

See napi-rs

Reference for instantiateNapiModule input parameters

// emnapi main thread (could be in a Worker)
instantiateNapiModule(input, {
  context: getDefaultContext(),
  asyncWorkPoolSize: 4, // the same effect to UV_THREADPOOL_SIZE, must less than `reuseWorker.size`
  wasi: new WASI(/* ... */),

  /**
   * Setting this to `true` or a delay (ms) makes
   * pthread_create() do not return until worker actually start.
   * It will throw error if emnapi runs in browser main thread
   * since browser disallow blocking the main thread (Atomics.wait).
   * @defaultValue false
   */
  waitThreadStart: isNode || (isBrowser && !isBrowserMainThread),

  /**
   * Reuse the thread worker after thread exit to avoid re-creatation
   * @defaultValue false
   */
  reuseWorker: {
    /**
     * @see {@link https://emscripten.org/docs/tools_reference/settings_reference.html#pthread-pool-size | PTHREAD_POOL_SIZE}
     */
    size: 0,

    /**
     * @see {@link https://emscripten.org/docs/tools_reference/settings_reference.html#pthread-pool-size-strict | PTHREAD_POOL_SIZE_STRICT}
     */
    strict: false
  },

  onCreateWorker () {
    return new Worker('./worker.js')
    // Node.js
    // const { Worker } = require('worker_threads')
    // return new Worker(join(__dirname, './worker.js'), {
    //   env: process.env,
    //   execArgv: ['--experimental-wasi-unstable-preview1']
    // })
  },
  overwriteImports (importObject) {
    importObject.env.memory = new WebAssembly.Memory({
      initial: 16777216 / 65536,
      maximum: 2147483648 / 65536,
      shared: true
    })
  }
})

Note: For browsers, all the multithreaded features relying on Web Workers (Emscripten pthread also relying on Web Workers) require cross-origin isolation to enable SharedArrayBuffer. You can make a page cross-origin isolated by serving the page with these headers:

Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin

Name		Name	Last commit message	Last commit date
Latest commit History 1,086 Commits
.github		.github
.vscode		.vscode
packages		packages
patches		patches
script		script
.gitattributes		.gitattributes
.gitignore		.gitignore
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
eslint.config.js		eslint.config.js
package.json		package.json
tsconfig.json		tsconfig.json

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emnapi

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This is 2.x branch, go stable 1.x branch here

Prerequests

Build from source

Quick Start

NPM Install

Using C

Using C++ and node-addon-api

Using CMake

Using node-gyp

Using Rust

Reference for instantiateNapiModule input parameters

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emnapi

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This is 2.x branch, go stable 1.x branch here

Prerequests

Build from source

Quick Start

NPM Install

Using C

Using C++ and node-addon-api

Using CMake

Using node-gyp

Using Rust

Reference for instantiateNapiModule input parameters

About

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