@rollup/plugin-wasm
v6.2.2
Published
Import WebAssembly code with Rollup
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@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
exclude
Type: String
| Array[...String]
Default: null
A picomatch pattern, or array of patterns, which specifies the files in the build the plugin should ignore. By default no files are ignored.
include
Type: String
| Array[...String]
Default: null
A picomatch pattern, or array of patterns, which specifies the files in the build the plugin should operate on. By default all wasm files are targeted.
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.
fileName
Type: String
Default: '[hash][extname]'
This option can be used to rename the emitted Wasm files. It accepts the following string replacements:
[hash]
- The hash value of the file's contents[name]
- The name of the imported file (without its file extension)[extname]
- The extension of the imported file (including the leading.
)
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 requiresfetch
Usage
This plugin looks for import
statements where the file specifier ends with .wasm
, such as:
import wasm from './example.wasm';
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.
When bundled, wasm
is a function you can use to instantiate the functionality inside of the WebAssembly module. This function returns a promise, so you can instantiate the module like this:
import wasm from './example.wasm';
wasm().then(({ instance }) => {
// use instance
});
// or use top-level await
const { instance } = await wasm();
The promise returns an object with an instance
property that is a WebAssembly.Module
object that you can use to interact with the WebAssembly module.
For 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().then(({ instance }) => {
console.log(instance.exports.main());
});
Passing Imports and Memory
If you'd like to pass any imports or memory into your WebAssembly module, you can do so by passing those as arguments to the WebAssembly loader function, like this:
import sample from './sample.wasm';
const memory = new WebAssembly.Memory({ initial: 10, maximum: 100 });
const options = {
js: {
mem: memory
},
imports: {
log: (arg) => console.log(arg)
}
};
sample(options).then(({ instance }) => {
console.log(instance.exports.main());
});
Because this example passes in imports
, the instance
becomes an instance of WebAssembly.Instance
and gives the WebAssembly code access to the imports and memory from JavaScript.
__Note: Just passing in memory will result in a WebAssembly.Module
as instance
; it's only imports
that triggers the creation of WebAssembly.Instance
.
Using with wasm-bindgen and wasm-pack
If you are writing Rust code and using wasm-bindgen
or wasm-pack
, you'll need to use a different process for instantiating your WebAssembly modules. Because WebAssembly files generated by these tools require specific imports, you cannot provide these yourself.
The best setting to use with wasm-bindgen
or wasm-pack
is --target web
. This will generate your WebAssembly files (such as sample_bg.wasm
) with a JavaScript wrapper (such as sample.js
). The JavaScript wrapper contains all of the instantiation code you'll need.
You'll need to import both the JavaScript file and the WebAssembly file into your project. Then, run the WebAssembly loading function and pass that into the init()
function from the JavaScript file. Here's an example:
import init, { main } from '../build/sample.js';
import sample from '../build/sample_bg.wasm';
sample()
.then({ instance } => init(instance))
.then(() => main());
// or using top-level await
await init(await sample());
main();
Unlike with the emscripten
example, you'll need to import the methods you want to use directly from the JavaScript file rather than accessing them on the WebAssembly.Instance
.
Synchronous Modules
JavaScript runtimes allow small modules (< 4KB) to be compiled synchronously. If you'd like to specify some files to be compiled synchronously, you can do so in your rollup.config.js
file.
import { wasm } from '@rollup/plugin-wasm';
export default {
input: 'src/index.js',
output: {
dir: 'output',
format: 'cjs'
},
plugins: [
wasm({
sync: ['web/sample.wasm', 'web/foobar.wasm']
});
]
};
Synchronous modules return a synchronous loader function that returns either a WebAssembly.Module
or WebAssembly.Instance
directly (not a promise). So you can use the module directly, like this:
import sample from './sample.wasm';
const instance = sample({ ...imports });
console.log(instance.exports.main());