# [`oro:extension`](/runtime/docs/javascript/extension/)

[`oro:extension`](/runtime/docs/javascript/extension/) loads app-bundled native extensions and Wasm extensions, then exposes their registered runtime state to
JavaScript.

Use it when ordinary JavaScript modules are not the right boundary: platform-specific code, a C/C++ library that already
exists, a small Wasm module, or a runtime route that needs to live beside native resources.

## Related guides

- [Native extensions](/runtime/docs/guides/native-extensions/)

Start with the guide when you need to write the C/C++ or Wasm extension itself.

## Authoring contract

At a high level:

- extension names are filesystem-safe identifiers such as `image_tools` or `simple-ipc-ping`,
- C/C++ extensions include `oro/extension.h` and export `__oapi_extension_init` through
  `ORO_RUNTIME_REGISTER_EXTENSION`,
- Wasm extensions use the same registration contract with `target = "wasm32"`,
- extension code usually maps one or more IPC routes with `oapi_ipc_router_map`,
- app code loads the extension with [`oro:extension`](/runtime/docs/javascript/extension/) and talks to those routes with [`oro:ipc`](/runtime/docs/javascript/ipc/),
- production apps should constrain load locations with `extensions.allowed_roots`.

## Example

```js
import extension from 'oro:extension'
import ipc from 'oro:ipc'

const imageTools = await extension.load('image_tools', {
  allow: ['ipc'],
})

const resized = await ipc.request('image_tools.resize', {
  path: 'input/avatar.png',
  width: 256,
  height: 256,
})

console.log(imageTools.type)
console.log(resized.data)

await imageTools.unload()
```

`allow` is the extension capability policy. If the native initializer or a route handler calls an API that is not
allowed, that call fails instead of silently expanding the extension's authority.

## API reference

<!-- GENERATED: ORO_API_REFERENCE_START -->

### Module specifiers

```text
oro:extension
```

### TypeScript declarations

These declarations are generated from the runtime's published TypeScript surface.

#### [`oro:extension`](/runtime/docs/javascript/extension/)

```ts
declare module "oro:extension" {
    /**
     * Load an extension by name.
     * @template {Record<string, any> T}
     * @param {string} name
     * @param {ExtensionLoadOptions} [options]
     * @return {Promise<Extension<T>>}
     */
    export function load<T extends Record<string, any>>(name: string, options?: ExtensionLoadOptions): Promise<Extension<T>>;
    /**
     * Provides current stats about the loaded extensions.
     * @return {Promise<ExtensionStats>}
     */
    export function stats(): Promise<ExtensionStats>;
    /**
     * @typedef {{
     *   allow: string[] | string,
     *   imports?: object,
     *   type?: 'shared' | 'wasm32',
     *   path?: string,
     *   stats?: object,
     *   instance?: WebAssembly.Instance,
     *   adapter?: WebAssemblyExtensionAdapter
     * }} ExtensionLoadOptions
     */
    /**
     * @typedef {{ abi: number, version: string, description: string }} ExtensionInfo
     */
    /**
     * @typedef {{ abi: number, loaded: number }} ExtensionStats
     */
    /**
     * A interface for a native extension.
     * @template {Record<string, any> T}
     */
    export class Extension<T extends Record<string, any>> extends EventTarget {
        /**
         * Load an extension by name.
         * @template {Record<string, any> T}
         * @param {string} name
         * @param {ExtensionLoadOptions} [options]
         * @return {Promise<Extension<T>>}
         */
        static load<T_1 extends Record<string, any>>(name: string, options?: ExtensionLoadOptions): Promise<Extension<T_1>>;
        /**
         * Query type of extension by name.
         * @param {string} name
         * @return {Promise<'shared'|'wasm32'|'unknown'|null>}
         */
        static type(name: string): Promise<"shared" | "wasm32" | "unknown" | null>;
        /**
         * Provides current stats about the loaded extensions or one by name.
         * @param {?string} name
         * @return {Promise<ExtensionStats|null>}
         */
        static stats(name: string | null): Promise<ExtensionStats | null>;
        /**
         * `Extension` class constructor.
         * @param {string} name
         * @param {ExtensionInfo} info
         * @param {ExtensionLoadOptions} [options]
         */
        constructor(name: string, info: ExtensionInfo, options?: ExtensionLoadOptions);
        /**
         * The name of the extension
         * @type {string?}
         */
        name: string | null;
        /**
         * The version of the extension
         * @type {string?}
         */
        version: string | null;
        /**
         * The description of the extension
         * @type {string?}
         */
        description: string | null;
        /**
         * The abi of the extension
         * @type {number}
         */
        abi: number;
        /**
         * @type {object}
         */
        options: object;
        /**
         * @type {T}
         */
        binding: T;
        /**
         * Not `null` if extension is of type 'wasm32'
         * @type {?WebAssemblyExtensionAdapter}
         */
        adapter: WebAssemblyExtensionAdapter | null;
        /**
         * `true` if the extension was loaded, otherwise `false`
         * @type {boolean}
         */
        get loaded(): boolean;
        /**
         * The extension type: 'shared' or  'wasm32'
         * @type {'shared'|'wasm32'}
         */
        get type(): "shared" | "wasm32";
        /**
         * Unloads the loaded extension.
         * @throws Error
         */
        unload(): Promise<boolean>;
        instance: any;
        [$type]: "shared" | "wasm32";
        [$loaded]: boolean;
    }
    namespace _default {
        export { load };
        export { stats };
    }
    export default _default;
    export type Pointer = number;
    export type ExtensionLoadOptions = {
        allow: string[] | string;
        imports?: object;
        type?: "shared" | "wasm32";
        path?: string;
        stats?: object;
        instance?: WebAssembly.Instance;
        adapter?: WebAssemblyExtensionAdapter;
    };
    export type ExtensionInfo = {
        abi: number;
        version: string;
        description: string;
    };
    export type ExtensionStats = {
        abi: number;
        loaded: number;
    };
    /**
     * An adapter for reading and writing various values from a WebAssembly instance's
     * memory buffer.
     * @ignore
     */
    class WebAssemblyExtensionAdapter {
        constructor({ instance, module, table, memory, policies }: {
            instance: any;
            module: any;
            table: any;
            memory: any;
            policies: any;
        });
        view: any;
        heap: any;
        table: any;
        stack: any;
        buffer: any;
        module: any;
        memory: any;
        context: any;
        policies: any[];
        externalReferences: Map<any, any>;
        instance: any;
        exitStatus: any;
        textDecoder: TextDecoder;
        textEncoder: TextEncoder;
        errorMessagePointers: {};
        indirectFunctionTable: any;
        get globalBaseOffset(): any;
        destroy(): void;
        init(): boolean;
        getExtensionExport(...names: any[]): any;
        get(pointer: any, size?: number): any;
        set(pointer: any, value: any): void;
        createExternalReferenceValue(value: any): any;
        getExternalReferenceValue(pointer: any): any;
        setExternalReferenceValue(pointer: any, value: any): Map<any, any>;
        removeExternalReferenceValue(pointer: any): void;
        getExternalReferencePointer(value: any): any;
        getFloat32(pointer: any): any;
        setFloat32(pointer: any, value: any): boolean;
        getFloat64(pointer: any): any;
        setFloat64(pointer: any, value: any): boolean;
        getInt8(pointer: any): any;
        setInt8(pointer: any, value: any): boolean;
        getInt16(pointer: any): any;
        setInt16(pointer: any, value: any): boolean;
        getInt32(pointer: any): any;
        setInt32(pointer: any, value: any): boolean;
        getUint8(pointer: any): any;
        setUint8(pointer: any, value: any): boolean;
        getUint16(pointer: any): any;
        setUint16(pointer: any, value: any): boolean;
        getUint32(pointer: any): any;
        setUint32(pointer: any, value: any): boolean;
        getString(pointer: any, buffer: any, size: any): string;
        setString(pointer: any, string: any, buffer?: any): boolean;
    }
    const $type: unique symbol;
    /**
     * @typedef {number} Pointer
     */
    const $loaded: unique symbol;
}
```

<!-- GENERATED: ORO_API_REFERENCE_END -->
## See also

- [JavaScript APIs overview](/runtime/docs/javascript/overview/)
- [All module specifiers](/runtime/docs/javascript/all-modules/)