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Filename : wasi.d.ts
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/**
 * **The `node:wasi` module does not currently provide the**
 * **comprehensive file system security properties provided by some WASI runtimes.**
 * **Full support for secure file system sandboxing may or may not be implemented in**
 * **future. In the mean time, do not rely on it to run untrusted code.**
 *
 * The WASI API provides an implementation of the [WebAssembly System Interface](https://wasi.dev/) specification. WASI gives WebAssembly applications access to the underlying
 * operating system via a collection of POSIX-like functions.
 *
 * ```js
 * import { readFile } from 'node:fs/promises';
 * import { WASI } from 'node:wasi';
 * import { argv, env } from 'node:process';
 *
 * const wasi = new WASI({
 *   version: 'preview1',
 *   args: argv,
 *   env,
 *   preopens: {
 *     '/local': '/some/real/path/that/wasm/can/access',
 *   },
 * });
 *
 * const wasm = await WebAssembly.compile(
 *   await readFile(new URL('./demo.wasm', import.meta.url)),
 * );
 * const instance = await WebAssembly.instantiate(wasm, wasi.getImportObject());
 *
 * wasi.start(instance);
 * ```
 *
 * To run the above example, create a new WebAssembly text format file named `demo.wat`:
 *
 * ```text
 * (module
 *     ;; Import the required fd_write WASI function which will write the given io vectors to stdout
 *     ;; The function signature for fd_write is:
 *     ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written
 *     (import "wasi_snapshot_preview1" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32)))
 *
 *     (memory 1)
 *     (export "memory" (memory 0))
 *
 *     ;; Write 'hello world\n' to memory at an offset of 8 bytes
 *     ;; Note the trailing newline which is required for the text to appear
 *     (data (i32.const 8) "hello world\n")
 *
 *     (func $main (export "_start")
 *         ;; Creating a new io vector within linear memory
 *         (i32.store (i32.const 0) (i32.const 8))  ;; iov.iov_base - This is a pointer to the start of the 'hello world\n' string
 *         (i32.store (i32.const 4) (i32.const 12))  ;; iov.iov_len - The length of the 'hello world\n' string
 *
 *         (call $fd_write
 *             (i32.const 1) ;; file_descriptor - 1 for stdout
 *             (i32.const 0) ;; *iovs - The pointer to the iov array, which is stored at memory location 0
 *             (i32.const 1) ;; iovs_len - We're printing 1 string stored in an iov - so one.
 *             (i32.const 20) ;; nwritten - A place in memory to store the number of bytes written
 *         )
 *         drop ;; Discard the number of bytes written from the top of the stack
 *     )
 * )
 * ```
 *
 * Use [wabt](https://github.com/WebAssembly/wabt) to compile `.wat` to `.wasm`
 *
 * ```bash
 * wat2wasm demo.wat
 * ```
 * @experimental
 * @see [source](https://github.com/nodejs/node/blob/v24.x/lib/wasi.js)
 */
declare module "wasi" {
    interface WASIOptions {
        /**
         * An array of strings that the WebAssembly application will
         * see as command line arguments. The first argument is the virtual path to the
         * WASI command itself.
         * @default []
         */
        args?: string[] | undefined;
        /**
         * An object similar to `process.env` that the WebAssembly
         * application will see as its environment.
         * @default {}
         */
        env?: object | undefined;
        /**
         * This object represents the WebAssembly application's
         * sandbox directory structure. The string keys of `preopens` are treated as
         * directories within the sandbox. The corresponding values in `preopens` are
         * the real paths to those directories on the host machine.
         */
        preopens?: NodeJS.Dict<string> | undefined;
        /**
         * By default, when WASI applications call `__wasi_proc_exit()`
         * `wasi.start()` will return with the exit code specified rather than terminatng the process.
         * Setting this option to `false` will cause the Node.js process to exit with
         * the specified exit code instead.
         * @default true
         */
        returnOnExit?: boolean | undefined;
        /**
         * The file descriptor used as standard input in the WebAssembly application.
         * @default 0
         */
        stdin?: number | undefined;
        /**
         * The file descriptor used as standard output in the WebAssembly application.
         * @default 1
         */
        stdout?: number | undefined;
        /**
         * The file descriptor used as standard error in the WebAssembly application.
         * @default 2
         */
        stderr?: number | undefined;
        /**
         * The version of WASI requested.
         * Currently the only supported versions are `'unstable'` and `'preview1'`. This option is mandatory.
         * @since v19.8.0
         */
        version: "unstable" | "preview1";
    }
    /**
     * The `WASI` class provides the WASI system call API and additional convenience
     * methods for working with WASI-based applications. Each `WASI` instance
     * represents a distinct environment.
     * @since v13.3.0, v12.16.0
     */
    class WASI {
        constructor(options?: WASIOptions);
        /**
         * Return an import object that can be passed to `WebAssembly.instantiate()` if no other WASM imports are needed beyond those provided by WASI.
         *
         * If version `unstable` was passed into the constructor it will return:
         *
         * ```js
         * { wasi_unstable: wasi.wasiImport }
         * ```
         *
         * If version `preview1` was passed into the constructor or no version was specified it will return:
         *
         * ```js
         * { wasi_snapshot_preview1: wasi.wasiImport }
         * ```
         * @since v19.8.0
         */
        getImportObject(): object;
        /**
         * Attempt to begin execution of `instance` as a WASI command by invoking its `_start()` export. If `instance` does not contain a `_start()` export, or if `instance` contains an `_initialize()`
         * export, then an exception is thrown.
         *
         * `start()` requires that `instance` exports a [`WebAssembly.Memory`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory) named `memory`. If
         * `instance` does not have a `memory` export an exception is thrown.
         *
         * If `start()` is called more than once, an exception is thrown.
         * @since v13.3.0, v12.16.0
         */
        start(instance: object): number; // TODO: avoid DOM dependency until WASM moved to own lib.
        /**
         * Attempt to initialize `instance` as a WASI reactor by invoking its `_initialize()` export, if it is present. If `instance` contains a `_start()` export, then an exception is thrown.
         *
         * `initialize()` requires that `instance` exports a [`WebAssembly.Memory`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory) named `memory`.
         * If `instance` does not have a `memory` export an exception is thrown.
         *
         * If `initialize()` is called more than once, an exception is thrown.
         * @since v14.6.0, v12.19.0
         */
        initialize(instance: object): void; // TODO: avoid DOM dependency until WASM moved to own lib.
        /**
         * `wasiImport` is an object that implements the WASI system call API. This object
         * should be passed as the `wasi_snapshot_preview1` import during the instantiation
         * of a [`WebAssembly.Instance`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Instance).
         * @since v13.3.0, v12.16.0
         */
        readonly wasiImport: NodeJS.Dict<any>; // TODO: Narrow to DOM types
    }
}
declare module "node:wasi" {
    export * from "wasi";
}