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PR-URL: https://github.com/nodejs/node/pull/31086 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
91 lines
3.1 KiB
Markdown
91 lines
3.1 KiB
Markdown
# WebAssembly System Interface (WASI)
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<!--introduced_in=v13.3.0-->
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> Stability: 1 - Experimental
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The WASI API provides an implementation of the [WebAssembly System Interface][]
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specification. WASI gives sandboxed WebAssembly applications access to the
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underlying operating system via a collection of POSIX-like functions.
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```js
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'use strict';
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const fs = require('fs');
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const { WASI } = require('wasi');
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const wasi = new WASI({
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args: process.argv,
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env: process.env,
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preopens: {
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'/sandbox': '/some/real/path/that/wasm/can/access'
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}
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});
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const importObject = { wasi_snapshot_preview1: wasi.wasiImport };
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(async () => {
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const wasm = await WebAssembly.compile(fs.readFileSync('./binary.wasm'));
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const instance = await WebAssembly.instantiate(wasm, importObject);
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wasi.start(instance);
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})();
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```
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The `--experimental-wasi-unstable-preview1` and `--experimental-wasm-bigint`
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CLI arguments are needed for the previous example to run.
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## Class: `WASI`
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<!-- YAML
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added: v13.3.0
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-->
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The `WASI` class provides the WASI system call API and additional convenience
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methods for working with WASI-based applications. Each `WASI` instance
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represents a distinct sandbox environment. For security purposes, each `WASI`
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instance must have its command line arguments, environment variables, and
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sandbox directory structure configured explicitly.
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### `new WASI([options])`
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<!-- YAML
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added: v13.3.0
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-->
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* `options` {Object}
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* `args` {Array} An array of strings that the WebAssembly application will
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see as command line arguments. The first argument is the virtual path to the
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WASI command itself. **Default:** `[]`.
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* `env` {Object} An object similar to `process.env` that the WebAssembly
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application will see as its environment. **Default:** `{}`.
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* `preopens` {Object} This object represents the WebAssembly application's
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sandbox directory structure. The string keys of `preopens` are treated as
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directories within the sandbox. The corresponding values in `preopens` are
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the real paths to those directories on the host machine.
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### `wasi.start(instance)`
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<!-- YAML
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added: v13.3.0
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-->
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* `instance` {WebAssembly.Instance}
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Attempt to begin execution of `instance` by invoking its `_start()` export.
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If `instance` does not contain a `_start()` export, then `start()` attempts to
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invoke the `__wasi_unstable_reactor_start()` export. If neither of those exports
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is present on `instance`, then `start()` does nothing.
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`start()` requires that `instance` exports a [`WebAssembly.Memory`][] named
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`memory`. If `instance` does not have a `memory` export an exception is thrown.
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### `wasi.wasiImport`
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<!-- YAML
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added: v13.3.0
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-->
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* {Object}
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`wasiImport` is an object that implements the WASI system call API. This object
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should be passed as the `wasi_snapshot_preview1` import during the instantiation
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of a [`WebAssembly.Instance`][].
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[`WebAssembly.Instance`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Instance
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[`WebAssembly.Memory`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory
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[WebAssembly System Interface]: https://wasi.dev/
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