Tiny WASI - A tiny WASI runtime written in typescript

This runtime implements the bare minimum set of functions to get most C/C++ libraries that have been compiled with the "reactor" exec model running.

The only thing it allows is writing to stdout/stderr, getting the current time and getting random numbers, which should really be enough for everyone.

Example

import { TinyWASI } from "tinywasi";

let tinywasi = new TinyWASI();

let imports = {
	<your_own_imports>,
	...tinywasi.imports
};

const { module, instance } = await WebAssembly.instantiate( <wasm_source>, imports );

tinywasi.initialize( instance );

API

new TinyWASI( trace?: boolean )

Instantiates a new TinyWASI runtime.

Parameters

• trace: boolean, optional. Wether or not to print all system calls to the console for debugging.

initialize( instance: WebAssembly.Instance )

Initializes the runtime and WASM instance. Call this before making any other calls.

Parameters

• instance: WebAssembly instance to connect to and initialize.

imports: array

Array containing the functions to be imported by the WebAssembly module.
Pass this directly to WebAssembly.instantiate or add it to your own imports.

Implemented system calls

Currently TinyWASI implements the following system calls:

fd_fdstat_get

Implemented for the proper function of stat and isatty which are needed for printing to stdout/stderr to work correctly.

fd_write

Implemented for writing to stdout and stderr. Writing to any other file descriptor returns ERRNO_BADF.

All writes to stdout (fd 1) are logged to the console using console.log.
All writes to stderr (fd 2) are logged to the console using console.error.

clock_res_get and clock_time_get

Implemented to make functions like time() work. Right now only the realtime clock (id 0) is supported.

random_get

Implemented to make C++ std::random_device work.

Unimplemented system calls

All other system calls are unimplemented and return ERRNO_NOSYS while printing an error message to the console.

Dependencies

None.

Dev-Dependencies

• typescript - for compiling the typescript source files to javascript
• @types/node - typescript definitions for node's API

Optionally:

• prettier - for code formatting using the included .prettierrc