cowasm VS memfs

For fun, I ported much of BSDutils to WebAssembly. Code [1] and live demo [2]. It was much, much easier porting BSDutils than GNU coreutils, since the source code is often much smaller, and hence easier to read and understand with simpler dependencies.

[1] https://github.com/sagemathinc/cowasm/tree/main/core/coreuti...

For what it is worth, I also care about building this with zig. https://github.com/sagemathinc/cowasm/blob/main/packages/sql...

If it fits your needs and is working, then fine. Please remain aware of a different approach to what pyodide is doing based on perceived weaknesses in pyodide.

CoWasm supports WASI right now via this library https://www.npmjs.com/package/wasi-js, which I actually develop as part of CoWasm . One unusually thing I did, which goes beyond what emscripten does, is I implemented a quite a bit of posix functionality, often by writing extension code to nodejs and calling it from Javascript, because there's a lot of POSIX that Node.js doesn't expose. This only works on Mac and Linux and is also available standalone in this library https://www.npmjs.com/package/posix-node, which is implemented in Zig. You can get a sense of the scope of POSIX functionality that goes beyond what WASI defines here: https://github.com/sagemathinc/cowasm/tree/main/packages/ker...

One motivation for doing this is to try to get the full Python test suite to pass, including all the functionality that involves subprocesses, posix calls, etc. I've only got to about 85% at this point. It can be a ton of tedious work, but at least Zig helps impose some discipline (e.g, it doesn't let you ignore handling errors until later), and makes it easy to test compilation for all supported targets on every change (due to excellent cross compilation support).

I am using the Python ecosystem (with full support for dynamic loading of C extension modules) as an initial motivating project. Also, the Python test suite is extremely useful to root out problems. I certainly hope that this can provide a more complete alternative to Emscripten to the community eventually. That said, Emscripten is huge, and the problems involved in creating a more maintainable modular WASM build tool are subtle. For example, when implementing a custom module loader for Python-wasm last week, I discovered several bugs in the memfs and unionfs Javascript libraries (https://github.com/streamich/memfs/pulls?q=is%3Apr+author%3A... and https://github.com/streamich/unionfs/pulls?q=is%3Apr+author%...). I had to learn the code sufficiently to fix all these bugs, submit PR's, etc. Emscripten has its own analogue of memfs, which is optimized specifically for WebAssembly in the browser, where memfs is a more general widely used library (with 10M+ downloads/week).

CoWasm has no support for asyncify. Where I've run into setjmp/longjmp so far, I've been rewriting the code instead. E.g., the dash shell uses setjmp/longjmp, and I'm rewriting that to use return error codes instead (see, e.g., https://github.com/sagemathinc/dash/commit/7117e1f6496728af0...).

> how would I go about porting a simple C->WASM w/ Typescript library project to CoWasm?

That's a great question, which I'm not sure how to quickly answer, so I've created a discussion item here https://github.com/sagemathinc/cowasm/discussions/40

Looks like this whole thing was motivated by the fact that, in order to get the encrypted PDF in a Buffer like they wanted, they had to save to disk and load it back. They could have instead used an in-memory filesystem such as https://github.com/streamich/memfs and just made the existing PDF library that was almost right use that.

How do I populate the input files? The filesystem API in emscripten talks about MEMFS, is that the same as this? https://github.com/streamich/memfs