OPFS support (WASI host file system access / File Access API)

[kesavkolla]

Can we use JavaScript File APIs or OPFS to store the document and load the document from there to zeta? This would be a killer feature. In general emscripten support WasmFS which can be used for any of the supported backends.

Another great thing would be to do WASI support. Some of the modern browsers (Chrome and Edge) do support WASI. WASI does have File access API.

[stbergmann]

Thanks for your interest in these areas. For now, ZetaOffice itself sees just the in-memory file system provided by Emscripten. Any interaction with other file systems (the system one, through File System API or File System Access API; or OPFS) would need to go via surrounding JS code like in https://github.com/allotropia/zetajs/tree/main/examples/convertpdf.

However, LibreOffice internally uses a file-system/general-URL-based-resources access abstraction (UCB) that would allow to add a new URL schema and handler for a file system. That might be a way to experiment with internal support for e.g. File System Access API or OPFS.

[kolAflash]

Sounds like some interesting thoughts!

You can simply use WASI and OPFS from JavaScript and pass the files to ZetaOffice. For many scenarios like a highly integrated web-app this should be well suited.
But for more general web-office approaches it would be nice, if ZetaOffice can directly see the hosts file system via WASI and OPFS.

On the other hand, something like "host file system access" will probably maybe be supported on host platforms which don't really expose a file system to the user. Thinking about iOS.

 

I'll add a few links for the abbreviations.

• WASI: WebAssembly System Interface
  • OPFS: File System API / Origin private file system
  • WASI + File System Access API demo:
    • https://github.com/GoogleChromeLabs/wasi-fs-access
    • https://web.dev/articles/asyncify#real-world_demos
• WasmFS (are these identical?)
  • Emscripten: https://emscripten.org/docs/api_reference/Filesystem-API.html#new-file-system-wasmfs
    • maybe helpful: Mounting filesystems
      https://github.com/petersalomonsen/wasm-git/issues/3
  • wasmerio: https://github.com/wasmerio/wasmfs

[kolAflash]

@kesavkolla
Can you give a hint on how to configure Emscripten, to mount a folder from the host into it's virtual file system?

I also found NODEFS. But it's said, that it only works in NodeJS but not in Chrome.
https://emscripten.org/docs/api_reference/Filesystem-API.html#nodefs
JS seems to be: FS.mount(NODEFS, { root: '.' }, '/mnt');
(not tested)

[tran4o]

I am also interested in building a nodejs version for document conversion. I was able to hack the dist version to run in nodejs but using the virtual FS. Any hints for building a nodejs version will be appreciated

[kolAflash]

FYI:
My colleague Mohit adjusted the web-office demo, so it uses the File System Access API when being used in Chromium/Chrome.
e82327a