Example of C class extending JS class

[Sytten]

Hi!

Does someone have an example of a C class extending a JS class? Essentially the inverse of the Point example.

I am trying to re-create the node Buffer class in C and I want to extend the ArrayBuffer class.

Thanks

[saghul]

IIRC the Buffer class extends Uint8Array.

Anyway. I think you can get the prototype with JS_GetPrototype and then add your custom methods.

[Sytten]

Yes sorry Uint8Array.

That would work for the prototype, I probably also need something for the constructor to call the parent one.

[saghul]

Good point. I'm not sure QuickJS provider the necessary APIs to do that... @chqrlie ?

[Sytten]

I tried to use JS_GetClassProto with the class id of Uint8Array (12 at the moment), but it always returns an empty prototype for some reason. JS_GetPrototype on the globals does return something though. I was thinking of calling the prototype.constructor function if that exists? I have not tested it yet.

In reality I am writing that for the rust library rquickjs so I need to massage it a bit more but I didn't want to add complexity to the example.

[saghul]

Calling constructor on the prototype might work indeed!

[chqrlie]

@saghul Sorry, cannot comment right now, travelling 1200 km from the North pole with very little Internet coverage :)

[Sytten]

@chqrlie If you have time, still looking for guidance on it

[Sytten]

I guess no resolution on this one

[bellard]

I though that using JS_GetClassProto() and then accessing the "constructor" property solved the issue.

[Sytten]

The prototype can get you the parent prototype but calling the constructor to create a subclass is really not self evident. Same idea to make instanceof work correctly. Anyway rquickjs moved to quickjs-ng so I will check with them.