Deno•2y ago

Passing C enum to function and read in TypeScript

First of all I am not a trained software developper, so please forgive me if I am missing some basics. I am trying to build a wrapper around a dynamic library to IEC 61850 communication.

On the the exposed functions of that library is

IedConnection_connect(..., IedClientError error, ...)

IedConnection_connect(..., IedClientError error, ...)

, where

IedClientError

IedClientError

is a enum with 23 entries.

To be able to use the library I need to

create the enumeration in TypeScript and change it to a type array? to be able to pass it down
but then I also need to read the changed error again in TypeScript

I am not sure how enumerations are coded and how to decode those in TypeScript again and I was hoping one of you can help me out

BR,
Jakob

marvinh.•4/30/24, 9:55 AM

There is a good page about enums in the TS documentation https://www.typescriptlang.org/docs/handbook/enums.html

Leokuma•4/30/24, 3:17 PM

They are just numbers
You need to find the enum declaration in the header file (something like ) and see what value is assigned to each enum option. If they are not assigned anything, by default they are assigned a number starting from . So if you want to use the first enum option, you pass

JakobOP•4/30/24, 6:36 PM

How would+

JakobOP•4/30/24, 6:42 PM

This means that I could do something like this?

let error = 0;
lib.symbols.IedConnection_connect(... , error, ...);
console.log(error)

JakobOP•4/30/24, 6:43 PM

This gives me a Segmentation fault (core dumped) error. I think the enum has to be instantiated as an ArrayBuffer, but do not know how to read that buffer correctly.

Leokuma•4/30/24, 9:12 PM

That should work, without an ArrayBuffer
Are you declaring the enum as ?

Leokuma•4/30/24, 9:16 PM

ooh sorry I just reread OP

Leokuma•4/30/24, 9:17 PM

the function will change the value of the

error

error

you pass?

JakobOP•4/30/24, 9:17 PM

Yes exactly that

Leokuma•4/30/24, 9:18 PM

I'm stupid

JakobOP•4/30/24, 9:20 PM

It does work like so for me. But I am not sure if this is the propper way of doing it:

const error = new Uint8Array(1);
lib.symbols.IedConnection_connect(conn, error, host, port);

JakobOP•4/30/24, 9:20 PM

The result is then error[0]

JakobOP•4/30/24, 9:20 PM

And I declare the variable as buffer in the symbols object

Leokuma•4/30/24, 9:21 PM

That's correct

JakobOP•4/30/24, 9:22 PM

Thank you for the fast response

Leokuma•4/30/24, 9:24 PM

BTW, to make sure the function is actually writing to the buffer, I suggest you fill up the buffer with something before calling it, just to see if it goes back to zero

Leokuma•4/30/24, 9:29 PM

If it doesn't change, I think we'll have to create a pointer to a buffer or something