Mqx•2w ago

FFI callback with multiple parameters

Hey could someone please help me with this interface definition:

MODULE_API auto getDevices(
  void (*callback_fn)(
      const char *name,
      const char *path,
      const char *manufacturer,
      const char *serial_number
  ),
  ErrorCallbackT error_callback = nullptr
) -> int;
const getDevices : Deno.ForeignFunction = {
  parameters: [
    'function',
    'function'
  ],
  result: 'i32',
  nonblocking: true
}

MODULE_API auto getDevices(
  void (*callback_fn)(
      const char *name,
      const char *path,
      const char *manufacturer,
      const char *serial_number
  ),
  ErrorCallbackT error_callback = nullptr
) -> int;
const getDevices : Deno.ForeignFunction = {
  parameters: [
    'function',
    'function'
  ],
  result: 'i32',
  nonblocking: true
}

const {symbols} = Deno.dlopen('', {
  getDevices
})

await symbols.getDevices(
  (
    name,
    path,
    manufacturer,
    serial_number
  ) => {
    devices.push({
      name,
      path,
      manufacturer,
      serial_number
    });
  },
  (error) => {console.log(error);}
)

console.log(devices);

const {symbols} = Deno.dlopen('', {
  getDevices
})

await symbols.getDevices(
  (
    name,
    path,
    manufacturer,
    serial_number
  ) => {
    devices.push({
      name,
      path,
      manufacturer,
      serial_number
    });
  },
  (error) => {console.log(error);}
)

console.log(devices);

I would like to know on how to properly define my FFI interface for that kind of C++ function. I want to understand how this works correctly, because I think my current approach is completely wrong 😅 I want to transmit kind of an „object“ from C++ to TypeScript. And I read somewhere that this is the preferred method, using a callback function. Thanks 😊

9 Replies

AapoAlas•2w ago

Right, you'll need to use the Deno.UnsafeCallback API to create the callbacks

MqxOP•2w ago

👍🏻 will try. Thanks

AapoAlas•2w ago

Did you succeed? 🙂

MqxOP•2w ago

I think so, yes. I currently don’t have a dll on my hand to test it 😅 but I think this should work: https://github.com/Serial-IO/serial/blob/main/src/ffi/get_devices.ts it still needs to refined, cleared up und refactored but I think this should work

GitHub

serial/src/ffi/get_devices.ts at main · Serial-IO/serial

Core library for the serial communication. Contribute to Serial-IO/serial development by creating an account on GitHub.

MqxOP•2w ago

@AapoAlas do you know if this works? https://discord.com/channels/684898665143206084/1438820103230849024

AapoAlas•2w ago

No idea unfortunately. I haven't really played around with JSR. You might be able to test with eg. a raw GitHub URL without publishing to JSR though.

MqxOP•2w ago

Okay. Problem is Deno.dlopen() supports a local path as a string or an URL object. Question is if the URL object needs to be an actual URL like https:// or if it also supports file:// URLs And if Deno is able to resolve these When installed as a JSR package

AapoAlas•2w ago

No idea.

MqxOP•2w ago

I will test that

FFI callback with multiple parameters

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