Get "prompt()" input from a web worker and return it from function?

Question

I'm working with the pyodide library and i've ran into an issue, I need to add a handler for stdin, however I'm running pyodide in a web worker and I don't have access to the window or any sort of prompt.

pyodide.setStdin({ stdin: () => { 
 // code here
}})

I have tried using the postMessage() function to ask the page for input and send it back, but since I am returning this from a function I am unable to receive the input before I have to return. I have also tried using SharedArrayBuffer and Atomics to freeze the web worker until the page responds, but I was unable to figure out a solution with those, however I think it's a good starting point. Most solutions I've seen so far have just been to restructure code, but since pyodide is an external library I am forced to return from the function I set in pyodide.setStdin

• ggorlen: Related: Pyodide - UI input instead of prompt

Answer 1

I found out how to solve this problem, so I thought I'd post it. I did end up using SharedArrayBuffers with Atomics. Andrea Giammarchi had a great article on passing strings between threads, but basically I would pass a buffer through postMessage to the main thread asking for the length of the string, then use Atomics.wait to pause until the worker recieved the length. I then would use that to make another buffer and pass it like before but instead encode a string into the buffer and decode it from the worker. The attached Medium article explains it better than I can.

• José Ramírez: Since now you should be able to write workers as ES modules, you should be able to easily release the worker thread with await so its message pump is checked. At this point the UI thread may send the prompt in a new message. Upon reception, the prompt data resolves the promise being awaited and the process resumes.