Implement hard cloning of data and vector

[kylebarron]

For #8

[kylebarron]

this is hard to test because node doesn't have ArrayBuffer.transfer available, but checked manually in chrome and, originally the geometryData was shared (loaded from IPC) but after hardClone, isShared accurately said it was no longer shared, and even when I transfer one of the original buffers, the cloned data is still accessible

[trevorgerhardt]

Could try testing with the web-worker plugin: https://github.com/vitest-dev/vitest/tree/main/packages/web-worker. Not 100% sure it would suit your needs.

[kylebarron]

Cool! I didn't know about that.

It does say

Transferring Buffer will not change its byteLength.

which means I don't think I'd be able to test what I want to test here. Maybe a better way to test this is just to check that the buffer backing the new Data instance is a different object

[trevorgerhardt]

Ah, yes, I now see that note. A "real" test might need automating running a browser like with Playwright.

Also, as you probably realize, this code doesn't appear GeoArrow specific. Could be useful to propose into the upstream Arrow-JS project?

(Note: I am casually investigating these tools and do not know the dynamics of the different projects.)

[kylebarron]

actually TIL node has a structuredClone method that correctly detaches arraybuffers:

Yeah, it's not geoarrow specific, but contributing upstream to arrow-js has a lot of overhead, so I might as well incubate functionality here, so I can move more quickly, and maybe later integrate with arrowjs