add methods for reading and writting data from an offset about js-ipfs-unixfs-engine

[daviddias]

There have been more requests for this feature - ipfs/js-ipfs#348 I agree that we should have it. A simple version of dropping bytes would be simple enough to achieve the API, then we can optimize its perf.

[daviddias]

The writer is a bit more complex, not sure if it belongs here. Essentially what would need to be done is to fetch the whole file, modify and chunk the whole thing again. There will be a bunch of nodes that get reused, but this slight bit modification would have to be aware of the graph builder and chunker used.

[wanderer]

this slight bit modification would have to be aware of the graph builder and chunker used.

right, and also different chunking schema are going to have different optimal offset units too

[achingbrain]

The ship this was shipped on set sail ages ago 🚢 ⚓️ 📦 🚀