file preview with sparse content

[joehand]

Still very much WIP. A few underlying deps need updates too.

• The files download and stuff but it is not sparse at all. I think this is because of the hypercore bug.
• Didn't hook up previews yet.

Not sure if the page files will fill with empty buffers or be sparse. We can switch to memory too but need to think about how to make sure that doesn't grow too large. Is there a LRU cache + random-access-memory thing floating around anywhere?

We dont need to use hyperdrive-http but I added those methods this morning and wanted to see if it worked =).

Uses branches of:

• hypercore-archiver: https://github.com/mafintosh/hypercore-archiver/tree/sparse
• hyperdrive-http: https://github.com/joehand/hyperdrive-http/tree/api-methods

[okdistribute]

Great work, let's see if it works after the hypercore fix lands!

[okdistribute]

Previewing only the dat.json file in a 4MB dat creates the page file at the max size (wrong) yet downloads only the dat.json file (correctly sparse).

karissa ~/node_modules/datproject.org
$ du -h archiver/
2.4M    archiver//data/f0/3cf5bca03120269ba7858e805cf32f102c234e703aa073b44aa207639f3bdf.data
2.4M    archiver//data/f0
4.0K    archiver//data/f7/02cd8e76187d355a7a806dc386d2532789b098b104bea73480e94f220714cb.data
4.0K    archiver//data/f7
2.5M    archiver//data
 36K    archiver//db
2.5M    archiver/

karissa ~/node_modules/datproject.org
$ tail archiver/data/f0/3cf5bca03120269ba7858e805cf32f102c234e703aa073b44aa207639f3bdf.data/0.page
{"title":"Powerpoint Karaoke","url":"dat://4c6322037b77afcf13fd1aa0467b39b1eeedaf12a6dc7a6291d466863890b2d9","name":"powerpoint-karaoke","description":"A slide deck that can be used for Power Point Karaoke, also known as BattleDecks"}

[okdistribute]

OK looks like the sparse mode is working now! Hooray!

I added capability to preview files, but there is some wonkyiness with rendering iframes (pdfs, maps, text files). @yoshuawuyts says that caching using el.isSameNode + onload/onunload could fix this.

[joehand]

Nice work hooking up the file previews! They look good. I released the updated versions of hypercore-archiver + hyperdrive-http, so should be all ready there!