CRC fails for streaming ZIP file if compression level set to 0

[harveylee]

How to reproduce
Zip the attached truck.jpg using the streaming ZIP interface with level set to 0. Try to extract it again using an off-the-shelf ZIP program.

// Node 14.15.4
import fs from 'fs'
import { Zip, AsyncZipDeflate } from 'fflate'

const buf = fs.readFileSync('truck.jpg')
const writeStream = fs.createWriteStream('truck.zip')
const zip = new Zip((err, data, final) => {
  if (err !== null) throw err
  writeStream.write(data)
  if (final) writeStream.end()
})

const file = new AsyncZipDeflate('truck.jpg', { level: 0 })
zip.add(file)
file.push(buf, true)
zip.end()

The problem
Both Windows Explorer and 7-ZIP reports a CRC error when trying to extract truck.jpg from the ZIP file. This doesn't seem to occur using the zip() interface nor at compression levels other than 0 (tried 1, 2, 6, 9). Also other files seem to work, there's something specific about this file and others.

[101arrowz]

Thanks for the bug report, I'll look into this in a few days.

[101arrowz]

Haven't gotten a chance to check this out yet, but I should have time this weekend, sorry for the delay.

[harveylee]

If it helps, I switched to using zip() for now, which doesn't seem to suffer from this problem?

i.e. this

import { zip } from 'fflate'
zip({ ... }, (err, data) => { ... })

I also recall running into some (related?) issues at other compression levels with other files, but I forgot to keep notes.

[101arrowz]

You mentioned it in your original issue, but it's kind of weird because zip and Zip call the same CRC function internally. I definitely need to investigate more.

[101arrowz]

I've finally been able to reproduce this error and will fix it as soon as possible.

[101arrowz]

Well this was an incredibly stupid error - this package has been unable to do level-0 compression of files above 64kB since its release, it's just never been noticed because level-0 compression for ZIP files doesn't actually use DEFLATE level-0, and most files I tested were under 64kB. Thank you for this bug report, should be fixed in v0.7.2.