Stuck on an issue?

How to reproduce

1. Create a zip file using a standard tool, or zipSync.
2. Use AsyncZipDeflate to add that zip file to a new zip file
3. Try to unzip using AsyncUnzipInflate

const fs = require('fs')
const { zipSync, Zip, Unzip, AsyncZipDeflate, AsyncUnzipInflate } = require('fflate')

function unzip (zipPath) {
  const zipped = fs.readFileSync(zipPath)
  const unzipper = new Unzip(stream => {
    const fileWriteStream = createWriteStream(`out_${stream.name}`)
    stream.ondata = (err, chunk, final) => {
      if (err !== null) throw err
      fileWriteStream.write(chunk)
      if (final) fileWriteStream.end()
    }
    stream.start()
  })
  unzipper.register(AsyncUnzipInflate)
  unzipper.push(zipped, true)
}

function streamZipAndUnzip (inputPath) {
  const outputPath = `stream_zipped_${inputPath}.zip`
  const writeStream = fs.createWriteStream(outputPath)
  writeStream.once('finish', () => unzip(outputPath))

  const zip = new Zip((err, data, final) => {
    if (err !== null) throw err
    writeStream.write(data)
    if (final) writeStream.end()
  })

  const file = new AsyncZipDeflate(inputPath)
  zip.add(file)
  file.push(fs.readFileSync(inputPath), true)

  zip.end()
}

function zipAndUnzip (inputPath) {
  const outputPath = `zipped_${inputPath}.zip`
  const zipped = zipSync({
    [inputPath]: fs.readFileSync(inputPath)
  })
  fs.writeFileSync(outputPath, zipped)
}

// Zipping and unzipping a plain JPG seems to work
streamZipAndUnzip('truck.jpg')

// Unzipping a zip file containing another zip file - both created using an off-the-shelf tool - seems to work
unzip('double.zip')

// Using zipSync to zip a zip file and then unzipping seems to work
zipAndUnzip('truck.zip')

// Using AsyncZipDeflate to zip a zip file - fails when unzipping with "Error: invalid distance"
streamZipAndUnzip('truck.zip')

The problem

Error: invalid distance when unzipping a zip file created using AsyncZipDeflate which contains another zip file.

It seems that when unzipping the outer zip file, it also tries to unzip the inner zip file, which is surprising behaviour?

double.zip truck.jpg truck.zip