Headers Error in 7-zip

[hrishikesh-k]

UPDATE: Looks like this problem exists only when unzipping with 7-zip - however the archive unzips fine and the files are also accessible.

Hello! Thank you for this wonderful package! I've just run into a problem, hoping if I can get some help.

I was trying to implement a solution to fetch files from API and add them to a zip (simply store - no compression). I am receiving a list of all files from an API - I'm then downloading the first file, adding it to zip, then downloading the next file, adding it to zip and so on... I was able to follow this: https://github.com/101arrowz/fflate/wiki/Guide:-Modern-(Buildless)

I'm doing this:

// callApi is my custom function using browser's fetch API that returns `response.blob()`
// files is the array of file list from API. It looks like [{path:'foo'},{path:'bar'}]

import {Zip, ZipPassThrough} from 'fflate'

downloadAll(index, zip, zipReadableStream) {

  const fflToRS = fflateStream => new ReadableStream({
    start(controller) {
      fflateStream.ondata = (error, data, final) => {
        if (error) {
          controller.error(error)
        } else {
          controller.enqueue(data)
          if (final) {
            controller.close()
          }
        }
      }
    },
    cancel() {
      fflateStream.terminate()
    }
  })

  const addFileToZip = async (fileData, fileObject, zip) => {
    const zippedFileStream = new ZipPassThrough(fileObject.path)
    zip.add(zippedFileStream)
    const fileReader = fileData.stream().getReader()
    while (true) {
      const {done, value} = await fileReader.read()
      if (done) {
        zippedFileStream.push(new Uint8Array(0), true)
        break
      }
      zippedFileStream.push(value)
    }
  }

  zip = zip ? zip : new Zip()
  zipReadableStream = zipReadableStream ? zipReadableStream : fflToRS(zip)

  callApi('url', true).then(file => {
    addFileToZip(file, files[index], zip).then(() => {
      if (index++ < files.length - 1) {
        downloadAll(index++, zip, zipReadableStream)
      } else {
        zip.end()
        const zipResponse = new Response(zipReadableStream)
        // rest
      }
    })
  })

}

I'm calling the function for the first time like downloadAll(0). I get the zip as needed, but when I try to extract it with 7-zip it gives me this error:

Just wondering if there's any way to get rid of that error/warning.

[101arrowz]

Does 7-zip provide any more details than "Headers Error"? Also, could you send a ZIP file that reproduces this?

The fact it unzips properly despite the "error" indicates to me that there might be some kind of incompatibility. Whether or not it's something fflate can resolve I'd like to investigate. It seems similar to this comment.

[dexgs]

It turns out 7-Zip in particular reads BOTH the local and central directory headers to cross-validate them

Thanks for this insight. I'm doing something unrelated with Zip files, but I ran into this issue myself and I'm not sure I would have discovered the solution on my own.

[AlttiRi]

v0.7.3 still has Header Errors while unzippid with 7-zip.

[tamasfoldi]

v0.7.4 still has the Header Errors issue with 7-zip. @101arrowz was your fix applied in 0.7.2?

[101arrowz]

It should be fixed now, are you sure you're using v0.7.4? If so please share your code so I can reproduce the issue.

[tamasfoldi]

You are right. It is fixed in 0.7.4. We have multiple modules and I've updated and tested two different modules 🤦