The code that I wrote to handle this is:
func writeZip(data []byte, filename string) error {
var fileGZ bytes.Buffer
zipper := gzip.NewWriter(&fileGZ)
_, err := zipper.Write(data)
if err != nil {
return err
}
// call the close explicitly
if err = zipper.Close(); err != nil {
return err
}
err = ioutil.WriteFile(filename, fileGZ.Bytes(), 0644)
if err != nil {
return err
}
return nil
}
On 29 October 2016 at 00:15, <ndi...@apigee.com> wrote:
> Hi could you share how you actually managed to do all of this? I am
> dealing with this same issue and really need help moving the data
> descriptor stuff to the file header. Thank you.
>
>
> On Saturday, May 16, 2015 at 12:06:23 AM UTC-7, Alex Skinner wrote:
>>
>> I took a look at this tonight mainly to learn about the zip format spec
>> since I've never bothered. I used your Go code to create a zip, then tried
>> to extract with java on linux as I don't have time to fiddle with testing
>> on Android at the moment. Here is what I found if it's relevant - and it's
>> very late, so expect errors below -
>> (I used this page as spec, if that matters - https://pkware.cachefly.net/
>> webdocs/casestudies/APPNOTE.TXT) .
>>
>> Using a ZipInputStream, java failed to parse the file with error 'only
>> DEFLATED entries can have EXT descriptor'. Further checking shows that Go
>> seems to consistently set bitflag 3(08) in byte 7. The spec says "Note:
>> PKZIP version 2.04g for DOS only recognizes this bit for method 8
>> compression, newer versions of PKZIP recognize this bit for any compression
>> method." This seems to imply to me that Java is behaving as described in
>> the above, because the Go version is in fact doing what bitflag 3 implies,
>> which is putting the data descriptor after the data, but not using
>> compression method 8. I honestly don't know what benefit this serves, if
>> any, though.
>>
>> The only way I could get java to successfully expand the Go zip was to -
>> 1 - Change byte 7 to '00' for each file
>> 2 - Move data in data descriptor into their fields in the file header
>> 3 - Remove the descriptor signature and descriptor
>> 4 - Change offset at end of file
>>
>> Or, take your Go created zip file(test.zip) and run 'zip -F test.zip
>> --out fixed.zip' which does all this in my tests. If that resulting file
>> then works, that may be the reason. If that is in fact the problem, it
>> should be straightforward to make a local copy of archive/zip and change
>> this behavior I think.
>>
>> Curious to know what you find,
>> Alex
>>
>> On Friday, May 8, 2015 at 9:32:32 AM UTC-4, JohnGB wrote:
>>>
>>> I've written some code that creates a .zip file from a number of other
>>> files (.png in case it matters). The zip file seems to be fine, and I can
>>> open it on both a mac and windows computer without a problem. However when
>>> an Android device (using the java.util.zip package) tries to open the file,
>>> it throws an error that the file is not a .zip file. Given how long
>>> java.util.zip has been in use, I doubt that the problem is there, and
>>> assume the issue is with the method that I've used to create the .zip file
>>> in the first place.
>>>
>>> Below (or in play <http://play.golang.org/p/Z8JTIret-K>) is the
>>> function that I'm using to zip the files:
>>>
>>> func createZip(zipDir, zipName string, filesToZip []string) error {
>>>
>>> // creat the file to zip the contents into
>>> newfile, err := os.Create(zipDir + zipName)
>>> if err != nil {
>>> return err
>>> }
>>> defer newfile.Close()
>>>
>>> zipit := zip.NewWriter(newfile)
>>> defer zipit.Close()
>>>
>>> for _, filename := range filesToZip {
>>> zipFile, err := os.Open(zipDir + filename)
>>> if err != nil {
>>> return err
>>> }
>>> defer zipFile.Close()
>>>
>>> // get the file information
>>> info, err := zipFile.Stat()
>>> if err != nil {
>>> return err
>>> }
>>>
>>> // create a zip header from the os.FileInfo
>>> header, err := zip.FileInfoHeader(info)
>>> if err != nil {
>>> return err
>>> }
>>>
>>> // write the header to the zip file
>>> writer, err := zipit.CreateHeader(header)
>>> if err != nil {
>>> return err
>>> }
>>>
>>> // copy the file to the zip file
>>> _, err = io.Copy(writer, zipFile)
>>> if err != nil {
>>> return err
>>> }
>>> }
>>> return nil
>>> }
>>>
>>> I would appreciate feedback on my code, or suggestions as to where I can
>>> look for the cause.
>>>
>> --
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