archive/zip: record time stamps in "Extended Timestamp Extra Field"

[mattn]

    out, err := ioutil.TempFile(os.TempDir(), "zip")
    if err != nil {
        t.Fatal("creating:", err)
    }
    zw := NewWriter(out)

    in, err := os.Open("writer_test.go")
    if err != nil {
        t.Fatal("opening:", err)
    }
    info, err := in.Stat()
    if err != nil {
        t.Fatal("stat:", err)
    }
    ftime := info.ModTime().Unix()

    header, err := FileInfoHeader(info)
    if err != nil {
        t.Fatal("FileInfoHeader:", err)
    }
    header.Name = info.Name()
    zf, err := zw.CreateHeader(header)
    if err != nil {
        t.Fatal("CreateHeader:", err)
    }
    if _, err = io.Copy(zf, in); err != nil {
        t.Fatal("copying:", err)
    }
    in.Close()
    zw.Close()
    out.Close()

timestamp of the file in the zip, is UTC timezone. So +9 hours in my location.

[mattn]

Most of zip archiver store timestamp as local timezone.

https://go-review.googlesource.com/#/c/8070/

[bradfitz]

I don't think we can safely make this change under the Go 1 compatibility guarantee.

[mattn]

I'm thinking this is a bug. So we must not keep compatibility.

$ LC_ALL=C ls -la
total 12
drwxrwxr-x  2 mattn mattn 4096 Apr  1 14:55 .
drwxr-x--- 49 mattn mattn 4096 Apr  1 14:55 ..
-rw-r--r--  1 mattn mattn  487 Apr  1 14:55 ziptest.go

make test.zip contained ziptest.go

$ zip test.zip ziptest.go
  adding: ziptest.go (deflated 45%)

package main

import (
        "archive/zip"
        "fmt"
        "log"
        "os"
)

func main() {
        in, err := os.Open("test.zip")
        if err != nil {
                log.Fatal("opening:", err)
        }
        defer in.Close()
        info, err := in.Stat()
        if err != nil {
                log.Fatal("stat:", err)
        }
        zr, err := zip.NewReader(in, info.Size())
        if err != nil {
                log.Fatal("NewReader:", err)
        }
        if len(zr.File) != 1 {
                log.Fatalf("File count should be 1 but %v", len(zr.File))
        }
        ztime := zr.File[0].ModTime()
        fmt.Println(ztime.String())
}

$ go run ziptest.go
2015-04-01 14:55:12 +0000 UTC

Note that this is not a joke at april fool.

[mattn]

I'm in JST+0900 offset

[ianlancetaylor]

As I understand it, the only possibly correct fix is to use the "Extended Timestamp Extra Field" defined at http://www.opensource.apple.com/source/zip/zip-6/unzip/unzip/proginfo/extra.fld .

[rsc]

This came up in #7592, which we fixed by updating the documentation for the ModTime and SetModTime methods. It is not possible to change the UTC default.

It may be that if we set this extended field as well, enough clients will use the Unix form in preference to the MS-DOS form that they will end up doing the right thing.

[mattn]

I looked code of unzip.

unzip command can extract timestamp as local timezon without looking extra field.
So we need to to add extra variable to change behavior of Reader/Writer into archive/zip.

Proposal

1. add DefaultTimeZone into archive/zip

   var DefaultTimeZone *time.Location

   This will be used as default timezone for Reader/ReadCloser/Writer.

2. add SetTimeZone() into Reader/ReadCloser/Writer. DefaultTimeZone is used as default timezone for them.

How do you think?

[ianlancetaylor]

Which version of unzip did you look at?

I don't know if extending the API is the way to go, but, if it is, why would we need both DefaultTimeZone and SetTimeZone?

[mattn]

I looked master branch of https://github.com/Distrotech/unzip

[rsc]

Too late for Go 1.5.