func buildWalker(root string, aw aci.ArchiveWriter, rootfs bool) filepath.WalkFunc {
// cache of inode -> filepath, used to leverage hard links in the archive
inos := map[uint64]string{}
return func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
relpath, err := filepath.Rel(root, path)
if err != nil {
return err
}
if rootfs {
if relpath == "." {
relpath = ""
}
relpath = "rootfs/" + relpath
}
if relpath == "." {
return nil
}
link := ""
var file *os.File
switch info.Mode() & os.ModeType {
default:
file, err = os.Open(path)
if err != nil {
return err
}
defer file.Close()
case os.ModeSymlink:
target, err := os.Readlink(path)
if err != nil {
return err
}
link = target
}
hdr, err := tar.FileInfoHeader(info, link)
if err != nil {
panic(err)
}
// Because os.FileInfo's Name method returns only the base
// name of the file it describes, it may be necessary to
// modify the Name field of the returned header to provide the
// full path name of the file.
hdr.Name = relpath
tarheader.Populate(hdr, info, inos)
// If the file is a hard link we don't need the contents
if hdr.Typeflag == tar.TypeLink {
hdr.Size = 0
file = nil
}
aw.AddFile(relpath, hdr, file)
return nil
}
}