func maybeDecompress(rs io.ReadSeeker) (io.Reader, error) {
// TODO(jonboulle): this is a bit redundant with detectValType
typ, err := aci.DetectFileType(rs)
if err != nil {
return nil, err
}
if _, err := rs.Seek(0, 0); err != nil {
return nil, err
}
var r io.Reader
switch typ {
case aci.TypeGzip:
r, err = gzip.NewReader(rs)
if err != nil {
return nil, fmt.Errorf("error reading gzip: %v", err)
}
case aci.TypeBzip2:
r = bzip2.NewReader(rs)
case aci.TypeXz:
r = aci.XzReader(rs)
case aci.TypeTar:
r = rs
case aci.TypeUnknown:
return nil, errors.New("unknown filetype")
default:
// should never happen
panic(fmt.Sprintf("bad type returned from DetectFileType: %v", typ))
}
return r, nil
}
// unpackRootfs unpacks a stage1 rootfs (compressed file, pointed to by rfs)
// into dir, returning any error encountered
func unpackRootfs(rfs string, dir string) error {
fh, err := os.Open(rfs)
if err != nil {
return fmt.Errorf("error opening stage1 rootfs: %v", err)
}
typ, err := aci.DetectFileType(fh)
if err != nil {
return fmt.Errorf("error detecting image type: %v", err)
}
if _, err := fh.Seek(0, 0); err != nil {
return fmt.Errorf("error seeking image: %v", err)
}
var r io.Reader
switch typ {
case aci.TypeGzip:
r, err = gzip.NewReader(fh)
if err != nil {
return fmt.Errorf("error reading gzip: %v", err)
}
case aci.TypeBzip2:
r = bzip2.NewReader(fh)
case aci.TypeXz:
r = aci.XzReader(fh)
case aci.TypeTar:
r = fh
case aci.TypeUnknown:
return fmt.Errorf("error: unknown image filetype")
default:
// should never happen
panic("no type returned from DetectFileType?")
}
return untarRootfs(r, dir)
}