func arExportData(archive io.ReadSeeker) (io.ReadSeeker, error) {
	if _, err := archive.Seek(0, io.SeekStart); err != nil {
		return nil, err
	}

	var buf [len(armag)]byte
	if _, err := archive.Read(buf[:]); err != nil {
		return nil, err
	}

	switch string(buf[:]) {
	case armag:
		return standardArExportData(archive)
	case armagt:
		return nil, errors.New("unsupported thin archive")
	case armagb:
		return aixBigArExportData(archive)

			}
			return
		}
		Exitf("cannot open file %s: %v", name, err)
	}
	defer f.Close()

	var magbuf [len(ARMAG)]byte
	if _, err := io.ReadFull(f, magbuf[:]); err != nil {
		Exitf("file %s too short", name)
	}

	if string(magbuf[:]) != ARMAG {
		Exitf("%s is not an archive file", name)
	}

	var arhdr ArHdr
	l := nextar(f, f.Offset(), &arhdr)
	if l <= 0 {

	}
	defer f.Close()
	defer func() {
		if pkg == "main" && !lib.Main {
			Exitf("%s: not package main", lib.File)
		}
	}()

	for i := 0; i < len(ARMAG); i++ {
		if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
			continue
		}

		/* load it as a regular file */
		l := f.MustSeek(0, 2)
		f.MustSeek(0, 0)
		ldobj(ctxt, f, lib, l, lib.File, lib.File)
		return
	}