switch string(buf[:]) {
	case armag:
		return standardArExportData(archive)
	case armagt:
		return nil, errors.New("unsupported thin archive")
	case armagb:
		return aixBigArExportData(archive)
	default:
		return nil, fmt.Errorf("unrecognized archive file format %q", buf[:])
	}
}

// standardArExportData returns export data from a standard archive.
func standardArExportData(archive io.ReadSeeker) (io.ReadSeeker, error) {