tw.err = tw.writeGNUHeader(&tw.hdr)
		return tw.err
	default:
		return err // Non-fatal error
	}
}

func (tw *Writer) writeUSTARHeader(hdr *Header) error {
	// Check if we can use USTAR prefix/suffix splitting.
	var namePrefix string
	if prefix, suffix, ok := splitUSTARPath(hdr.Name); ok {
		namePrefix, hdr.Name = prefix, suffix
	}

	// Pack the main header.
	var f formatter

	//	name and comment fields as whatever the local system encoding is.
	//
	// In order to avoid breaking readers without UTF-8 support,
	// we avoid setting the UTF-8 flag if the strings are CP-437 compatible.
	// However, if the strings require multibyte UTF-8 encoding and is a
	// valid UTF-8 string, then we set the UTF-8 bit.
	//
	// For the case, where the user explicitly wants to specify the encoding