return FormatUnknown
	}

	// Guess the magic values.
	magic := string(b.toUSTAR().magic())
	version := string(b.toUSTAR().version())
	trailer := string(b.toSTAR().trailer())
	switch {
	case magic == magicUSTAR && trailer == trailerSTAR:
		return formatSTAR
	case magic == magicUSTAR:
		return FormatUSTAR | FormatPAX
	case magic == magicGNU && version == versionGNU:
		return FormatGNU

// then this returns an error.
func (tw *Writer) Close() error {
	if tw.err == ErrWriteAfterClose {
		return nil
	}
	if tw.err != nil {
		return tw.err
	}

	// Trailer: two zero blocks.
	err := tw.Flush()
	for i := 0; i < 2 && err == nil; i++ {
		_, err = tw.w.Write(zeroBlock[:])
	}

	// Ensure all future actions are invalid.
	tw.err = ErrWriteAfterClose

//
// Given asm line:
//
//	VP4DPWSSDS Z5, [Z10-Z13], (AX)
//
// zmm2 is Z10, and Z13 is the only valid value for it (Z10+3).
// Only simple ranges are accepted, like [Z0-Z3].
//
// The opening bracket has been consumed.
func (p *Parser) registerList(a *obj.Addr) {
	if p.arch.InFamily(sys.I386, sys.AMD64) {
		p.registerListX86(a)
	} else {
		p.registerListARM(a)
	}
}

		}
		if err := w.Close(); err != nil {
			t.Fatalf("Unable to write archive: %s", err)
		}

		// TODO: We may want to check if the archive roundtrips. This would require
		// taking into account addition of the two zero trailer blocks that Writer.Close
		// appends.
	})

	if err != nil || numEntries < 0 || int(2*numEntries) < int(numEntries) {
		return nil, ErrHeader
	}

	// Parse for all member entries.
	// numEntries is trusted after this since a potential attacker must have
	// committed resources proportional to what this library used.
	if err := feedTokens(2 * numEntries); err != nil {
		return nil, err
	}
	spd := make(sparseDatas, 0, numEntries)