if err := cfw.writeHeader(metaFileHash); err != nil {
		return err
	}
	return cfw.AppendSegment(args, visitor)
}

func padToFourByteBoundary(ws *slicewriter.WriteSeeker) error {
	sz := len(ws.BytesWritten())
	zeros := []byte{0, 0, 0, 0}
	rem := uint32(sz) % 4
	if rem != 0 {
		pad := zeros[:(4 - rem)]
		if nw, err := ws.Write(pad); err != nil {
			return err

	log.SetPrefix("emitToWriter: ")
	var slwm slicewriter.WriteSeeker
	if err := coverage.WriteMeta(&slwm); err != nil {
		log.Fatalf("error: WriteMeta returns %v", err)
	}
	mf := filepath.Join(*outdirflag, "covmeta.0abcdef")
	if err := os.WriteFile(mf, slwm.BytesWritten(), 0666); err != nil {
		log.Fatalf("error: writing %s: %v", mf, err)
	}
	var slwc slicewriter.WriteSeeker
	if err := coverage.WriteCounters(&slwc); err != nil {

	for k := range p.counterLengths {
		cvn := mkCounterVarName(k)
		fmt.Fprintf(w, "var %s [%d]uint32\n", cvn, p.counterLengths[k])
	}

	// Emit encoded meta-data.
	var sws slicewriter.WriteSeeker
	digest, err := p.mdb.Emit(&sws)
	if err != nil {
		log.Fatalf("encoding meta-data: %v", err)
	}
	p.mdb = nil
	fmt.Fprintf(w, "var %s = [...]byte{\n", mkMetaVar())
	payload := sws.BytesWritten()