func WriteBackupStreamFromTarFile()

in backuptar/tar.go [359:480]
119 lines of code
28 McCabe index (conditional complexity)

func WriteBackupStreamFromTarFile(w io.Writer, t *tar.Reader, hdr *tar.Header) (*tar.Header, error) {
	bw := winio.NewBackupStreamWriter(w)
	var sd []byte
	var err error
	// Maintaining old SDDL-based behavior for backward compatibility.  All new tar headers written
	// by this library will have raw binary for the security descriptor.
	if sddl, ok := hdr.PAXRecords[hdrSecurityDescriptor]; ok {
		sd, err = winio.SddlToSecurityDescriptor(sddl)
		if err != nil {
			return nil, err
		}
	}
	if sdraw, ok := hdr.PAXRecords[hdrRawSecurityDescriptor]; ok {
		sd, err = base64.StdEncoding.DecodeString(sdraw)
		if err != nil {
			return nil, err
		}
	}
	if len(sd) != 0 {
		bhdr := winio.BackupHeader{
			Id:   winio.BackupSecurity,
			Size: int64(len(sd)),
		}
		err := bw.WriteHeader(&bhdr)
		if err != nil {
			return nil, err
		}
		_, err = bw.Write(sd)
		if err != nil {
			return nil, err
		}
	}
	var eas []winio.ExtendedAttribute
	for k, v := range hdr.PAXRecords {
		if !strings.HasPrefix(k, hdrEaPrefix) {
			continue
		}
		data, err := base64.StdEncoding.DecodeString(v)
		if err != nil {
			return nil, err
		}
		eas = append(eas, winio.ExtendedAttribute{
			Name:  k[len(hdrEaPrefix):],
			Value: data,
		})
	}
	if len(eas) != 0 {
		eadata, err := winio.EncodeExtendedAttributes(eas)
		if err != nil {
			return nil, err
		}
		bhdr := winio.BackupHeader{
			Id:   winio.BackupEaData,
			Size: int64(len(eadata)),
		}
		err = bw.WriteHeader(&bhdr)
		if err != nil {
			return nil, err
		}
		_, err = bw.Write(eadata)
		if err != nil {
			return nil, err
		}
	}
	if hdr.Typeflag == tar.TypeSymlink {
		_, isMountPoint := hdr.PAXRecords[hdrMountPoint]
		rp := winio.ReparsePoint{
			Target:       filepath.FromSlash(hdr.Linkname),
			IsMountPoint: isMountPoint,
		}
		reparse := winio.EncodeReparsePoint(&rp)
		bhdr := winio.BackupHeader{
			Id:   winio.BackupReparseData,
			Size: int64(len(reparse)),
		}
		err := bw.WriteHeader(&bhdr)
		if err != nil {
			return nil, err
		}
		_, err = bw.Write(reparse)
		if err != nil {
			return nil, err
		}
	}
	if hdr.Typeflag == tar.TypeReg || hdr.Typeflag == tar.TypeRegA {
		bhdr := winio.BackupHeader{
			Id:   winio.BackupData,
			Size: hdr.Size,
		}
		err := bw.WriteHeader(&bhdr)
		if err != nil {
			return nil, err
		}
		_, err = io.Copy(bw, t)
		if err != nil {
			return nil, err
		}
	}
	// Copy all the alternate data streams and return the next non-ADS header.
	for {
		ahdr, err := t.Next()
		if err != nil {
			return nil, err
		}
		if ahdr.Typeflag != tar.TypeReg || !strings.HasPrefix(ahdr.Name, hdr.Name+":") {
			return ahdr, nil
		}
		bhdr := winio.BackupHeader{
			Id:   winio.BackupAlternateData,
			Size: ahdr.Size,
			Name: ahdr.Name[len(hdr.Name):] + ":$DATA",
		}
		err = bw.WriteHeader(&bhdr)
		if err != nil {
			return nil, err
		}
		_, err = io.Copy(bw, t)
		if err != nil {
			return nil, err
		}
	}
}