add DirLister interface

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

internal/sftpd/scp.go

@@ -384,47 +384,65 @@ func (c *scpCommand) handleRecursiveDownload(fs vfs.Fs, dirPath, virtualPath str
 		if err != nil {
 			return err
 		}
-		files, err := fs.ReadDir(dirPath)
+		// dirPath is a fs path, not a virtual path
+		lister, err := fs.ReadDir(dirPath)
 		if err != nil {
 			c.sendErrorMessage(fs, err)
 			return err
 		}
-		files = c.connection.User.FilterListDir(files, fs.GetRelativePath(dirPath))
+		defer lister.Close()
+
+		vdirs := c.connection.User.GetVirtualFoldersInfo(virtualPath)
+
 		var dirs []string
-		for _, file := range files {
-			filePath := fs.GetRelativePath(fs.Join(dirPath, file.Name()))
-			if file.Mode().IsRegular() || file.Mode()&os.ModeSymlink != 0 {
-				err = c.handleDownload(filePath)
-				if err != nil {
-					break
-				}
-			} else if file.IsDir() {
-				dirs = append(dirs, filePath)
+		for {
+			files, err := lister.Next(vfs.ListerBatchSize)
+			finished := errors.Is(err, io.EOF)
+			if err != nil && !finished {
+				c.sendErrorMessage(fs, err)
+				return err
 			}
-		}
-		if err != nil {
-			c.sendErrorMessage(fs, err)
-			return err
-		}
-		for _, dir := range dirs {
-			err = c.handleDownload(dir)
-			if err != nil {
+			files = c.connection.User.FilterListDir(files, fs.GetRelativePath(dirPath))
+			if len(vdirs) > 0 {
+				files = append(files, vdirs...)
+				vdirs = nil
+			}
+			for _, file := range files {
+				filePath := fs.GetRelativePath(fs.Join(dirPath, file.Name()))
+				if file.Mode().IsRegular() || file.Mode()&os.ModeSymlink != 0 {
+					err = c.handleDownload(filePath)
+					if err != nil {
+						c.sendErrorMessage(fs, err)
+						return err
+					}
+				} else if file.IsDir() {
+					dirs = append(dirs, filePath)
+				}
+			}
+			if finished {
 				break
 			}
 		}
-		if err != nil {
+		lister.Close()
+
+		return c.downloadDirs(fs, dirs)
+	}
+	err = errors.New("unable to send directory for non recursive copy")
+	c.sendErrorMessage(nil, err)
+	return err
+}
+
+func (c *scpCommand) downloadDirs(fs vfs.Fs, dirs []string) error {
+	for _, dir := range dirs {
+		if err := c.handleDownload(dir); err != nil {
 			c.sendErrorMessage(fs, err)
 			return err
 		}
-		err = c.sendProtocolMessage("E\n")
-		if err != nil {
-			return err
-		}
-		return c.readConfirmationMessage()
 	}
-	err = fmt.Errorf("unable to send directory for non recursive copy")
-	c.sendErrorMessage(nil, err)
-	return err
+	if err := c.sendProtocolMessage("E\n"); err != nil {
+		return err
+	}
+	return c.readConfirmationMessage()
 }
 
 func (c *scpCommand) sendDownloadFileData(fs vfs.Fs, filePath string, stat os.FileInfo, transfer *transfer) error {