(require 'dired)

(defvar nodots "^\\([^.]\\|\\.\\([^.]\\|\\..\\)\\).*")

(defun dired-go-to-first ()
    (interactive)
    (goto-char (point-min))
    (dired-next-line 1)
    (skip-chars-forward " \n\t"))

(defun dired-is-empty-p (directory-name)
  (null (directory-files directory-name nil nodots t 1)))

(defun directory-number-files (directory-name &optional omit-filter)
  (length (directory-files directory-name nil omit-filter t)))

(defun dired-mark-empty-dirs ()
  (interactive)
  (when (equal major-mode 'dired-mode)
    (let ((curr-dir))
      (save-excursion
        (dired-go-to-first)
        
        (while (not (eobp))
          (setq curr-dir (dired-file-name-at-point))
          (cond ((or (null curr-dir)
                     (string= curr-dir ".")
                     (string= curr-dir ".."))
                     ;; do nothing here
                 )
                ((file-directory-p curr-dir)
                 (when (dired-is-empty-p curr-dir)
                   (dired-mark 1)
                   (dired-previous-line 1))))
          (dired-next-line 1))))))

(defun test-1 (dir-name count)
  "Ask for COUNT number of files from directory DIR-NAME."
  (let ((max (length (directory-files dir-name nil nil t)))
        (res (length (directory-files dir-name nil nil t count))))
    (cond ((>= max count)
           (if (= res count)
               (message "passed: asked: %d get: %d number files in dir: %d" count
                        res max)
             (message "not-passed: asked: %s get: %s number files in dir: %s" count
                      res max)))
          ((< max count)
           (if (< res count)
              (message "passed: asked: %d get: %d number files in dir: %d" count
                       res max)
            (message "not-passed: asked: %s get: %s number files in dir: %s" count
                     res max)))
          (t
           (message "Invalid case!")))))

(defun test-2 (dir-name count)
  "Ask for random number of files in interval [1,COUNT] files from every subdir
of directory DIR-NAME."
  (let ((dirs (directory-files dir-name t nodots t)))
    (dolist (curr-dir dirs)
      (when (file-directory-p curr-dir)
        (test-1 curr-dir (+ 1 (random count)))))))

;;(benchmark-run-compiled 10 (dired-is-empty-p "/some/path"))

;; must be in some dired buffer for this
;;(benchmark-run-compiled 10 (dired-mark-empty-dirs))