Search for selected tex

[Lorenzo Isella <lorenzo.isella@gmail.com>]

Dear All,
I would like to be able to select some text with C-space and then look 
for it inside the buffer.
I found some functions online which I modified to get:

;; a function to search the selected text

(defun my-search-forward (begin end)
  (interactive (list (point) (mark)))
  (let ((text (filter-buffer-substring begin end nil t)))
    (goto-char (max begin end))
    (let ((found-pos (search-forward text nil t)))
      (if (not found-pos)
          (progn
            (goto-char begin)
            (error "not found"))
          (progn
            (goto-char found-pos)
            (set-mark (- found-pos (length text))))))))


(define-key global-map [(control q )] 'my-search-forward)


It is almost there but not yet...
If I highlight some text, I can look for it with C-q, but once at the 
end of the buffer, it stops searching (whereas I would like it to search 
from the beginning of the buffer).
If then I move to the beginning of the buffer, not everything above my 
last position is selected, but also the function loses memory of what I 
was looking for...
Anybody can give me some help? Apologies if there is already and emacs 
command for that, but my online search was not fruitful.
Cheers

Lorenzo