1 ;;; fifo.el --- FIFO queue.

     2 

     3 ;; Copyright (c) 2015 Chris Done.

     4 

     5 ;; This file is free software; you can redistribute it and/or modify

     6 ;; it under the terms of the GNU General Public License as published by

     7 ;; the Free Software Foundation; either version 3, or (at your option)

     8 ;; any later version.

     9 

    10 ;; This file is distributed in the hope that it will be useful,

    11 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of

    12 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    13 ;; GNU General Public License for more details.

    14 

    15 ;; You should have received a copy of the GNU General Public License

    16 ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.

    17 

    18 ;;; Code:

    19 

    20 (require 'cl-lib)

    21 

    22 (defun fifo-make ()

    23   "Make a fifo queue."

    24   (cons 0 nil))

    25 

    26 (defun fifo-push (q a)

    27   "Push a new item onto the queue."

    28   (cl-assert (consp q) nil "Must be a queue.")

    29   (setcar q (1+ (car q)))

    30   (let ((next q)

    31         (continue t))

    32     (while (not (null (cdr next)))

    33       (setq next (cdr next)))

    34     (setcdr next (cons a nil)))

    35   q)

    36 

    37 (defun fifo-pop (q)

    38   "Pop the next item on the queue."

    39   (cl-assert (consp q) nil "Must be a queue.")

    40   (cl-assert (consp (cdr q)) nil "No items to pop from queue.")

    41   (setcar q (1- (car q)))

    42   (let ((a (car (cdr q))))

    43     (setcdr q (cdr (cdr q)))

    44     a))

    45 

    46 (defun fifo-size (q)

    47   "Get the size of the queue."

    48   (cl-assert (consp q) nil "Must be a queue.")

    49   (car q))

    50 

    51 (defun fifo-null-p (q)

    52   "Is the queue empty?"

    53   (= (fifo-size q) 0))

    54 

    55 (provide 'fifo)