;;; ring.el --- handle rings of items
-;; Copyright (C) 1992, 2001, 2002, 2003, 2004, 2005,
-;; 2006, 2007, 2008 Free Software Foundation, Inc.
+;; Copyright (C) 1992, 2001-2015 Free Software Foundation, Inc.
-;; Maintainer: FSF
+;; Maintainer: emacs-devel@gnu.org
;; Keywords: extensions
;; This file is part of GNU Emacs.
(unless curr-index (error "Item is not in the ring: `%s'" item))
(ring-ref ring (ring-minus1 curr-index (ring-length ring)))))
+(defun ring-extend (ring x)
+ "Increase the size of RING by X."
+ (when (and (integerp x) (> x 0))
+ (let* ((hd (car ring))
+ (length (ring-length ring))
+ (size (ring-size ring))
+ (old-vec (cddr ring))
+ (new-vec (make-vector (+ size x) nil)))
+ (setcdr ring (cons length new-vec))
+ ;; If the ring is wrapped, the existing elements must be written
+ ;; out in the right order.
+ (dotimes (j length)
+ (aset new-vec j (aref old-vec (mod (+ hd j) size))))
+ (setcar ring 0))))
+
(defun ring-insert+extend (ring item &optional grow-p)
"Like `ring-insert', but if GROW-P is non-nil, then enlarge ring.
Insert onto ring RING the item ITEM, as the newest (last) item.
If the ring is full, behavior depends on GROW-P:
If GROW-P is non-nil, enlarge the ring to accommodate the new item.
If GROW-P is nil, dump the oldest item to make room for the new."
- (let* ((vec (cddr ring))
- (veclen (length vec))
- (hd (car ring))
- (ringlen (ring-length ring)))
- (prog1
- (cond ((and grow-p (= ringlen veclen)) ; Full ring. Enlarge it.
- (setq veclen (1+ veclen))
- (setcdr ring (cons (setq ringlen (1+ ringlen))
- (setq vec (vconcat vec (vector item)))))
- (setcar ring hd))
- (t (aset vec (mod (+ hd ringlen) veclen) item)))
- (if (= ringlen veclen)
- (setcar ring (ring-plus1 hd veclen))
- (setcar (cdr ring) (1+ ringlen))))))
+ (and grow-p
+ (= (ring-length ring) (ring-size ring))
+ (ring-extend ring 1))
+ (ring-insert ring item))
(defun ring-remove+insert+extend (ring item &optional grow-p)
"`ring-remove' ITEM from RING, then `ring-insert+extend' it.
(provide 'ring)
-;; arch-tag: e707682b-ed69-47c9-b20f-cf2c68cc92d2
;;; ring.el ends here