;;; ring.el --- handle rings of items
-;; Copyright (C) 1992 Free Software Foundation, Inc.
+;; Copyright (C) 1992, 2001, 2002, 2003, 2004, 2005,
+;; 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
;; Maintainer: FSF
;; Keywords: extensions
;; This file is part of GNU Emacs.
-;; GNU Emacs is free software; you can redistribute it and/or modify
+;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
-;; the Free Software Foundation; either version 2, or (at your option)
-;; any later version.
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
-;; along with GNU Emacs; see the file COPYING. If not, write to the
-;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-;; Boston, MA 02111-1307, USA.
+;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
-;; This code defines a ring data structure. A ring is a
+;; This code defines a ring data structure. A ring is a
;; (hd-index length . vector)
;; list. You can insert to, remove from, and rotate a ring. When the ring
;; fills up, insertions cause the oldest elts to be quietly dropped.
;;;###autoload
(defun ring-p (x)
- "Returns t if X is a ring; nil otherwise."
+ "Return t if X is a ring; nil otherwise."
(and (consp x) (integerp (car x))
- (consp (cdr x)) (integerp (car (cdr x)))
- (vectorp (cdr (cdr x)))))
+ (consp (cdr x)) (integerp (cadr x))
+ (vectorp (cddr x))))
;;;###autoload
(defun make-ring (size)
(cons 0 (cons 0 (make-vector size nil))))
(defun ring-insert-at-beginning (ring item)
- "Add to RING the item ITEM. Add it at the front, as the oldest item."
- (let* ((vec (cdr (cdr ring)))
+ "Add to RING the item ITEM, at the front, as the oldest item."
+ (let* ((vec (cddr ring))
(veclen (length vec))
(hd (car ring))
- (ln (car (cdr ring))))
+ (ln (cadr ring)))
(setq ln (min veclen (1+ ln))
hd (ring-minus1 hd veclen))
(aset vec hd item)
(setcar (cdr ring) ln)))
(defun ring-plus1 (index veclen)
- "Returns INDEX+1, with wraparound."
- (let ((new-index (+ index 1)))
+ "Return INDEX+1, with wraparound."
+ (let ((new-index (1+ index)))
(if (= new-index veclen) 0 new-index)))
(defun ring-minus1 (index veclen)
- "Returns INDEX-1, with wraparound."
- (- (if (= 0 index) veclen index) 1))
+ "Return INDEX-1, with wraparound."
+ (- (if (zerop index) veclen index) 1))
(defun ring-length (ring)
- "Returns the number of elements in the RING."
- (car (cdr ring)))
+ "Return the number of elements in the RING."
+ (cadr ring))
(defun ring-index (index head ringlen veclen)
- "Converts nominal ring index INDEX to an internal index.
+ "Convert nominal ring index INDEX to an internal index.
The internal index refers to the items ordered from newest to oldest.
HEAD is the index of the oldest element in the ring.
RINGLEN is the number of elements currently in the ring.
(mod (1- (+ head (- ringlen index))) veclen))
(defun ring-empty-p (ring)
- "Returns t if RING is empty; nil otherwise."
- (= 0 (car (cdr ring))))
+ "Return t if RING is empty; nil otherwise."
+ (zerop (cadr ring)))
(defun ring-size (ring)
- "Returns the size of RING, the maximum number of elements it can contain."
- (length (cdr (cdr ring))))
+ "Return the size of RING, the maximum number of elements it can contain."
+ (length (cddr ring)))
(defun ring-copy (ring)
- "Returns a copy of RING."
- (let* ((vec (cdr (cdr ring)))
- (hd (car ring))
- (ln (car (cdr ring))))
+ "Return a copy of RING."
+ (let ((vec (cddr ring))
+ (hd (car ring))
+ (ln (cadr ring)))
(cons hd (cons ln (copy-sequence vec)))))
(defun ring-insert (ring item)
"Insert onto ring RING the item ITEM, as the newest (last) item.
If the ring is full, dump the oldest item to make room."
- (let* ((vec (cdr (cdr ring)))
+ (let* ((vec (cddr ring))
(veclen (length vec))
(hd (car ring))
- (ln (car (cdr ring))))
+ (ln (cadr ring)))
(prog1
(aset vec (mod (+ hd ln) veclen) item)
(if (= ln veclen)
(if (ring-empty-p ring)
(error "Ring empty")
(let* ((hd (car ring))
- (ln (car (cdr ring)))
- (vec (cdr (cdr ring)))
+ (ln (cadr ring))
+ (vec (cddr ring))
(veclen (length vec))
(tl (mod (1- (+ hd ln)) veclen))
oldelt)
- (if (null index)
- (setq index (1- ln)))
+ (when (null index)
+ (setq index (1- ln)))
(setq index (ring-index index hd ln veclen))
(setq oldelt (aref vec index))
(while (/= index tl)
oldelt)))
(defun ring-ref (ring index)
- "Returns RING's INDEX element.
+ "Return RING's INDEX element.
INDEX = 0 is the most recently inserted; higher indices
correspond to older elements.
INDEX need not be <= the ring length; the appropriate modulo operation
will be performed."
(if (ring-empty-p ring)
(error "Accessing an empty ring")
- (let* ((hd (car ring)) (ln (car (cdr ring))) (vec (cdr (cdr ring))))
+ (let ((hd (car ring))
+ (ln (cadr ring))
+ (vec (cddr ring)))
(aref vec (ring-index index hd ln (length vec))))))
+(defun ring-elements (ring)
+ "Return a list of the elements of RING, in order, newest first."
+ (let ((start (car ring))
+ (size (ring-size ring))
+ (vect (cddr ring))
+ lst)
+ (dotimes (var (cadr ring) lst)
+ (push (aref vect (mod (+ start var) size)) lst))))
+
+(defun ring-member (ring item)
+ "Return index of ITEM if on RING, else nil.
+Comparison is done via `equal'. The index is 0-based."
+ (catch 'found
+ (dotimes (ind (ring-length ring) nil)
+ (when (equal item (ring-ref ring ind))
+ (throw 'found ind)))))
+
+(defun ring-next (ring item)
+ "Return the next item in the RING, after ITEM.
+Raise error if ITEM is not in the RING."
+ (let ((curr-index (ring-member ring item)))
+ (unless curr-index (error "Item is not in the ring: `%s'" item))
+ (ring-ref ring (ring-plus1 curr-index (ring-length ring)))))
+
+(defun ring-previous (ring item)
+ "Return the previous item in the RING, before ITEM.
+Raise error if ITEM is not in the RING."
+ (let ((curr-index (ring-member ring item)))
+ (unless curr-index (error "Item is not in the ring: `%s'" item))
+ (ring-ref ring (ring-minus1 curr-index (ring-length ring)))))
+
+(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))))))
+
+(defun ring-remove+insert+extend (ring item &optional grow-p)
+ "`ring-remove' ITEM from RING, then `ring-insert+extend' it.
+This ensures that there is only one ITEM on RING.
+
+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 (ind)
+ (while (setq ind (ring-member ring item))
+ (ring-remove ring ind)))
+ (ring-insert+extend ring item grow-p))
+
+(defun ring-convert-sequence-to-ring (seq)
+ "Convert sequence SEQ to a ring. Return the ring.
+If SEQ is already a ring, return it."
+ (if (ring-p seq)
+ seq
+ (let* ((size (length seq))
+ (ring (make-ring size)))
+ (dotimes (count size)
+ (when (or (ring-empty-p ring)
+ (not (equal (ring-ref ring 0) (elt seq count))))
+ (ring-insert-at-beginning ring (elt seq count))))
+ ring)))
+
;;; provide ourself:
(provide 'ring)
+;; arch-tag: e707682b-ed69-47c9-b20f-cf2c68cc92d2
;;; ring.el ends here