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30764597 | 1 | ;;; syntax.el --- helper functions to find syntactic context |
88a05faf SM |
2 | |
3 | ;; Copyright (C) 2000 Free Software Foundation, Inc. | |
4 | ||
30764597 PJ |
5 | ;; Maintainer: FSF |
6 | ;; Keywords: internal | |
7 | ||
88a05faf SM |
8 | ;; This file is part of GNU Emacs. |
9 | ||
10 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
11 | ;; it under the terms of the GNU General Public License as published by | |
12 | ;; the Free Software Foundation; either version 2, or (at your option) | |
13 | ;; any later version. | |
14 | ||
15 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
16 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | ;; GNU General Public License for more details. | |
19 | ||
20 | ;; You should have received a copy of the GNU General Public License | |
21 | ;; along with GNU Emacs; see the file COPYING. If not, write to the | |
22 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
23 | ;; Boston, MA 02111-1307, USA. | |
24 | ||
25 | ;;; Commentary: | |
26 | ||
27 | ;; The main exported function is `syntax-ppss'. You might also need | |
28 | ;; to call `syntax-ppss-after-change-function' or to add it to | |
29 | ;; after-change-functions'(although this is automatically done by | |
30 | ;; syntax-ppss when needed, but that might fail if syntax-ppss is | |
31 | ;; called in a context where after-change-functions is temporarily | |
32 | ;; let-bound to nil). | |
33 | ||
34 | ;;; Todo: | |
35 | ||
36 | ;; - do something about the case where the syntax-table is changed. | |
37 | ;; This typically happens with tex-mode and its `$' operator. | |
38 | ;; - move font-lock-syntactic-keywords in here. Then again, maybe not. | |
39 | ;; - new functions `syntax-state', ... to replace uses of parse-partial-state | |
40 | ;; with something higher-level (similar to syntax-ppss-context). | |
41 | ;; - interaction with mmm-mode. | |
42 | ;; - what to do when the buffer is narrowed ? | |
43 | ||
44 | ;;; Code: | |
45 | ||
46 | ;; Note: PPSS stands for `parse-partial-sexp state' | |
47 | ||
48 | (eval-when-compile (require 'cl)) | |
49 | ||
50 | (defsubst syntax-ppss-depth (ppss) | |
51 | (nth 0 ppss)) | |
52 | ||
53 | (defsubst syntax-ppss-context (ppss) | |
54 | (cond | |
55 | ((nth 3 ppss) 'string) | |
56 | ((nth 4 ppss) 'comment) | |
57 | (t nil))) | |
58 | ||
59 | (defvar syntax-ppss-max-span 20000 | |
60 | "Threshold below which cache info is deemed unnecessary. | |
61 | We try to make sure that cache entries are at least this far apart | |
62 | from each other, to avoid keeping too much useless info.") | |
63 | ||
64 | (defvar syntax-begin-function nil | |
65 | "Function to move back outside of any comment/string/paren. | |
66 | This function should move the cursor back to some syntactically safe | |
67 | point (where the PPSS is equivalent to nil).") | |
68 | ||
69 | (defvar syntax-ppss-cache nil | |
70 | "List of (POS . PPSS) pairs, in decreasing POS order.") | |
71 | (make-variable-buffer-local 'syntax-ppss-cache) | |
72 | (defvar syntax-ppss-last nil | |
73 | "Cache of (LAST-POS . LAST-PPSS).") | |
74 | (make-variable-buffer-local 'syntax-ppss-last) | |
75 | ||
76 | (defun syntax-ppss-after-change-function (beg &rest ignored) | |
77 | ;; Flush invalid cache entries. | |
78 | (while (and syntax-ppss-cache (> (caar syntax-ppss-cache) beg)) | |
79 | (setq syntax-ppss-cache (cdr syntax-ppss-cache))) | |
80 | ;; Throw away `last' value if made invalid. | |
81 | (when (< beg (or (car syntax-ppss-last) 0)) | |
82 | (if (< beg (or (car (nth 10 syntax-ppss-last)) | |
83 | (nth 9 syntax-ppss-last) | |
84 | (nth 2 syntax-ppss-last) | |
85 | 0)) | |
86 | (setq syntax-ppss-last nil) | |
87 | (setcar syntax-ppss-last nil))) | |
88 | ;; Unregister if there's no cache left. Sadly this doesn't work | |
89 | ;; because `after-change-functions' is temporarily bound to nil here. | |
90 | ;; (unless syntax-ppss-cache | |
91 | ;; (remove-hook 'after-change-functions | |
92 | ;; 'syntax-ppss-after-change-function t)) | |
93 | ) | |
94 | ||
95 | (defvar syntax-ppss-stats | |
96 | [(0 . 0.0) (0 . 0.0) (0 . 0.0) (0 . 0.0) (0 . 0.0) (1 . 2500.0)]) | |
97 | (defun syntax-ppss-stats () | |
e8ac59b8 SM |
98 | (mapcar (lambda (x) |
99 | (condition-case nil | |
100 | (cons (car x) (truncate (/ (cdr x) (car x)))) | |
101 | (error nil))) | |
88a05faf SM |
102 | syntax-ppss-stats)) |
103 | ||
71f34313 | 104 | ;;;###autoload |
88a05faf SM |
105 | (defun syntax-ppss (&optional pos) |
106 | "Parse-Partial-Sexp State at POS. | |
107 | The returned value is the same as `parse-partial-sexp' except that | |
108 | the 2nd and 6th values of the returned state cannot be relied upon. | |
109 | ||
110 | If the caller knows the PPSS of a nearby position, she can pass it | |
111 | in OLP-PPSS (with or without its corresponding OLD-POS) to try and | |
112 | avoid a more expansive scan. | |
113 | Point is at POS when this function returns." | |
114 | ;; Default values. | |
115 | (unless pos (setq pos (point))) | |
a1506d29 | 116 | ;; |
88a05faf SM |
117 | (let ((old-ppss (cdr syntax-ppss-last)) |
118 | (old-pos (car syntax-ppss-last)) | |
119 | (ppss nil) | |
120 | (pt-min (point-min))) | |
121 | (if (and old-pos (> old-pos pos)) (setq old-pos nil)) | |
122 | ;; Use the OLD-POS if usable and close. Don't update the `last' cache. | |
123 | (if (and old-pos (< (- pos old-pos) | |
124 | ;; The time to find PPSS using syntax-begin-function | |
125 | ;; is assumed to be about 2 * distance. | |
126 | (* 2 (/ (cdr (aref syntax-ppss-stats 5)) | |
127 | (1+ (car (aref syntax-ppss-stats 5))))))) | |
128 | (progn | |
129 | (incf (car (aref syntax-ppss-stats 0))) | |
130 | (incf (cdr (aref syntax-ppss-stats 0)) (- pos old-pos)) | |
131 | (parse-partial-sexp old-pos pos nil nil old-ppss)) | |
a1506d29 | 132 | |
88a05faf SM |
133 | (cond |
134 | ;; Use OLD-PPSS if possible and close enough. | |
135 | ((and (not old-pos) old-ppss | |
136 | ;; BEWARE! We rely on the undocumented 9th field. | |
137 | ;; The 9th field currently contains the list of positions | |
138 | ;; of open-parens of the enclosing parens. I.e. those positions | |
139 | ;; are outside of any string/comment and the first of those is | |
140 | ;; outside of any paren (i.e. corresponds to a nil ppss). | |
141 | ;; If this list is empty but we are in a string or comment, | |
142 | ;; then the 8th field contains a similar "toplevel" position. | |
143 | ;; If `pt-min' is too far from `pos', we could try to use | |
144 | ;; other positions in (nth 9 old-ppss), but that doesn't seem | |
145 | ;; to happen in practice and it would complicate this code | |
146 | ;; (and the after-change-function code even more). But maybe it | |
147 | ;; would be useful in "degenerate" cases such as when the whole | |
148 | ;; file is wrapped in a set of parenthesis. | |
149 | (setq pt-min (or (car (nth 9 old-ppss)) | |
150 | (nth 8 old-ppss) | |
151 | (nth 2 old-ppss))) | |
152 | (<= pt-min pos) (< (- pos pt-min) syntax-ppss-max-span)) | |
153 | (incf (car (aref syntax-ppss-stats 1))) | |
154 | (incf (cdr (aref syntax-ppss-stats 1)) (- pos pt-min)) | |
155 | (setq ppss (parse-partial-sexp pt-min pos))) | |
156 | ;; The OLD-* data can't be used. Consult the cache. | |
157 | (t | |
158 | (let ((cache-pred nil) | |
159 | (cache syntax-ppss-cache) | |
160 | (pt-min (point-min)) | |
161 | ;; I differentiate between PT-MIN and PT-BEST because I feel | |
162 | ;; like it might be important to ensure that the cache is only | |
163 | ;; filled with 100% sure data (whereas syntax-begin-function | |
164 | ;; might return incorrect data). Maybe that's just stupid. | |
165 | (pt-best (point-min)) | |
166 | (ppss-best nil)) | |
167 | ;; look for a usable cache entry. | |
168 | (while (and cache (< pos (caar cache))) | |
169 | (setq cache-pred cache) | |
170 | (setq cache (cdr cache))) | |
171 | (if cache (setq pt-min (caar cache) ppss (cdar cache))) | |
172 | ||
173 | ;; Setup the after-change function if necessary. | |
174 | (unless (or syntax-ppss-cache syntax-ppss-last) | |
175 | (add-hook 'after-change-functions | |
176 | 'syntax-ppss-after-change-function nil t)) | |
177 | ||
178 | ;; Use the best of OLD-POS and CACHE. | |
179 | (if (or (not old-pos) (< old-pos pt-min)) | |
180 | (setq pt-best pt-min ppss-best ppss) | |
181 | (incf (car (aref syntax-ppss-stats 4))) | |
182 | (incf (cdr (aref syntax-ppss-stats 4)) (- pos old-pos)) | |
183 | (setq pt-best old-pos ppss-best old-ppss)) | |
184 | ||
185 | ;; Use the `syntax-begin-function' if available. | |
186 | ;; We could try using that function earlier, but: | |
187 | ;; - The result might not be 100% reliable, so it's better to use | |
188 | ;; the cache if available. | |
189 | ;; - The function might be slow. | |
190 | ;; - If this function almost always finds a safe nearby spot, | |
191 | ;; the cache won't be populated, so consulting it is cheap. | |
192 | (unless (or syntax-begin-function | |
193 | (not (boundp 'font-lock-beginning-of-syntax-function)) | |
194 | (not font-lock-beginning-of-syntax-function)) | |
195 | (set (make-local-variable 'syntax-begin-function) | |
196 | font-lock-beginning-of-syntax-function)) | |
197 | (when (and syntax-begin-function | |
198 | (progn (goto-char pos) | |
199 | (funcall syntax-begin-function) | |
200 | ;; Make sure it's better. | |
201 | (> (point) pt-best)) | |
202 | ;; Simple sanity check. | |
203 | (not (memq (get-text-property (point) 'face) | |
204 | '(font-lock-string-face font-lock-comment-face | |
205 | font-lock-doc-face)))) | |
206 | (incf (car (aref syntax-ppss-stats 5))) | |
207 | (incf (cdr (aref syntax-ppss-stats 5)) (- pos (point))) | |
208 | (setq pt-best (point) ppss-best nil)) | |
209 | ||
210 | (cond | |
211 | ;; Quick case when we found a nearby pos. | |
212 | ((< (- pos pt-best) syntax-ppss-max-span) | |
213 | (incf (car (aref syntax-ppss-stats 2))) | |
214 | (incf (cdr (aref syntax-ppss-stats 2)) (- pos pt-best)) | |
215 | (setq ppss (parse-partial-sexp pt-best pos nil nil ppss-best))) | |
216 | ;; Slow case: compute the state from some known position and | |
217 | ;; populate the cache so we won't need to do it again soon. | |
218 | (t | |
219 | (incf (car (aref syntax-ppss-stats 3))) | |
220 | (incf (cdr (aref syntax-ppss-stats 3)) (- pos pt-min)) | |
221 | ||
222 | ;; If `pt-min' is too far, add a few intermediate entries. | |
223 | (while (> (- pos pt-min) (* 2 syntax-ppss-max-span)) | |
224 | (setq ppss (parse-partial-sexp | |
225 | pt-min (setq pt-min (/ (+ pt-min pos) 2)) | |
226 | nil nil ppss)) | |
227 | (let ((pair (cons pt-min ppss))) | |
228 | (if cache-pred | |
229 | (push pair (cdr cache-pred)) | |
230 | (push pair syntax-ppss-cache)))) | |
231 | ||
232 | ;; Compute the actual return value. | |
233 | (setq ppss (parse-partial-sexp pt-min pos nil nil ppss)) | |
234 | ||
235 | ;; Debugging check. | |
236 | ;; (let ((real-ppss (parse-partial-sexp (point-min) pos))) | |
237 | ;; (setcar (last ppss 4) 0) | |
238 | ;; (setcar (last real-ppss 4) 0) | |
239 | ;; (setcar (last ppss 8) nil) | |
240 | ;; (setcar (last real-ppss 8) nil) | |
241 | ;; (unless (equal ppss real-ppss) | |
242 | ;; (message "!!Syntax: %s != %s" ppss real-ppss) | |
243 | ;; (setq ppss real-ppss))) | |
244 | ||
245 | ;; Store it in the cache. | |
246 | (let ((pair (cons pos ppss))) | |
247 | (if cache-pred | |
248 | (if (> (- (caar cache-pred) pos) syntax-ppss-max-span) | |
249 | (push pair (cdr cache-pred)) | |
250 | (setcar cache-pred pair)) | |
251 | (if (or (null syntax-ppss-cache) | |
252 | (> (- (caar syntax-ppss-cache) pos) | |
253 | syntax-ppss-max-span)) | |
254 | (push pair syntax-ppss-cache) | |
255 | (setcar syntax-ppss-cache pair))))))))) | |
a1506d29 | 256 | |
88a05faf SM |
257 | (setq syntax-ppss-last (cons pos ppss)) |
258 | ppss))) | |
259 | ||
260 | ;; Debugging functions | |
261 | ||
262 | (defun syntax-ppss-debug () | |
263 | (let ((pt nil) | |
264 | (min-diffs nil)) | |
265 | (dolist (x (append syntax-ppss-cache (list (cons (point-min) nil)))) | |
266 | (when pt (push (- pt (car x)) min-diffs)) | |
267 | (setq pt (car x))) | |
268 | min-diffs)) | |
269 | ||
270 | ;; XEmacs compatibility functions | |
271 | ||
272 | ;; (defun buffer-syntactic-context (&optional buffer) | |
273 | ;; "Syntactic context at point in BUFFER. | |
274 | ;; Either of `string', `comment' or `nil'. | |
275 | ;; This is an XEmacs compatibility function." | |
276 | ;; (with-current-buffer (or buffer (current-buffer)) | |
277 | ;; (syntax-ppss-context (syntax-ppss)))) | |
278 | ||
279 | ;; (defun buffer-syntactic-context-depth (&optional buffer) | |
280 | ;; "Syntactic parenthesis depth at point in BUFFER. | |
281 | ;; This is an XEmacs compatibility function." | |
282 | ;; (with-current-buffer (or buffer (current-buffer)) | |
283 | ;; (syntax-ppss-depth (syntax-ppss)))) | |
284 | ||
88a05faf SM |
285 | (provide 'syntax) |
286 | ;;; syntax.el ends here |