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+;;; fast-lock.el --- Automagic text properties saving for fast font-lock-mode.
+
+;; Copyright (C) 1994 Free Software Foundation, Inc.
+
+;; Author: Simon Marshall <Simon.Marshall@mail.esrin.esa.it>
+;; Keywords: faces files
+;; Version: 3.05
+
+;;; This file is part of GNU Emacs.
+
+;; 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.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Commentary:
+
+;; Purpose:
+;;
+;; To make visiting a file in `font-lock-mode' faster by restoring its face
+;; text properties from automatically saved associated font lock cache files.
+;;
+;; See also the face-lock package.
+;; See also the lazy-lock package.  (But don't use the two at the same time!)
+
+;; Note that:
+;;
+;; - A cache will be saved when visiting a compressed file using crypt++, but
+;;   not be read.  This is a "feature"/"consequence"/"bug" of crypt++.
+
+;; Installation:
+;; 
+;; Put this file somewhere where Emacs can find it (i.e., in one of the paths
+;; in your `load-path'), `byte-compile-file' it, and put in your ~/.emacs:
+;;
+;; (autoload 'turn-on-fast-lock "fast-lock"
+;;   "Unconditionally turn on Fast Lock mode.")
+;;
+;; (add-hook 'font-lock-mode-hook 'turn-on-fast-lock)
+;;
+;; Start up a new Emacs and use font-lock as usual (except that you can use the
+;; so-called "gaudier" fontification regexps on big files without frustration).
+;;
+;; When you visit a file (which has `font-lock-mode' enabled) that has a
+;; corresponding font lock cache file associated with it, the font lock cache
+;; will be loaded from that file instead of being generated by font-lock code.
+;;
+;; Font lock caches will be saved:
+;;  - For all buffers with Fast Lock mode enabled when you exit from Emacs.
+;;  - For a buffer with Fast Lock mode enabled when you kill the buffer.
+;; To provide control over how such cache files are written automagically, see
+;; variable `fast-lock-cache-directories'.  To provide control over which such
+;; cache files are written, see variables `fast-lock-save-others' and
+;; `fast-lock-save-size'.  Only cache files which were generated using the same
+;; `font-lock-keywords' as you are using will be used.
+;;
+;; As an illustration of the time saving, a 115k file of Emacs C code took 95
+;; seconds to fontify using Emacs 19.25 on a Sun SparcStation 2 LX (using
+;; `c-font-lock-keywords-2').  The font lock cache file takes around 2 seconds
+;; to load (with around 4 seconds to generate and save).  Bite it.  Believe it.
+;; (For Lucid Emacs 19.10, the figures on a similar machine, file, and regexps,
+;; are 70, around 4, and around 4, seconds, respectively; for Emacs 19.28 the
+;; fontification takes around 26 seconds.)
+
+;; Feedback:
+;;
+;; Please send me bug reports, bug fixes, and extensions, so that I can
+;; merge them into the master source.
+;;     - Simon Marshall (Simon.Marshall@mail.esrin.esa.it)
+
+(require 'font-lock)
+
+(eval-when-compile
+  ;; Shut Emacs' byte-compiler up (cf. stop me getting mail from users).
+  (setq byte-compile-warnings '(free-vars callargs redefine)))
+
+;; User variables:
+
+(defvar fast-lock-cache-directories '("." "~/.emacs-flc")
+; - `internal', keep each file's font lock cache file in the same file.
+; - `external', keep each file's font lock cache file in the same directory.
+  "Directories in which font lock cache files are saved and read.
+Each item should be either DIR or a cons pair of the form (REGEXP . DIR) where
+DIR is a directory name (relative or absolute) and REGEXP is a regexp.
+
+An attempt will be made to save or read font lock cache files using these items
+until one succeeds (i.e., until a readable or writable one is found).  If an
+item contains REGEXP, DIR is used only if the buffer file name matches REGEXP.
+For example:
+
+ (list (cons (concat \"^\" (regexp-quote (expand-file-name \"~\"))) \".\")
+       \"~/.emacs-flc\")
+
+would cause a file's current directory to be used if the file is under your
+home directory hierarchy, and the absolute directory otherwise.")
+
+(defvar fast-lock-save-size (* 10 1024)
+  "If non-nil, the minimum size for buffer files.
+Only buffer files at least this size can have associated font lock cache files
+saved.  If nil, means size is irrelevant.")
+
+(defvar fast-lock-save-others t
+  "If non-nil, save font lock cache files irrespective of file owner.
+If nil, means only buffer files owned by you have a font lock cache saved.")
+
+(defvar fast-lock-mode nil)             ; for modeline
+(defvar fast-lock-cache-timestamp nil)  ; for saving/reading
+(make-variable-buffer-local 'fast-lock-cache-timestamp)
+
+;; Functions:
+
+(defun fast-lock-mode (&optional arg)
+  "Toggle Fast Lock mode.
+With arg, turn Fast Lock mode on if and only if arg is positive and the buffer
+is associated with a file.
+
+If Fast Lock mode is enabled, and the current buffer does not contain any text
+properties, any associated font lock cache is used (by `fast-lock-read-cache')
+if the same `font-lock-keywords' were used for the cache as you are using.
+
+Font lock caches will be saved:
+ - For all buffers with Fast Lock mode enabled when you exit from Emacs.
+ - For a buffer with Fast Lock mode enabled when you kill the buffer.
+Saving is done by `fast-lock-save-cache' and `fast-lock-save-caches'.
+
+Various methods of control are provided for the font lock cache.  In general,
+see variable `fast-lock-cache-directories' and function `fast-lock-cache-name'.
+For saving, see variables `fast-lock-save-others' and `fast-lock-save-size'."
+  (interactive "P")
+  (set (make-local-variable 'fast-lock-mode)
+       (and (buffer-file-name)
+            (if arg (> (prefix-numeric-value arg) 0) (not fast-lock-mode))))
+  (if (and fast-lock-mode (not font-lock-fontified))
+      (fast-lock-read-cache)))
+
+(defun fast-lock-read-cache ()
+  "Read the font lock cache for the current buffer.
+Returns t if the font lock cache file is read.
+
+The following criteria must be met for a font lock cache file to be read:
+ - Fast Lock mode must be turned on in the buffer.
+ - The buffer's `font-lock-keywords' must match the cache's.
+ - The buffer file's timestamp must match the cache's.
+ - Criteria imposed by `fast-lock-cache-directories'.
+
+See also `fast-lock-save-cache' and `fast-lock-cache-name'."
+  (interactive)
+  (let ((directories fast-lock-cache-directories) directory
+        (modified (buffer-modified-p))
+        (fontified font-lock-fontified))
+    (set (make-local-variable 'font-lock-fontified) nil)
+    ;; Keep trying directories until fontification is turned off.
+    (while (and directories (not font-lock-fontified))
+      (setq directory (fast-lock-cache-directory (car directories) nil)
+            directories (cdr directories))
+      (if directory
+          (condition-case nil
+              (load (fast-lock-cache-name directory) t t t)
+            (error nil) (quit nil))))
+    (set-buffer-modified-p modified)
+    (or font-lock-fontified (setq font-lock-fontified fontified))))
+
+(defun fast-lock-save-cache (&optional buffer)
+  "Save the font lock cache of BUFFER or the current buffer.
+Returns t if the font lock cache file is saved.
+
+The following criteria must be met for a font lock cache file to be saved:
+ - Fast Lock mode must be turned on in the buffer.
+ - The buffer must be at least `fast-lock-save-size' bytes long.
+ - The buffer file must be owned by you, or `fast-lock-save-others' must be t.
+ - The buffer must contain at least one `face' text property.
+ - The buffer file's timestamp must be different than its associated text
+   properties file's timestamp.
+ - Criteria imposed by `fast-lock-cache-directories'.
+
+See also `fast-lock-save-caches', `fast-lock-read-cache' and `fast-lock-mode'."
+  (interactive)
+  (let* ((bufile (buffer-file-name buffer))
+         (buatts (and bufile (file-attributes bufile)))
+         (bufile-timestamp (nth 5 buatts))
+         (bufuid (nth 2 buatts)) (saved nil))
+    (save-excursion
+      (and buffer (set-buffer buffer))
+      (if (and fast-lock-mode
+               ;; Only save if the timestamp of the file has changed.
+               (not (equal fast-lock-cache-timestamp bufile-timestamp))
+               ;; User's restrictions?
+               (or fast-lock-save-others (eq (user-uid) bufuid))
+               (<= (or fast-lock-save-size 0) (buffer-size))
+               ;; Only save if there are properties to save.
+               (text-property-not-all (point-min) (point-max) 'face nil))
+          (let ((directories fast-lock-cache-directories) directory)
+            (while (and directories (not saved))
+              (setq directory (fast-lock-cache-directory (car directories) t)
+                    directories (cdr directories))
+              (if directory
+                  (setq saved (fast-lock-save-cache-data
+                               directory bufile-timestamp))))))
+      ;; Set the buffer's timestamp if saved.
+      (and saved (setq fast-lock-cache-timestamp bufile-timestamp)))
+    saved))
+
+(defun fast-lock-save-cache-data (directory timestamp)
+  ;; Save the file with the timestamp, if we can, in the given directory, as:
+  ;; (fast-lock-cache-data Version=2 TIMESTAMP font-lock-keywords PROPERTIES).
+  (let ((buname (buffer-name))
+        (tpfile (fast-lock-cache-name directory))
+        (saved nil))
+    (if (file-writable-p tpfile)
+        (let ((tpbuf (generate-new-buffer " *fast-lock*")))
+          (message "Saving %s font lock cache..." buname)
+          (unwind-protect
+              (save-excursion
+                (print (list 'fast-lock-cache-data 2
+                             (list 'quote timestamp)
+                             (list 'quote font-lock-keywords)
+                             (list 'quote (fast-lock-get-face-properties)))
+                       tpbuf)
+                (set-buffer tpbuf)
+                (write-region (point-min) (point-max) tpfile nil 'quietly)
+                (setq saved t))
+            (kill-buffer tpbuf))
+          (message "Saving %s font lock cache... done." buname)))
+    saved))
+
+;; Miscellaneous functions:
+
+(defun turn-on-fast-lock ()
+  "Unconditionally turn on Fast Lock mode."
+  (fast-lock-mode 1))
+
+(defun fast-lock-save-caches ()
+  "Save the font lock caches of all buffers.
+Returns list of cache save success of buffers in `buffer-list'.
+See `fast-lock-save-cache' for details of save criteria."
+  (mapcar 'fast-lock-save-cache (buffer-list)))
+
+(defun fast-lock-cache-directory (directory create)
+  "Return usable directory based on DIRECTORY.
+Returns nil if the directory does not exist, or, if CREATE non-nil, cannot be
+created.  DIRECTORY may be a string or a cons pair of the form (REGEXP . DIR).
+See `fast-lock-cache-directories'."
+  (let ((dir (cond ((not buffer-file-name)
+                    nil)
+                   ((stringp directory)
+                    directory)
+                   (t
+                    (let ((bufile (expand-file-name
+                                   (abbreviate-file-name
+                                    (file-truename buffer-file-name))))
+                          (case-fold-search nil))
+                      (if (string-match (car directory) bufile)
+                          (cdr directory)))))))
+    (cond ((not dir)
+           nil)
+          ((not create)
+           (and (file-accessible-directory-p dir) dir))
+          (t
+           (if (file-accessible-directory-p dir)
+               dir
+             (condition-case nil (make-directory dir t) (error nil))
+             (and (file-accessible-directory-p dir) dir))))))
+
+(defun fast-lock-cache-name (directory)
+  "Return full cache path name using caching DIRECTORY.
+If DIRECTORY is `.', the path is the buffer file name appended with `.flc'.
+Otherwise, the path name is constructed from DIRECTORY and the buffer's true
+abbreviated file name, with all `/' characters in the name replaced with `#'
+characters, and appended with `.flc'.
+
+See `fast-lock-mode'."
+  (if (string-equal directory ".")
+      (concat buffer-file-name ".flc")
+    (let* ((bufile (expand-file-name
+                    (abbreviate-file-name (file-truename buffer-file-name))))
+           (chars-alist
+            (if (eq system-type 'emx)
+                '((?/ . (?#)) (?# . (?# ?#)) (?: . (?\;)) (?\; . (?\; ?\;)))
+              '((?/ . (?#)) (?# . (?# ?#)))))
+           (mapchars
+            (function (lambda (c) (or (cdr (assq c chars-alist)) (list c))))))
+      (concat
+       (file-name-as-directory (expand-file-name directory))
+       (mapconcat 'char-to-string (apply 'append (mapcar mapchars bufile)) "")
+       ".flc"))))
+
+;; Font lock cache processing functions:
+
+(defun fast-lock-cache-data (version timestamp keywords properties
+                             &rest ignored)
+  ;; Use the font lock cache PROPERTIES if we're using cache VERSION format 2,
+  ;; the current buffer's file timestamp matches the TIMESTAMP, and the current
+  ;; buffer's font-lock-keywords are the same as KEYWORDS.
+  (let ((buf-timestamp (nth 5 (file-attributes buffer-file-name)))
+        (buname (buffer-name)) (inhibit-read-only t) (loaded t))
+    (if (or (/= version 2)
+            (not (equal timestamp buf-timestamp))
+            (not (equal keywords font-lock-keywords)))
+        (setq loaded nil)
+      (message "Loading %s font lock cache..." buname)
+      (condition-case nil
+          (fast-lock-set-face-properties properties)
+        (error (setq loaded nil)) (quit (setq loaded nil)))
+      (message "Loading %s font lock cache... done." buname))
+    ;; If we used the text properties, stop fontification and keep timestamp.
+    (setq font-lock-fontified loaded
+          fast-lock-cache-timestamp (and loaded timestamp))))
+
+(defun fast-lock-get-face-properties (&optional buffer)
+  "Return a list of all `face' text properties in BUFFER.
+Each element of the list is of the form (VALUE START1 END1 START2 END2 ...)
+where VALUE is a `face' property value and STARTx and ENDx are positions."
+  (save-excursion
+    (and buffer (set-buffer buffer))
+    (save-restriction
+      (widen)
+      (let ((start (text-property-not-all (point-min) (point-max) 'face nil))
+            (limit (point-max)) end properties value cell)
+        (while start
+          (setq end (next-single-property-change start 'face nil limit)
+                value (get-text-property start 'face))
+          ;; Make or add to existing list of regions with same `face' property.
+          (if (setq cell (assq value properties))
+              (setcdr cell (cons start (cons end (cdr cell))))
+            (setq properties (cons (list value start end) properties)))
+          (setq start (next-single-property-change end 'face)))
+        properties))))
+
+(defun fast-lock-set-face-properties (properties &optional buffer)
+  "Set all `face' text properties to PROPERTIES in BUFFER.
+Any existing `face' text properties are removed first.  Leaves BUFFER modified.
+See `fast-lock-get-face-properties' for the format of PROPERTIES."
+  (save-excursion
+    (and buffer (set-buffer buffer))
+    (save-restriction
+      (widen)
+      (font-lock-unfontify-region (point-min) (point-max))
+      (while properties
+        (let ((plist (list 'face (car (car properties))))
+              (regions (cdr (car properties))))
+          ;; Set the `face' property for each start/end region.
+          (while regions
+            (set-text-properties (nth 0 regions) (nth 1 regions) plist buffer)
+            (setq regions (nthcdr 2 regions)))
+          (setq properties (cdr properties)))))))
+
+;; Functions for Lucid:
+
+(or (fboundp 'face-list)
+    (defalias 'face-list 'list-faces))
+
+(if (save-match-data (string-match "Lucid" (emacs-version)))
+    ;; This is about a bazillion times faster at generating the cache in Lucid.
+    (defun fast-lock-get-face-properties (&optional buffer)
+      "Return a list of all `face' text properties in BUFFER.
+Each element of the list is of the form (VALUE START1 END1 START2 END2 ...)
+where VALUE is a `face' property value and STARTx and ENDx are positions."
+      (save-excursion
+        (and buffer (set-buffer buffer))
+        (save-restriction
+          (widen)
+          (let ((properties ()))
+            (map-extents
+             (function (lambda (extent ignore)
+              (let* ((face (extent-face extent))
+                     (start (extent-start-position extent))
+                     (end (extent-end-position extent))
+                     (facedata (assoc face properties)))
+                (if facedata
+                    ;; Prepend the new start and end points onto the list.
+                    (setcdr facedata (cons start (cons end (cdr facedata))))
+                  (setq properties (cons (list face start end) properties)))
+                ;; Return nil to keep `map-extents' going.
+                nil))))
+            properties)))))
+
+(if (save-match-data (string-match "Lucid" (emacs-version)))
+    ;; This is faster at using the cache in Lucid.
+    (defun fast-lock-set-face-properties (properties &optional buffer)
+      "Set all `face' text properties to PROPERTIES in BUFFER.
+Any existing `face' text properties are removed first.  Leaves BUFFER modified.
+See `fast-lock-get-face-properties' for the format of PROPERTIES."
+      (save-excursion
+        (and buffer (set-buffer buffer))
+        (save-restriction
+          (widen)
+          (font-lock-unfontify-region (point-min) (point-max))
+          (while properties
+            (let ((property (car (car properties)))
+                  (regions (cdr (car properties))) extent)
+              ;; Set the `face' property for each start/end region.
+              (while regions
+                (setq extent (make-extent (nth 0 regions) (nth 1 regions))
+                      regions (nthcdr 2 regions))
+                (set-extent-face extent property)
+                (set-extent-property extent 'text-prop 'face))
+              (setq properties (cdr properties))))))))
+
+(if (and (boundp 'emacs-minor-version) (< emacs-minor-version 12))
+    ;; Must be [LX]Emacs; fix the 19.11 (at least) `text-property-not-all' bug.
+    (defun text-property-not-all (start end prop value &optional buffer)
+      "Check text from START to END to see if PROP is ever not `eq' to VALUE.
+If so, return the position of the first character whose PROP is not
+`eq' to VALUE.  Otherwise, return nil."
+      (let ((maxend start))
+        (map-extents
+         (function
+          (lambda (e ignore)
+            ;;### no, actually, this is harder.  We need to collect all props
+            ;; for a given character, and then determine whether no extent
+            ;; contributes the given value.  Doing this without consing lots
+            ;; of lists is the tricky part.
+            (if (not (eq value (extent-property e prop)))
+                (max start maxend)
+              (setq maxend (extent-end-position e))
+              nil)))
+         nil start end buffer))))
+
+;; Install ourselves:
+
+(or (assq 'fast-lock-mode minor-mode-alist)
+    (setq minor-mode-alist (cons '(fast-lock-mode " Fast") minor-mode-alist)))
+
+(add-hook 'kill-buffer-hook 'fast-lock-save-cache)
+(add-hook 'kill-emacs-hook 'fast-lock-save-caches)
+
+;; Provide ourselves:
+
+(provide 'fast-lock)
+
+;;; fast-lock.el ends here
+