lisp/filenotify.el

   1 ;;; filenotify.el --- watch files for changes on disk  -*- lexical-binding:t -*-
   2
   3 ;; Copyright (C) 2013-2015 Free Software Foundation, Inc.
   4
   5 ;; Author: Michael Albinus <michael.albinus@gmx.de>
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software: you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation, either version 3 of the License, or
  12 ;; (at your option) any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  21
  22 ;;; Commentary
  23
  24 ;; This package is an abstraction layer from the different low-level
  25 ;; file notification packages `gfilenotify', `inotify' and
  26 ;; `w32notify'.
  27
  28 ;;; Code:
  29
  30 (defconst file-notify--library
  31   (cond
  32    ((featurep 'gfilenotify) 'gfilenotify)
  33    ((featurep 'inotify) 'inotify)
  34    ((featurep 'w32notify) 'w32notify))
  35   "Non-nil when Emacs has been compiled with file notification support.
  36 The value is the name of the low-level file notification package
  37 to be used for local file systems.  Remote file notifications
  38 could use another implementation.")
  39
  40 (defvar file-notify-descriptors (make-hash-table :test 'equal)
  41   "Hash table for registered file notification descriptors.
  42 A key in this hash table is the descriptor as returned from
  43 `gfilenotify', `inotify', `w32notify' or a file name handler.
  44 The value in the hash table is a list
  45
  46   (DIR (FILE . CALLBACK) (FILE . CALLBACK) ...)
  47
  48 Several values for a given DIR happen only for `inotify', when
  49 different files from the same directory are watched.")
  50
  51 (defun file-notify--rm-descriptor (descriptor &optional what)
  52   "Remove DESCRIPTOR from `file-notify-descriptors'.
  53 DESCRIPTOR should be an object returned by `file-notify-add-watch'.
  54 If it is registered in `file-notify-descriptors', a stopped event is sent.
  55 WHAT is a file or directory name to be removed, needed just for `inotify'."
  56   (let* ((desc (if (consp descriptor) (car descriptor) descriptor))
  57          (file (if (consp descriptor) (cdr descriptor)))
  58          (registered (gethash desc file-notify-descriptors))
  59          (dir (car registered)))
  60
  61     (when (and (consp registered) (or (null what) (string-equal dir what)))
  62       ;; Send `stopped' event.
  63       (dolist (entry (cdr registered))
  64         (funcall (cdr entry)
  65                  `(,(file-notify--descriptor desc) stopped
  66                    ,(or (and (stringp (car entry))
  67                              (expand-file-name (car entry) dir))
  68                         dir))))
  69
  70       ;; Modify `file-notify-descriptors'.
  71       (if (not file)
  72           (remhash desc file-notify-descriptors)
  73         (setcdr registered
  74                 (delete (assoc file (cdr registered)) (cdr registered)))
  75         (if (null (cdr registered))
  76             (remhash desc file-notify-descriptors)
  77           (puthash desc registered file-notify-descriptors))))))
  78
  79 ;; This function is used by `gfilenotify', `inotify' and `w32notify' events.
  80 ;;;###autoload
  81 (defun file-notify-handle-event (event)
  82   "Handle file system monitoring event.
  83 If EVENT is a filewatch event, call its callback.  It has the format
  84
  85   (file-notify (DESCRIPTOR ACTIONS FILE [FILE1-OR-COOKIE]) CALLBACK)
  86
  87 Otherwise, signal a `file-notify-error'."
  88   (interactive "e")
  89   ;;(message "file-notify-handle-event %S" event)
  90   (if (and (eq (car event) 'file-notify)
  91            (>= (length event) 3))
  92       (funcall (nth 2 event) (nth 1 event))
  93     (signal 'file-notify-error
  94             (cons "Not a valid file-notify event" event))))
  95
  96 ;; Needed for `inotify' and `w32notify'.  In the latter case, COOKIE is nil.
  97 (defvar file-notify--pending-event nil
  98   "A pending file notification events for a future `renamed' action.
  99 It is a form ((DESCRIPTOR ACTION FILE [FILE1-OR-COOKIE]) CALLBACK).")
 100
 101 (defun file-notify--event-file-name (event)
 102   "Return file name of file notification event, or nil."
 103   (directory-file-name
 104    (expand-file-name
 105     (or  (and (stringp (nth 2 event)) (nth 2 event)) "")
 106     (car (gethash (car event) file-notify-descriptors)))))
 107
 108 ;; Only `gfilenotify' could return two file names.
 109 (defun file-notify--event-file1-name (event)
 110   "Return second file name of file notification event, or nil.
 111 This is available in case a file has been moved."
 112   (and (stringp (nth 3 event))
 113        (directory-file-name
 114         (expand-file-name
 115          (nth 3 event) (car (gethash (car event) file-notify-descriptors))))))
 116
 117 ;; Cookies are offered by `inotify' only.
 118 (defun file-notify--event-cookie (event)
 119   "Return cookie of file notification event, or nil.
 120 This is available in case a file has been moved."
 121   (nth 3 event))
 122
 123 ;; `inotify' returns the same descriptor when the file (directory)
 124 ;; uses the same inode.  We want to distinguish, and apply a virtual
 125 ;; descriptor which make the difference.
 126 (defun file-notify--descriptor (descriptor)
 127   "Return the descriptor to be used in `file-notify-*-watch'.
 128 For `gfilenotify' and `w32notify' it is the same descriptor as
 129 used in the low-level file notification package."
 130   (if (and (natnump descriptor) (eq file-notify--library 'inotify))
 131       (cons descriptor
 132             (car (cadr (gethash descriptor file-notify-descriptors))))
 133     descriptor))
 134
 135 ;; The callback function used to map between specific flags of the
 136 ;; respective file notifications, and the ones we return.
 137 (defun file-notify-callback (event)
 138   "Handle an EVENT returned from file notification.
 139 EVENT is the cadr of the event in `file-notify-handle-event'
 140 \(DESCRIPTOR ACTIONS FILE [FILE1-OR-COOKIE])."
 141   (let* ((desc (car event))
 142          (registered (gethash desc file-notify-descriptors))
 143          (actions (nth 1 event))
 144          (file (file-notify--event-file-name event))
 145          file1 callback pending-event stopped)
 146
 147     ;; Make actions a list.
 148     (unless (consp actions) (setq actions (cons actions nil)))
 149
 150     ;; Loop over registered entries.  In fact, more than one entry
 151     ;; happens only for `inotify'.
 152     (dolist (entry (cdr registered))
 153
 154       ;; Check, that event is meant for us.
 155       (unless (setq callback (cdr entry))
 156         (setq actions nil))
 157
 158       ;; Loop over actions.  In fact, more than one action happens only
 159       ;; for `inotify'.
 160       (dolist (action actions)
 161
 162         ;; Send pending event, if it doesn't match.
 163         (when (and file-notify--pending-event
 164                    ;; The cookie doesn't match.
 165                    (not (eq (file-notify--event-cookie
 166                              (car file-notify--pending-event))
 167                             (file-notify--event-cookie event)))
 168                    (or
 169                     ;; inotify.
 170                     (and (eq (nth 1 (car file-notify--pending-event))
 171                              'moved-from)
 172                          (not (eq action 'moved-to)))
 173                     ;; w32notify.
 174                     (and (eq (nth 1 (car file-notify--pending-event))
 175                              'renamed-from)
 176                          (not (eq action 'renamed-to)))))
 177           (setq pending-event file-notify--pending-event
 178                 file-notify--pending-event nil)
 179           (setcar (cdar pending-event) 'deleted))
 180
 181         ;; Map action.  We ignore all events which cannot be mapped.
 182         (setq action
 183               (cond
 184                ;; gfilenotify.
 185                ((memq action '(attribute-changed changed created deleted))
 186                 action)
 187                ((eq action 'moved)
 188                 (setq file1 (file-notify--event-file1-name event))
 189                 'renamed)
 190
 191                ;; inotify, w32notify.
 192                ((eq action 'ignored)
 193                 (setq stopped t actions nil))
 194                ((eq action 'attrib) 'attribute-changed)
 195                ((memq action '(create added)) 'created)
 196                ((memq action '(modify modified)) 'changed)
 197                ((memq action '(delete delete-self move-self removed)) 'deleted)
 198                ;; Make the event pending.
 199                ((memq action '(moved-from renamed-from))
 200                 (setq file-notify--pending-event
 201                       `((,desc ,action ,file ,(file-notify--event-cookie event))
 202                         ,callback))
 203                 nil)
 204                ;; Look for pending event.
 205                ((memq action '(moved-to renamed-to))
 206                 (if (null file-notify--pending-event)
 207                     'created
 208                   (setq file1 file
 209                         file (file-notify--event-file-name
 210                               (car file-notify--pending-event)))
 211                   ;; If the source is handled by another watch, we
 212                   ;; must fire the rename event there as well.
 213                   (when (not (equal (file-notify--descriptor desc)
 214                                     (file-notify--descriptor
 215                                      (caar file-notify--pending-event))))
 216                     (setq pending-event
 217                           `((,(caar file-notify--pending-event)
 218                              renamed ,file ,file1)
 219                             ,(cadr file-notify--pending-event))))
 220                   (setq file-notify--pending-event nil)
 221                   'renamed))))
 222
 223         ;; Apply pending callback.
 224         (when pending-event
 225           (setcar
 226            (car pending-event) (file-notify--descriptor (caar pending-event)))
 227           (funcall (cadr pending-event) (car pending-event))
 228           (setq pending-event nil))
 229
 230         ;; Check for stopped.
 231         ;;(message "file-notify-callback %S %S" file registered)
 232         (setq
 233          stopped
 234          (or
 235           stopped
 236           (and
 237            (memq action '(deleted renamed))
 238            (= (length (cdr registered)) 1)
 239            (string-equal
 240             (file-name-nondirectory file)
 241             (or (file-name-nondirectory (car registered))
 242                 (car (cadr registered)))))))
 243
 244         ;; Apply callback.
 245         (when (and action
 246                    (or
 247                     ;; If there is no relative file name for that watch,
 248                     ;; we watch the whole directory.
 249                     (null (nth 0 entry))
 250                     ;; File matches.
 251                     (string-equal
 252                      (nth 0 entry) (file-name-nondirectory file))
 253                     ;; File1 matches.
 254                     (and (stringp file1)
 255                          (string-equal
 256                           (nth 0 entry) (file-name-nondirectory file1)))))
 257           (if file1
 258               (funcall
 259                callback
 260                `(,(file-notify--descriptor desc) ,action ,file ,file1))
 261             (funcall
 262              callback
 263              `(,(file-notify--descriptor desc) ,action ,file)))))
 264
 265       ;; Modify `file-notify-descriptors'.
 266       (when stopped
 267         (file-notify--rm-descriptor (file-notify--descriptor desc) file)))))
 268
 269 ;; `gfilenotify' and `w32notify' return a unique descriptor for every
 270 ;; `file-notify-add-watch', while `inotify' returns a unique
 271 ;; descriptor per inode only.
 272 (defun file-notify-add-watch (file flags callback)
 273   "Add a watch for filesystem events pertaining to FILE.
 274 This arranges for filesystem events pertaining to FILE to be reported
 275 to Emacs.  Use `file-notify-rm-watch' to cancel the watch.
 276
 277 The returned value is a descriptor for the added watch.  If the
 278 file cannot be watched for some reason, this function signals a
 279 `file-notify-error' error.
 280
 281 FLAGS is a list of conditions to set what will be watched for.  It can
 282 include the following symbols:
 283
 284   `change'           -- watch for file changes
 285   `attribute-change' -- watch for file attributes changes, like
 286                         permissions or modification time
 287
 288 If FILE is a directory, `change' watches for file creation or
 289 deletion in that directory.  This does not work recursively.
 290
 291 When any event happens, Emacs will call the CALLBACK function passing
 292 it a single argument EVENT, which is of the form
 293
 294   (DESCRIPTOR ACTION FILE [FILE1])
 295
 296 DESCRIPTOR is the same object as the one returned by this function.
 297 ACTION is the description of the event.  It could be any one of the
 298 following:
 299
 300   `created'           -- FILE was created
 301   `deleted'           -- FILE was deleted
 302   `changed'           -- FILE has changed
 303   `renamed'           -- FILE has been renamed to FILE1
 304   `attribute-changed' -- a FILE attribute was changed
 305   `stopped'           -- watching FILE has been stopped
 306
 307 FILE is the name of the file whose event is being reported."
 308   ;; Check arguments.
 309   (unless (stringp file)
 310     (signal 'wrong-type-argument `(,file)))
 311   (setq file (expand-file-name file))
 312   (unless (and (consp flags)
 313                (null (delq 'change (delq 'attribute-change (copy-tree flags)))))
 314     (signal 'wrong-type-argument `(,flags)))
 315   (unless (functionp callback)
 316     (signal 'wrong-type-argument `(,callback)))
 317
 318   (let* ((handler (find-file-name-handler file 'file-notify-add-watch))
 319          (dir (directory-file-name
 320                (if (file-directory-p file)
 321                    file
 322                  (file-name-directory file))))
 323         desc func l-flags registered)
 324
 325     (unless (file-directory-p dir)
 326       (signal 'file-notify-error `("Directory does not exist" ,dir)))
 327
 328     (if handler
 329         ;; A file name handler could exist even if there is no local
 330         ;; file notification support.
 331         (setq desc (funcall
 332                     handler 'file-notify-add-watch dir flags callback))
 333
 334       ;; Check, whether Emacs has been compiled with file notification
 335       ;; support.
 336       (unless file-notify--library
 337         (signal 'file-notify-error
 338                 '("No file notification package available")))
 339
 340       ;; Determine low-level function to be called.
 341       (setq func
 342             (cond
 343              ((eq file-notify--library 'gfilenotify) 'gfile-add-watch)
 344              ((eq file-notify--library 'inotify) 'inotify-add-watch)
 345              ((eq file-notify--library 'w32notify) 'w32notify-add-watch)))
 346
 347       ;; Determine respective flags.
 348       (if (eq file-notify--library 'gfilenotify)
 349           (setq l-flags (append '(watch-mounts send-moved) flags))
 350         (when (memq 'change flags)
 351           (setq
 352            l-flags
 353            (cond
 354             ((eq file-notify--library 'inotify)
 355              '(create delete delete-self modify move-self move))
 356             ((eq file-notify--library 'w32notify)
 357              '(file-name directory-name size last-write-time)))))
 358         (when (memq 'attribute-change flags)
 359           (push (cond
 360                  ((eq file-notify--library 'inotify) 'attrib)
 361                  ((eq file-notify--library 'w32notify) 'attributes))
 362                 l-flags)))
 363
 364       ;; Call low-level function.
 365       (setq desc (funcall func dir l-flags 'file-notify-callback)))
 366
 367     ;; Modify `file-notify-descriptors'.
 368     (setq registered (gethash desc file-notify-descriptors))
 369     (puthash
 370      desc
 371      `(,dir
 372        (,(unless (file-directory-p file) (file-name-nondirectory file))
 373         . ,callback)
 374        . ,(cdr registered))
 375      file-notify-descriptors)
 376
 377     ;; Return descriptor.
 378     (file-notify--descriptor desc)))
 379
 380 (defun file-notify-rm-watch (descriptor)
 381   "Remove an existing watch specified by its DESCRIPTOR.
 382 DESCRIPTOR should be an object returned by `file-notify-add-watch'."
 383   (let* ((desc (if (consp descriptor) (car descriptor) descriptor))
 384          (file (if (consp descriptor) (cdr descriptor)))
 385          (registered (gethash desc file-notify-descriptors))
 386          (dir (car registered))
 387          (handler (and (stringp dir)
 388                        (find-file-name-handler dir 'file-notify-rm-watch))))
 389
 390     (when (stringp dir)
 391       ;; Call low-level function.
 392       (when (or (not file)
 393                 (and (= (length (cdr registered)) 1)
 394                      (assoc file (cdr registered))))
 395         (condition-case nil
 396             (if handler
 397                 ;; A file name handler could exist even if there is no local
 398                 ;; file notification support.
 399                 (funcall handler 'file-notify-rm-watch desc)
 400
 401               (funcall
 402                (cond
 403                 ((eq file-notify--library 'gfilenotify) 'gfile-rm-watch)
 404                 ((eq file-notify--library 'inotify) 'inotify-rm-watch)
 405                 ((eq file-notify--library 'w32notify) 'w32notify-rm-watch))
 406                desc))
 407           (file-notify-error nil)))
 408
 409       ;; Modify `file-notify-descriptors'.
 410       (file-notify--rm-descriptor descriptor))))
 411
 412 (defun file-notify-valid-p (descriptor)
 413   "Check a watch specified by its DESCRIPTOR.
 414 DESCRIPTOR should be an object returned by `file-notify-add-watch'."
 415   (let* ((desc (if (consp descriptor) (car descriptor) descriptor))
 416          (file (if (consp descriptor) (cdr descriptor)))
 417          (registered (gethash desc file-notify-descriptors))
 418          (dir (car registered))
 419          handler)
 420
 421     (when (stringp dir)
 422       (setq handler (find-file-name-handler dir 'file-notify-valid-p))
 423
 424       (and (or ;; It is a directory.
 425                (not file)
 426                ;; The file is registered.
 427                (assoc file (cdr registered)))
 428            (if handler
 429                ;; A file name handler could exist even if there is no
 430                ;; local file notification support.
 431                (funcall handler 'file-notify-valid-p descriptor)
 432              (funcall
 433               (cond
 434                ((eq file-notify--library 'gfilenotify) 'gfile-valid-p)
 435                ((eq file-notify--library 'inotify) 'inotify-valid-p)
 436                ((eq file-notify--library 'w32notify) 'w32notify-valid-p))
 437               desc))
 438            t))))
 439
 440 ;; The end:
 441 (provide 'filenotify)
 442
 443 ;;; filenotify.el ends here