lisp/filenotify.el

   1 ;;; filenotify.el --- watch files for changes on disk  -*- lexical-binding:t -*-
   2
   3 ;; Copyright (C) 2013-2016 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 `inotify', `kqueue', `gfilenotify' and
  26 ;; `w32notify'.
  27
  28 ;;; Code:
  29
  30 (require 'cl-lib)
  31
  32 (defconst file-notify--library
  33   (cond
  34    ((featurep 'inotify) 'inotify)
  35    ((featurep 'kqueue) 'kqueue)
  36    ((featurep 'gfilenotify) 'gfilenotify)
  37    ((featurep 'w32notify) 'w32notify))
  38   "Non-nil when Emacs has been compiled with file notification support.
  39 The value is the name of the low-level file notification package
  40 to be used for local file systems.  Remote file notifications
  41 could use another implementation.")
  42
  43 (defvar file-notify-descriptors (make-hash-table :test 'equal)
  44   "Hash table for registered file notification descriptors.
  45 A key in this hash table is the descriptor as returned from
  46 `inotify', `kqueue', `gfilenotify', `w32notify' or a file name
  47 handler.  The value in the hash table is a list
  48
  49   (DIR (FILE . CALLBACK) (FILE . CALLBACK) ...)
  50
  51 Several values for a given DIR happen only for `inotify', when
  52 different files from the same directory are watched.")
  53
  54 (defun file-notify--rm-descriptor (descriptor)
  55   "Remove DESCRIPTOR from `file-notify-descriptors'.
  56 DESCRIPTOR should be an object returned by `file-notify-add-watch'.
  57 If it is registered in `file-notify-descriptors', a stopped event is sent."
  58   (let* ((desc (if (consp descriptor) (car descriptor) descriptor))
  59          (registered (gethash desc file-notify-descriptors))
  60          (file (if (consp descriptor) (cdr descriptor) (cl-caadr registered)))
  61          (dir (car registered)))
  62
  63     (when (consp registered)
  64       ;; Send `stopped' event.
  65       (funcall
  66        (cdr (assoc file (cdr registered)))
  67        `(,descriptor stopped ,(if file (expand-file-name file dir) dir)))
  68
  69       ;; Modify `file-notify-descriptors'.
  70       (if (not file)
  71           (remhash desc file-notify-descriptors)
  72         (setcdr registered
  73                 (delete (assoc file (cdr registered)) (cdr registered)))
  74         (if (null (cdr registered))
  75             (remhash desc file-notify-descriptors)
  76           (puthash desc registered file-notify-descriptors))))))
  77
  78 ;; This function is used by `inotify', `kqueue', `gfilenotify' and
  79 ;; `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-watched-file (event)
 102   "Return file or directory being watched.
 103 Could be different from the directory watched by the backend library."
 104   (let* ((desc (if (consp (car event)) (caar event) (car event)))
 105          (registered (gethash desc file-notify-descriptors))
 106          (file (if (consp (car event)) (cdar event) (cl-caadr registered)))
 107          (dir (car registered)))
 108     (if file (expand-file-name file dir) dir)))
 109
 110 (defun file-notify--event-file-name (event)
 111   "Return file name of file notification event, or nil."
 112   (directory-file-name
 113    (expand-file-name
 114     (or  (and (stringp (nth 2 event)) (nth 2 event)) "")
 115     (car (gethash (car event) file-notify-descriptors)))))
 116
 117 ;; Only `gfilenotify' could return two file names.
 118 (defun file-notify--event-file1-name (event)
 119   "Return second file name of file notification event, or nil.
 120 This is available in case a file has been moved."
 121   (and (stringp (nth 3 event))
 122        (directory-file-name
 123         (expand-file-name
 124          (nth 3 event) (car (gethash (car event) file-notify-descriptors))))))
 125
 126 ;; Cookies are offered by `inotify' only.
 127 (defun file-notify--event-cookie (event)
 128   "Return cookie of file notification event, or nil.
 129 This is available in case a file has been moved."
 130   (nth 3 event))
 131
 132 ;; `inotify' returns the same descriptor when the file (directory)
 133 ;; uses the same inode.  We want to distinguish, and apply a virtual
 134 ;; descriptor which make the difference.
 135 (defun file-notify--descriptor (desc file)
 136   "Return the descriptor to be used in `file-notify-*-watch'.
 137 For `gfilenotify' and `w32notify' it is the same descriptor as
 138 used in the low-level file notification package."
 139   (if (and (natnump desc) (eq file-notify--library 'inotify))
 140       (cons desc
 141             (and (stringp file)
 142                  (car (assoc
 143                        (file-name-nondirectory file)
 144                        (gethash desc file-notify-descriptors)))))
 145     desc))
 146
 147 ;; The callback function used to map between specific flags of the
 148 ;; respective file notifications, and the ones we return.
 149 (defun file-notify-callback (event)
 150   "Handle an EVENT returned from file notification.
 151 EVENT is the cadr of the event in `file-notify-handle-event'
 152 \(DESCRIPTOR ACTIONS FILE [FILE1-OR-COOKIE])."
 153   (let* ((desc (car event))
 154          (registered (gethash desc file-notify-descriptors))
 155          (actions (nth 1 event))
 156          (file (file-notify--event-file-name event))
 157          file1 callback pending-event stopped)
 158
 159     ;; Make actions a list.
 160     (unless (consp actions) (setq actions (cons actions nil)))
 161
 162     ;; Loop over registered entries.  In fact, more than one entry
 163     ;; happens only for `inotify'.
 164     (dolist (entry (cdr registered))
 165
 166       ;; Check, that event is meant for us.
 167       (unless (setq callback (cdr entry))
 168         (setq actions nil))
 169
 170       ;; Loop over actions.  In fact, more than one action happens only
 171       ;; for `inotify' and `kqueue'.
 172       (dolist (action actions)
 173
 174         ;; Send pending event, if it doesn't match.
 175         (when (and file-notify--pending-event
 176                    ;; The cookie doesn't match.
 177                    (not (eq (file-notify--event-cookie
 178                              (car file-notify--pending-event))
 179                             (file-notify--event-cookie event)))
 180                    (or
 181                     ;; inotify.
 182                     (and (eq (nth 1 (car file-notify--pending-event))
 183                              'moved-from)
 184                          (not (eq action 'moved-to)))
 185                     ;; w32notify.
 186                     (and (eq (nth 1 (car file-notify--pending-event))
 187                              'renamed-from)
 188                          (not (eq action 'renamed-to)))))
 189           (setq pending-event file-notify--pending-event
 190                 file-notify--pending-event nil)
 191           (setcar (cdar pending-event) 'deleted))
 192
 193         ;; Map action.  We ignore all events which cannot be mapped.
 194         (setq action
 195               (cond
 196                ((memq action
 197                       '(attribute-changed changed created deleted renamed))
 198                 action)
 199                ((memq action '(moved rename))
 200                 (setq file1 (file-notify--event-file1-name event))
 201                 'renamed)
 202                ((eq action 'ignored)
 203                 (setq stopped t actions nil))
 204                ((memq action '(attrib link)) 'attribute-changed)
 205                ((memq action '(create added)) 'created)
 206                ((memq action '(modify modified write)) 'changed)
 207                ((memq action '(delete delete-self move-self removed)) 'deleted)
 208                ;; Make the event pending.
 209                ((memq action '(moved-from renamed-from))
 210                 (setq file-notify--pending-event
 211                       `((,desc ,action ,file ,(file-notify--event-cookie event))
 212                         ,callback))
 213                 nil)
 214                ;; Look for pending event.
 215                ((memq action '(moved-to renamed-to))
 216                 (if (null file-notify--pending-event)
 217                     'created
 218                   (setq file1 file
 219                         file (file-notify--event-file-name
 220                               (car file-notify--pending-event)))
 221                   ;; If the source is handled by another watch, we
 222                   ;; must fire the rename event there as well.
 223                   (when (not (equal (file-notify--descriptor desc file1)
 224                                     (file-notify--descriptor
 225                                      (caar file-notify--pending-event)
 226                                      (file-notify--event-file-name
 227                                       file-notify--pending-event))))
 228                     (setq pending-event
 229                           `((,(caar file-notify--pending-event)
 230                              renamed ,file ,file1)
 231                             ,(cadr file-notify--pending-event))))
 232                   (setq file-notify--pending-event nil)
 233                   'renamed))))
 234
 235         ;; Apply pending callback.
 236         (when pending-event
 237           (setcar
 238            (car pending-event)
 239            (file-notify--descriptor
 240             (caar pending-event)
 241             (file-notify--event-file-name file-notify--pending-event)))
 242           (funcall (cadr pending-event) (car pending-event))
 243           (setq pending-event nil))
 244
 245         ;; Apply callback.
 246         (when (and action
 247                    (or
 248                     ;; If there is no relative file name for that watch,
 249                     ;; we watch the whole directory.
 250                     (null (nth 0 entry))
 251                     ;; File matches.
 252                     (string-equal
 253                      (nth 0 entry) (file-name-nondirectory file))
 254                     ;; Directory matches.
 255                     (string-equal
 256                      (file-name-nondirectory file)
 257                      (file-name-nondirectory (car registered)))
 258                     ;; File1 matches.
 259                     (and (stringp file1)
 260                          (string-equal
 261                           (nth 0 entry) (file-name-nondirectory file1)))))
 262           ;;(message
 263            ;;"file-notify-callback %S %S %S %S %S"
 264            ;;(file-notify--descriptor desc (car entry))
 265            ;;action file file1 registered)
 266           (if file1
 267               (funcall
 268                callback
 269                `(,(file-notify--descriptor desc (car entry))
 270                  ,action ,file ,file1))
 271             (funcall
 272              callback
 273              `(,(file-notify--descriptor desc (car entry)) ,action ,file))))
 274
 275         ;; Send `stopped' event.
 276         (when (or stopped
 277                   (and (memq action '(deleted renamed))
 278                        ;; Not, when a file is backed up.
 279                        (not (and (stringp file1) (backup-file-name-p file1)))
 280                        ;; Watched file or directory is concerned.
 281                        (string-equal
 282                         file (file-notify--event-watched-file event))))
 283           (file-notify-rm-watch (file-notify--descriptor desc (car entry))))))))
 284
 285 ;; `kqueue', `gfilenotify' and `w32notify' return a unique descriptor
 286 ;; for every `file-notify-add-watch', while `inotify' returns a unique
 287 ;; descriptor per inode only.
 288 (defun file-notify-add-watch (file flags callback)
 289   "Add a watch for filesystem events pertaining to FILE.
 290 This arranges for filesystem events pertaining to FILE to be reported
 291 to Emacs.  Use `file-notify-rm-watch' to cancel the watch.
 292
 293 The returned value is a descriptor for the added watch.  If the
 294 file cannot be watched for some reason, this function signals a
 295 `file-notify-error' error.
 296
 297 FLAGS is a list of conditions to set what will be watched for.  It can
 298 include the following symbols:
 299
 300   `change'           -- watch for file changes
 301   `attribute-change' -- watch for file attributes changes, like
 302                         permissions or modification time
 303
 304 If FILE is a directory, `change' watches for file creation or
 305 deletion in that directory.  This does not work recursively.
 306
 307 When any event happens, Emacs will call the CALLBACK function passing
 308 it a single argument EVENT, which is of the form
 309
 310   (DESCRIPTOR ACTION FILE [FILE1])
 311
 312 DESCRIPTOR is the same object as the one returned by this function.
 313 ACTION is the description of the event.  It could be any one of the
 314 following:
 315
 316   `created'           -- FILE was created
 317   `deleted'           -- FILE was deleted
 318   `changed'           -- FILE has changed
 319   `renamed'           -- FILE has been renamed to FILE1
 320   `attribute-changed' -- a FILE attribute was changed
 321   `stopped'           -- watching FILE has been stopped
 322
 323 FILE is the name of the file whose event is being reported."
 324   ;; Check arguments.
 325   (unless (stringp file)
 326     (signal 'wrong-type-argument `(,file)))
 327   (setq file (expand-file-name file))
 328   (unless (and (consp flags)
 329                (null (delq 'change (delq 'attribute-change (copy-tree flags)))))
 330     (signal 'wrong-type-argument `(,flags)))
 331   (unless (functionp callback)
 332     (signal 'wrong-type-argument `(,callback)))
 333
 334   (let* ((handler (find-file-name-handler file 'file-notify-add-watch))
 335          (dir (directory-file-name
 336                (if (file-directory-p file)
 337                    file
 338                  (file-name-directory file))))
 339         desc func l-flags registered entry)
 340
 341     (unless (file-directory-p dir)
 342       (signal 'file-notify-error `("Directory does not exist" ,dir)))
 343
 344     (if handler
 345         ;; A file name handler could exist even if there is no local
 346         ;; file notification support.
 347         (setq desc (funcall
 348                     handler 'file-notify-add-watch
 349                     ;; kqueue does not report file changes in
 350                     ;; directory monitor.  So we must watch the file
 351                     ;; itself.
 352                     (if (eq file-notify--library 'kqueue) file dir)
 353                     flags callback))
 354
 355       ;; Check, whether Emacs has been compiled with file notification
 356       ;; support.
 357       (unless file-notify--library
 358         (signal 'file-notify-error
 359                 '("No file notification package available")))
 360
 361       ;; Determine low-level function to be called.
 362       (setq func
 363             (cond
 364              ((eq file-notify--library 'inotify) 'inotify-add-watch)
 365              ((eq file-notify--library 'kqueue) 'kqueue-add-watch)
 366              ((eq file-notify--library 'gfilenotify) 'gfile-add-watch)
 367              ((eq file-notify--library 'w32notify) 'w32notify-add-watch)))
 368
 369       ;; Determine respective flags.
 370       (if (eq file-notify--library 'gfilenotify)
 371           (setq l-flags (append '(watch-mounts send-moved) flags))
 372         (when (memq 'change flags)
 373           (setq
 374            l-flags
 375            (cond
 376             ((eq file-notify--library 'inotify)
 377              '(create delete delete-self modify move-self move))
 378             ((eq file-notify--library 'kqueue)
 379              '(create delete write extend rename))
 380             ((eq file-notify--library 'w32notify)
 381              '(file-name directory-name size last-write-time)))))
 382         (when (memq 'attribute-change flags)
 383           (push (cond
 384                  ((eq file-notify--library 'inotify) 'attrib)
 385                  ((eq file-notify--library 'kqueue) 'attrib)
 386                  ((eq file-notify--library 'w32notify) 'attributes))
 387                 l-flags)))
 388
 389       ;; Call low-level function.
 390       (setq desc (funcall
 391                   func (if (eq file-notify--library 'kqueue) file dir)
 392                   l-flags 'file-notify-callback)))
 393
 394     ;; Modify `file-notify-descriptors'.
 395     (setq file (unless (file-directory-p file) (file-name-nondirectory file))
 396           desc (if (consp desc) (car desc) desc)
 397           registered (gethash desc file-notify-descriptors)
 398           entry `(,file . ,callback))
 399     (unless (member entry (cdr registered))
 400       (puthash desc `(,dir ,entry . ,(cdr registered)) file-notify-descriptors))
 401
 402     ;; Return descriptor.
 403     (file-notify--descriptor desc file)))
 404
 405 (defun file-notify-rm-watch (descriptor)
 406   "Remove an existing watch specified by its DESCRIPTOR.
 407 DESCRIPTOR should be an object returned by `file-notify-add-watch'."
 408   (let* ((desc (if (consp descriptor) (car descriptor) descriptor))
 409          (file (if (consp descriptor) (cdr descriptor)))
 410          (registered (gethash desc file-notify-descriptors))
 411          (dir (car registered))
 412          (handler (and (stringp dir)
 413                        (find-file-name-handler dir 'file-notify-rm-watch))))
 414
 415     (when (stringp dir)
 416       ;; Call low-level function.
 417       (when (or (not file)
 418                 (and (= (length (cdr registered)) 1)
 419                      (assoc file (cdr registered))))
 420         (condition-case nil
 421             (if handler
 422                 ;; A file name handler could exist even if there is no local
 423                 ;; file notification support.
 424                 (funcall handler 'file-notify-rm-watch descriptor)
 425
 426               (funcall
 427                (cond
 428                 ((eq file-notify--library 'inotify) 'inotify-rm-watch)
 429                 ((eq file-notify--library 'kqueue) 'kqueue-rm-watch)
 430                 ((eq file-notify--library 'gfilenotify) 'gfile-rm-watch)
 431                 ((eq file-notify--library 'w32notify) 'w32notify-rm-watch))
 432                desc))
 433           (file-notify-error nil)))
 434
 435       ;; Modify `file-notify-descriptors'.
 436       (file-notify--rm-descriptor descriptor))))
 437
 438 (defun file-notify-valid-p (descriptor)
 439   "Check a watch specified by its DESCRIPTOR.
 440 DESCRIPTOR should be an object returned by `file-notify-add-watch'."
 441   (let* ((desc (if (consp descriptor) (car descriptor) descriptor))
 442          (file (if (consp descriptor) (cdr descriptor)))
 443          (registered (gethash desc file-notify-descriptors))
 444          (dir (car registered))
 445          handler)
 446
 447     (when (stringp dir)
 448       (setq handler (find-file-name-handler dir 'file-notify-valid-p))
 449
 450       (and (or ;; It is a directory.
 451                (not file)
 452                ;; The file is registered.
 453                (assoc file (cdr registered)))
 454            (if handler
 455                ;; A file name handler could exist even if there is no
 456                ;; local file notification support.
 457                (funcall handler 'file-notify-valid-p descriptor)
 458              (funcall
 459               (cond
 460                ((eq file-notify--library 'inotify) 'inotify-valid-p)
 461                ((eq file-notify--library 'kqueue) 'kqueue-valid-p)
 462                ((eq file-notify--library 'gfilenotify) 'gfile-valid-p)
 463                ((eq file-notify--library 'w32notify) 'w32notify-valid-p))
 464               desc))
 465            t))))
 466
 467 ;; The end:
 468 (provide 'filenotify)
 469
 470 ;;; filenotify.el ends here