lisp/tar-mode.el

   1 ;;; tar-mode.el --- simple editing of tar files from GNU emacs
   2
   3 ;;; Copyright (C) 1990, 1991 Free Software Foundation, Inc.
   4
   5 ;; Author: Jamie Zawinski <jwz@lucid.com>
   6 ;; Created: 04 Apr 1990
   7 ;; Version: 1.21
   8 ;; Keywords: unix
   9
  10 ;;; This file is part of GNU Emacs.
  11 ;;;
  12 ;;; GNU Emacs is free software; you can redistribute it and/or modify
  13 ;;; it under the terms of the GNU General Public License as published by
  14 ;;; the Free Software Foundation; either version 2, or (at your option)
  15 ;;; any later version.
  16 ;;;
  17 ;;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;;; GNU General Public License for more details.
  21 ;;;
  22 ;;; You should have received a copy of the GNU General Public License
  23 ;;; along with GNU Emacs; see the file COPYING.  If not, write to
  24 ;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  25
  26 ;;; Commentary:
  27
  28 ;;; This package attempts to make dealing with Unix 'tar' archives easier.
  29 ;;; When this code is loaded, visiting a file whose name ends in '.tar' will
  30 ;;; cause the contents of that archive file to be displayed in a Dired-like
  31 ;;; listing.  It is then possible to use the customary Dired keybindings to
  32 ;;; extract sub-files from that archive, either by reading them into their own
  33 ;;; editor buffers, or by copying them directly to arbitrary files on disk.
  34 ;;; It is also possible to delete sub-files from within the tar file and write
  35 ;;; the modified archive back to disk, or to edit sub-files within the archive
  36 ;;; and re-insert the modified files into the archive.  See the documentation
  37 ;;; string of tar-mode for more info.
  38
  39 ;;; To autoload, add this to your .emacs file:
  40 ;;;
  41 ;;;  (setq auto-mode-alist (cons '("\\.tar$" . tar-mode) auto-mode-alist))
  42 ;;;  (autoload 'tar-mode "tar-mode")
  43 ;;;
  44 ;;; But beware: for certain tar files - those whose very first file has
  45 ;;; a -*- property line - autoloading won't work.  See the function
  46 ;;; "tar-normal-mode" to understand why.
  47
  48 ;;; This code now understands the extra fields that GNU tar adds to tar files.
  49
  50 ;;; This interacts correctly with "uncompress.el" in the Emacs library,
  51 ;;; which you get with
  52 ;;;
  53 ;;;  (autoload 'uncompress-while-visiting "uncompress")
  54 ;;;  (setq auto-mode-alist (cons '("\\.Z$" . uncompress-while-visiting)
  55 ;;;                        auto-mode-alist))
  56 ;;;
  57 ;;; Do not attempt to use tar-mode.el with crypt.el, you will lose.
  58
  59 ;;;    ***************   TO DO   ***************
  60 ;;;
  61 ;;; o  chmod should understand "a+x,og-w".
  62 ;;;
  63 ;;; o  It's not possible to add a NEW file to a tar archive; not that
  64 ;;;    important, but still...
  65 ;;;
  66 ;;; o  In the directory listing, we don't show creation times because I don't
  67 ;;;    know how to print an arbitrary date, and I don't really want to have to
  68 ;;;    implement decode-universal-time.
  69 ;;;
  70 ;;; o  The code is less efficient that it could be - in a lot of places, I
  71 ;;;    pull a 512-character string out of the buffer and parse it, when I could
  72 ;;;    be parsing it in place, not garbaging a string.  Should redo that.
  73 ;;;
  74 ;;; o  I'd like a command that searches for a string/regexp in every subfile
  75 ;;;    of an archive, where <esc> would leave you in a subfile-edit buffer.
  76 ;;;    (Like the Meta-R command of the Zmacs mail reader.)
  77 ;;;
  78 ;;; o  Sometimes (but not always) reverting the tar-file buffer does not
  79 ;;;    re-grind the listing, and you are staring at the binary tar data.
  80 ;;;    Typing 'g' again immediately after that will always revert and re-grind
  81 ;;;    it, though.  I have no idea why this happens.
  82 ;;;
  83 ;;; o  Tar-mode interacts poorly with crypt.el and zcat.el because the tar
  84 ;;;    write-file-hook actually writes the file.  Instead it should remove the
  85 ;;;    header (and conspire to put it back afterwards) so that other write-file
  86 ;;;    hooks which frob the buffer have a chance to do their dirty work.  There
  87 ;;;    might be a problem if the tar write-file-hook does not come *first* on
  88 ;;;    the list.
  89 ;;;
  90 ;;; o  Block files, sparse files, continuation files, and the various header
  91 ;;;    types aren't editable.  Actually I don't know that they work at all.
  92
  93 ;;; Code:
  94
  95 (defvar tar-anal-blocksize 20
  96   "*The blocksize of tar files written by Emacs, or nil, meaning don't care.
  97 The blocksize of a tar file is not really the size of the blocks; rather, it is
  98 the number of blocks written with one system call.  When tarring to a tape,
  99 this is the size of the *tape* blocks, but when writing to a file, it doesn't
 100 matter much.  The only noticeable difference is that if a tar file does not
 101 have a blocksize of 20, tar will tell you that; all this really controls is
 102 how many null padding bytes go on the end of the tar file.")
 103
 104 (defvar tar-update-datestamp nil
 105   "*Whether tar-mode should play fast and loose with sub-file datestamps;
 106 if this is true, then editing and saving a tar file entry back into its
 107 tar file will update its datestamp.  If false, the datestamp is unchanged.
 108 You may or may not want this - it is good in that you can tell when a file
 109 in a tar archive has been changed, but it is bad for the same reason that
 110 editing a file in the tar archive at all is bad - the changed version of
 111 the file never exists on disk.")
 112
 113
 114 \f
 115 ;;; First, duplicate some Common Lisp functions; I used to just (require 'cl)
 116 ;;; but "cl.el" was messing some people up (also it's really big).
 117
 118 (defmacro tar-setf (form val)
 119   "A mind-numbingly simple implementation of setf."
 120   (let ((mform (macroexpand form (and (boundp 'byte-compile-macro-environment)
 121                                       byte-compile-macro-environment))))
 122     (cond ((symbolp mform) (list 'setq mform val))
 123           ((not (consp mform)) (error "can't setf %s" form))
 124           ((eq (car mform) 'aref)
 125            (list 'aset (nth 1 mform) (nth 2 mform) val))
 126           ((eq (car mform) 'car)
 127            (list 'setcar (nth 1 mform) val))
 128           ((eq (car mform) 'cdr)
 129            (list 'setcdr (nth 1 mform) val))
 130           (t (error "don't know how to setf %s" form)))))
 131
 132 (defmacro tar-dolist (control &rest body)
 133   "syntax: (dolist (var-name list-expr &optional return-value) &body body)"
 134   (let ((var (car control))
 135         (init (car (cdr control)))
 136         (val (car (cdr (cdr control)))))
 137     (list 'let (list (list '_dolist_iterator_ init))
 138           (list 'while '_dolist_iterator_
 139             (cons 'let
 140               (cons (list (list var '(car _dolist_iterator_)))
 141                     (append body
 142                             (list (list 'setq '_dolist_iterator_
 143                                         (list 'cdr '_dolist_iterator_)))))))
 144           val)))
 145
 146 (defmacro tar-dotimes (control &rest body)
 147   "syntax: (dolist (var-name count-expr &optional return-value) &body body)"
 148   (let ((var (car control))
 149         (n (car (cdr control)))
 150         (val (car (cdr (cdr control)))))
 151     (list 'let (list (list '_dotimes_end_ n)
 152                      (list var 0))
 153           (cons 'while
 154                 (cons (list '< var '_dotimes_end_)
 155                       (append body
 156                               (list (list 'setq var (list '1+ var))))))
 157           val)))
 158
 159 \f
 160 ;;; down to business.
 161
 162 (defmacro make-tar-header (name mode uid git size date ck lt ln
 163                            magic uname gname devmaj devmin)
 164   (list 'vector name mode uid git size date ck lt ln
 165         magic uname gname devmaj devmin))
 166
 167 (defmacro tar-header-name (x) (list 'aref x 0))
 168 (defmacro tar-header-mode (x) (list 'aref x 1))
 169 (defmacro tar-header-uid  (x) (list 'aref x 2))
 170 (defmacro tar-header-gid  (x) (list 'aref x 3))
 171 (defmacro tar-header-size (x) (list 'aref x 4))
 172 (defmacro tar-header-date (x) (list 'aref x 5))
 173 (defmacro tar-header-checksum  (x) (list 'aref x 6))
 174 (defmacro tar-header-link-type (x) (list 'aref x 7))
 175 (defmacro tar-header-link-name (x) (list 'aref x 8))
 176 (defmacro tar-header-magic (x) (list 'aref x 9))
 177 (defmacro tar-header-uname (x) (list 'aref x 10))
 178 (defmacro tar-header-gname (x) (list 'aref x 11))
 179 (defmacro tar-header-dmaj (x) (list 'aref x 12))
 180 (defmacro tar-header-dmin (x) (list 'aref x 13))
 181
 182 (defmacro make-tar-desc (data-start tokens)
 183   (list 'cons data-start tokens))
 184
 185 (defmacro tar-desc-data-start (x) (list 'car x))
 186 (defmacro tar-desc-tokens     (x) (list 'cdr x))
 187
 188 (defconst tar-name-offset 0)
 189 (defconst tar-mode-offset (+ tar-name-offset 100))
 190 (defconst tar-uid-offset  (+ tar-mode-offset 8))
 191 (defconst tar-gid-offset  (+ tar-uid-offset 8))
 192 (defconst tar-size-offset (+ tar-gid-offset 8))
 193 (defconst tar-time-offset (+ tar-size-offset 12))
 194 (defconst tar-chk-offset  (+ tar-time-offset 12))
 195 (defconst tar-linkp-offset (+ tar-chk-offset 8))
 196 (defconst tar-link-offset (+ tar-linkp-offset 1))
 197 ;;; GNU-tar specific slots.
 198 (defconst tar-magic-offset (+ tar-link-offset 100))
 199 (defconst tar-uname-offset (+ tar-magic-offset 8))
 200 (defconst tar-gname-offset (+ tar-uname-offset 32))
 201 (defconst tar-dmaj-offset (+ tar-gname-offset 32))
 202 (defconst tar-dmin-offset (+ tar-dmaj-offset 8))
 203 (defconst tar-end-offset (+ tar-dmin-offset 8))
 204
 205 (defun tokenize-tar-header-block (string)
 206   "Returns a 'tar-header' structure (a list of name, mode, uid, gid, size,
 207 write-date, checksum, link-type, and link-name)."
 208   (cond ((< (length string) 512) nil)
 209         (;(some 'plusp string)           ; <-- oops, massive cycle hog!
 210          (or (not (= 0 (aref string 0))) ; This will do.
 211              (not (= 0 (aref string 101))))
 212          (let* ((name-end (1- tar-mode-offset))
 213                 (link-end (1- tar-magic-offset))
 214                 (uname-end (1- tar-gname-offset))
 215                 (gname-end (1- tar-dmaj-offset))
 216                 (link-p (aref string tar-linkp-offset))
 217                 (magic-str (substring string tar-magic-offset (1- tar-uname-offset)))
 218                 (uname-valid-p (or (string= "ustar  " magic-str) (string= "GNUtar " magic-str)))
 219                 name
 220                 (nulsexp   "[^\000]*\000"))
 221            (and (string-match nulsexp string tar-name-offset) (setq name-end (min name-end (1- (match-end 0)))))
 222            (and (string-match nulsexp string tar-link-offset) (setq link-end (min link-end (1- (match-end 0)))))
 223            (and (string-match nulsexp string tar-uname-offset) (setq uname-end (min uname-end (1- (match-end 0)))))
 224            (and (string-match nulsexp string tar-gname-offset) (setq gname-end (min gname-end (1- (match-end 0)))))
 225            (setq name (substring string tar-name-offset name-end)
 226                  link-p (if (or (= link-p 0) (= link-p ?0))
 227                             nil
 228                           (- link-p ?0)))
 229            (if (and (null link-p) (string-match "/$" name)) (setq link-p 5)) ; directory
 230            (make-tar-header
 231              name
 232              (tar-parse-octal-integer string tar-mode-offset (1- tar-uid-offset))
 233              (tar-parse-octal-integer string tar-uid-offset (1- tar-gid-offset))
 234              (tar-parse-octal-integer string tar-gid-offset (1- tar-size-offset))
 235              (tar-parse-octal-integer string tar-size-offset (1- tar-time-offset))
 236              (tar-parse-octal-integer string tar-time-offset (1- tar-chk-offset))
 237              (tar-parse-octal-integer string tar-chk-offset (1- tar-linkp-offset))
 238              link-p
 239              (substring string tar-link-offset link-end)
 240              uname-valid-p
 241              (and uname-valid-p (substring string tar-uname-offset uname-end))
 242              (and uname-valid-p (substring string tar-gname-offset gname-end))
 243              (tar-parse-octal-integer string tar-dmaj-offset (1- tar-dmin-offset))
 244              (tar-parse-octal-integer string tar-dmin-offset (1- tar-end-offset))
 245              )))
 246         (t 'empty-tar-block)))
 247
 248
 249 (defun tar-parse-octal-integer (string &optional start end)
 250   "deletes all your files, and then reboots."
 251   (if (null start) (setq start 0))
 252   (if (null end) (setq end (length string)))
 253   (if (= (aref string start) 0)
 254       0
 255     (let ((n 0))
 256       (while (< start end)
 257         (setq n (if (< (aref string start) ?0) n
 258                   (+ (* n 8) (- (aref string start) 48)))
 259               start (1+ start)))
 260       n)))
 261
 262 (defun tar-parse-octal-integer-safe (string)
 263   (let ((L (length string)))
 264     (if (= L 0) (error "empty string"))
 265     (tar-dotimes (i L)
 266        (if (or (< (aref string i) ?0)
 267                (> (aref string i) ?7))
 268            (error "'%c' is not an octal digit."))))
 269   (tar-parse-octal-integer string))
 270
 271
 272 (defun checksum-tar-header-block (string)
 273   "Computes and returns a tar-acceptable checksum for this block."
 274   (let* ((chk-field-start tar-chk-offset)
 275          (chk-field-end (+ chk-field-start 8))
 276          (sum 0)
 277          (i 0))
 278     ;; Add up all of the characters except the ones in the checksum field.
 279     ;; Add that field as if it were filled with spaces.
 280     (while (< i chk-field-start)
 281       (setq sum (+ sum (aref string i))
 282             i (1+ i)))
 283     (setq i chk-field-end)
 284     (while (< i 512)
 285       (setq sum (+ sum (aref string i))
 286             i (1+ i)))
 287     (+ sum (* 32 8))))
 288
 289 (defun check-tar-header-block-checksum (hblock desired-checksum file-name)
 290   "Beep and print a warning if the checksum doesn't match."
 291   (if (not (= desired-checksum (checksum-tar-header-block hblock)))
 292       (progn (beep) (message "Invalid checksum for file %s!" file-name))))
 293
 294 (defun recompute-tar-header-block-checksum (hblock)
 295   "Modifies the given string to have a valid checksum field."
 296   (let* ((chk (checksum-tar-header-block hblock))
 297          (chk-string (format "%6o" chk))
 298          (l (length chk-string)))
 299     (aset hblock 154 0)
 300     (aset hblock 155 32)
 301     (tar-dotimes (i l) (aset hblock (- 153 i) (aref chk-string (- l i 1)))))
 302   hblock)
 303
 304
 305 (defun tar-grind-file-mode (mode string start)
 306   "Write a \"-rw--r--r-\" representing MODE into STRING beginning at START."
 307   (aset string start       (if (zerop (logand 256 mode)) ?- ?r))
 308   (aset string (+ start 1) (if (zerop (logand 128 mode)) ?- ?w))
 309   (aset string (+ start 2) (if (zerop (logand  64 mode)) ?- ?x))
 310   (aset string (+ start 3) (if (zerop (logand  32 mode)) ?- ?r))
 311   (aset string (+ start 4) (if (zerop (logand  16 mode)) ?- ?w))
 312   (aset string (+ start 5) (if (zerop (logand   8 mode)) ?- ?x))
 313   (aset string (+ start 6) (if (zerop (logand   4 mode)) ?- ?r))
 314   (aset string (+ start 7) (if (zerop (logand   2 mode)) ?- ?w))
 315   (aset string (+ start 8) (if (zerop (logand   1 mode)) ?- ?x))
 316   (if (zerop (logand 1024 mode)) nil (aset string (+ start 2) ?s))
 317   (if (zerop (logand 2048 mode)) nil (aset string (+ start 5) ?s))
 318   string)
 319
 320 (defun summarize-tar-header-block (tar-hblock &optional mod-p)
 321   "Returns a line similar to the output of 'tar -vtf'."
 322   (let ((name (tar-header-name tar-hblock))
 323         (mode (tar-header-mode tar-hblock))
 324         (uid (tar-header-uid tar-hblock))
 325         (gid (tar-header-gid tar-hblock))
 326         (uname (tar-header-uname tar-hblock))
 327         (gname (tar-header-gname tar-hblock))
 328         (size (tar-header-size tar-hblock))
 329         (time (tar-header-date tar-hblock))
 330         (ck (tar-header-checksum tar-hblock))
 331         (link-p (tar-header-link-type tar-hblock))
 332         (link-name (tar-header-link-name tar-hblock))
 333         )
 334     (let* ((left 11)
 335            (namew 8)
 336            (groupw 8)
 337            (sizew 8)
 338            (datew 2)
 339            (slash (1- (+ left namew)))
 340            (lastdigit (+ slash groupw sizew))
 341            (namestart (+ lastdigit datew))
 342            (string (make-string (+ namestart (length name) (if link-p (+ 5 (length link-name)) 0)) 32))
 343            (type (tar-header-link-type tar-hblock)))
 344       (aset string 0 (if mod-p ?* ? ))
 345       (aset string 1
 346             (cond ((or (eq type nil) (eq type 0)) ?-)
 347                   ((eq type 1) ?l)  ; link
 348                   ((eq type 2) ?s)  ; symlink
 349                   ((eq type 3) ?c)  ; char special
 350                   ((eq type 4) ?b)  ; block special
 351                   ((eq type 5) ?d)  ; directory
 352                   ((eq type 6) ?p)  ; FIFO/pipe
 353                   ((eq type 20) ?*) ; directory listing
 354                   ((eq type 29) ?M) ; multivolume continuation
 355                   ((eq type 35) ?S) ; sparse
 356                   ((eq type 38) ?V) ; volume header
 357                   ))
 358       (tar-grind-file-mode mode string 2)
 359       (setq uid (if (= 0 (length uname)) (int-to-string uid) uname))
 360       (setq gid (if (= 0 (length gname)) (int-to-string gid) gname))
 361       (setq size (int-to-string size))
 362       (tar-dotimes (i (min (1- namew) (length uid))) (aset string (- slash i) (aref uid (- (length uid) i 1))))
 363       (aset string (1+ slash) ?/)
 364       (tar-dotimes (i (min (1- groupw) (length gid))) (aset string (+ (+ slash 2) i) (aref gid i)))
 365       (tar-dotimes (i (min sizew (length size))) (aset string (- lastdigit i) (aref size (- (length size) i 1))))
 366       ;; ## bloody hell, how do I print an arbitrary date??
 367       (tar-dotimes (i (length name)) (aset string (+ namestart i) (aref name i)))
 368       (if (or (eq link-p 1) (eq link-p 2))
 369           (progn
 370             (tar-dotimes (i 3) (aset string (+ namestart 1 (length name) i) (aref (if (= link-p 1) "==>" "-->") i)))
 371             (tar-dotimes (i (length link-name)) (aset string (+ namestart 5 (length name) i) (aref link-name i)))))
 372       string)))
 373
 374
 375 (defun tar-summarize-buffer ()
 376   "Parse the contents of the tar file in the current buffer, and place a
 377 dired-like listing on the front; then narrow to it, so that only that listing
 378 is visible (and the real data of the buffer is hidden)."
 379   (message "parsing tar file...")
 380   (let* ((result '())
 381          (pos 1)
 382          (bs (max 1 (- (buffer-size) 1024))) ; always 2+ empty blocks at end.
 383          (bs100 (max 1 (/ bs 100)))
 384         (tokens nil))
 385     (while (not (eq tokens 'empty-tar-block))
 386       (let* ((hblock (buffer-substring pos (+ pos 512))))
 387         (setq tokens (tokenize-tar-header-block hblock))
 388         (setq pos (+ pos 512))
 389         (message "parsing tar file...%s%%"
 390                  ;(/ (* pos 100) bs)   ; this gets round-off lossage
 391                  (/ pos bs100)         ; this doesn't
 392                  )
 393         (if (eq tokens 'empty-tar-block)
 394             nil
 395           (if (null tokens) (error "premature EOF parsing tar file."))
 396           (if (eq (tar-header-link-type tokens) 20)
 397               ;; Foo.  There's an extra empty block after these.
 398               (setq pos (+ pos 512)))
 399           (let ((size (tar-header-size tokens)))
 400             (if (< size 0)
 401                 (error "%s has size %s - corrupted."
 402                        (tar-header-name tokens) size))
 403             ;
 404             ; This is just too slow.  Don't really need it anyway....
 405             ;(check-tar-header-block-checksum
 406             ;  hblock (checksum-tar-header-block hblock)
 407             ;  (tar-header-name tokens))
 408
 409             (setq result (cons (make-tar-desc pos tokens) result))
 410
 411             (if (and (null (tar-header-link-type tokens))
 412                      (> size 0))
 413                 (setq pos
 414                   (+ pos 512 (ash (ash (1- size) -9) 9))        ; this works
 415                   ;(+ pos (+ size (- 512 (rem (1- size) 512)))) ; this doesn't
 416                   ))
 417             ))))
 418     (make-local-variable 'tar-parse-info)
 419     (setq tar-parse-info (nreverse result)))
 420   (save-excursion
 421     (goto-char (point-min))
 422     (let ((buffer-read-only nil))
 423       (tar-dolist (tar-desc tar-parse-info)
 424         (insert-string
 425           (summarize-tar-header-block (tar-desc-tokens tar-desc)))
 426         (insert-string "\n"))
 427       (make-local-variable 'tar-header-offset)
 428       (setq tar-header-offset (point))
 429       (narrow-to-region 1 tar-header-offset)
 430       (set-buffer-modified-p nil)))
 431   (message "parsing tar file...done."))
 432
 433
 434 (defvar tar-mode-map nil "*Local keymap for tar-mode listings.")
 435
 436 (if tar-mode-map
 437     nil
 438   (setq tar-mode-map (make-keymap))
 439   (suppress-keymap tar-mode-map)
 440   (define-key tar-mode-map " " 'tar-next-line)
 441   (define-key tar-mode-map "c" 'tar-copy)
 442   (define-key tar-mode-map "d" 'tar-flag-deleted)
 443   (define-key tar-mode-map "\^D" 'tar-flag-deleted)
 444   (define-key tar-mode-map "e" 'tar-extract)
 445   (define-key tar-mode-map "f" 'tar-extract)
 446   (define-key tar-mode-map "g" 'revert-buffer)
 447   (define-key tar-mode-map "h" 'describe-mode)
 448   (define-key tar-mode-map "n" 'tar-next-line)
 449   (define-key tar-mode-map "\^N" 'tar-next-line)
 450   (define-key tar-mode-map "o" 'tar-extract-other-window)
 451   (define-key tar-mode-map "\^C" 'tar-copy)
 452   (define-key tar-mode-map "p" 'tar-previous-line)
 453   (define-key tar-mode-map "\^P" 'tar-previous-line)
 454   (define-key tar-mode-map "r" 'tar-rename-entry)
 455   (define-key tar-mode-map "u" 'tar-unflag)
 456   (define-key tar-mode-map "v" 'tar-view)
 457   (define-key tar-mode-map "x" 'tar-expunge)
 458   (define-key tar-mode-map "\177" 'tar-unflag-backwards)
 459   (define-key tar-mode-map "E" 'tar-extract-other-window)
 460   (define-key tar-mode-map "M" 'tar-chmod-entry)
 461   (define-key tar-mode-map "G" 'tar-chgrp-entry)
 462   (define-key tar-mode-map "O" 'tar-chown-entry)
 463   )
 464
 465 ;; tar mode is suitable only for specially formatted data.
 466 (put 'tar-mode 'mode-class 'special)
 467 (put 'tar-subfile-mode 'mode-class 'special)
 468
 469 (defun tar-mode ()
 470   "Major mode for viewing a tar file as a dired-like listing of its contents.
 471 You can move around using the usual cursor motion commands.
 472 Letters no longer insert themselves.
 473 Type 'e' to pull a file out of the tar file and into its own buffer.
 474 Type 'c' to copy an entry from the tar file into another file on disk.
 475
 476 If you edit a sub-file of this archive (as with the 'e' command) and
 477 save it with Control-X Control-S, the contents of that buffer will be
 478 saved back into the tar-file buffer; in this way you can edit a file
 479 inside of a tar archive without extracting it and re-archiving it.
 480
 481 See also: variables tar-update-datestamp and tar-anal-blocksize.
 482 \\{tar-mode-map}"
 483   ;; this is not interactive because you shouldn't be turning this
 484   ;; mode on and off.  You can corrupt things that way.
 485   (make-local-variable 'tar-header-offset)
 486   (make-local-variable 'tar-parse-info)
 487   (make-local-variable 'require-final-newline)
 488   (setq require-final-newline nil) ; binary data, dude...
 489   (make-local-variable 'revert-buffer-function)
 490   (setq revert-buffer-function 'tar-mode-revert)
 491   (setq major-mode 'tar-mode)
 492   (setq mode-name "Tar")
 493   (use-local-map tar-mode-map)
 494   (auto-save-mode 0)
 495   (widen)
 496   (if (and (boundp 'tar-header-offset) tar-header-offset)
 497       (narrow-to-region 1 tar-header-offset)
 498       (tar-summarize-buffer))
 499   (run-hooks 'tar-mode-hook)
 500   )
 501
 502
 503 (defun tar-subfile-mode (p)
 504   "Minor mode for editing an element of a tar-file.
 505 This mode redefines ^X^S to save the current buffer back into its
 506 associated tar-file buffer.  You must save that buffer to actually
 507 save your changes to disk."
 508   (interactive "P")
 509   (or (and (boundp 'superior-tar-buffer) superior-tar-buffer)
 510       (error "This buffer is not an element of a tar file."))
 511   (or (assq 'tar-subfile-mode minor-mode-alist)
 512       (setq minor-mode-alist (append minor-mode-alist
 513                                      (list '(tar-subfile-mode
 514                                              " TarFile")))))
 515   (make-local-variable 'tar-subfile-mode)
 516   (setq tar-subfile-mode
 517         (if (null p)
 518             (not tar-subfile-mode)
 519             (> (prefix-numeric-value p) 0)))
 520   (cond (tar-subfile-mode
 521          ;; copy the local keymap so that we don't accidentally
 522          ;; alter a keymap like 'lisp-mode-map' which is shared
 523          ;; by all buffers in that mode.
 524          (let ((m (current-local-map)))
 525            (if m (use-local-map (copy-keymap m))))
 526          (local-set-key "\^X\^S" 'tar-subfile-save-buffer)
 527          ;; turn off auto-save.
 528          (auto-save-mode nil)
 529          (setq buffer-auto-save-file-name nil)
 530          (run-hooks 'tar-subfile-mode-hook))
 531         (t (local-set-key "\^X\^S" 'save-buffer)))
 532   )
 533
 534
 535 (defun tar-mode-revert (&optional no-autosave no-confirm)
 536   "Revert this buffer and turn on tar mode again, to re-compute the
 537 directory listing."
 538   (setq tar-header-offset nil)
 539   (let ((revert-buffer-function nil))
 540     (revert-buffer t no-confirm)
 541     (widen))
 542   (tar-mode))
 543
 544
 545 (defun tar-next-line (p)
 546   (interactive "p")
 547   (forward-line p)
 548   (if (eobp) nil (forward-char 36)))
 549
 550 (defun tar-previous-line (p)
 551   (interactive "p")
 552   (tar-next-line (- p)))
 553
 554 (defun tar-current-descriptor (&optional noerror)
 555   "Returns the tar-descriptor of the current line, or signals an error."
 556   ;; I wish lines had plists, like in ZMACS...
 557   (or (nth (count-lines (point-min)
 558                         (save-excursion (beginning-of-line) (point)))
 559            tar-parse-info)
 560       (if noerror
 561           nil
 562           (error "This line does not describe a tar-file entry."))))
 563
 564
 565 (defun tar-extract (&optional other-window-p)
 566   "*In tar-mode, extract this entry of the tar file into its own buffer."
 567   (interactive)
 568   (let* ((view-p (eq other-window-p 'view))
 569          (descriptor (tar-current-descriptor))
 570          (tokens (tar-desc-tokens descriptor))
 571          (name (tar-header-name tokens))
 572          (size (tar-header-size tokens))
 573          (link-p (tar-header-link-type tokens))
 574          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 575          (end (+ start size)))
 576     (if link-p
 577         (error "This is a %s, not a real file."
 578                (cond ((eq link-p 5) "directory")
 579                      ((eq link-p 20) "tar directory header")
 580                      ((eq link-p 29) "multivolume-continuation")
 581                      ((eq link-p 35) "sparse entry")
 582                      ((eq link-p 38) "volume header")
 583                      (t "link"))))
 584     (if (zerop size) (error "This is a zero-length file."))
 585     (let* ((tar-buffer (current-buffer))
 586            (bufname (concat (file-name-nondirectory name)
 587                             " (" name " in "
 588                             (file-name-nondirectory (buffer-file-name))
 589                             ")"))
 590            (read-only-p (or buffer-read-only view-p))
 591            (buffer (get-buffer bufname))
 592            (just-created nil))
 593       (if buffer
 594           nil
 595         (setq buffer (get-buffer-create bufname))
 596         (setq just-created t)
 597         (unwind-protect
 598             (progn
 599               (widen)
 600               (save-excursion
 601                 (set-buffer buffer)
 602                 (insert-buffer-substring tar-buffer start end)
 603                 (goto-char 0)
 604                 (set-visited-file-name name) ; give it a name to decide mode.
 605                 (normal-mode)  ; pick a mode.
 606                 (set-visited-file-name nil)  ; nuke the name - not meaningful.
 607                 (rename-buffer bufname)
 608
 609                 (make-local-variable 'superior-tar-buffer)
 610                 (make-local-variable 'superior-tar-descriptor)
 611                 (setq superior-tar-buffer tar-buffer)
 612                 (setq superior-tar-descriptor descriptor)
 613                 (tar-subfile-mode 1)
 614
 615                 (setq buffer-read-only read-only-p)
 616                 (set-buffer-modified-p nil))
 617               (set-buffer tar-buffer))
 618           (narrow-to-region 1 tar-header-offset)))
 619       (if view-p
 620           (progn
 621             (view-buffer buffer)
 622             (and just-created (kill-buffer buffer)))
 623           (if other-window-p
 624               (switch-to-buffer-other-window buffer)
 625               (switch-to-buffer buffer))))))
 626
 627
 628 (defun tar-extract-other-window ()
 629   "*In tar-mode, extract this entry of the tar file into its own buffer."
 630   (interactive)
 631   (tar-extract t))
 632
 633 (defun tar-view ()
 634   "*In tar-mode, view the tar file entry on this line."
 635   (interactive)
 636   (tar-extract 'view))
 637
 638
 639 (defun tar-read-file-name (&optional prompt)
 640   "Calls read-file-name, with the default being the file of the current
 641 tar-file descriptor."
 642   (or prompt (setq prompt "Copy to: "))
 643   (let* ((default-file (expand-file-name
 644                         (tar-header-name (tar-desc-tokens
 645                                           (tar-current-descriptor)))))
 646          (target (expand-file-name
 647                   (read-file-name prompt
 648                                   (file-name-directory default-file)
 649                                   default-file nil))))
 650     (if (or (string= "" (file-name-nondirectory target))
 651             (file-directory-p target))
 652         (setq target (concat (if (string-match "/$" target)
 653                                  (substring target 0 (1- (match-end 0)))
 654                                  target)
 655                              "/"
 656                              (file-name-nondirectory default-file))))
 657     target))
 658
 659
 660 (defun tar-copy (&optional to-file)
 661   "*In tar-mode, extract this entry of the tar file into a file on disk.
 662 If TO-FILE is not supplied, it is prompted for, defaulting to the name of
 663 the current tar-entry."
 664   (interactive (list (tar-read-file-name)))
 665   (let* ((descriptor (tar-current-descriptor))
 666          (tokens (tar-desc-tokens descriptor))
 667          (name (tar-header-name tokens))
 668          (size (tar-header-size tokens))
 669          (link-p (tar-header-link-type tokens))
 670          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 671          (end (+ start size)))
 672     (if link-p (error "This is a link, not a real file."))
 673     (if (zerop size) (error "This is a zero-length file."))
 674     (let* ((tar-buffer (current-buffer))
 675            buffer)
 676       (unwind-protect
 677           (progn
 678             (setq buffer (generate-new-buffer "*tar-copy-tmp*"))
 679             (widen)
 680             (save-excursion
 681               (set-buffer buffer)
 682               (insert-buffer-substring tar-buffer start end)
 683               (set-buffer-modified-p nil) ; in case we abort
 684               (write-file to-file)
 685               (message "Copied tar entry %s to %s" name to-file)
 686               (set-buffer tar-buffer)))
 687         (narrow-to-region 1 tar-header-offset)
 688         (if buffer (kill-buffer buffer)))
 689       )))
 690
 691
 692 (defun tar-flag-deleted (p &optional unflag)
 693   "*In tar mode, mark this sub-file to be deleted from the tar file.
 694 With a prefix argument, mark that many files."
 695   (interactive "p")
 696   (beginning-of-line)
 697   (tar-dotimes (i (if (< p 0) (- p) p))
 698     (if (tar-current-descriptor unflag) ; barf if we're not on an entry-line.
 699         (progn
 700           (delete-char 1)
 701           (insert (if unflag " " "D"))))
 702     (forward-line (if (< p 0) -1 1)))
 703   (if (eobp) nil (forward-char 36)))
 704
 705 (defun tar-unflag (p)
 706   "*In tar mode, un-mark this sub-file if it is marked to be deleted.
 707 With a prefix argument, un-mark that many files forward."
 708   (interactive "p")
 709   (tar-flag-deleted p t))
 710
 711 (defun tar-unflag-backwards (p)
 712   "*In tar mode, un-mark this sub-file if it is marked to be deleted.
 713 With a prefix argument, un-mark that many files backward."
 714   (interactive "p")
 715   (tar-flag-deleted (- p) t))
 716
 717
 718 (defun tar-expunge-internal ()
 719   "Expunge the tar-entry specified by the current line."
 720   (let* ((descriptor (tar-current-descriptor))
 721          (tokens (tar-desc-tokens descriptor))
 722          (line (tar-desc-data-start descriptor))
 723          (name (tar-header-name tokens))
 724          (size (tar-header-size tokens))
 725          (link-p (tar-header-link-type tokens))
 726          (start (tar-desc-data-start descriptor))
 727          (following-descs (cdr (memq descriptor tar-parse-info))))
 728     (if link-p (setq size 0)) ; size lies for hard-links.
 729     ;;
 730     ;; delete the current line...
 731     (beginning-of-line)
 732     (let ((line-start (point)))
 733       (end-of-line) (forward-char)
 734       (let ((line-len (- (point) line-start)))
 735         (delete-region line-start (point))
 736         ;;
 737         ;; decrement the header-pointer to be in synch...
 738         (setq tar-header-offset (- tar-header-offset line-len))))
 739     ;;
 740     ;; delete the data pointer...
 741     (setq tar-parse-info (delq descriptor tar-parse-info))
 742     ;;
 743     ;; delete the data from inside the file...
 744     (widen)
 745     (let* ((data-start (+ start tar-header-offset -513))
 746            (data-end (+ data-start 512 (ash (ash (+ size 511) -9) 9))))
 747       (delete-region data-start data-end)
 748       ;;
 749       ;; and finally, decrement the start-pointers of all following
 750       ;; entries in the archive.  This is a pig when deleting a bunch
 751       ;; of files at once - we could optimize this to only do the
 752       ;; iteration over the files that remain, or only iterate up to
 753       ;; the next file to be deleted.
 754       (let ((data-length (- data-end data-start)))
 755         (tar-dolist (desc following-descs)
 756           (tar-setf (tar-desc-data-start desc)
 757                     (- (tar-desc-data-start desc) data-length))))
 758       ))
 759   (narrow-to-region 1 tar-header-offset))
 760
 761
 762 (defun tar-expunge (&optional noconfirm)
 763   "*In tar-mode, delete all the archived files flagged for deletion.
 764 This does not modify the disk image; you must save the tar file itself
 765 for this to be permanent."
 766   (interactive)
 767   (if (or noconfirm
 768           (y-or-n-p "expunge files marked for deletion? "))
 769       (let ((n 0))
 770         (save-excursion
 771           (goto-char 0)
 772           (while (not (eobp))
 773             (if (looking-at "D")
 774                 (progn (tar-expunge-internal)
 775                        (setq n (1+ n)))
 776                 (forward-line 1)))
 777           ;; after doing the deletions, add any padding that may be necessary.
 778           (tar-pad-to-blocksize)
 779           (narrow-to-region 1 tar-header-offset)
 780           )
 781         (if (zerop n)
 782             (message "nothing to expunge.")
 783             (message "%s expunged.  Be sure to save this buffer." n)))))
 784
 785
 786 (defun tar-clear-modification-flags ()
 787   "remove the stars at the beginning of each line."
 788   (save-excursion
 789     (goto-char 0)
 790     (while (< (point) tar-header-offset)
 791       (if (looking-at "*")
 792           (progn (delete-char 1) (insert " ")))
 793       (forward-line 1))))
 794
 795
 796 (defun tar-chown-entry (new-uid)
 797   "*Change the user-id associated with this entry in the tar file.
 798 If this tar file was written by GNU tar, then you will be able to edit
 799 the user id as a string; otherwise, you must edit it as a number.
 800 You can force editing as a number by calling this with a prefix arg.
 801 This does not modify the disk image; you must save the tar file itself
 802 for this to be permanent."
 803   (interactive (list
 804                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 805                    (if (or current-prefix-arg
 806                            (not (tar-header-magic tokens)))
 807                        (let (n)
 808                          (while (not (numberp (setq n (read-minibuffer
 809                                                         "New UID number: "
 810                                                         (format "%s" (tar-header-uid tokens)))))))
 811                          n)
 812                        (read-string "New UID string: " (tar-header-uname tokens))))))
 813   (cond ((stringp new-uid)
 814          (tar-setf (tar-header-uname (tar-desc-tokens (tar-current-descriptor)))
 815                    new-uid)
 816          (tar-alter-one-field tar-uname-offset (concat new-uid "\000")))
 817         (t
 818          (tar-setf (tar-header-uid (tar-desc-tokens (tar-current-descriptor)))
 819                    new-uid)
 820          (tar-alter-one-field tar-uid-offset
 821            (concat (substring (format "%6o" new-uid) 0 6) "\000 ")))))
 822
 823
 824 (defun tar-chgrp-entry (new-gid)
 825   "*Change the group-id associated with this entry in the tar file.
 826 If this tar file was written by GNU tar, then you will be able to edit
 827 the group id as a string; otherwise, you must edit it as a number.
 828 You can force editing as a number by calling this with a prefix arg.
 829 This does not modify the disk image; you must save the tar file itself
 830 for this to be permanent."
 831   (interactive (list
 832                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 833                    (if (or current-prefix-arg
 834                            (not (tar-header-magic tokens)))
 835                        (let (n)
 836                          (while (not (numberp (setq n (read-minibuffer
 837                                                         "New GID number: "
 838                                                         (format "%s" (tar-header-gid tokens)))))))
 839                          n)
 840                        (read-string "New GID string: " (tar-header-gname tokens))))))
 841   (cond ((stringp new-gid)
 842          (tar-setf (tar-header-gname (tar-desc-tokens (tar-current-descriptor)))
 843                    new-gid)
 844          (tar-alter-one-field tar-gname-offset
 845            (concat new-gid "\000")))
 846         (t
 847          (tar-setf (tar-header-gid (tar-desc-tokens (tar-current-descriptor)))
 848                    new-gid)
 849          (tar-alter-one-field tar-gid-offset
 850            (concat (substring (format "%6o" new-gid) 0 6) "\000 ")))))
 851
 852 (defun tar-rename-entry (new-name)
 853   "*Change the name associated with this entry in the tar file.
 854 This does not modify the disk image; you must save the tar file itself
 855 for this to be permanent."
 856   (interactive
 857     (list (read-string "New name: "
 858             (tar-header-name (tar-desc-tokens (tar-current-descriptor))))))
 859   (if (string= "" new-name) (error "zero length name."))
 860   (if (> (length new-name) 98) (error "name too long."))
 861   (tar-setf (tar-header-name (tar-desc-tokens (tar-current-descriptor)))
 862             new-name)
 863   (tar-alter-one-field 0
 864     (substring (concat new-name (make-string 99 0)) 0 99)))
 865
 866
 867 (defun tar-chmod-entry (new-mode)
 868   "*Change the protection bits associated with this entry in the tar file.
 869 This does not modify the disk image; you must save the tar file itself
 870 for this to be permanent."
 871   (interactive (list (tar-parse-octal-integer-safe
 872                        (read-string "New protection (octal): "))))
 873   (tar-setf (tar-header-mode (tar-desc-tokens (tar-current-descriptor)))
 874             new-mode)
 875   (tar-alter-one-field tar-mode-offset
 876     (concat (substring (format "%6o" new-mode) 0 6) "\000 ")))
 877
 878
 879 (defun tar-alter-one-field (data-position new-data-string)
 880   (let* ((descriptor (tar-current-descriptor))
 881          (tokens (tar-desc-tokens descriptor)))
 882     (unwind-protect
 883         (save-excursion
 884           ;;
 885           ;; update the header-line.
 886           (beginning-of-line)
 887           (let ((p (point)))
 888             (forward-line 1)
 889             (delete-region p (point))
 890             (insert (summarize-tar-header-block tokens) "\n")
 891             (setq tar-header-offset (point-max)))
 892
 893           (widen)
 894           (let* ((start (+ (tar-desc-data-start descriptor) tar-header-offset -513)))
 895             ;;
 896             ;; delete the old field and insert a new one.
 897             (goto-char (+ start data-position))
 898             (delete-region (point) (+ (point) (length new-data-string))) ; <--
 899             (insert new-data-string) ; <--
 900             ;;
 901             ;; compute a new checksum and insert it.
 902             (let ((chk (checksum-tar-header-block
 903                         (buffer-substring start (+ start 512)))))
 904               (goto-char (+ start tar-chk-offset))
 905               (delete-region (point) (+ (point) 8))
 906               (insert (format "%6o" chk))
 907               (insert 0)
 908               (insert ? )
 909               (tar-setf (tar-header-checksum tokens) chk)
 910               ;;
 911               ;; ok, make sure we didn't botch it.
 912               (check-tar-header-block-checksum
 913                 (buffer-substring start (+ start 512))
 914                 chk (tar-header-name tokens))
 915               )))
 916       (narrow-to-region 1 tar-header-offset))))
 917
 918
 919 (defun tar-subfile-save-buffer ()
 920   "In tar subfile mode, write this buffer back into its parent tar-file buffer.
 921 This doesn't write anything to disk - you must save the parent tar-file buffer
 922 to make your changes permanent."
 923   (interactive)
 924   (if (not (and (boundp 'superior-tar-buffer) superior-tar-buffer))
 925     (error "this buffer has no superior tar file buffer."))
 926   (if (not (and (boundp 'superior-tar-descriptor) superior-tar-descriptor))
 927     (error "this buffer doesn't have an index into its superior tar file!"))
 928   (save-excursion
 929   (let ((subfile (current-buffer))
 930         (subfile-size (buffer-size))
 931         (descriptor superior-tar-descriptor))
 932     (set-buffer superior-tar-buffer)
 933     (let* ((tokens (tar-desc-tokens descriptor))
 934            (start (tar-desc-data-start descriptor))
 935            (name (tar-header-name tokens))
 936            (size (tar-header-size tokens))
 937            (size-pad (ash (ash (+ size 511) -9) 9))
 938            (head (memq descriptor tar-parse-info))
 939            (following-descs (cdr head)))
 940       (if (not head)
 941         (error "Can't find this tar file entry in its parent tar file!"))
 942       (unwind-protect
 943        (save-excursion
 944         (widen)
 945         ;; delete the old data...
 946         (let* ((data-start (+ start tar-header-offset -1))
 947                (data-end (+ data-start (ash (ash (+ size 511) -9) 9))))
 948           (delete-region data-start data-end)
 949           ;; insert the new data...
 950           (goto-char data-start)
 951           (insert-buffer subfile)
 952           ;;
 953           ;; pad the new data out to a multiple of 512...
 954           (let ((subfile-size-pad (ash (ash (+ subfile-size 511) -9) 9)))
 955             (goto-char (+ data-start subfile-size))
 956             (insert (make-string (- subfile-size-pad subfile-size) 0))
 957             ;;
 958             ;; update the data pointer of this and all following files...
 959             (tar-setf (tar-header-size tokens) subfile-size)
 960             (let ((difference (- subfile-size-pad size-pad)))
 961               (tar-dolist (desc following-descs)
 962                 (tar-setf (tar-desc-data-start desc)
 963                           (+ (tar-desc-data-start desc) difference))))
 964             ;;
 965             ;; Update the size field in the header block.
 966             (let ((header-start (- data-start 512)))
 967               (goto-char (+ header-start tar-size-offset))
 968               (delete-region (point) (+ (point) 12))
 969               (insert (format "%11o" subfile-size))
 970               (insert ? )
 971               ;;
 972               ;; Maybe update the datestamp.
 973               (if (not tar-update-datestamp)
 974                   nil
 975                 (goto-char (+ header-start tar-time-offset))
 976                 (delete-region (point) (+ (point) 12))
 977                 (insert (format "%11o" (current-time)))
 978                 (insert ? ))
 979               ;;
 980               ;; compute a new checksum and insert it.
 981               (let ((chk (checksum-tar-header-block
 982                           (buffer-substring header-start data-start))))
 983                 (goto-char (+ header-start tar-chk-offset))
 984                 (delete-region (point) (+ (point) 8))
 985                 (insert (format "%6o" chk))
 986                 (insert 0)
 987                 (insert ? )
 988                 (tar-setf (tar-header-checksum tokens) chk)))
 989             ;;
 990             ;; alter the descriptor-line...
 991             ;;
 992             (let ((position (- (length tar-parse-info) (length head))))
 993               (goto-char 1)
 994               (next-line position)
 995               (beginning-of-line)
 996               (let ((p (point))
 997                     (m (set-marker (make-marker) tar-header-offset)))
 998                 (forward-line 1)
 999                 (delete-region p (point))
1000                 (insert-before-markers (summarize-tar-header-block tokens t) "\n")
1001                 (setq tar-header-offset (marker-position m)))
1002               )))
1003         ;; after doing the insertion, add any final padding that may be necessary.
1004         (tar-pad-to-blocksize))
1005        (narrow-to-region 1 tar-header-offset)))
1006     (set-buffer-modified-p t)   ; mark the tar file as modified
1007     (set-buffer subfile)
1008     (set-buffer-modified-p nil) ; mark the tar subfile as unmodified
1009     (message "saved into tar-buffer \"%s\" - remember to save that buffer!"
1010              (buffer-name superior-tar-buffer))
1011     )))
1012
1013
1014 (defun tar-pad-to-blocksize ()
1015   "If we are being anal about tar file blocksizes, fix up the current buffer.
1016 Leaves the region wide."
1017   (if (null tar-anal-blocksize)
1018       nil
1019     (widen)
1020     (let* ((last-desc (nth (1- (length tar-parse-info)) tar-parse-info))
1021            (start (tar-desc-data-start last-desc))
1022            (tokens (tar-desc-tokens last-desc))
1023            (link-p (tar-header-link-type tokens))
1024            (size (if link-p 0 (tar-header-size tokens)))
1025            (data-end (+ start size))
1026            (bbytes (ash tar-anal-blocksize 9))
1027            (pad-to (+ bbytes (* bbytes (/ (1- data-end) bbytes))))
1028            (buffer-read-only nil) ; ##
1029            )
1030       ;; If the padding after the last data is too long, delete some;
1031       ;; else insert some until we are padded out to the right number of blocks.
1032       ;;
1033       (goto-char (+ (or tar-header-offset 0) data-end))
1034       (if (> (1+ (buffer-size)) (+ (or tar-header-offset 0) pad-to))
1035           (delete-region (+ (or tar-header-offset 0) pad-to) (1+ (buffer-size)))
1036           (insert (make-string (- (+ (or tar-header-offset 0) pad-to)
1037                                   (1+ (buffer-size)))
1038                                0)))
1039       )))
1040
1041
1042 (defun maybe-write-tar-file ()
1043   "Used as a write-file-hook to write tar-files out correctly."
1044   ;;
1045   ;; If the current buffer is in tar-mode and has its header-offset set,
1046   ;; only write out the part of the file after the header-offset.
1047   ;;
1048   (if (and (eq major-mode 'tar-mode)
1049            (and (boundp 'tar-header-offset) tar-header-offset))
1050       (unwind-protect
1051         (save-excursion
1052           (tar-clear-modification-flags)
1053           (widen)
1054           ;; Doing this here confuses things - the region gets left too wide!
1055           ;; I suppose this is run in a context where changing the buffer is bad.
1056           ;; (tar-pad-to-blocksize)
1057           (write-region tar-header-offset (1+ (buffer-size)) buffer-file-name nil t)
1058           ;; return T because we've written the file.
1059           t)
1060         (narrow-to-region 1 tar-header-offset)
1061         t)
1062       ;; return NIL because we haven't.
1063       nil))
1064
1065 \f
1066 ;;; Patch it in.
1067
1068 (defvar tar-regexp "\\.tar$"
1069   "The regular expression used to identify tar file names.")
1070
1071 (setq auto-mode-alist
1072       (cons (cons tar-regexp 'tar-mode) auto-mode-alist))
1073
1074 (or (boundp 'write-file-hooks) (setq write-file-hooks nil))
1075 (or (listp write-file-hooks)
1076     (setq write-file-hooks (list write-file-hooks)))
1077 (or (memq 'maybe-write-tar-file write-file-hooks)
1078     (setq write-file-hooks
1079           (cons 'maybe-write-tar-file write-file-hooks)))
1080
1081 \f
1082 ;;; This is a hack.  For files ending in .tar, we want -*- lines to be
1083 ;;; completely ignored - if there is one, it applies to the first file
1084 ;;; in the archive, and not the archive itself!
1085
1086 (defun tar-normal-mode (&optional find-file)
1087   "Choose the major mode for this buffer automatically.
1088 Also sets up any specified local variables of the file.
1089 Uses the visited file name, the -*- line, and the local variables spec.
1090
1091 This function is called automatically from `find-file'.  In that case,
1092 if `inhibit-local-variables' is non-`nil' we require confirmation before
1093 processing a local variables spec.  If you run `normal-mode' explicitly,
1094 confirmation is never required.
1095
1096 Note that this version of this function has been hacked to interact
1097 correctly with tar files - when visiting a file which matches
1098 'tar-regexp', the -*- line and local-variables are not examined,
1099 as they would apply to a file within the archive rather than the archive
1100 itself."
1101   (interactive)
1102   (if (and buffer-file-name
1103            (string-match tar-regexp buffer-file-name))
1104       (tar-mode)
1105       (tar-real-normal-mode find-file)))
1106
1107
1108 (if (not (fboundp 'tar-real-normal-mode))
1109     (fset 'tar-real-normal-mode (symbol-function 'normal-mode)))
1110 (fset 'normal-mode 'tar-normal-mode)
1111
1112 (provide 'tar-mode)
1113
1114 ;;; tar-mode.el ends here