lisp/tar-mode.el

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