lisp/tar-mode.el

   1 ;;; -*- Mode: Emacs-Lisp -*-
   2
   3 ;;; File:               tar-mode.el
   4 ;;; Description:        simple editing of tar files from GNU emacs
   5 ;;; Author:             Jamie Zawinski <jwz@lucid.com>
   6 ;;; Created:            4 Apr 1990
   7 ;;; Version:            1.21, 10 Mar 91
   8
   9 ;;; Copyright (C) 1990, 1991 Free Software Foundation, Inc.
  10 ;;;
  11 ;;; This file is part of GNU Emacs.
  12 ;;;
  13 ;;; GNU Emacs is free software; you can redistribute it and/or modify
  14 ;;; it under the terms of the GNU General Public License as published by
  15 ;;; the Free Software Foundation; either version 1, or (at your option)
  16 ;;; any later version.
  17 ;;;
  18 ;;; GNU Emacs is distributed in the hope that it will be useful,
  19 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ;;; GNU General Public License for more details.
  22 ;;;
  23 ;;; You should have received a copy of the GNU General Public License
  24 ;;; along with GNU Emacs; see the file COPYING.  If not, write to
  25 ;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  26
  27 ;;; This package attempts to make dealing with Unix 'tar' archives easier.
  28 ;;; When this code is loaded, visiting a file whose name ends in '.tar' will
  29 ;;; cause the contents of that archive file to be displayed in a Dired-like
  30 ;;; listing.  It is then possible to use the customary Dired keybindings to
  31 ;;; extract sub-files from that archive, either by reading them into their own
  32 ;;; editor buffers, or by copying them directly to arbitrary files on disk.
  33 ;;; It is also possible to delete sub-files from within the tar file and write
  34 ;;; the modified archive back to disk, or to edit sub-files within the archive
  35 ;;; and re-insert the modified files into the archive.  See the documentation
  36 ;;; string of tar-mode for more info.
  37
  38 ;;; To autoload, add this to your .emacs file:
  39 ;;;
  40 ;;;  (setq auto-mode-alist (cons '("\\.tar$" . tar-mode) auto-mode-alist))
  41 ;;;  (autoload 'tar-mode "tar-mode")
  42 ;;;
  43 ;;; But beware: for certain tar files - those whose very first file has
  44 ;;; a -*- property line - autoloading won't work.  See the function
  45 ;;; "tar-normal-mode" to understand why.
  46
  47 ;;; This code now understands the extra fields that GNU tar adds to tar files.
  48
  49 ;;; This interacts correctly with "uncompress.el" in the Emacs library,
  50 ;;; which you get with
  51 ;;;
  52 ;;;  (autoload 'uncompress-while-visiting "uncompress")
  53 ;;;  (setq auto-mode-alist (cons '("\\.Z$" . uncompress-while-visiting)
  54 ;;;                        auto-mode-alist))
  55 ;;;
  56 ;;; Do not attempt to use tar-mode.el with crypt.el, you will lose.
  57
  58 ;;;    ***************   TO DO   ***************
  59 ;;;
  60 ;;; o  chmod should understand "a+x,og-w".
  61 ;;;
  62 ;;; o  It's not possible to add a NEW file to a tar archive; not that
  63 ;;;    important, but still...
  64 ;;;
  65 ;;; o  In the directory listing, we don't show creation times because I don't
  66 ;;;    know how to print an arbitrary date, and I don't really want to have to
  67 ;;;    implement decode-universal-time.
  68 ;;;
  69 ;;; o  There's code to update the datestamp of edited subfiles, but we set it
  70 ;;;    to zero because I don't know how to get the current time as an integer.
  71 ;;;
  72 ;;; o  The code is less efficient that it could be - in a lot of places, I
  73 ;;;    pull a 512-character string out of the buffer and parse it, when I could
  74 ;;;    be parsing it in place, not garbaging a string.  Should redo that.
  75 ;;;
  76 ;;; o  I'd like a command that searches for a string/regexp in every subfile
  77 ;;;    of an archive, where <esc> would leave you in a subfile-edit buffer.
  78 ;;;    (Like the Meta-R command of the Zmacs mail reader.)
  79 ;;;
  80 ;;; o  Sometimes (but not always) reverting the tar-file buffer does not
  81 ;;;    re-grind the listing, and you are staring at the binary tar data.
  82 ;;;    Typing 'g' again immediately after that will always revert and re-grind
  83 ;;;    it, though.  I have no idea why this happens.
  84 ;;;
  85 ;;; o  Tar-mode interacts poorly with crypt.el and zcat.el because the tar
  86 ;;;    write-file-hook actually writes the file.  Instead it should remove the
  87 ;;;    header (and conspire to put it back afterwards) so that other write-file
  88 ;;;    hooks which frob the buffer have a chance to do their dirty work.  There
  89 ;;;    might be a problem if the tar write-file-hook does not come *first* on
  90 ;;;    the list.
  91 ;;;
  92 ;;; o  Block files, sparse files, continuation files, and the various header
  93 ;;;    types aren't editable.  Actually I don't know that they work at all.
  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 ## This doesn't work yet because there's no way to get the current time as
 114 ## an integer - if this var is true, then editing a file sets its date to
 115 ## December 31, 1969 (which happens to be what 0 encodes).")
 116
 117
 118 \f
 119 ;;; First, duplicate some Common Lisp functions; I used to just (require 'cl)
 120 ;;; but "cl.el" was messing some people up (also it's really big).
 121
 122 (defmacro tar-setf (form val)
 123   "A mind-numbingly simple implementation of setf."
 124   (let ((mform (macroexpand form (and (boundp 'byte-compile-macro-environment)
 125                                       byte-compile-macro-environment))))
 126     (cond ((symbolp mform) (list 'setq mform val))
 127           ((not (consp mform)) (error "can't setf %s" form))
 128           ((eq (car mform) 'aref)
 129            (list 'aset (nth 1 mform) (nth 2 mform) val))
 130           ((eq (car mform) 'car)
 131            (list 'setcar (nth 1 mform) val))
 132           ((eq (car mform) 'cdr)
 133            (list 'setcdr (nth 1 mform) val))
 134           (t (error "don't know how to setf %s" form)))))
 135
 136 (defmacro tar-dolist (control &rest body)
 137   "syntax: (dolist (var-name list-expr &optional return-value) &body body)"
 138   (let ((var (car control))
 139         (init (car (cdr control)))
 140         (val (car (cdr (cdr control)))))
 141     (list 'let (list (list '_dolist_iterator_ init))
 142           (list 'while '_dolist_iterator_
 143             (cons 'let
 144               (cons (list (list var '(car _dolist_iterator_)))
 145                     (append body
 146                             (list (list 'setq '_dolist_iterator_
 147                                         (list 'cdr '_dolist_iterator_)))))))
 148           val)))
 149
 150 (defmacro tar-dotimes (control &rest body)
 151   "syntax: (dolist (var-name count-expr &optional return-value) &body body)"
 152   (let ((var (car control))
 153         (n (car (cdr control)))
 154         (val (car (cdr (cdr control)))))
 155     (list 'let (list (list '_dotimes_end_ n)
 156                      (list var 0))
 157           (cons 'while
 158                 (cons (list '< var '_dotimes_end_)
 159                       (append body
 160                               (list (list 'setq var (list '1+ var))))))
 161           val)))
 162
 163 \f
 164 ;;; down to business.
 165
 166 (defmacro make-tar-header (name mode uid git size date ck lt ln
 167                            magic uname gname devmaj devmin)
 168   (list 'vector name mode uid git size date ck lt ln
 169         magic uname gname devmaj devmin))
 170
 171 (defmacro tar-header-name (x) (list 'aref x 0))
 172 (defmacro tar-header-mode (x) (list 'aref x 1))
 173 (defmacro tar-header-uid  (x) (list 'aref x 2))
 174 (defmacro tar-header-gid  (x) (list 'aref x 3))
 175 (defmacro tar-header-size (x) (list 'aref x 4))
 176 (defmacro tar-header-date (x) (list 'aref x 5))
 177 (defmacro tar-header-checksum  (x) (list 'aref x 6))
 178 (defmacro tar-header-link-type (x) (list 'aref x 7))
 179 (defmacro tar-header-link-name (x) (list 'aref x 8))
 180 (defmacro tar-header-magic (x) (list 'aref x 9))
 181 (defmacro tar-header-uname (x) (list 'aref x 10))
 182 (defmacro tar-header-gname (x) (list 'aref x 11))
 183 (defmacro tar-header-dmaj (x) (list 'aref x 12))
 184 (defmacro tar-header-dmin (x) (list 'aref x 13))
 185
 186 (defmacro make-tar-desc (data-start tokens)
 187   (list 'cons data-start tokens))
 188
 189 (defmacro tar-desc-data-start (x) (list 'car x))
 190 (defmacro tar-desc-tokens     (x) (list 'cdr x))
 191
 192 (defconst tar-name-offset 0)
 193 (defconst tar-mode-offset (+ tar-name-offset 100))
 194 (defconst tar-uid-offset  (+ tar-mode-offset 8))
 195 (defconst tar-gid-offset  (+ tar-uid-offset 8))
 196 (defconst tar-size-offset (+ tar-gid-offset 8))
 197 (defconst tar-time-offset (+ tar-size-offset 12))
 198 (defconst tar-chk-offset  (+ tar-time-offset 12))
 199 (defconst tar-linkp-offset (+ tar-chk-offset 8))
 200 (defconst tar-link-offset (+ tar-linkp-offset 1))
 201 ;;; GNU-tar specific slots.
 202 (defconst tar-magic-offset (+ tar-link-offset 100))
 203 (defconst tar-uname-offset (+ tar-magic-offset 8))
 204 (defconst tar-gname-offset (+ tar-uname-offset 32))
 205 (defconst tar-dmaj-offset (+ tar-gname-offset 32))
 206 (defconst tar-dmin-offset (+ tar-dmaj-offset 8))
 207 (defconst tar-end-offset (+ tar-dmin-offset 8))
 208
 209 (defun tokenize-tar-header-block (string)
 210   "Returns a 'tar-header' structure (a list of name, mode, uid, gid, size,
 211 write-date, checksum, link-type, and link-name)."
 212   (cond ((< (length string) 512) nil)
 213         (;(some 'plusp string)           ; <-- oops, massive cycle hog!
 214          (or (not (= 0 (aref string 0))) ; This will do.
 215              (not (= 0 (aref string 101))))
 216          (let* ((name-end (1- tar-mode-offset))
 217                 (link-end (1- tar-magic-offset))
 218                 (uname-end (1- tar-gname-offset))
 219                 (gname-end (1- tar-dmaj-offset))
 220                 (link-p (aref string tar-linkp-offset))
 221                 (magic-str (substring string tar-magic-offset (1- tar-uname-offset)))
 222                 (uname-valid-p (or (string= "ustar  " magic-str) (string= "GNUtar " magic-str)))
 223                 name
 224                 (nulsexp   "[^\000]*\000"))
 225            (and (string-match nulsexp string tar-name-offset) (setq name-end (min name-end (1- (match-end 0)))))
 226            (and (string-match nulsexp string tar-link-offset) (setq link-end (min link-end (1- (match-end 0)))))
 227            (and (string-match nulsexp string tar-uname-offset) (setq uname-end (min uname-end (1- (match-end 0)))))
 228            (and (string-match nulsexp string tar-gname-offset) (setq gname-end (min gname-end (1- (match-end 0)))))
 229            (setq name (substring string tar-name-offset name-end)
 230                  link-p (if (or (= link-p 0) (= link-p ?0))
 231                             nil
 232                           (- link-p ?0)))
 233            (if (and (null link-p) (string-match "/$" name)) (setq link-p 5)) ; directory
 234            (make-tar-header
 235              name
 236              (tar-parse-octal-integer string tar-mode-offset (1- tar-uid-offset))
 237              (tar-parse-octal-integer string tar-uid-offset (1- tar-gid-offset))
 238              (tar-parse-octal-integer string tar-gid-offset (1- tar-size-offset))
 239              (tar-parse-octal-integer string tar-size-offset (1- tar-time-offset))
 240              (tar-parse-octal-integer string tar-time-offset (1- tar-chk-offset))
 241              (tar-parse-octal-integer string tar-chk-offset (1- tar-linkp-offset))
 242              link-p
 243              (substring string tar-link-offset link-end)
 244              uname-valid-p
 245              (and uname-valid-p (substring string tar-uname-offset uname-end))
 246              (and uname-valid-p (substring string tar-gname-offset gname-end))
 247              (tar-parse-octal-integer string tar-dmaj-offset (1- tar-dmin-offset))
 248              (tar-parse-octal-integer string tar-dmin-offset (1- tar-end-offset))
 249              )))
 250         (t 'empty-tar-block)))
 251
 252
 253 (defun tar-parse-octal-integer (string &optional start end)
 254   "deletes all your files, and then reboots."
 255   (if (null start) (setq start 0))
 256   (if (null end) (setq end (length string)))
 257   (if (= (aref string start) 0)
 258       0
 259     (let ((n 0))
 260       (while (< start end)
 261         (setq n (if (< (aref string start) ?0) n
 262                   (+ (* n 8) (- (aref string start) 48)))
 263               start (1+ start)))
 264       n)))
 265
 266 (defun tar-parse-octal-integer-safe (string)
 267   (let ((L (length string)))
 268     (if (= L 0) (error "empty string"))
 269     (tar-dotimes (i L)
 270        (if (or (< (aref string i) ?0)
 271                (> (aref string i) ?7))
 272            (error "'%c' is not an octal digit."))))
 273   (tar-parse-octal-integer string))
 274
 275
 276 (defun checksum-tar-header-block (string)
 277   "Computes and returns a tar-acceptable checksum for this block."
 278   (let* ((chk-field-start tar-chk-offset)
 279          (chk-field-end (+ chk-field-start 8))
 280          (sum 0)
 281          (i 0))
 282     ;; Add up all of the characters except the ones in the checksum field.
 283     ;; Add that field as if it were filled with spaces.
 284     (while (< i chk-field-start)
 285       (setq sum (+ sum (aref string i))
 286             i (1+ i)))
 287     (setq i chk-field-end)
 288     (while (< i 512)
 289       (setq sum (+ sum (aref string i))
 290             i (1+ i)))
 291     (+ sum (* 32 8))))
 292
 293 (defun check-tar-header-block-checksum (hblock desired-checksum file-name)
 294   "Beep and print a warning if the checksum doesn't match."
 295   (if (not (= desired-checksum (checksum-tar-header-block hblock)))
 296       (progn (beep) (message "Invalid checksum for file %s!" file-name))))
 297
 298 (defun recompute-tar-header-block-checksum (hblock)
 299   "Modifies the given string to have a valid checksum field."
 300   (let* ((chk (checksum-tar-header-block hblock))
 301          (chk-string (format "%6o" chk))
 302          (l (length chk-string)))
 303     (aset hblock 154 0)
 304     (aset hblock 155 32)
 305     (tar-dotimes (i l) (aset hblock (- 153 i) (aref chk-string (- l i 1)))))
 306   hblock)
 307
 308
 309 (defun tar-grind-file-mode (mode string start)
 310   "Write a \"-rw--r--r-\" representing MODE into STRING beginning at START."
 311   (aset string start       (if (zerop (logand 256 mode)) ?- ?r))
 312   (aset string (+ start 1) (if (zerop (logand 128 mode)) ?- ?w))
 313   (aset string (+ start 2) (if (zerop (logand  64 mode)) ?- ?x))
 314   (aset string (+ start 3) (if (zerop (logand  32 mode)) ?- ?r))
 315   (aset string (+ start 4) (if (zerop (logand  16 mode)) ?- ?w))
 316   (aset string (+ start 5) (if (zerop (logand   8 mode)) ?- ?x))
 317   (aset string (+ start 6) (if (zerop (logand   4 mode)) ?- ?r))
 318   (aset string (+ start 7) (if (zerop (logand   2 mode)) ?- ?w))
 319   (aset string (+ start 8) (if (zerop (logand   1 mode)) ?- ?x))
 320   (if (zerop (logand 1024 mode)) nil (aset string (+ start 2) ?s))
 321   (if (zerop (logand 2048 mode)) nil (aset string (+ start 5) ?s))
 322   string)
 323
 324 (defun summarize-tar-header-block (tar-hblock &optional mod-p)
 325   "Returns a line similar to the output of 'tar -vtf'."
 326   (let ((name (tar-header-name tar-hblock))
 327         (mode (tar-header-mode tar-hblock))
 328         (uid (tar-header-uid tar-hblock))
 329         (gid (tar-header-gid tar-hblock))
 330         (uname (tar-header-uname tar-hblock))
 331         (gname (tar-header-gname tar-hblock))
 332         (size (tar-header-size tar-hblock))
 333         (time (tar-header-date tar-hblock))
 334         (ck (tar-header-checksum tar-hblock))
 335         (link-p (tar-header-link-type tar-hblock))
 336         (link-name (tar-header-link-name tar-hblock))
 337         )
 338     (let* ((left 11)
 339            (namew 8)
 340            (groupw 8)
 341            (sizew 8)
 342            (datew 2)
 343            (slash (1- (+ left namew)))
 344            (lastdigit (+ slash groupw sizew))
 345            (namestart (+ lastdigit datew))
 346            (string (make-string (+ namestart (length name) (if link-p (+ 5 (length link-name)) 0)) 32))
 347            (type (tar-header-link-type tar-hblock)))
 348       (aset string 0 (if mod-p ?* ? ))
 349       (aset string 1
 350             (cond ((or (eq type nil) (eq type 0)) ?-)
 351                   ((eq type 1) ?l)  ; link
 352                   ((eq type 2) ?s)  ; symlink
 353                   ((eq type 3) ?c)  ; char special
 354                   ((eq type 4) ?b)  ; block special
 355                   ((eq type 5) ?d)  ; directory
 356                   ((eq type 6) ?p)  ; FIFO/pipe
 357                   ((eq type 20) ?*) ; directory listing
 358                   ((eq type 29) ?M) ; multivolume continuation
 359                   ((eq type 35) ?S) ; sparse
 360                   ((eq type 38) ?V) ; volume header
 361                   ))
 362       (tar-grind-file-mode mode string 2)
 363       (setq uid (if (= 0 (length uname)) (int-to-string uid) uname))
 364       (setq gid (if (= 0 (length gname)) (int-to-string gid) gname))
 365       (setq size (int-to-string size))
 366       (tar-dotimes (i (min (1- namew) (length uid))) (aset string (- slash i) (aref uid (- (length uid) i 1))))
 367       (aset string (1+ slash) ?/)
 368       (tar-dotimes (i (min (1- groupw) (length gid))) (aset string (+ (+ slash 2) i) (aref gid i)))
 369       (tar-dotimes (i (min sizew (length size))) (aset string (- lastdigit i) (aref size (- (length size) i 1))))
 370       ;; ## bloody hell, how do I print an arbitrary date??
 371       (tar-dotimes (i (length name)) (aset string (+ namestart i) (aref name i)))
 372       (if (or (eq link-p 1) (eq link-p 2))
 373           (progn
 374             (tar-dotimes (i 3) (aset string (+ namestart 1 (length name) i) (aref (if (= link-p 1) "==>" "-->") i)))
 375             (tar-dotimes (i (length link-name)) (aset string (+ namestart 5 (length name) i) (aref link-name i)))))
 376       string)))
 377
 378
 379 (defun tar-summarize-buffer ()
 380   "Parse the contents of the tar file in the current buffer, and place a
 381 dired-like listing on the front; then narrow to it, so that only that listing
 382 is visible (and the real data of the buffer is hidden)."
 383   (message "parsing tar file...")
 384   (let* ((result '())
 385          (pos 1)
 386          (bs (max 1 (- (buffer-size) 1024))) ; always 2+ empty blocks at end.
 387          (bs100 (max 1 (/ bs 100)))
 388         (tokens nil))
 389     (while (not (eq tokens 'empty-tar-block))
 390       (let* ((hblock (buffer-substring pos (+ pos 512))))
 391         (setq tokens (tokenize-tar-header-block hblock))
 392         (setq pos (+ pos 512))
 393         (message "parsing tar file...%s%%"
 394                  ;(/ (* pos 100) bs)   ; this gets round-off lossage
 395                  (/ pos bs100)         ; this doesn't
 396                  )
 397         (if (eq tokens 'empty-tar-block)
 398             nil
 399           (if (null tokens) (error "premature EOF parsing tar file."))
 400           (if (eq (tar-header-link-type tokens) 20)
 401               ;; Foo.  There's an extra empty block after these.
 402               (setq pos (+ pos 512)))
 403           (let ((size (tar-header-size tokens)))
 404             (if (< size 0)
 405                 (error "%s has size %s - corrupted."
 406                        (tar-header-name tokens) size))
 407             ;
 408             ; This is just too slow.  Don't really need it anyway....
 409             ;(check-tar-header-block-checksum
 410             ;  hblock (checksum-tar-header-block hblock)
 411             ;  (tar-header-name tokens))
 412
 413             (setq result (cons (make-tar-desc pos tokens) result))
 414
 415             (if (and (null (tar-header-link-type tokens))
 416                      (> size 0))
 417                 (setq pos
 418                   (+ pos 512 (ash (ash (1- size) -9) 9))        ; this works
 419                   ;(+ pos (+ size (- 512 (rem (1- size) 512)))) ; this doesn't
 420                   ))
 421             ))))
 422     (make-local-variable 'tar-parse-info)
 423     (setq tar-parse-info (nreverse result)))
 424   (save-excursion
 425     (goto-char (point-min))
 426     (let ((buffer-read-only nil))
 427       (tar-dolist (tar-desc tar-parse-info)
 428         (insert-string
 429           (summarize-tar-header-block (tar-desc-tokens tar-desc)))
 430         (insert-string "\n"))
 431       (make-local-variable 'tar-header-offset)
 432       (setq tar-header-offset (point))
 433       (narrow-to-region 1 tar-header-offset)
 434       (set-buffer-modified-p nil)))
 435   (message "parsing tar file...done."))
 436
 437
 438 (defvar tar-mode-map nil "*Local keymap for tar-mode listings.")
 439
 440 (if tar-mode-map
 441     nil
 442   (setq tar-mode-map (make-keymap))
 443   (suppress-keymap tar-mode-map)
 444   (define-key tar-mode-map " " 'tar-next-line)
 445   (define-key tar-mode-map "c" 'tar-copy)
 446   (define-key tar-mode-map "d" 'tar-flag-deleted)
 447   (define-key tar-mode-map "\^D" 'tar-flag-deleted)
 448   (define-key tar-mode-map "e" 'tar-extract)
 449   (define-key tar-mode-map "f" 'tar-extract)
 450   (define-key tar-mode-map "g" 'revert-buffer)
 451   (define-key tar-mode-map "h" 'describe-mode)
 452   (define-key tar-mode-map "n" 'tar-next-line)
 453   (define-key tar-mode-map "\^N" 'tar-next-line)
 454   (define-key tar-mode-map "o" 'tar-extract-other-window)
 455   (define-key tar-mode-map "\^C" 'tar-copy)
 456   (define-key tar-mode-map "p" 'tar-previous-line)
 457   (define-key tar-mode-map "\^P" 'tar-previous-line)
 458   (define-key tar-mode-map "r" 'tar-rename-entry)
 459   (define-key tar-mode-map "u" 'tar-unflag)
 460   (define-key tar-mode-map "v" 'tar-view)
 461   (define-key tar-mode-map "x" 'tar-expunge)
 462   (define-key tar-mode-map "\177" 'tar-unflag-backwards)
 463   (define-key tar-mode-map "E" 'tar-extract-other-window)
 464   (define-key tar-mode-map "M" 'tar-chmod-entry)
 465   (define-key tar-mode-map "G" 'tar-chgrp-entry)
 466   (define-key tar-mode-map "O" 'tar-chown-entry)
 467   )
 468
 469 ;; tar mode is suitable only for specially formatted data.
 470 (put 'tar-mode 'mode-class 'special)
 471 (put 'tar-subfile-mode 'mode-class 'special)
 472
 473 (defun tar-mode ()
 474   "Major mode for viewing a tar file as a dired-like listing of its contents.
 475 You can move around using the usual cursor motion commands.
 476 Letters no longer insert themselves.
 477 Type 'e' to pull a file out of the tar file and into its own buffer.
 478 Type 'c' to copy an entry from the tar file into another file on disk.
 479
 480 If you edit a sub-file of this archive (as with the 'e' command) and
 481 save it with Control-X Control-S, the contents of that buffer will be
 482 saved back into the tar-file buffer; in this way you can edit a file
 483 inside of a tar archive without extracting it and re-archiving it.
 484
 485 See also: variables tar-update-datestamp and tar-anal-blocksize.
 486 \\{tar-mode-map}"
 487   ;; this is not interactive because you shouldn't be turning this
 488   ;; mode on and off.  You can corrupt things that way.
 489   (make-local-variable 'tar-header-offset)
 490   (make-local-variable 'tar-parse-info)
 491   (make-local-variable 'require-final-newline)
 492   (setq require-final-newline nil) ; binary data, dude...
 493   (make-local-variable 'revert-buffer-function)
 494   (setq revert-buffer-function 'tar-mode-revert)
 495   (setq major-mode 'tar-mode)
 496   (setq mode-name "Tar")
 497   (use-local-map tar-mode-map)
 498   (auto-save-mode 0)
 499   (widen)
 500   (if (and (boundp 'tar-header-offset) tar-header-offset)
 501       (narrow-to-region 1 tar-header-offset)
 502       (tar-summarize-buffer))
 503   (run-hooks 'tar-mode-hook)
 504   )
 505
 506
 507 (defun tar-subfile-mode (p)
 508   "Minor mode for editing an element of a tar-file.
 509 This mode redefines ^X^S to save the current buffer back into its
 510 associated tar-file buffer.  You must save that buffer to actually
 511 save your changes to disk."
 512   (interactive "P")
 513   (or (and (boundp 'superior-tar-buffer) superior-tar-buffer)
 514       (error "This buffer is not an element of a tar file."))
 515   (or (assq 'tar-subfile-mode minor-mode-alist)
 516       (setq minor-mode-alist (append minor-mode-alist
 517                                      (list '(tar-subfile-mode
 518                                              " TarFile")))))
 519   (make-local-variable 'tar-subfile-mode)
 520   (setq tar-subfile-mode
 521         (if (null p)
 522             (not tar-subfile-mode)
 523             (> (prefix-numeric-value p) 0)))
 524   (cond (tar-subfile-mode
 525          ;; copy the local keymap so that we don't accidentally
 526          ;; alter a keymap like 'lisp-mode-map' which is shared
 527          ;; by all buffers in that mode.
 528          (let ((m (current-local-map)))
 529            (if m (use-local-map (copy-keymap m))))
 530          (local-set-key "\^X\^S" 'tar-subfile-save-buffer)
 531          ;; turn off auto-save.
 532          (auto-save-mode nil)
 533          (setq buffer-auto-save-file-name nil)
 534          (run-hooks 'tar-subfile-mode-hook))
 535         (t (local-set-key "\^X\^S" 'save-buffer)))
 536   )
 537
 538
 539 (defun tar-mode-revert (&optional no-autosave no-confirm)
 540   "Revert this buffer and turn on tar mode again, to re-compute the
 541 directory listing."
 542   (setq tar-header-offset nil)
 543   (let ((revert-buffer-function nil))
 544     (revert-buffer t no-confirm)
 545     (widen))
 546   (tar-mode))
 547
 548
 549 (defun tar-next-line (p)
 550   (interactive "p")
 551   (forward-line p)
 552   (if (eobp) nil (forward-char 36)))
 553
 554 (defun tar-previous-line (p)
 555   (interactive "p")
 556   (tar-next-line (- p)))
 557
 558 (defun tar-current-descriptor (&optional noerror)
 559   "Returns the tar-descriptor of the current line, or signals an error."
 560   ;; I wish lines had plists, like in ZMACS...
 561   (or (nth (count-lines (point-min)
 562                         (save-excursion (beginning-of-line) (point)))
 563            tar-parse-info)
 564       (if noerror
 565           nil
 566           (error "This line does not describe a tar-file entry."))))
 567
 568
 569 (defun tar-extract (&optional other-window-p)
 570   "*In tar-mode, extract this entry of the tar file into its own buffer."
 571   (interactive)
 572   (let* ((view-p (eq other-window-p 'view))
 573          (descriptor (tar-current-descriptor))
 574          (tokens (tar-desc-tokens descriptor))
 575          (name (tar-header-name tokens))
 576          (size (tar-header-size tokens))
 577          (link-p (tar-header-link-type tokens))
 578          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 579          (end (+ start size)))
 580     (if link-p
 581         (error "This is a %s, not a real file."
 582                (cond ((eq link-p 5) "directory")
 583                      ((eq link-p 20) "tar directory header")
 584                      ((eq link-p 29) "multivolume-continuation")
 585                      ((eq link-p 35) "sparse entry")
 586                      ((eq link-p 38) "volume header")
 587                      (t "link"))))
 588     (if (zerop size) (error "This is a zero-length file."))
 589     (let* ((tar-buffer (current-buffer))
 590            (bufname (concat (file-name-nondirectory name)
 591                             " (" name " in "
 592                             (file-name-nondirectory (buffer-file-name))
 593                             ")"))
 594            (read-only-p (or buffer-read-only view-p))
 595            (buffer (get-buffer bufname))
 596            (just-created nil))
 597       (if buffer
 598           nil
 599         (setq buffer (get-buffer-create bufname))
 600         (setq just-created t)
 601         (unwind-protect
 602             (progn
 603               (widen)
 604               (save-excursion
 605                 (set-buffer buffer)
 606                 (insert-buffer-substring tar-buffer start end)
 607                 (goto-char 0)
 608                 (set-visited-file-name name) ; give it a name to decide mode.
 609                 (normal-mode)  ; pick a mode.
 610                 (set-visited-file-name nil)  ; nuke the name - not meaningful.
 611                 (rename-buffer bufname)
 612
 613                 (make-local-variable 'superior-tar-buffer)
 614                 (make-local-variable 'superior-tar-descriptor)
 615                 (setq superior-tar-buffer tar-buffer)
 616                 (setq superior-tar-descriptor descriptor)
 617                 (tar-subfile-mode 1)
 618
 619                 (setq buffer-read-only read-only-p)
 620                 (set-buffer-modified-p nil))
 621               (set-buffer tar-buffer))
 622           (narrow-to-region 1 tar-header-offset)))
 623       (if view-p
 624           (progn
 625             (view-buffer buffer)
 626             (and just-created (kill-buffer buffer)))
 627           (if other-window-p
 628               (switch-to-buffer-other-window buffer)
 629               (switch-to-buffer buffer))))))
 630
 631
 632 (defun tar-extract-other-window ()
 633   "*In tar-mode, extract this entry of the tar file into its own buffer."
 634   (interactive)
 635   (tar-extract t))
 636
 637 (defun tar-view ()
 638   "*In tar-mode, view the tar file entry on this line."
 639   (interactive)
 640   (tar-extract 'view))
 641
 642
 643 (defun tar-read-file-name (&optional prompt)
 644   "Calls read-file-name, with the default being the file of the current
 645 tar-file descriptor."
 646   (or prompt (setq prompt "Copy to: "))
 647   (let* ((default-file (expand-file-name
 648                         (tar-header-name (tar-desc-tokens
 649                                           (tar-current-descriptor)))))
 650          (target (expand-file-name
 651                   (read-file-name prompt
 652                                   (file-name-directory default-file)
 653                                   default-file nil))))
 654     (if (or (string= "" (file-name-nondirectory target))
 655             (file-directory-p target))
 656         (setq target (concat (if (string-match "/$" target)
 657                                  (substring target 0 (1- (match-end 0)))
 658                                  target)
 659                              "/"
 660                              (file-name-nondirectory default-file))))
 661     target))
 662
 663
 664 (defun tar-copy (&optional to-file)
 665   "*In tar-mode, extract this entry of the tar file into a file on disk.
 666 If TO-FILE is not supplied, it is prompted for, defaulting to the name of
 667 the current tar-entry."
 668   (interactive (list (tar-read-file-name)))
 669   (let* ((descriptor (tar-current-descriptor))
 670          (tokens (tar-desc-tokens descriptor))
 671          (name (tar-header-name tokens))
 672          (size (tar-header-size tokens))
 673          (link-p (tar-header-link-type tokens))
 674          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 675          (end (+ start size)))
 676     (if link-p (error "This is a link, not a real file."))
 677     (if (zerop size) (error "This is a zero-length file."))
 678     (let* ((tar-buffer (current-buffer))
 679            buffer)
 680       (unwind-protect
 681           (progn
 682             (setq buffer (generate-new-buffer "*tar-copy-tmp*"))
 683             (widen)
 684             (save-excursion
 685               (set-buffer buffer)
 686               (insert-buffer-substring tar-buffer start end)
 687               (set-buffer-modified-p nil) ; in case we abort
 688               (write-file to-file)
 689               (message "Copied tar entry %s to %s" name to-file)
 690               (set-buffer tar-buffer)))
 691         (narrow-to-region 1 tar-header-offset)
 692         (if buffer (kill-buffer buffer)))
 693       )))
 694
 695
 696 (defun tar-flag-deleted (p &optional unflag)
 697   "*In tar mode, mark this sub-file to be deleted from the tar file.
 698 With a prefix argument, mark that many files."
 699   (interactive "p")
 700   (beginning-of-line)
 701   (tar-dotimes (i (if (< p 0) (- p) p))
 702     (if (tar-current-descriptor unflag) ; barf if we're not on an entry-line.
 703         (progn
 704           (delete-char 1)
 705           (insert (if unflag " " "D"))))
 706     (forward-line (if (< p 0) -1 1)))
 707   (if (eobp) nil (forward-char 36)))
 708
 709 (defun tar-unflag (p)
 710   "*In tar mode, un-mark this sub-file if it is marked to be deleted.
 711 With a prefix argument, un-mark that many files forward."
 712   (interactive "p")
 713   (tar-flag-deleted p t))
 714
 715 (defun tar-unflag-backwards (p)
 716   "*In tar mode, un-mark this sub-file if it is marked to be deleted.
 717 With a prefix argument, un-mark that many files backward."
 718   (interactive "p")
 719   (tar-flag-deleted (- p) t))
 720
 721
 722 (defun tar-expunge-internal ()
 723   "Expunge the tar-entry specified by the current line."
 724   (let* ((descriptor (tar-current-descriptor))
 725          (tokens (tar-desc-tokens descriptor))
 726          (line (tar-desc-data-start descriptor))
 727          (name (tar-header-name tokens))
 728          (size (tar-header-size tokens))
 729          (link-p (tar-header-link-type tokens))
 730          (start (tar-desc-data-start descriptor))
 731          (following-descs (cdr (memq descriptor tar-parse-info))))
 732     (if link-p (setq size 0)) ; size lies for hard-links.
 733     ;;
 734     ;; delete the current line...
 735     (beginning-of-line)
 736     (let ((line-start (point)))
 737       (end-of-line) (forward-char)
 738       (let ((line-len (- (point) line-start)))
 739         (delete-region line-start (point))
 740         ;;
 741         ;; decrement the header-pointer to be in synch...
 742         (setq tar-header-offset (- tar-header-offset line-len))))
 743     ;;
 744     ;; delete the data pointer...
 745     (setq tar-parse-info (delq descriptor tar-parse-info))
 746     ;;
 747     ;; delete the data from inside the file...
 748     (widen)
 749     (let* ((data-start (+ start tar-header-offset -513))
 750            (data-end (+ data-start 512 (ash (ash (+ size 511) -9) 9))))
 751       (delete-region data-start data-end)
 752       ;;
 753       ;; and finally, decrement the start-pointers of all following
 754       ;; entries in the archive.  This is a pig when deleting a bunch
 755       ;; of files at once - we could optimize this to only do the
 756       ;; iteration over the files that remain, or only iterate up to
 757       ;; the next file to be deleted.
 758       (let ((data-length (- data-end data-start)))
 759         (tar-dolist (desc following-descs)
 760           (tar-setf (tar-desc-data-start desc)
 761                     (- (tar-desc-data-start desc) data-length))))
 762       ))
 763   (narrow-to-region 1 tar-header-offset))
 764
 765
 766 (defun tar-expunge (&optional noconfirm)
 767   "*In tar-mode, delete all the archived files flagged for deletion.
 768 This does not modify the disk image; you must save the tar file itself
 769 for this to be permanent."
 770   (interactive)
 771   (if (or noconfirm
 772           (y-or-n-p "expunge files marked for deletion? "))
 773       (let ((n 0))
 774         (save-excursion
 775           (goto-char 0)
 776           (while (not (eobp))
 777             (if (looking-at "D")
 778                 (progn (tar-expunge-internal)
 779                        (setq n (1+ n)))
 780                 (forward-line 1)))
 781           ;; after doing the deletions, add any padding that may be necessary.
 782           (tar-pad-to-blocksize)
 783           (narrow-to-region 1 tar-header-offset)
 784           )
 785         (if (zerop n)
 786             (message "nothing to expunge.")
 787             (message "%s expunged.  Be sure to save this buffer." n)))))
 788
 789
 790 (defun tar-clear-modification-flags ()
 791   "remove the stars at the beginning of each line."
 792   (save-excursion
 793     (goto-char 0)
 794     (while (< (point) tar-header-offset)
 795       (if (looking-at "*")
 796           (progn (delete-char 1) (insert " ")))
 797       (forward-line 1))))
 798
 799
 800 (defun tar-chown-entry (new-uid)
 801   "*Change the user-id associated with this entry in the tar file.
 802 If this tar file was written by GNU tar, then you will be able to edit
 803 the user id as a string; otherwise, you must edit it as a number.
 804 You can force editing as a number by calling this with a prefix arg.
 805 This does not modify the disk image; you must save the tar file itself
 806 for this to be permanent."
 807   (interactive (list
 808                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 809                    (if (or current-prefix-arg
 810                            (not (tar-header-magic tokens)))
 811                        (let (n)
 812                          (while (not (numberp (setq n (read-minibuffer
 813                                                         "New UID number: "
 814                                                         (format "%s" (tar-header-uid tokens)))))))
 815                          n)
 816                        (read-string "New UID string: " (tar-header-uname tokens))))))
 817   (cond ((stringp new-uid)
 818          (tar-setf (tar-header-uname (tar-desc-tokens (tar-current-descriptor)))
 819                    new-uid)
 820          (tar-alter-one-field tar-uname-offset (concat new-uid "\000")))
 821         (t
 822          (tar-setf (tar-header-uid (tar-desc-tokens (tar-current-descriptor)))
 823                    new-uid)
 824          (tar-alter-one-field tar-uid-offset
 825            (concat (substring (format "%6o" new-uid) 0 6) "\000 ")))))
 826
 827
 828 (defun tar-chgrp-entry (new-gid)
 829   "*Change the group-id associated with this entry in the tar file.
 830 If this tar file was written by GNU tar, then you will be able to edit
 831 the group id as a string; otherwise, you must edit it as a number.
 832 You can force editing as a number by calling this with a prefix arg.
 833 This does not modify the disk image; you must save the tar file itself
 834 for this to be permanent."
 835   (interactive (list
 836                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 837                    (if (or current-prefix-arg
 838                            (not (tar-header-magic tokens)))
 839                        (let (n)
 840                          (while (not (numberp (setq n (read-minibuffer
 841                                                         "New GID number: "
 842                                                         (format "%s" (tar-header-gid tokens)))))))
 843                          n)
 844                        (read-string "New GID string: " (tar-header-gname tokens))))))
 845   (cond ((stringp new-gid)
 846          (tar-setf (tar-header-gname (tar-desc-tokens (tar-current-descriptor)))
 847                    new-gid)
 848          (tar-alter-one-field tar-gname-offset
 849            (concat new-gid "\000")))
 850         (t
 851          (tar-setf (tar-header-gid (tar-desc-tokens (tar-current-descriptor)))
 852                    new-gid)
 853          (tar-alter-one-field tar-gid-offset
 854            (concat (substring (format "%6o" new-gid) 0 6) "\000 ")))))
 855
 856 (defun tar-rename-entry (new-name)
 857   "*Change the name associated with this entry in the tar file.
 858 This does not modify the disk image; you must save the tar file itself
 859 for this to be permanent."
 860   (interactive
 861     (list (read-string "New name: "
 862             (tar-header-name (tar-desc-tokens (tar-current-descriptor))))))
 863   (if (string= "" new-name) (error "zero length name."))
 864   (if (> (length new-name) 98) (error "name too long."))
 865   (tar-setf (tar-header-name (tar-desc-tokens (tar-current-descriptor)))
 866             new-name)
 867   (tar-alter-one-field 0
 868     (substring (concat new-name (make-string 99 0)) 0 99)))
 869
 870
 871 (defun tar-chmod-entry (new-mode)
 872   "*Change the protection bits associated with this entry in the tar file.
 873 This does not modify the disk image; you must save the tar file itself
 874 for this to be permanent."
 875   (interactive (list (tar-parse-octal-integer-safe
 876                        (read-string "New protection (octal): "))))
 877   (tar-setf (tar-header-mode (tar-desc-tokens (tar-current-descriptor)))
 878             new-mode)
 879   (tar-alter-one-field tar-mode-offset
 880     (concat (substring (format "%6o" new-mode) 0 6) "\000 ")))
 881
 882
 883 (defun tar-alter-one-field (data-position new-data-string)
 884   (let* ((descriptor (tar-current-descriptor))
 885          (tokens (tar-desc-tokens descriptor)))
 886     (unwind-protect
 887         (save-excursion
 888           ;;
 889           ;; update the header-line.
 890           (beginning-of-line)
 891           (let ((p (point)))
 892             (forward-line 1)
 893             (delete-region p (point))
 894             (insert (summarize-tar-header-block tokens) "\n")
 895             (setq tar-header-offset (point-max)))
 896
 897           (widen)
 898           (let* ((start (+ (tar-desc-data-start descriptor) tar-header-offset -513)))
 899             ;;
 900             ;; delete the old field and insert a new one.
 901             (goto-char (+ start data-position))
 902             (delete-region (point) (+ (point) (length new-data-string))) ; <--
 903             (insert new-data-string) ; <--
 904             ;;
 905             ;; compute a new checksum and insert it.
 906             (let ((chk (checksum-tar-header-block
 907                         (buffer-substring start (+ start 512)))))
 908               (goto-char (+ start tar-chk-offset))
 909               (delete-region (point) (+ (point) 8))
 910               (insert (format "%6o" chk))
 911               (insert 0)
 912               (insert ? )
 913               (tar-setf (tar-header-checksum tokens) chk)
 914               ;;
 915               ;; ok, make sure we didn't botch it.
 916               (check-tar-header-block-checksum
 917                 (buffer-substring start (+ start 512))
 918                 chk (tar-header-name tokens))
 919               )))
 920       (narrow-to-region 1 tar-header-offset))))
 921
 922
 923 (defun tar-subfile-save-buffer ()
 924   "In tar subfile mode, write this buffer back into its parent tar-file buffer.
 925 This doesn't write anything to disk - you must save the parent tar-file buffer
 926 to make your changes permanent."
 927   (interactive)
 928   (if (not (and (boundp 'superior-tar-buffer) superior-tar-buffer))
 929     (error "this buffer has no superior tar file buffer."))
 930   (if (not (and (boundp 'superior-tar-descriptor) superior-tar-descriptor))
 931     (error "this buffer doesn't have an index into its superior tar file!"))
 932   (save-excursion
 933   (let ((subfile (current-buffer))
 934         (subfile-size (buffer-size))
 935         (descriptor superior-tar-descriptor))
 936     (set-buffer superior-tar-buffer)
 937     (let* ((tokens (tar-desc-tokens descriptor))
 938            (start (tar-desc-data-start descriptor))
 939            (name (tar-header-name tokens))
 940            (size (tar-header-size tokens))
 941            (size-pad (ash (ash (+ size 511) -9) 9))
 942            (head (memq descriptor tar-parse-info))
 943            (following-descs (cdr head)))
 944       (if (not head)
 945         (error "Can't find this tar file entry in its parent tar file!"))
 946       (unwind-protect
 947        (save-excursion
 948         (widen)
 949         ;; delete the old data...
 950         (let* ((data-start (+ start tar-header-offset -1))
 951                (data-end (+ data-start (ash (ash (+ size 511) -9) 9))))
 952           (delete-region data-start data-end)
 953           ;; insert the new data...
 954           (goto-char data-start)
 955           (insert-buffer subfile)
 956           ;;
 957           ;; pad the new data out to a multiple of 512...
 958           (let ((subfile-size-pad (ash (ash (+ subfile-size 511) -9) 9)))
 959             (goto-char (+ data-start subfile-size))
 960             (insert (make-string (- subfile-size-pad subfile-size) 0))
 961             ;;
 962             ;; update the data pointer of this and all following files...
 963             (tar-setf (tar-header-size tokens) subfile-size)
 964             (let ((difference (- subfile-size-pad size-pad)))
 965               (tar-dolist (desc following-descs)
 966                 (tar-setf (tar-desc-data-start desc)
 967                           (+ (tar-desc-data-start desc) difference))))
 968             ;;
 969             ;; Update the size field in the header block.
 970             (let ((header-start (- data-start 512)))
 971               (goto-char (+ header-start tar-size-offset))
 972               (delete-region (point) (+ (point) 12))
 973               (insert (format "%11o" subfile-size))
 974               (insert ? )
 975               ;;
 976               ;; Maybe update the datestamp.
 977               (if (not tar-update-datestamp)
 978                   nil
 979                 (goto-char (+ header-start tar-time-offset))
 980                 (delete-region (point) (+ (point) 12))
 981                 (insert (format "%11o" 0))  ; ## oops - how to get it??
 982                 (insert ? ))
 983               ;;
 984               ;; compute a new checksum and insert it.
 985               (let ((chk (checksum-tar-header-block
 986                           (buffer-substring header-start data-start))))
 987                 (goto-char (+ header-start tar-chk-offset))
 988                 (delete-region (point) (+ (point) 8))
 989                 (insert (format "%6o" chk))
 990                 (insert 0)
 991                 (insert ? )
 992                 (tar-setf (tar-header-checksum tokens) chk)))
 993             ;;
 994             ;; alter the descriptor-line...
 995             ;;
 996             (let ((position (- (length tar-parse-info) (length head))))
 997               (goto-char 1)
 998               (next-line position)
 999               (beginning-of-line)
1000               (let ((p (point))
1001                     (m (set-marker (make-marker) tar-header-offset)))
1002                 (forward-line 1)
1003                 (delete-region p (point))
1004                 (insert-before-markers (summarize-tar-header-block tokens t) "\n")
1005                 (setq tar-header-offset (marker-position m)))
1006               )))
1007         ;; after doing the insertion, add any final padding that may be necessary.
1008         (tar-pad-to-blocksize))
1009        (narrow-to-region 1 tar-header-offset)))
1010     (set-buffer-modified-p t)   ; mark the tar file as modified
1011     (set-buffer subfile)
1012     (set-buffer-modified-p nil) ; mark the tar subfile as unmodified
1013     (message "saved into tar-buffer \"%s\" - remember to save that buffer!"
1014              (buffer-name superior-tar-buffer))
1015     )))
1016
1017
1018 (defun tar-pad-to-blocksize ()
1019   "If we are being anal about tar file blocksizes, fix up the current buffer.
1020 Leaves the region wide."
1021   (if (null tar-anal-blocksize)
1022       nil
1023     (widen)
1024     (let* ((last-desc (nth (1- (length tar-parse-info)) tar-parse-info))
1025            (start (tar-desc-data-start last-desc))
1026            (tokens (tar-desc-tokens last-desc))
1027            (link-p (tar-header-link-type tokens))
1028            (size (if link-p 0 (tar-header-size tokens)))
1029            (data-end (+ start size))
1030            (bbytes (ash tar-anal-blocksize 9))
1031            (pad-to (+ bbytes (* bbytes (/ (1- data-end) bbytes))))
1032            (buffer-read-only nil) ; ##
1033            )
1034       ;; If the padding after the last data is too long, delete some;
1035       ;; else insert some until we are padded out to the right number of blocks.
1036       ;;
1037       (goto-char (+ (or tar-header-offset 0) data-end))
1038       (if (> (1+ (buffer-size)) (+ (or tar-header-offset 0) pad-to))
1039           (delete-region (+ (or tar-header-offset 0) pad-to) (1+ (buffer-size)))
1040           (insert (make-string (- (+ (or tar-header-offset 0) pad-to)
1041                                   (1+ (buffer-size)))
1042                                0)))
1043       )))
1044
1045
1046 (defun maybe-write-tar-file ()
1047   "Used as a write-file-hook to write tar-files out correctly."
1048   ;;
1049   ;; If the current buffer is in tar-mode and has its header-offset set,
1050   ;; only write out the part of the file after the header-offset.
1051   ;;
1052   (if (and (eq major-mode 'tar-mode)
1053            (and (boundp 'tar-header-offset) tar-header-offset))
1054       (unwind-protect
1055         (save-excursion
1056           (tar-clear-modification-flags)
1057           (widen)
1058           ;; Doing this here confuses things - the region gets left too wide!
1059           ;; I suppose this is run in a context where changing the buffer is bad.
1060           ;; (tar-pad-to-blocksize)
1061           (write-region tar-header-offset (1+ (buffer-size)) buffer-file-name nil t)
1062           ;; return T because we've written the file.
1063           t)
1064         (narrow-to-region 1 tar-header-offset)
1065         t)
1066       ;; return NIL because we haven't.
1067       nil))
1068
1069 \f
1070 ;;; Patch it in.
1071
1072 (defvar tar-regexp "\\.tar$"
1073   "The regular expression used to identify tar file names.")
1074
1075 (setq auto-mode-alist
1076       (cons (cons tar-regexp 'tar-mode) auto-mode-alist))
1077
1078 (or (boundp 'write-file-hooks) (setq write-file-hooks nil))
1079 (or (listp write-file-hooks)
1080     (setq write-file-hooks (list write-file-hooks)))
1081 (or (memq 'maybe-write-tar-file write-file-hooks)
1082     (setq write-file-hooks
1083           (cons 'maybe-write-tar-file write-file-hooks)))
1084
1085 \f
1086 ;;; This is a hack.  For files ending in .tar, we want -*- lines to be
1087 ;;; completely ignored - if there is one, it applies to the first file
1088 ;;; in the archive, and not the archive itself!
1089
1090 (defun tar-normal-mode (&optional find-file)
1091   "Choose the major mode for this buffer automatically.
1092 Also sets up any specified local variables of the file.
1093 Uses the visited file name, the -*- line, and the local variables spec.
1094
1095 This function is called automatically from `find-file'.  In that case,
1096 if `inhibit-local-variables' is non-`nil' we require confirmation before
1097 processing a local variables spec.  If you run `normal-mode' explicitly,
1098 confirmation is never required.
1099
1100 Note that this version of this function has been hacked to interact
1101 correctly with tar files - when visiting a file which matches
1102 'tar-regexp', the -*- line and local-variables are not examined,
1103 as they would apply to a file within the archive rather than the archive
1104 itself."
1105   (interactive)
1106   (if (and buffer-file-name
1107            (string-match tar-regexp buffer-file-name))
1108       (tar-mode)
1109       (tar-real-normal-mode find-file)))
1110
1111
1112 (if (not (fboundp 'tar-real-normal-mode))
1113     (fset 'tar-real-normal-mode (symbol-function 'normal-mode)))
1114 (fset 'normal-mode 'tar-normal-mode)
1115
1116 (provide 'tar-mode)
1117