lisp/tar-mode.el

   1 ;;; tar-mode.el --- simple editing of tar files from GNU emacs
   2
   3 ;;; Copyright (C) 1990, 1991, 1993 Free Software Foundation, Inc.
   4
   5 ;; Author: Jamie Zawinski <jwz@lucid.com>
   6 ;; Created: 04 Apr 1990
   7 ;; Version: 1.21bis (some cleanup by ESR)
   8 ;; Keywords: unix
   9
  10 ;;; This file is part of GNU Emacs.
  11 ;;;
  12 ;;; GNU Emacs is free software; you can redistribute it and/or modify
  13 ;;; it under the terms of the GNU General Public License as published by
  14 ;;; the Free Software Foundation; either version 2, or (at your option)
  15 ;;; any later version.
  16 ;;;
  17 ;;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;;; GNU General Public License for more details.
  21 ;;;
  22 ;;; You should have received a copy of the GNU General Public License
  23 ;;; along with GNU Emacs; see the file COPYING.  If not, write to
  24 ;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  25
  26 ;;; Commentary:
  27
  28 ;;; This package attempts to make dealing with Unix 'tar' archives easier.
  29 ;;; When this code is loaded, visiting a file whose name ends in '.tar' will
  30 ;;; cause the contents of that archive file to be displayed in a Dired-like
  31 ;;; listing.  It is then possible to use the customary Dired keybindings to
  32 ;;; extract sub-files from that archive, either by reading them into their own
  33 ;;; editor buffers, or by copying them directly to arbitrary files on disk.
  34 ;;; It is also possible to delete sub-files from within the tar file and write
  35 ;;; the modified archive back to disk, or to edit sub-files within the archive
  36 ;;; and re-insert the modified files into the archive.  See the documentation
  37 ;;; string of tar-mode for more info.
  38
  39 ;;; This code now understands the extra fields that GNU tar adds to tar files.
  40
  41 ;;; This interacts correctly with "uncompress.el" in the Emacs library,
  42 ;;; which you get with
  43 ;;;
  44 ;;;  (autoload 'uncompress-while-visiting "uncompress")
  45 ;;;  (setq auto-mode-alist (cons '("\\.Z$" . uncompress-while-visiting)
  46 ;;;                        auto-mode-alist))
  47 ;;;
  48 ;;; Do not attempt to use tar-mode.el with crypt.el, you will lose.
  49
  50 ;;;    ***************   TO DO   ***************
  51 ;;;
  52 ;;; o  chmod should understand "a+x,og-w".
  53 ;;;
  54 ;;; o  It's not possible to add a NEW file to a tar archive; not that
  55 ;;;    important, but still...
  56 ;;;
  57 ;;; o  In the directory listing, we don't show creation times because I don't
  58 ;;;    know how to print an arbitrary date, and I don't really want to have to
  59 ;;;    implement decode-universal-time.
  60 ;;;
  61 ;;; o  The code is less efficient that it could be - in a lot of places, I
  62 ;;;    pull a 512-character string out of the buffer and parse it, when I could
  63 ;;;    be parsing it in place, not garbaging a string.  Should redo that.
  64 ;;;
  65 ;;; o  I'd like a command that searches for a string/regexp in every subfile
  66 ;;;    of an archive, where <esc> would leave you in a subfile-edit buffer.
  67 ;;;    (Like the Meta-R command of the Zmacs mail reader.)
  68 ;;;
  69 ;;; o  Sometimes (but not always) reverting the tar-file buffer does not
  70 ;;;    re-grind the listing, and you are staring at the binary tar data.
  71 ;;;    Typing 'g' again immediately after that will always revert and re-grind
  72 ;;;    it, though.  I have no idea why this happens.
  73 ;;;
  74 ;;; o  Tar-mode interacts poorly with crypt.el and zcat.el because the tar
  75 ;;;    write-file-hook actually writes the file.  Instead it should remove the
  76 ;;;    header (and conspire to put it back afterwards) so that other write-file
  77 ;;;    hooks which frob the buffer have a chance to do their dirty work.  There
  78 ;;;    might be a problem if the tar write-file-hook does not come *first* on
  79 ;;;    the list.
  80 ;;;
  81 ;;; o  Block files, sparse files, continuation files, and the various header
  82 ;;;    types aren't editable.  Actually I don't know that they work at all.
  83
  84 ;;; Code:
  85
  86 (defvar tar-anal-blocksize 20
  87   "*The blocksize of tar files written by Emacs, or nil, meaning don't care.
  88 The blocksize of a tar file is not really the size of the blocks; rather, it is
  89 the number of blocks written with one system call.  When tarring to a tape,
  90 this is the size of the *tape* blocks, but when writing to a file, it doesn't
  91 matter much.  The only noticeable difference is that if a tar file does not
  92 have a blocksize of 20, tar will tell you that; all this really controls is
  93 how many null padding bytes go on the end of the tar file.")
  94
  95 (defvar tar-update-datestamp nil
  96   "*Whether tar-mode should play fast and loose with sub-file datestamps;
  97 if this is true, then editing and saving a tar file entry back into its
  98 tar file will update its datestamp.  If false, the datestamp is unchanged.
  99 You may or may not want this - it is good in that you can tell when a file
 100 in a tar archive has been changed, but it is bad for the same reason that
 101 editing a file in the tar archive at all is bad - the changed version of
 102 the file never exists on disk.")
 103
 104 (defvar tar-parse-info nil)
 105 (defvar tar-header-offset nil)
 106 (defvar tar-superior-buffer nil)
 107 (defvar tar-superior-descriptor nil)
 108 (defvar tar-subfile-mode nil)
 109
 110 (put 'tar-parse-info 'permanent-local t)
 111 (put 'tar-header-offset 'permanent-local t)
 112 (put 'tar-superior-buffer 'permanent-local t)
 113 (put 'tar-superior-descriptor 'permanent-local t)
 114 \f
 115 ;;; First, duplicate some Common Lisp functions; I used to just (require 'cl)
 116 ;;; but "cl.el" was messing some people up (also it's really big).
 117
 118 (defmacro tar-setf (form val)
 119   "A mind-numbingly simple implementation of setf."
 120   (let ((mform (macroexpand form (and (boundp 'byte-compile-macro-environment)
 121                                       byte-compile-macro-environment))))
 122     (cond ((symbolp mform) (list 'setq mform val))
 123           ((not (consp mform)) (error "can't setf %s" form))
 124           ((eq (car mform) 'aref)
 125            (list 'aset (nth 1 mform) (nth 2 mform) val))
 126           ((eq (car mform) 'car)
 127            (list 'setcar (nth 1 mform) val))
 128           ((eq (car mform) 'cdr)
 129            (list 'setcdr (nth 1 mform) val))
 130           (t (error "don't know how to setf %s" form)))))
 131
 132 (defmacro tar-dolist (control &rest body)
 133   "syntax: (dolist (var-name list-expr &optional return-value) &body body)"
 134   (let ((var (car control))
 135         (init (car (cdr control)))
 136         (val (car (cdr (cdr control)))))
 137     (list 'let (list (list '_dolist_iterator_ init))
 138           (list 'while '_dolist_iterator_
 139             (cons 'let
 140               (cons (list (list var '(car _dolist_iterator_)))
 141                     (append body
 142                             (list (list 'setq '_dolist_iterator_
 143                                         (list 'cdr '_dolist_iterator_)))))))
 144           val)))
 145
 146 (defmacro tar-dotimes (control &rest body)
 147   "syntax: (dolist (var-name count-expr &optional return-value) &body body)"
 148   (let ((var (car control))
 149         (n (car (cdr control)))
 150         (val (car (cdr (cdr control)))))
 151     (list 'let (list (list '_dotimes_end_ n)
 152                      (list var 0))
 153           (cons 'while
 154                 (cons (list '< var '_dotimes_end_)
 155                       (append body
 156                               (list (list 'setq var (list '1+ var))))))
 157           val)))
 158
 159 \f
 160 ;;; down to business.
 161
 162 (defmacro make-tar-header (name mode uid git size date ck lt ln
 163                            magic uname gname devmaj devmin)
 164   (list 'vector name mode uid git size date ck lt ln
 165         magic uname gname devmaj devmin))
 166
 167 (defmacro tar-header-name (x) (list 'aref x 0))
 168 (defmacro tar-header-mode (x) (list 'aref x 1))
 169 (defmacro tar-header-uid  (x) (list 'aref x 2))
 170 (defmacro tar-header-gid  (x) (list 'aref x 3))
 171 (defmacro tar-header-size (x) (list 'aref x 4))
 172 (defmacro tar-header-date (x) (list 'aref x 5))
 173 (defmacro tar-header-checksum  (x) (list 'aref x 6))
 174 (defmacro tar-header-link-type (x) (list 'aref x 7))
 175 (defmacro tar-header-link-name (x) (list 'aref x 8))
 176 (defmacro tar-header-magic (x) (list 'aref x 9))
 177 (defmacro tar-header-uname (x) (list 'aref x 10))
 178 (defmacro tar-header-gname (x) (list 'aref x 11))
 179 (defmacro tar-header-dmaj (x) (list 'aref x 12))
 180 (defmacro tar-header-dmin (x) (list 'aref x 13))
 181
 182 (defmacro make-tar-desc (data-start tokens)
 183   (list 'cons data-start tokens))
 184
 185 (defmacro tar-desc-data-start (x) (list 'car x))
 186 (defmacro tar-desc-tokens     (x) (list 'cdr x))
 187
 188 (defconst tar-name-offset 0)
 189 (defconst tar-mode-offset (+ tar-name-offset 100))
 190 (defconst tar-uid-offset  (+ tar-mode-offset 8))
 191 (defconst tar-gid-offset  (+ tar-uid-offset 8))
 192 (defconst tar-size-offset (+ tar-gid-offset 8))
 193 (defconst tar-time-offset (+ tar-size-offset 12))
 194 (defconst tar-chk-offset  (+ tar-time-offset 12))
 195 (defconst tar-linkp-offset (+ tar-chk-offset 8))
 196 (defconst tar-link-offset (+ tar-linkp-offset 1))
 197 ;;; GNU-tar specific slots.
 198 (defconst tar-magic-offset (+ tar-link-offset 100))
 199 (defconst tar-uname-offset (+ tar-magic-offset 8))
 200 (defconst tar-gname-offset (+ tar-uname-offset 32))
 201 (defconst tar-dmaj-offset (+ tar-gname-offset 32))
 202 (defconst tar-dmin-offset (+ tar-dmaj-offset 8))
 203 (defconst tar-end-offset (+ tar-dmin-offset 8))
 204
 205 (defun tokenize-tar-header-block (string)
 206   "Return a `tar-header' structure.
 207 This is a list of name, mode, uid, gid, size,
 208 write-date, checksum, link-type, and link-name."
 209   (cond ((< (length string) 512) nil)
 210         (;(some 'plusp string)           ; <-- oops, massive cycle hog!
 211          (or (not (= 0 (aref string 0))) ; This will do.
 212              (not (= 0 (aref string 101))))
 213          (let* ((name-end (1- tar-mode-offset))
 214                 (link-end (1- tar-magic-offset))
 215                 (uname-end (1- tar-gname-offset))
 216                 (gname-end (1- tar-dmaj-offset))
 217                 (link-p (aref string tar-linkp-offset))
 218                 (magic-str (substring string tar-magic-offset (1- tar-uname-offset)))
 219                 (uname-valid-p (or (string= "ustar  " magic-str) (string= "GNUtar " magic-str)))
 220                 name
 221                 (nulsexp   "[^\000]*\000"))
 222            (and (string-match nulsexp string tar-name-offset) (setq name-end (min name-end (1- (match-end 0)))))
 223            (and (string-match nulsexp string tar-link-offset) (setq link-end (min link-end (1- (match-end 0)))))
 224            (and (string-match nulsexp string tar-uname-offset) (setq uname-end (min uname-end (1- (match-end 0)))))
 225            (and (string-match nulsexp string tar-gname-offset) (setq gname-end (min gname-end (1- (match-end 0)))))
 226            (setq name (substring string tar-name-offset name-end)
 227                  link-p (if (or (= link-p 0) (= link-p ?0))
 228                             nil
 229                           (- link-p ?0)))
 230            (if (and (null link-p) (string-match "/$" name)) (setq link-p 5)) ; directory
 231            (make-tar-header
 232              name
 233              (tar-parse-octal-integer string tar-mode-offset (1- tar-uid-offset))
 234              (tar-parse-octal-integer string tar-uid-offset (1- tar-gid-offset))
 235              (tar-parse-octal-integer string tar-gid-offset (1- tar-size-offset))
 236              (tar-parse-octal-integer string tar-size-offset (1- tar-time-offset))
 237              (tar-parse-octal-integer string tar-time-offset (1- tar-chk-offset))
 238              (tar-parse-octal-integer string tar-chk-offset (1- tar-linkp-offset))
 239              link-p
 240              (substring string tar-link-offset link-end)
 241              uname-valid-p
 242              (and uname-valid-p (substring string tar-uname-offset uname-end))
 243              (and uname-valid-p (substring string tar-gname-offset gname-end))
 244              (tar-parse-octal-integer string tar-dmaj-offset (1- tar-dmin-offset))
 245              (tar-parse-octal-integer string tar-dmin-offset (1- tar-end-offset))
 246              )))
 247         (t 'empty-tar-block)))
 248
 249
 250 (defun tar-parse-octal-integer (string &optional start end)
 251   (if (null start) (setq start 0))
 252   (if (null end) (setq end (length string)))
 253   (if (= (aref string start) 0)
 254       0
 255     (let ((n 0))
 256       (while (< start end)
 257         (setq n (if (< (aref string start) ?0) n
 258                   (+ (* n 8) (- (aref string start) 48)))
 259               start (1+ start)))
 260       n)))
 261
 262 (defun tar-parse-octal-integer-safe (string)
 263   (let ((L (length string)))
 264     (if (= L 0) (error "empty string"))
 265     (tar-dotimes (i L)
 266        (if (or (< (aref string i) ?0)
 267                (> (aref string i) ?7))
 268            (error "'%c' is not an octal digit."))))
 269   (tar-parse-octal-integer string))
 270
 271
 272 (defun checksum-tar-header-block (string)
 273   "Compute and return a tar-acceptable checksum for this block."
 274   (let* ((chk-field-start tar-chk-offset)
 275          (chk-field-end (+ chk-field-start 8))
 276          (sum 0)
 277          (i 0))
 278     ;; Add up all of the characters except the ones in the checksum field.
 279     ;; Add that field as if it were filled with spaces.
 280     (while (< i chk-field-start)
 281       (setq sum (+ sum (aref string i))
 282             i (1+ i)))
 283     (setq i chk-field-end)
 284     (while (< i 512)
 285       (setq sum (+ sum (aref string i))
 286             i (1+ i)))
 287     (+ sum (* 32 8))))
 288
 289 (defun check-tar-header-block-checksum (hblock desired-checksum file-name)
 290   "Beep and print a warning if the checksum doesn't match."
 291   (if (not (= desired-checksum (checksum-tar-header-block hblock)))
 292       (progn (beep) (message "Invalid checksum for file %s!" file-name))))
 293
 294 (defun recompute-tar-header-block-checksum (hblock)
 295   "Modifies the given string to have a valid checksum field."
 296   (let* ((chk (checksum-tar-header-block hblock))
 297          (chk-string (format "%6o" chk))
 298          (l (length chk-string)))
 299     (aset hblock 154 0)
 300     (aset hblock 155 32)
 301     (tar-dotimes (i l) (aset hblock (- 153 i) (aref chk-string (- l i 1)))))
 302   hblock)
 303
 304
 305 (defun tar-grind-file-mode (mode string start)
 306   "Write a \"-rw--r--r-\" representing MODE into STRING beginning at START."
 307   (aset string start       (if (zerop (logand 256 mode)) ?- ?r))
 308   (aset string (+ start 1) (if (zerop (logand 128 mode)) ?- ?w))
 309   (aset string (+ start 2) (if (zerop (logand  64 mode)) ?- ?x))
 310   (aset string (+ start 3) (if (zerop (logand  32 mode)) ?- ?r))
 311   (aset string (+ start 4) (if (zerop (logand  16 mode)) ?- ?w))
 312   (aset string (+ start 5) (if (zerop (logand   8 mode)) ?- ?x))
 313   (aset string (+ start 6) (if (zerop (logand   4 mode)) ?- ?r))
 314   (aset string (+ start 7) (if (zerop (logand   2 mode)) ?- ?w))
 315   (aset string (+ start 8) (if (zerop (logand   1 mode)) ?- ?x))
 316   (if (zerop (logand 1024 mode)) nil (aset string (+ start 2) ?s))
 317   (if (zerop (logand 2048 mode)) nil (aset string (+ start 5) ?s))
 318   string)
 319
 320 (defun summarize-tar-header-block (tar-hblock &optional mod-p)
 321   "Returns a line similar to the output of `tar -vtf'."
 322   (let ((name (tar-header-name tar-hblock))
 323         (mode (tar-header-mode tar-hblock))
 324         (uid (tar-header-uid tar-hblock))
 325         (gid (tar-header-gid tar-hblock))
 326         (uname (tar-header-uname tar-hblock))
 327         (gname (tar-header-gname tar-hblock))
 328         (size (tar-header-size tar-hblock))
 329         (time (tar-header-date tar-hblock))
 330         (ck (tar-header-checksum tar-hblock))
 331         (link-p (tar-header-link-type tar-hblock))
 332         (link-name (tar-header-link-name tar-hblock))
 333         )
 334     (let* ((left 11)
 335            (namew 8)
 336            (groupw 8)
 337            (sizew 8)
 338            (datew 2)
 339            (slash (1- (+ left namew)))
 340            (lastdigit (+ slash groupw sizew))
 341            (namestart (+ lastdigit datew))
 342            (string (make-string (+ namestart (length name) (if link-p (+ 5 (length link-name)) 0)) 32))
 343            (type (tar-header-link-type tar-hblock)))
 344       (aset string 0 (if mod-p ?* ? ))
 345       (aset string 1
 346             (cond ((or (eq type nil) (eq type 0)) ?-)
 347                   ((eq type 1) ?l)  ; link
 348                   ((eq type 2) ?s)  ; symlink
 349                   ((eq type 3) ?c)  ; char special
 350                   ((eq type 4) ?b)  ; block special
 351                   ((eq type 5) ?d)  ; directory
 352                   ((eq type 6) ?p)  ; FIFO/pipe
 353                   ((eq type 20) ?*) ; directory listing
 354                   ((eq type 29) ?M) ; multivolume continuation
 355                   ((eq type 35) ?S) ; sparse
 356                   ((eq type 38) ?V) ; volume header
 357                   ))
 358       (tar-grind-file-mode mode string 2)
 359       (setq uid (if (= 0 (length uname)) (int-to-string uid) uname))
 360       (setq gid (if (= 0 (length gname)) (int-to-string gid) gname))
 361       (setq size (int-to-string size))
 362       (tar-dotimes (i (min (1- namew) (length uid))) (aset string (- slash i) (aref uid (- (length uid) i 1))))
 363       (aset string (1+ slash) ?/)
 364       (tar-dotimes (i (min (1- groupw) (length gid))) (aset string (+ (+ slash 2) i) (aref gid i)))
 365       (tar-dotimes (i (min sizew (length size))) (aset string (- lastdigit i) (aref size (- (length size) i 1))))
 366       ;; ## bloody hell, how do I print an arbitrary date??
 367       (tar-dotimes (i (length name)) (aset string (+ namestart i) (aref name i)))
 368       (if (or (eq link-p 1) (eq link-p 2))
 369           (progn
 370             (tar-dotimes (i 3) (aset string (+ namestart 1 (length name) i) (aref (if (= link-p 1) "==>" "-->") i)))
 371             (tar-dotimes (i (length link-name)) (aset string (+ namestart 5 (length name) i) (aref link-name i)))))
 372       string)))
 373
 374
 375 (defun tar-summarize-buffer ()
 376   "Parse the contents of the tar file in the current buffer.
 377 Place a dired-like listing on the front;
 378 then narrow to it, so that only that listing
 379 is visible (and the real data of the buffer is hidden)."
 380   (message "parsing tar file...")
 381   (let* ((result '())
 382          (pos 1)
 383          (bs (max 1 (- (buffer-size) 1024))) ; always 2+ empty blocks at end.
 384          (bs100 (max 1 (/ bs 100)))
 385         (tokens nil))
 386     (while (not (eq tokens 'empty-tar-block))
 387       (let* ((hblock (buffer-substring pos (+ pos 512))))
 388         (setq tokens (tokenize-tar-header-block hblock))
 389         (setq pos (+ pos 512))
 390         (message "parsing tar file...%s%%"
 391                  ;(/ (* pos 100) bs)   ; this gets round-off lossage
 392                  (/ pos bs100)         ; this doesn't
 393                  )
 394         (if (eq tokens 'empty-tar-block)
 395             nil
 396           (if (null tokens) (error "premature EOF parsing tar file."))
 397           (if (eq (tar-header-link-type tokens) 20)
 398               ;; Foo.  There's an extra empty block after these.
 399               (setq pos (+ pos 512)))
 400           (let ((size (tar-header-size tokens)))
 401             (if (< size 0)
 402                 (error "%s has size %s - corrupted."
 403                        (tar-header-name tokens) size))
 404             ;
 405             ; This is just too slow.  Don't really need it anyway....
 406             ;(check-tar-header-block-checksum
 407             ;  hblock (checksum-tar-header-block hblock)
 408             ;  (tar-header-name tokens))
 409
 410             (setq result (cons (make-tar-desc pos tokens) result))
 411
 412             (if (and (null (tar-header-link-type tokens))
 413                      (> size 0))
 414                 (setq pos
 415                   (+ pos 512 (ash (ash (1- size) -9) 9))        ; this works
 416                   ;(+ pos (+ size (- 512 (rem (1- size) 512)))) ; this doesn't
 417                   ))
 418             ))))
 419     (make-local-variable 'tar-parse-info)
 420     (setq tar-parse-info (nreverse result)))
 421   (save-excursion
 422     (goto-char (point-min))
 423     (let ((buffer-read-only nil))
 424       (tar-dolist (tar-desc tar-parse-info)
 425         (insert-string
 426           (summarize-tar-header-block (tar-desc-tokens tar-desc)))
 427         (insert-string "\n"))
 428       (make-local-variable 'tar-header-offset)
 429       (setq tar-header-offset (point))
 430       (narrow-to-region 1 tar-header-offset)
 431       (set-buffer-modified-p nil)))
 432   (message "parsing tar file...done."))
 433 \f
 434 (defvar tar-mode-map nil "*Local keymap for tar-mode listings.")
 435
 436 (if tar-mode-map
 437     nil
 438   (setq tar-mode-map (make-keymap))
 439   (suppress-keymap tar-mode-map)
 440   (define-key tar-mode-map " " 'tar-next-line)
 441   (define-key tar-mode-map "c" 'tar-copy)
 442   (define-key tar-mode-map "d" 'tar-flag-deleted)
 443   (define-key tar-mode-map "\^D" 'tar-flag-deleted)
 444   (define-key tar-mode-map "e" 'tar-extract)
 445   (define-key tar-mode-map "f" 'tar-extract)
 446   (define-key tar-mode-map "g" 'revert-buffer)
 447   (define-key tar-mode-map "h" 'describe-mode)
 448   (define-key tar-mode-map "n" 'tar-next-line)
 449   (define-key tar-mode-map "\^N" 'tar-next-line)
 450   (define-key tar-mode-map "o" 'tar-extract-other-window)
 451   (define-key tar-mode-map "p" 'tar-previous-line)
 452   (define-key tar-mode-map "\^P" 'tar-previous-line)
 453   (define-key tar-mode-map "r" 'tar-rename-entry)
 454   (define-key tar-mode-map "u" 'tar-unflag)
 455   (define-key tar-mode-map "v" 'tar-view)
 456   (define-key tar-mode-map "x" 'tar-expunge)
 457   (define-key tar-mode-map "\177" 'tar-unflag-backwards)
 458   (define-key tar-mode-map "E" 'tar-extract-other-window)
 459   (define-key tar-mode-map "M" 'tar-chmod-entry)
 460   (define-key tar-mode-map "G" 'tar-chgrp-entry)
 461   (define-key tar-mode-map "O" 'tar-chown-entry)
 462   )
 463 \f
 464 ;; Make menu bar items.
 465
 466 ;; Get rid of the Edit menu bar item to save space.
 467 (define-key tar-mode-map [menu-bar edit] 'undefined)
 468
 469 (define-key tar-mode-map [menu-bar immediate]
 470   (cons "Immediate" (make-sparse-keymap "Immediate")))
 471
 472 (define-key tar-mode-map [menu-bar immediate view]
 473   '("View This File" . tar-view))
 474 (define-key tar-mode-map [menu-bar immediate display]
 475   '("Display in Other Window" . tar-display-file))
 476 (define-key tar-mode-map [menu-bar immediate find-file-other-window]
 477   '("Find in Other Window" . tar-extract-other-window))
 478 (define-key tar-mode-map [menu-bar immediate find-file]
 479   '("Find This File" . tar-extract))
 480
 481 (define-key tar-mode-map [menu-bar mark]
 482   (cons "Mark" (make-sparse-keymap "Mark")))
 483
 484 (define-key tar-mode-map [menu-bar mark unmark-all]
 485   '("Unmark All" . tar-clear-modification-flags))
 486 (define-key tar-mode-map [menu-bar mark deletion]
 487   '("Flag" . tar-flag-deleted))
 488 (define-key tar-mode-map [menu-bar mark unmark]
 489   '("Unflag" . tar-unflag))
 490
 491 (define-key tar-mode-map [menu-bar operate]
 492   (cons "Operate" (make-sparse-keymap "Operate")))
 493
 494 (define-key tar-mode-map [menu-bar operate chown]
 495   '("Change Owner..." . tar-chown-entry))
 496 (define-key tar-mode-map [menu-bar operate chgrp]
 497   '("Change Group..." . tar-chgrp-entry))
 498 (define-key tar-mode-map [menu-bar operate chmod]
 499   '("Change Mode..." . tar-chmod-entry))
 500 (define-key tar-mode-map [menu-bar operate rename]
 501   '("Rename to..." . tar-rename-entry))
 502 (define-key tar-mode-map [menu-bar operate copy]
 503   '("Copy to..." . tar-copy))
 504 (define-key tar-mode-map [menu-bar operate expunge]
 505   '("Expunge marked files" . tar-expunge))
 506 \f
 507 ;; tar mode is suitable only for specially formatted data.
 508 (put 'tar-mode 'mode-class 'special)
 509 (put 'tar-subfile-mode 'mode-class 'special)
 510
 511 ;;;###autoload
 512 (defun tar-mode ()
 513   "Major mode for viewing a tar file as a dired-like listing of its contents.
 514 You can move around using the usual cursor motion commands.
 515 Letters no longer insert themselves.
 516 Type `e' to pull a file out of the tar file and into its own buffer.
 517 Type `c' to copy an entry from the tar file into another file on disk.
 518
 519 If you edit a sub-file of this archive (as with the `e' command) and
 520 save it with Control-x Control-s, the contents of that buffer will be
 521 saved back into the tar-file buffer; in this way you can edit a file
 522 inside of a tar archive without extracting it and re-archiving it.
 523
 524 See also: variables `tar-update-datestamp' and `tar-anal-blocksize'.
 525 \\{tar-mode-map}"
 526   ;; this is not interactive because you shouldn't be turning this
 527   ;; mode on and off.  You can corrupt things that way.
 528   ;; rms: with permanent locals, it should now be possible to make this work
 529   ;; interactively in some reasonable fashion.
 530   (kill-all-local-variables)
 531   (make-local-variable 'tar-header-offset)
 532   (make-local-variable 'tar-parse-info)
 533   (make-local-variable 'require-final-newline)
 534   (setq require-final-newline nil) ; binary data, dude...
 535   (make-local-variable 'revert-buffer-function)
 536   (setq revert-buffer-function 'tar-mode-revert)
 537   (make-local-variable 'enable-local-variables)
 538   (setq enable-local-variables nil)
 539   (setq major-mode 'tar-mode)
 540   (setq mode-name "Tar")
 541   (use-local-map tar-mode-map)
 542   (auto-save-mode 0)
 543   (widen)
 544   (if (and (boundp 'tar-header-offset) tar-header-offset)
 545       (narrow-to-region 1 tar-header-offset)
 546       (tar-summarize-buffer))
 547   (run-hooks 'tar-mode-hook)
 548   )
 549
 550
 551 ;; This should be converted to use a minor mode keymap.
 552
 553 (defun tar-subfile-mode (p)
 554   "Minor mode for editing an element of a tar-file.
 555 This mode redefines C-x C-s to save the current buffer back into its
 556 associated tar-file buffer.  You must save that buffer to actually
 557 save your changes to disk."
 558   (interactive "P")
 559   (or (and (boundp 'tar-superior-buffer) tar-superior-buffer)
 560       (error "This buffer is not an element of a tar file"))
 561   (or (assq 'tar-subfile-mode minor-mode-alist)
 562       (setq minor-mode-alist (append minor-mode-alist
 563                                      (list '(tar-subfile-mode
 564                                              " TarFile")))))
 565   (make-local-variable 'tar-subfile-mode)
 566   (setq tar-subfile-mode
 567         (if (null p)
 568             (not tar-subfile-mode)
 569             (> (prefix-numeric-value p) 0)))
 570   (cond (tar-subfile-mode
 571          (make-local-variable 'local-write-file-hooks)
 572          (setq local-write-file-hooks '(tar-subfile-save-buffer))
 573          ;; turn off auto-save.
 574          (auto-save-mode nil)
 575          (setq buffer-auto-save-file-name nil)
 576          (run-hooks 'tar-subfile-mode-hook))
 577         (t
 578          (kill-local-variable 'local-write-file-hooks))))
 579
 580
 581 ;; Revert the buffer and recompute the dired-like listing.
 582 (defun tar-mode-revert (&optional no-autosave no-confirm)
 583   (setq tar-header-offset nil)
 584   (let ((revert-buffer-function nil))
 585     (revert-buffer t no-confirm)
 586     (widen))
 587   (tar-mode))
 588
 589
 590 (defun tar-next-line (p)
 591   (interactive "p")
 592   (forward-line p)
 593   (if (eobp) nil (forward-char 36)))
 594
 595 (defun tar-previous-line (p)
 596   (interactive "p")
 597   (tar-next-line (- p)))
 598
 599 (defun tar-current-descriptor (&optional noerror)
 600   "Return the tar-descriptor of the current line, or signals an error."
 601   ;; I wish lines had plists, like in ZMACS...
 602   (or (nth (count-lines (point-min)
 603                         (save-excursion (beginning-of-line) (point)))
 604            tar-parse-info)
 605       (if noerror
 606           nil
 607           (error "This line does not describe a tar-file entry."))))
 608
 609
 610 (defun tar-extract (&optional other-window-p)
 611   "In Tar mode, extract this entry of the tar file into its own buffer."
 612   (interactive)
 613   (let* ((view-p (eq other-window-p 'view))
 614          (descriptor (tar-current-descriptor))
 615          (tokens (tar-desc-tokens descriptor))
 616          (name (tar-header-name tokens))
 617          (size (tar-header-size tokens))
 618          (link-p (tar-header-link-type tokens))
 619          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 620          (end (+ start size)))
 621     (if link-p
 622         (error "This is a %s, not a real file."
 623                (cond ((eq link-p 5) "directory")
 624                      ((eq link-p 20) "tar directory header")
 625                      ((eq link-p 29) "multivolume-continuation")
 626                      ((eq link-p 35) "sparse entry")
 627                      ((eq link-p 38) "volume header")
 628                      (t "link"))))
 629     (if (zerop size) (error "This is a zero-length file."))
 630     (let* ((tar-buffer (current-buffer))
 631            (bufname (concat (file-name-nondirectory name)
 632                             " (" name " in "
 633                             (file-name-nondirectory (buffer-file-name))
 634                             ")"))
 635            (read-only-p (or buffer-read-only view-p))
 636            (buffer (get-buffer bufname))
 637            (just-created nil))
 638       (if buffer
 639           nil
 640         (setq buffer (get-buffer-create bufname))
 641         (setq just-created t)
 642         (unwind-protect
 643             (progn
 644               (widen)
 645               (save-excursion
 646                 (set-buffer buffer)
 647                 (insert-buffer-substring tar-buffer start end)
 648                 (goto-char 0)
 649                 (set-visited-file-name name) ; give it a name to decide mode.
 650                 (normal-mode)  ; pick a mode.
 651                 (set-visited-file-name nil)  ; nuke the name - not meaningful.
 652                 (rename-buffer bufname)
 653
 654                 (make-local-variable 'tar-superior-buffer)
 655                 (make-local-variable 'tar-superior-descriptor)
 656                 (setq tar-superior-buffer tar-buffer)
 657                 (setq tar-superior-descriptor descriptor)
 658                 (tar-subfile-mode 1)
 659
 660                 (setq buffer-read-only read-only-p)
 661                 (set-buffer-modified-p nil))
 662               (set-buffer tar-buffer))
 663           (narrow-to-region 1 tar-header-offset)))
 664       (if view-p
 665           (progn
 666             (view-buffer buffer)
 667             (and just-created
 668                  (setq view-exit-action 'kill-buffer)))
 669         (if (eq other-window-p 'display)
 670             (display-buffer buffer)
 671           (if other-window-p
 672               (switch-to-buffer-other-window buffer)
 673             (switch-to-buffer buffer)))))))
 674
 675
 676 (defun tar-extract-other-window ()
 677   "*In Tar mode, find this entry of the tar file in another window."
 678   (interactive)
 679   (tar-extract t))
 680
 681 (defun tar-display-other-window ()
 682   "*In Tar mode, display this entry of the tar file in another window."
 683   (interactive)
 684   (tar-extract 'display))
 685
 686 (defun tar-view ()
 687   "*In Tar mode, view the tar file entry on this line."
 688   (interactive)
 689   (tar-extract 'view))
 690
 691
 692 (defun tar-read-file-name (&optional prompt)
 693   "Read a file name with this line's entry as the default."
 694   (or prompt (setq prompt "Copy to: "))
 695   (let* ((default-file (expand-file-name
 696                         (tar-header-name (tar-desc-tokens
 697                                           (tar-current-descriptor)))))
 698          (target (expand-file-name
 699                   (read-file-name prompt
 700                                   (file-name-directory default-file)
 701                                   default-file nil))))
 702     (if (or (string= "" (file-name-nondirectory target))
 703             (file-directory-p target))
 704         (setq target (concat (if (string-match "/$" target)
 705                                  (substring target 0 (1- (match-end 0)))
 706                                  target)
 707                              "/"
 708                              (file-name-nondirectory default-file))))
 709     target))
 710
 711
 712 (defun tar-copy (&optional to-file)
 713   "*In Tar mode, extract this entry of the tar file into a file on disk.
 714 If TO-FILE is not supplied, it is prompted for, defaulting to the name of
 715 the current tar-entry."
 716   (interactive (list (tar-read-file-name)))
 717   (let* ((descriptor (tar-current-descriptor))
 718          (tokens (tar-desc-tokens descriptor))
 719          (name (tar-header-name tokens))
 720          (size (tar-header-size tokens))
 721          (link-p (tar-header-link-type tokens))
 722          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 723          (end (+ start size)))
 724     (if link-p (error "This is a link, not a real file."))
 725     (if (zerop size) (error "This is a zero-length file."))
 726     (let* ((tar-buffer (current-buffer))
 727            buffer)
 728       (unwind-protect
 729           (progn
 730             (setq buffer (generate-new-buffer "*tar-copy-tmp*"))
 731             (widen)
 732             (save-excursion
 733               (set-buffer buffer)
 734               (insert-buffer-substring tar-buffer start end)
 735               (set-buffer-modified-p nil) ; in case we abort
 736               (write-file to-file)
 737               (message "Copied tar entry %s to %s" name to-file)
 738               (set-buffer tar-buffer)))
 739         (narrow-to-region 1 tar-header-offset)
 740         (if buffer (kill-buffer buffer)))
 741       )))
 742
 743
 744 (defun tar-flag-deleted (p &optional unflag)
 745   "*In Tar mode, mark this sub-file to be deleted from the tar file.
 746 With a prefix argument, mark that many files."
 747   (interactive "p")
 748   (beginning-of-line)
 749   (tar-dotimes (i (if (< p 0) (- p) p))
 750     (if (tar-current-descriptor unflag) ; barf if we're not on an entry-line.
 751         (progn
 752           (delete-char 1)
 753           (insert (if unflag " " "D"))))
 754     (forward-line (if (< p 0) -1 1)))
 755   (if (eobp) nil (forward-char 36)))
 756
 757 (defun tar-unflag (p)
 758   "*In Tar mode, un-mark this sub-file if it is marked to be deleted.
 759 With a prefix argument, un-mark that many files forward."
 760   (interactive "p")
 761   (tar-flag-deleted p t))
 762
 763 (defun tar-unflag-backwards (p)
 764   "*In Tar mode, un-mark this sub-file if it is marked to be deleted.
 765 With a prefix argument, un-mark that many files backward."
 766   (interactive "p")
 767   (tar-flag-deleted (- p) t))
 768
 769
 770 (defun tar-expunge-internal ()
 771   "Expunge the tar-entry specified by the current line."
 772   (let* ((descriptor (tar-current-descriptor))
 773          (tokens (tar-desc-tokens descriptor))
 774          (line (tar-desc-data-start descriptor))
 775          (name (tar-header-name tokens))
 776          (size (tar-header-size tokens))
 777          (link-p (tar-header-link-type tokens))
 778          (start (tar-desc-data-start descriptor))
 779          (following-descs (cdr (memq descriptor tar-parse-info))))
 780     (if link-p (setq size 0)) ; size lies for hard-links.
 781     ;;
 782     ;; delete the current line...
 783     (beginning-of-line)
 784     (let ((line-start (point)))
 785       (end-of-line) (forward-char)
 786       (let ((line-len (- (point) line-start)))
 787         (delete-region line-start (point))
 788         ;;
 789         ;; decrement the header-pointer to be in synch...
 790         (setq tar-header-offset (- tar-header-offset line-len))))
 791     ;;
 792     ;; delete the data pointer...
 793     (setq tar-parse-info (delq descriptor tar-parse-info))
 794     ;;
 795     ;; delete the data from inside the file...
 796     (widen)
 797     (let* ((data-start (+ start tar-header-offset -513))
 798            (data-end (+ data-start 512 (ash (ash (+ size 511) -9) 9))))
 799       (delete-region data-start data-end)
 800       ;;
 801       ;; and finally, decrement the start-pointers of all following
 802       ;; entries in the archive.  This is a pig when deleting a bunch
 803       ;; of files at once - we could optimize this to only do the
 804       ;; iteration over the files that remain, or only iterate up to
 805       ;; the next file to be deleted.
 806       (let ((data-length (- data-end data-start)))
 807         (tar-dolist (desc following-descs)
 808           (tar-setf (tar-desc-data-start desc)
 809                     (- (tar-desc-data-start desc) data-length))))
 810       ))
 811   (narrow-to-region 1 tar-header-offset))
 812
 813
 814 (defun tar-expunge (&optional noconfirm)
 815   "*In Tar mode, delete all the archived files flagged for deletion.
 816 This does not modify the disk image; you must save the tar file itself
 817 for this to be permanent."
 818   (interactive)
 819   (if (or noconfirm
 820           (y-or-n-p "expunge files marked for deletion? "))
 821       (let ((n 0))
 822         (save-excursion
 823           (goto-char 0)
 824           (while (not (eobp))
 825             (if (looking-at "D")
 826                 (progn (tar-expunge-internal)
 827                        (setq n (1+ n)))
 828                 (forward-line 1)))
 829           ;; after doing the deletions, add any padding that may be necessary.
 830           (tar-pad-to-blocksize)
 831           (narrow-to-region 1 tar-header-offset)
 832           )
 833         (if (zerop n)
 834             (message "nothing to expunge.")
 835             (message "%s expunged.  Be sure to save this buffer." n)))))
 836
 837
 838 (defun tar-clear-modification-flags ()
 839   "Remove the stars at the beginning of each line."
 840   (save-excursion
 841     (goto-char 0)
 842     (while (< (point) tar-header-offset)
 843       (if (looking-at "*")
 844           (progn (delete-char 1) (insert " ")))
 845       (forward-line 1))))
 846
 847
 848 (defun tar-chown-entry (new-uid)
 849   "*Change the user-id associated with this entry in the tar file.
 850 If this tar file was written by GNU tar, then you will be able to edit
 851 the user id as a string; otherwise, you must edit it as a number.
 852 You can force editing as a number by calling this with a prefix arg.
 853 This does not modify the disk image; you must save the tar file itself
 854 for this to be permanent."
 855   (interactive (list
 856                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 857                    (if (or current-prefix-arg
 858                            (not (tar-header-magic tokens)))
 859                        (let (n)
 860                          (while (not (numberp (setq n (read-minibuffer
 861                                                         "New UID number: "
 862                                                         (format "%s" (tar-header-uid tokens)))))))
 863                          n)
 864                        (read-string "New UID string: " (tar-header-uname tokens))))))
 865   (cond ((stringp new-uid)
 866          (tar-setf (tar-header-uname (tar-desc-tokens (tar-current-descriptor)))
 867                    new-uid)
 868          (tar-alter-one-field tar-uname-offset (concat new-uid "\000")))
 869         (t
 870          (tar-setf (tar-header-uid (tar-desc-tokens (tar-current-descriptor)))
 871                    new-uid)
 872          (tar-alter-one-field tar-uid-offset
 873            (concat (substring (format "%6o" new-uid) 0 6) "\000 ")))))
 874
 875
 876 (defun tar-chgrp-entry (new-gid)
 877   "*Change the group-id associated with this entry in the tar file.
 878 If this tar file was written by GNU tar, then you will be able to edit
 879 the group id as a string; otherwise, you must edit it as a number.
 880 You can force editing as a number by calling this with a prefix arg.
 881 This does not modify the disk image; you must save the tar file itself
 882 for this to be permanent."
 883   (interactive (list
 884                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 885                    (if (or current-prefix-arg
 886                            (not (tar-header-magic tokens)))
 887                        (let (n)
 888                          (while (not (numberp (setq n (read-minibuffer
 889                                                         "New GID number: "
 890                                                         (format "%s" (tar-header-gid tokens)))))))
 891                          n)
 892                        (read-string "New GID string: " (tar-header-gname tokens))))))
 893   (cond ((stringp new-gid)
 894          (tar-setf (tar-header-gname (tar-desc-tokens (tar-current-descriptor)))
 895                    new-gid)
 896          (tar-alter-one-field tar-gname-offset
 897            (concat new-gid "\000")))
 898         (t
 899          (tar-setf (tar-header-gid (tar-desc-tokens (tar-current-descriptor)))
 900                    new-gid)
 901          (tar-alter-one-field tar-gid-offset
 902            (concat (substring (format "%6o" new-gid) 0 6) "\000 ")))))
 903
 904 (defun tar-rename-entry (new-name)
 905   "*Change the name associated with this entry in the tar file.
 906 This does not modify the disk image; you must save the tar file itself
 907 for this to be permanent."
 908   (interactive
 909     (list (read-string "New name: "
 910             (tar-header-name (tar-desc-tokens (tar-current-descriptor))))))
 911   (if (string= "" new-name) (error "zero length name."))
 912   (if (> (length new-name) 98) (error "name too long."))
 913   (tar-setf (tar-header-name (tar-desc-tokens (tar-current-descriptor)))
 914             new-name)
 915   (tar-alter-one-field 0
 916     (substring (concat new-name (make-string 99 0)) 0 99)))
 917
 918
 919 (defun tar-chmod-entry (new-mode)
 920   "*Change the protection bits associated with this entry in the tar file.
 921 This does not modify the disk image; you must save the tar file itself
 922 for this to be permanent."
 923   (interactive (list (tar-parse-octal-integer-safe
 924                        (read-string "New protection (octal): "))))
 925   (tar-setf (tar-header-mode (tar-desc-tokens (tar-current-descriptor)))
 926             new-mode)
 927   (tar-alter-one-field tar-mode-offset
 928     (concat (substring (format "%6o" new-mode) 0 6) "\000 ")))
 929
 930
 931 (defun tar-alter-one-field (data-position new-data-string)
 932   (let* ((descriptor (tar-current-descriptor))
 933          (tokens (tar-desc-tokens descriptor)))
 934     (unwind-protect
 935         (save-excursion
 936           ;;
 937           ;; update the header-line.
 938           (beginning-of-line)
 939           (let ((p (point)))
 940             (forward-line 1)
 941             (delete-region p (point))
 942             (insert (summarize-tar-header-block tokens) "\n")
 943             (setq tar-header-offset (point-max)))
 944
 945           (widen)
 946           (let* ((start (+ (tar-desc-data-start descriptor) tar-header-offset -513)))
 947             ;;
 948             ;; delete the old field and insert a new one.
 949             (goto-char (+ start data-position))
 950             (delete-region (point) (+ (point) (length new-data-string))) ; <--
 951             (insert new-data-string) ; <--
 952             ;;
 953             ;; compute a new checksum and insert it.
 954             (let ((chk (checksum-tar-header-block
 955                         (buffer-substring start (+ start 512)))))
 956               (goto-char (+ start tar-chk-offset))
 957               (delete-region (point) (+ (point) 8))
 958               (insert (format "%6o" chk))
 959               (insert 0)
 960               (insert ? )
 961               (tar-setf (tar-header-checksum tokens) chk)
 962               ;;
 963               ;; ok, make sure we didn't botch it.
 964               (check-tar-header-block-checksum
 965                 (buffer-substring start (+ start 512))
 966                 chk (tar-header-name tokens))
 967               )))
 968       (narrow-to-region 1 tar-header-offset))))
 969
 970
 971 (defun tar-octal-time (timeval)
 972   ;; Format a timestamp as 11 octal digits.  Ghod, I hope this works...
 973   (let ((hibits (car timeval)) (lobits (car (cdr timeval))))
 974     (insert (format "%05o%01o%05o"
 975                     (lsh hibits -2)
 976                     (logior (lsh (logand 3 hibits) 1) (> (logand lobits 32768) 0))
 977                     (logand 32767 lobits)
 978                     ))))
 979
 980 (defun tar-subfile-save-buffer ()
 981   "In tar subfile mode, save this buffer into its parent tar-file buffer.
 982 This doesn't write anything to disk; you must save the parent tar-file buffer
 983 to make your changes permanent."
 984   (interactive)
 985   (if (not (and (boundp 'tar-superior-buffer) tar-superior-buffer))
 986     (error "this buffer has no superior tar file buffer."))
 987   (if (not (and (boundp 'tar-superior-descriptor) tar-superior-descriptor))
 988     (error "this buffer doesn't have an index into its superior tar file!"))
 989   (save-excursion
 990   (let ((subfile (current-buffer))
 991         (subfile-size (buffer-size))
 992         (descriptor tar-superior-descriptor))
 993     (set-buffer tar-superior-buffer)
 994     (let* ((tokens (tar-desc-tokens descriptor))
 995            (start (tar-desc-data-start descriptor))
 996            (name (tar-header-name tokens))
 997            (size (tar-header-size tokens))
 998            (size-pad (ash (ash (+ size 511) -9) 9))
 999            (head (memq descriptor tar-parse-info))
1000            (following-descs (cdr head)))
1001       (if (not head)
1002         (error "Can't find this tar file entry in its parent tar file!"))
1003       (unwind-protect
1004        (save-excursion
1005         (widen)
1006         ;; delete the old data...
1007         (let* ((data-start (+ start tar-header-offset -1))
1008                (data-end (+ data-start (ash (ash (+ size 511) -9) 9))))
1009           (delete-region data-start data-end)
1010           ;; insert the new data...
1011           (goto-char data-start)
1012           (insert-buffer subfile)
1013           ;;
1014           ;; pad the new data out to a multiple of 512...
1015           (let ((subfile-size-pad (ash (ash (+ subfile-size 511) -9) 9)))
1016             (goto-char (+ data-start subfile-size))
1017             (insert (make-string (- subfile-size-pad subfile-size) 0))
1018             ;;
1019             ;; update the data pointer of this and all following files...
1020             (tar-setf (tar-header-size tokens) subfile-size)
1021             (let ((difference (- subfile-size-pad size-pad)))
1022               (tar-dolist (desc following-descs)
1023                 (tar-setf (tar-desc-data-start desc)
1024                           (+ (tar-desc-data-start desc) difference))))
1025             ;;
1026             ;; Update the size field in the header block.
1027             (let ((header-start (- data-start 512)))
1028               (goto-char (+ header-start tar-size-offset))
1029               (delete-region (point) (+ (point) 12))
1030               (insert (format "%11o" subfile-size))
1031               (insert ? )
1032               ;;
1033               ;; Maybe update the datestamp.
1034               (if (not tar-update-datestamp)
1035                   nil
1036                 (goto-char (+ header-start tar-time-offset))
1037                 (delete-region (point) (+ (point) 12))
1038                 (insert (tar-octal-time (current-time)))
1039                 (insert ? ))
1040               ;;
1041               ;; compute a new checksum and insert it.
1042               (let ((chk (checksum-tar-header-block
1043                           (buffer-substring header-start data-start))))
1044                 (goto-char (+ header-start tar-chk-offset))
1045                 (delete-region (point) (+ (point) 8))
1046                 (insert (format "%6o" chk))
1047                 (insert 0)
1048                 (insert ? )
1049                 (tar-setf (tar-header-checksum tokens) chk)))
1050             ;;
1051             ;; alter the descriptor-line...
1052             ;;
1053             (let ((position (- (length tar-parse-info) (length head))))
1054               (goto-char 1)
1055               (next-line position)
1056               (beginning-of-line)
1057               (let ((p (point))
1058                     (m (set-marker (make-marker) tar-header-offset)))
1059                 (forward-line 1)
1060                 (delete-region p (point))
1061                 (insert-before-markers (summarize-tar-header-block tokens t) "\n")
1062                 (setq tar-header-offset (marker-position m)))
1063               )))
1064         ;; after doing the insertion, add any final padding that may be necessary.
1065         (tar-pad-to-blocksize))
1066        (narrow-to-region 1 tar-header-offset)))
1067     (set-buffer-modified-p t)   ; mark the tar file as modified
1068     (set-buffer subfile)
1069     (set-buffer-modified-p nil) ; mark the tar subfile as unmodified
1070     (message "saved into tar-buffer \"%s\" - remember to save that buffer!"
1071              (buffer-name tar-superior-buffer))
1072     ;; Prevent ordinary saving from happening.
1073     t)))
1074
1075
1076 (defun tar-pad-to-blocksize ()
1077   "If we are being anal about tar file blocksizes, fix up the current buffer.
1078 Leaves the region wide."
1079   (if (null tar-anal-blocksize)
1080       nil
1081     (widen)
1082     (let* ((last-desc (nth (1- (length tar-parse-info)) tar-parse-info))
1083            (start (tar-desc-data-start last-desc))
1084            (tokens (tar-desc-tokens last-desc))
1085            (link-p (tar-header-link-type tokens))
1086            (size (if link-p 0 (tar-header-size tokens)))
1087            (data-end (+ start size))
1088            (bbytes (ash tar-anal-blocksize 9))
1089            (pad-to (+ bbytes (* bbytes (/ (1- data-end) bbytes))))
1090            (inhibit-read-only t) ; ##
1091            )
1092       ;; If the padding after the last data is too long, delete some;
1093       ;; else insert some until we are padded out to the right number of blocks.
1094       ;;
1095       (goto-char (+ (or tar-header-offset 0) data-end))
1096       (if (> (1+ (buffer-size)) (+ (or tar-header-offset 0) pad-to))
1097           (delete-region (+ (or tar-header-offset 0) pad-to) (1+ (buffer-size)))
1098           (insert (make-string (- (+ (or tar-header-offset 0) pad-to)
1099                                   (1+ (buffer-size)))
1100                                0)))
1101       )))
1102
1103
1104 (defun maybe-write-tar-file ()
1105   "Used as a write-file-hook to write tar-files out correctly."
1106   ;;
1107   ;; If the current buffer is in Tar mode and has its header-offset set,
1108   ;; only write out the part of the file after the header-offset.
1109   ;;
1110   (if (and (eq major-mode 'tar-mode)
1111            (and (boundp 'tar-header-offset) tar-header-offset))
1112       (unwind-protect
1113         (save-excursion
1114           (tar-clear-modification-flags)
1115           (widen)
1116           ;; Doing this here confuses things - the region gets left too wide!
1117           ;; I suppose this is run in a context where changing the buffer is bad.
1118           ;; (tar-pad-to-blocksize)
1119           (write-region tar-header-offset (1+ (buffer-size)) buffer-file-name nil t)
1120           ;; return T because we've written the file.
1121           t)
1122         (narrow-to-region 1 tar-header-offset)
1123         t)
1124       ;; return NIL because we haven't.
1125       nil))
1126
1127 \f
1128 ;;; Patch it in.
1129
1130 (or (memq 'maybe-write-tar-file write-file-hooks)
1131     (setq write-file-hooks
1132           (cons 'maybe-write-tar-file write-file-hooks)))
1133
1134 (provide 'tar-mode)
1135
1136 ;;; tar-mode.el ends here