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 ;;; Rationale:
  85
  86 ;;; Why does tar-mode edit the file itself instead of using tar?
  87
  88 ;;; That means that you can edit tar files which you don't have room for
  89 ;;; on your local disk.
  90
  91 ;;; I don't know about recent features in gnu tar, but old versions of tar
  92 ;;; can't replace a file in the middle of a tar file with a new version.
  93 ;;; Tar-mode can.  I don't think tar can do things like chmod the subfiles.
  94 ;;; An implementation which involved unpacking and repacking the file into
  95 ;;; some scratch directory would be very wasteful, and wouldn't be able to
  96 ;;; preserve the file owners.
  97
  98 ;;; Code:
  99
 100 (defvar tar-anal-blocksize 20
 101   "*The blocksize of tar files written by Emacs, or nil, meaning don't care.
 102 The blocksize of a tar file is not really the size of the blocks; rather, it is
 103 the number of blocks written with one system call.  When tarring to a tape,
 104 this is the size of the *tape* blocks, but when writing to a file, it doesn't
 105 matter much.  The only noticeable difference is that if a tar file does not
 106 have a blocksize of 20, tar will tell you that; all this really controls is
 107 how many null padding bytes go on the end of the tar file.")
 108
 109 (defvar tar-update-datestamp nil
 110   "*Whether tar-mode should play fast and loose with sub-file datestamps;
 111 if this is true, then editing and saving a tar file entry back into its
 112 tar file will update its datestamp.  If false, the datestamp is unchanged.
 113 You may or may not want this - it is good in that you can tell when a file
 114 in a tar archive has been changed, but it is bad for the same reason that
 115 editing a file in the tar archive at all is bad - the changed version of
 116 the file never exists on disk.")
 117
 118 (defvar tar-parse-info nil)
 119 (defvar tar-header-offset nil)
 120 (defvar tar-superior-buffer nil)
 121 (defvar tar-superior-descriptor nil)
 122 (defvar tar-subfile-mode nil)
 123
 124 (put 'tar-parse-info 'permanent-local t)
 125 (put 'tar-header-offset 'permanent-local t)
 126 (put 'tar-superior-buffer 'permanent-local t)
 127 (put 'tar-superior-descriptor 'permanent-local t)
 128 \f
 129 ;;; First, duplicate some Common Lisp functions; I used to just (require 'cl)
 130 ;;; but "cl.el" was messing some people up (also it's really big).
 131
 132 (defmacro tar-setf (form val)
 133   "A mind-numbingly simple implementation of setf."
 134   (let ((mform (macroexpand form (and (boundp 'byte-compile-macro-environment)
 135                                       byte-compile-macro-environment))))
 136     (cond ((symbolp mform) (list 'setq mform val))
 137           ((not (consp mform)) (error "can't setf %s" form))
 138           ((eq (car mform) 'aref)
 139            (list 'aset (nth 1 mform) (nth 2 mform) val))
 140           ((eq (car mform) 'car)
 141            (list 'setcar (nth 1 mform) val))
 142           ((eq (car mform) 'cdr)
 143            (list 'setcdr (nth 1 mform) val))
 144           (t (error "don't know how to setf %s" form)))))
 145
 146 (defmacro tar-dolist (control &rest body)
 147   "syntax: (dolist (var-name list-expr &optional return-value) &body body)"
 148   (let ((var (car control))
 149         (init (car (cdr control)))
 150         (val (car (cdr (cdr control)))))
 151     (list 'let (list (list '_dolist_iterator_ init))
 152           (list 'while '_dolist_iterator_
 153             (cons 'let
 154               (cons (list (list var '(car _dolist_iterator_)))
 155                     (append body
 156                             (list (list 'setq '_dolist_iterator_
 157                                         (list 'cdr '_dolist_iterator_)))))))
 158           val)))
 159
 160 (defmacro tar-dotimes (control &rest body)
 161   "syntax: (dolist (var-name count-expr &optional return-value) &body body)"
 162   (let ((var (car control))
 163         (n (car (cdr control)))
 164         (val (car (cdr (cdr control)))))
 165     (list 'let (list (list '_dotimes_end_ n)
 166                      (list var 0))
 167           (cons 'while
 168                 (cons (list '< var '_dotimes_end_)
 169                       (append body
 170                               (list (list 'setq var (list '1+ var))))))
 171           val)))
 172
 173 \f
 174 ;;; down to business.
 175
 176 (defmacro make-tar-header (name mode uid git size date ck lt ln
 177                            magic uname gname devmaj devmin)
 178   (list 'vector name mode uid git size date ck lt ln
 179         magic uname gname devmaj devmin))
 180
 181 (defmacro tar-header-name (x) (list 'aref x 0))
 182 (defmacro tar-header-mode (x) (list 'aref x 1))
 183 (defmacro tar-header-uid  (x) (list 'aref x 2))
 184 (defmacro tar-header-gid  (x) (list 'aref x 3))
 185 (defmacro tar-header-size (x) (list 'aref x 4))
 186 (defmacro tar-header-date (x) (list 'aref x 5))
 187 (defmacro tar-header-checksum  (x) (list 'aref x 6))
 188 (defmacro tar-header-link-type (x) (list 'aref x 7))
 189 (defmacro tar-header-link-name (x) (list 'aref x 8))
 190 (defmacro tar-header-magic (x) (list 'aref x 9))
 191 (defmacro tar-header-uname (x) (list 'aref x 10))
 192 (defmacro tar-header-gname (x) (list 'aref x 11))
 193 (defmacro tar-header-dmaj (x) (list 'aref x 12))
 194 (defmacro tar-header-dmin (x) (list 'aref x 13))
 195
 196 (defmacro make-tar-desc (data-start tokens)
 197   (list 'cons data-start tokens))
 198
 199 (defmacro tar-desc-data-start (x) (list 'car x))
 200 (defmacro tar-desc-tokens     (x) (list 'cdr x))
 201
 202 (defconst tar-name-offset 0)
 203 (defconst tar-mode-offset (+ tar-name-offset 100))
 204 (defconst tar-uid-offset  (+ tar-mode-offset 8))
 205 (defconst tar-gid-offset  (+ tar-uid-offset 8))
 206 (defconst tar-size-offset (+ tar-gid-offset 8))
 207 (defconst tar-time-offset (+ tar-size-offset 12))
 208 (defconst tar-chk-offset  (+ tar-time-offset 12))
 209 (defconst tar-linkp-offset (+ tar-chk-offset 8))
 210 (defconst tar-link-offset (+ tar-linkp-offset 1))
 211 ;;; GNU-tar specific slots.
 212 (defconst tar-magic-offset (+ tar-link-offset 100))
 213 (defconst tar-uname-offset (+ tar-magic-offset 8))
 214 (defconst tar-gname-offset (+ tar-uname-offset 32))
 215 (defconst tar-dmaj-offset (+ tar-gname-offset 32))
 216 (defconst tar-dmin-offset (+ tar-dmaj-offset 8))
 217 (defconst tar-end-offset (+ tar-dmin-offset 8))
 218
 219 (defun tokenize-tar-header-block (string)
 220   "Return a `tar-header' structure.
 221 This is a list of name, mode, uid, gid, size,
 222 write-date, checksum, link-type, and link-name."
 223   (cond ((< (length string) 512) nil)
 224         (;(some 'plusp string)           ; <-- oops, massive cycle hog!
 225          (or (not (= 0 (aref string 0))) ; This will do.
 226              (not (= 0 (aref string 101))))
 227          (let* ((name-end (1- tar-mode-offset))
 228                 (link-end (1- tar-magic-offset))
 229                 (uname-end (1- tar-gname-offset))
 230                 (gname-end (1- tar-dmaj-offset))
 231                 (link-p (aref string tar-linkp-offset))
 232                 (magic-str (substring string tar-magic-offset (1- tar-uname-offset)))
 233                 (uname-valid-p (or (string= "ustar  " magic-str) (string= "GNUtar " magic-str)))
 234                 name
 235                 (nulsexp   "[^\000]*\000"))
 236            (and (string-match nulsexp string tar-name-offset) (setq name-end (min name-end (1- (match-end 0)))))
 237            (and (string-match nulsexp string tar-link-offset) (setq link-end (min link-end (1- (match-end 0)))))
 238            (and (string-match nulsexp string tar-uname-offset) (setq uname-end (min uname-end (1- (match-end 0)))))
 239            (and (string-match nulsexp string tar-gname-offset) (setq gname-end (min gname-end (1- (match-end 0)))))
 240            (setq name (substring string tar-name-offset name-end)
 241                  link-p (if (or (= link-p 0) (= link-p ?0))
 242                             nil
 243                           (- link-p ?0)))
 244            (if (and (null link-p) (string-match "/$" name)) (setq link-p 5)) ; directory
 245            (make-tar-header
 246              name
 247              (tar-parse-octal-integer string tar-mode-offset (1- tar-uid-offset))
 248              (tar-parse-octal-integer string tar-uid-offset (1- tar-gid-offset))
 249              (tar-parse-octal-integer string tar-gid-offset (1- tar-size-offset))
 250              (tar-parse-octal-integer string tar-size-offset (1- tar-time-offset))
 251              (tar-parse-octal-integer string tar-time-offset (1- tar-chk-offset))
 252              (tar-parse-octal-integer string tar-chk-offset (1- tar-linkp-offset))
 253              link-p
 254              (substring string tar-link-offset link-end)
 255              uname-valid-p
 256              (and uname-valid-p (substring string tar-uname-offset uname-end))
 257              (and uname-valid-p (substring string tar-gname-offset gname-end))
 258              (tar-parse-octal-integer string tar-dmaj-offset (1- tar-dmin-offset))
 259              (tar-parse-octal-integer string tar-dmin-offset (1- tar-end-offset))
 260              )))
 261         (t 'empty-tar-block)))
 262
 263
 264 (defun tar-parse-octal-integer (string &optional start end)
 265   (if (null start) (setq start 0))
 266   (if (null end) (setq end (length string)))
 267   (if (= (aref string start) 0)
 268       0
 269     (let ((n 0))
 270       (while (< start end)
 271         (setq n (if (< (aref string start) ?0) n
 272                   (+ (* n 8) (- (aref string start) 48)))
 273               start (1+ start)))
 274       n)))
 275
 276 (defun tar-parse-octal-integer-safe (string)
 277   (let ((L (length string)))
 278     (if (= L 0) (error "empty string"))
 279     (tar-dotimes (i L)
 280        (if (or (< (aref string i) ?0)
 281                (> (aref string i) ?7))
 282            (error "'%c' is not an octal digit"))))
 283   (tar-parse-octal-integer string))
 284
 285
 286 (defun checksum-tar-header-block (string)
 287   "Compute and return a tar-acceptable checksum for this block."
 288   (let* ((chk-field-start tar-chk-offset)
 289          (chk-field-end (+ chk-field-start 8))
 290          (sum 0)
 291          (i 0))
 292     ;; Add up all of the characters except the ones in the checksum field.
 293     ;; Add that field as if it were filled with spaces.
 294     (while (< i chk-field-start)
 295       (setq sum (+ sum (aref string i))
 296             i (1+ i)))
 297     (setq i chk-field-end)
 298     (while (< i 512)
 299       (setq sum (+ sum (aref string i))
 300             i (1+ i)))
 301     (+ sum (* 32 8))))
 302
 303 (defun check-tar-header-block-checksum (hblock desired-checksum file-name)
 304   "Beep and print a warning if the checksum doesn't match."
 305   (if (not (= desired-checksum (checksum-tar-header-block hblock)))
 306       (progn (beep) (message "Invalid checksum for file %s!" file-name))))
 307
 308 (defun recompute-tar-header-block-checksum (hblock)
 309   "Modifies the given string to have a valid checksum field."
 310   (let* ((chk (checksum-tar-header-block hblock))
 311          (chk-string (format "%6o" chk))
 312          (l (length chk-string)))
 313     (aset hblock 154 0)
 314     (aset hblock 155 32)
 315     (tar-dotimes (i l) (aset hblock (- 153 i) (aref chk-string (- l i 1)))))
 316   hblock)
 317
 318
 319 (defun tar-grind-file-mode (mode string start)
 320   "Write a \"-rw--r--r-\" representing MODE into STRING beginning at START."
 321   (aset string start       (if (zerop (logand 256 mode)) ?- ?r))
 322   (aset string (+ start 1) (if (zerop (logand 128 mode)) ?- ?w))
 323   (aset string (+ start 2) (if (zerop (logand  64 mode)) ?- ?x))
 324   (aset string (+ start 3) (if (zerop (logand  32 mode)) ?- ?r))
 325   (aset string (+ start 4) (if (zerop (logand  16 mode)) ?- ?w))
 326   (aset string (+ start 5) (if (zerop (logand   8 mode)) ?- ?x))
 327   (aset string (+ start 6) (if (zerop (logand   4 mode)) ?- ?r))
 328   (aset string (+ start 7) (if (zerop (logand   2 mode)) ?- ?w))
 329   (aset string (+ start 8) (if (zerop (logand   1 mode)) ?- ?x))
 330   (if (zerop (logand 1024 mode)) nil (aset string (+ start 2) ?s))
 331   (if (zerop (logand 2048 mode)) nil (aset string (+ start 5) ?s))
 332   string)
 333
 334 (defun summarize-tar-header-block (tar-hblock &optional mod-p)
 335   "Returns a line similar to the output of `tar -vtf'."
 336   (let ((name (tar-header-name tar-hblock))
 337         (mode (tar-header-mode tar-hblock))
 338         (uid (tar-header-uid tar-hblock))
 339         (gid (tar-header-gid tar-hblock))
 340         (uname (tar-header-uname tar-hblock))
 341         (gname (tar-header-gname tar-hblock))
 342         (size (tar-header-size tar-hblock))
 343         (time (tar-header-date tar-hblock))
 344         (ck (tar-header-checksum tar-hblock))
 345         (link-p (tar-header-link-type tar-hblock))
 346         (link-name (tar-header-link-name tar-hblock))
 347         )
 348     (let* ((left 11)
 349            (namew 8)
 350            (groupw 8)
 351            (sizew 8)
 352            (datew 2)
 353            (slash (1- (+ left namew)))
 354            (lastdigit (+ slash groupw sizew))
 355            (namestart (+ lastdigit datew))
 356            (string (make-string (+ namestart (length name) (if link-p (+ 5 (length link-name)) 0)) 32))
 357            (type (tar-header-link-type tar-hblock)))
 358       (aset string 0 (if mod-p ?* ? ))
 359       (aset string 1
 360             (cond ((or (eq type nil) (eq type 0)) ?-)
 361                   ((eq type 1) ?l)  ; link
 362                   ((eq type 2) ?s)  ; symlink
 363                   ((eq type 3) ?c)  ; char special
 364                   ((eq type 4) ?b)  ; block special
 365                   ((eq type 5) ?d)  ; directory
 366                   ((eq type 6) ?p)  ; FIFO/pipe
 367                   ((eq type 20) ?*) ; directory listing
 368                   ((eq type 29) ?M) ; multivolume continuation
 369                   ((eq type 35) ?S) ; sparse
 370                   ((eq type 38) ?V) ; volume header
 371                   ))
 372       (tar-grind-file-mode mode string 2)
 373       (setq uid (if (= 0 (length uname)) (int-to-string uid) uname))
 374       (setq gid (if (= 0 (length gname)) (int-to-string gid) gname))
 375       (setq size (int-to-string size))
 376       (tar-dotimes (i (min (1- namew) (length uid))) (aset string (- slash i) (aref uid (- (length uid) i 1))))
 377       (aset string (1+ slash) ?/)
 378       (tar-dotimes (i (min (1- groupw) (length gid))) (aset string (+ (+ slash 2) i) (aref gid i)))
 379       (tar-dotimes (i (min sizew (length size))) (aset string (- lastdigit i) (aref size (- (length size) i 1))))
 380       ;; ## bloody hell, how do I print an arbitrary date??
 381       (tar-dotimes (i (length name)) (aset string (+ namestart i) (aref name i)))
 382       (if (or (eq link-p 1) (eq link-p 2))
 383           (progn
 384             (tar-dotimes (i 3) (aset string (+ namestart 1 (length name) i) (aref (if (= link-p 1) "==>" "-->") i)))
 385             (tar-dotimes (i (length link-name)) (aset string (+ namestart 5 (length name) i) (aref link-name i)))))
 386       (put-text-property namestart (length string)
 387                          'mouse-face 'highlight string)
 388       string)))
 389
 390
 391 (defun tar-summarize-buffer ()
 392   "Parse the contents of the tar file in the current buffer.
 393 Place a dired-like listing on the front;
 394 then narrow to it, so that only that listing
 395 is visible (and the real data of the buffer is hidden)."
 396   (message "parsing tar file...")
 397   (let* ((result '())
 398          (pos 1)
 399          (bs (max 1 (- (buffer-size) 1024))) ; always 2+ empty blocks at end.
 400          (bs100 (max 1 (/ bs 100)))
 401         (tokens nil))
 402     (while (not (eq tokens 'empty-tar-block))
 403       (let* ((hblock (buffer-substring pos (+ pos 512))))
 404         (setq tokens (tokenize-tar-header-block hblock))
 405         (setq pos (+ pos 512))
 406         (message "parsing tar file...%s%%"
 407                  ;(/ (* pos 100) bs)   ; this gets round-off lossage
 408                  (/ pos bs100)         ; this doesn't
 409                  )
 410         (if (eq tokens 'empty-tar-block)
 411             nil
 412           (if (null tokens) (error "premature EOF parsing tar file"))
 413           (if (eq (tar-header-link-type tokens) 20)
 414               ;; Foo.  There's an extra empty block after these.
 415               (setq pos (+ pos 512)))
 416           (let ((size (tar-header-size tokens)))
 417             (if (< size 0)
 418                 (error "%s has size %s - corrupted"
 419                        (tar-header-name tokens) size))
 420             ;
 421             ; This is just too slow.  Don't really need it anyway....
 422             ;(check-tar-header-block-checksum
 423             ;  hblock (checksum-tar-header-block hblock)
 424             ;  (tar-header-name tokens))
 425
 426             (setq result (cons (make-tar-desc pos tokens) result))
 427
 428             (if (and (null (tar-header-link-type tokens))
 429                      (> size 0))
 430                 (setq pos
 431                   (+ pos 512 (ash (ash (1- size) -9) 9))        ; this works
 432                   ;(+ pos (+ size (- 512 (rem (1- size) 512)))) ; this doesn't
 433                   ))
 434             ))))
 435     (make-local-variable 'tar-parse-info)
 436     (setq tar-parse-info (nreverse result)))
 437   (save-excursion
 438     (goto-char (point-min))
 439     (let ((buffer-read-only nil))
 440       (tar-dolist (tar-desc tar-parse-info)
 441         (insert-string
 442           (summarize-tar-header-block (tar-desc-tokens tar-desc)))
 443         (insert-string "\n"))
 444       (make-local-variable 'tar-header-offset)
 445       (setq tar-header-offset (point))
 446       (narrow-to-region 1 tar-header-offset)
 447       (set-buffer-modified-p nil)))
 448   (message "parsing tar file...done."))
 449 \f
 450 (defvar tar-mode-map nil "*Local keymap for Tar mode listings.")
 451
 452 (if tar-mode-map
 453     nil
 454   (setq tar-mode-map (make-keymap))
 455   (suppress-keymap tar-mode-map)
 456   (define-key tar-mode-map " " 'tar-next-line)
 457   (define-key tar-mode-map "c" 'tar-copy)
 458   (define-key tar-mode-map "d" 'tar-flag-deleted)
 459   (define-key tar-mode-map "\^D" 'tar-flag-deleted)
 460   (define-key tar-mode-map "e" 'tar-extract)
 461   (define-key tar-mode-map "f" 'tar-extract)
 462   (define-key tar-mode-map [mouse-2] 'tar-mouse-extract)
 463   (define-key tar-mode-map "g" 'revert-buffer)
 464   (define-key tar-mode-map "h" 'describe-mode)
 465   (define-key tar-mode-map "n" 'tar-next-line)
 466   (define-key tar-mode-map "\^N" 'tar-next-line)
 467   (define-key tar-mode-map "o" 'tar-extract-other-window)
 468   (define-key tar-mode-map "p" 'tar-previous-line)
 469   (define-key tar-mode-map "\^P" 'tar-previous-line)
 470   (define-key tar-mode-map "r" 'tar-rename-entry)
 471   (define-key tar-mode-map "u" 'tar-unflag)
 472   (define-key tar-mode-map "v" 'tar-view)
 473   (define-key tar-mode-map "x" 'tar-expunge)
 474   (define-key tar-mode-map "\177" 'tar-unflag-backwards)
 475   (define-key tar-mode-map "E" 'tar-extract-other-window)
 476   (define-key tar-mode-map "M" 'tar-chmod-entry)
 477   (define-key tar-mode-map "G" 'tar-chgrp-entry)
 478   (define-key tar-mode-map "O" 'tar-chown-entry)
 479   )
 480 \f
 481 ;; Make menu bar items.
 482
 483 ;; Get rid of the Edit menu bar item to save space.
 484 (define-key tar-mode-map [menu-bar edit] 'undefined)
 485
 486 (define-key tar-mode-map [menu-bar immediate]
 487   (cons "Immediate" (make-sparse-keymap "Immediate")))
 488
 489 (define-key tar-mode-map [menu-bar immediate view]
 490   '("View This File" . tar-view))
 491 (define-key tar-mode-map [menu-bar immediate display]
 492   '("Display in Other Window" . tar-display-file))
 493 (define-key tar-mode-map [menu-bar immediate find-file-other-window]
 494   '("Find in Other Window" . tar-extract-other-window))
 495 (define-key tar-mode-map [menu-bar immediate find-file]
 496   '("Find This File" . tar-extract))
 497
 498 (define-key tar-mode-map [menu-bar mark]
 499   (cons "Mark" (make-sparse-keymap "Mark")))
 500
 501 (define-key tar-mode-map [menu-bar mark unmark-all]
 502   '("Unmark All" . tar-clear-modification-flags))
 503 (define-key tar-mode-map [menu-bar mark deletion]
 504   '("Flag" . tar-flag-deleted))
 505 (define-key tar-mode-map [menu-bar mark unmark]
 506   '("Unflag" . tar-unflag))
 507
 508 (define-key tar-mode-map [menu-bar operate]
 509   (cons "Operate" (make-sparse-keymap "Operate")))
 510
 511 (define-key tar-mode-map [menu-bar operate chown]
 512   '("Change Owner..." . tar-chown-entry))
 513 (define-key tar-mode-map [menu-bar operate chgrp]
 514   '("Change Group..." . tar-chgrp-entry))
 515 (define-key tar-mode-map [menu-bar operate chmod]
 516   '("Change Mode..." . tar-chmod-entry))
 517 (define-key tar-mode-map [menu-bar operate rename]
 518   '("Rename to..." . tar-rename-entry))
 519 (define-key tar-mode-map [menu-bar operate copy]
 520   '("Copy to..." . tar-copy))
 521 (define-key tar-mode-map [menu-bar operate expunge]
 522   '("Expunge marked files" . tar-expunge))
 523 \f
 524 ;; tar mode is suitable only for specially formatted data.
 525 (put 'tar-mode 'mode-class 'special)
 526 (put 'tar-subfile-mode 'mode-class 'special)
 527
 528 ;;;###autoload
 529 (defun tar-mode ()
 530   "Major mode for viewing a tar file as a dired-like listing of its contents.
 531 You can move around using the usual cursor motion commands.
 532 Letters no longer insert themselves.
 533 Type `e' to pull a file out of the tar file and into its own buffer;
 534 or click mouse-2 on the file's line in the Tar mode buffer.
 535 Type `c' to copy an entry from the tar file into another file on disk.
 536
 537 If you edit a sub-file of this archive (as with the `e' command) and
 538 save it with Control-x Control-s, the contents of that buffer will be
 539 saved back into the tar-file buffer; in this way you can edit a file
 540 inside of a tar archive without extracting it and re-archiving it.
 541
 542 See also: variables `tar-update-datestamp' and `tar-anal-blocksize'.
 543 \\{tar-mode-map}"
 544   ;; this is not interactive because you shouldn't be turning this
 545   ;; mode on and off.  You can corrupt things that way.
 546   ;; rms: with permanent locals, it should now be possible to make this work
 547   ;; interactively in some reasonable fashion.
 548   (kill-all-local-variables)
 549   (make-local-variable 'tar-header-offset)
 550   (make-local-variable 'tar-parse-info)
 551   (make-local-variable 'require-final-newline)
 552   (setq require-final-newline nil) ; binary data, dude...
 553   (make-local-variable 'revert-buffer-function)
 554   (setq revert-buffer-function 'tar-mode-revert)
 555   (make-local-variable 'enable-local-variables)
 556   (setq enable-local-variables nil)
 557   (setq major-mode 'tar-mode)
 558   (setq mode-name "Tar")
 559   (use-local-map tar-mode-map)
 560   (auto-save-mode 0)
 561   (widen)
 562   (if (and (boundp 'tar-header-offset) tar-header-offset)
 563       (narrow-to-region 1 tar-header-offset)
 564       (tar-summarize-buffer))
 565   (run-hooks 'tar-mode-hook)
 566   )
 567
 568
 569 ;; This should be converted to use a minor mode keymap.
 570
 571 (defun tar-subfile-mode (p)
 572   "Minor mode for editing an element of a tar-file.
 573 This mode redefines C-x C-s to save the current buffer back into its
 574 associated tar-file buffer.  You must save that buffer to actually
 575 save your changes to disk."
 576   (interactive "P")
 577   (or (and (boundp 'tar-superior-buffer) tar-superior-buffer)
 578       (error "This buffer is not an element of a tar file"))
 579 ;;; Don't do this, because it is redundant and wastes mode line space.
 580 ;;;  (or (assq 'tar-subfile-mode minor-mode-alist)
 581 ;;;      (setq minor-mode-alist (append minor-mode-alist
 582 ;;;                                  (list '(tar-subfile-mode " TarFile")))))
 583   (make-local-variable 'tar-subfile-mode)
 584   (setq tar-subfile-mode
 585         (if (null p)
 586             (not tar-subfile-mode)
 587             (> (prefix-numeric-value p) 0)))
 588   (cond (tar-subfile-mode
 589          (make-local-variable 'local-write-file-hooks)
 590          (setq local-write-file-hooks '(tar-subfile-save-buffer))
 591          ;; turn off auto-save.
 592          (auto-save-mode nil)
 593          (setq buffer-auto-save-file-name nil)
 594          (run-hooks 'tar-subfile-mode-hook))
 595         (t
 596          (kill-local-variable 'local-write-file-hooks))))
 597
 598
 599 ;; Revert the buffer and recompute the dired-like listing.
 600 (defun tar-mode-revert (&optional no-autosave no-confirm)
 601   (setq tar-header-offset nil)
 602   (let ((revert-buffer-function nil))
 603     (revert-buffer t no-confirm)
 604     (widen))
 605   (tar-mode))
 606
 607
 608 (defun tar-next-line (p)
 609   (interactive "p")
 610   (forward-line p)
 611   (if (eobp) nil (forward-char 36)))
 612
 613 (defun tar-previous-line (p)
 614   (interactive "p")
 615   (tar-next-line (- p)))
 616
 617 (defun tar-current-descriptor (&optional noerror)
 618   "Return the tar-descriptor of the current line, or signals an error."
 619   ;; I wish lines had plists, like in ZMACS...
 620   (or (nth (count-lines (point-min)
 621                         (save-excursion (beginning-of-line) (point)))
 622            tar-parse-info)
 623       (if noerror
 624           nil
 625           (error "This line does not describe a tar-file entry"))))
 626
 627 (defun tar-get-descriptor ()
 628   (let* ((descriptor (tar-current-descriptor))
 629          (tokens (tar-desc-tokens descriptor))
 630          (size (tar-header-size tokens))
 631          (link-p (tar-header-link-type tokens)))
 632     (if link-p
 633         (error "This is a %s, not a real file"
 634                (cond ((eq link-p 5) "directory")
 635                      ((eq link-p 20) "tar directory header")
 636                      ((eq link-p 29) "multivolume-continuation")
 637                      ((eq link-p 35) "sparse entry")
 638                      ((eq link-p 38) "volume header")
 639                      (t "link"))))
 640     (if (zerop size) (error "This is a zero-length file"))
 641     descriptor))
 642
 643 (defun tar-mouse-extract (event)
 644   "Extract a file whose tar directory line you click on."
 645   (interactive "e")
 646   (save-excursion
 647     (set-buffer (window-buffer (posn-window (event-end event))))
 648     (save-excursion
 649       (goto-char (posn-point (event-end event)))
 650       ;; Just make sure this doesn't get an error.
 651       (tar-get-descriptor)))
 652   (select-window (posn-window (event-end event)))
 653   (goto-char (posn-point (event-end event)))
 654   (tar-extract))
 655
 656 (defun tar-extract (&optional other-window-p)
 657   "In Tar mode, extract this entry of the tar file into its own buffer."
 658   (interactive)
 659   (let* ((view-p (eq other-window-p 'view))
 660          (descriptor (tar-get-descriptor))
 661          (tokens (tar-desc-tokens descriptor))
 662          (name (tar-header-name tokens))
 663          (size (tar-header-size tokens))
 664          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 665          (end (+ start size)))
 666     (let* ((tar-buffer (current-buffer))
 667            (tarname (file-name-nondirectory (buffer-file-name)))
 668            (bufname (concat (file-name-nondirectory name)
 669                             " ("
 670                             tarname
 671                             ")"))
 672            (read-only-p (or buffer-read-only view-p))
 673            (buffer (get-buffer bufname))
 674            (just-created nil))
 675       (if buffer
 676           nil
 677         (setq buffer (get-buffer-create bufname))
 678         (setq just-created t)
 679         (unwind-protect
 680             (progn
 681               (widen)
 682               (save-excursion
 683                 (set-buffer buffer)
 684                 (insert-buffer-substring tar-buffer start end)
 685                 (goto-char 0)
 686                 (set-visited-file-name name) ; give it a name to decide mode.
 687                 (normal-mode)  ; pick a mode.
 688                 (set-visited-file-name nil)  ; nuke the name - not meaningful.
 689                 (rename-buffer bufname)
 690
 691                 (make-local-variable 'tar-superior-buffer)
 692                 (make-local-variable 'tar-superior-descriptor)
 693                 (setq tar-superior-buffer tar-buffer)
 694                 (setq tar-superior-descriptor descriptor)
 695
 696                 ;; Since the "real" file name is not in buffer-file-name,
 697                 ;; put it here for list-buffers.
 698                 (make-local-variable 'list-buffers-directory)
 699                 (setq list-buffers-directory name)
 700
 701                 (tar-subfile-mode 1)
 702
 703                 (setq buffer-read-only read-only-p)
 704                 (set-buffer-modified-p nil))
 705               (set-buffer tar-buffer))
 706           (narrow-to-region 1 tar-header-offset)))
 707       (if view-p
 708           (progn
 709             (view-buffer buffer)
 710             (and just-created
 711                  (setq view-exit-action 'kill-buffer)))
 712         (if (eq other-window-p 'display)
 713             (display-buffer buffer)
 714           (if other-window-p
 715               (switch-to-buffer-other-window buffer)
 716             (switch-to-buffer buffer)))))))
 717
 718
 719 (defun tar-extract-other-window ()
 720   "*In Tar mode, find this entry of the tar file in another window."
 721   (interactive)
 722   (tar-extract t))
 723
 724 (defun tar-display-other-window ()
 725   "*In Tar mode, display this entry of the tar file in another window."
 726   (interactive)
 727   (tar-extract 'display))
 728
 729 (defun tar-view ()
 730   "*In Tar mode, view the tar file entry on this line."
 731   (interactive)
 732   (tar-extract 'view))
 733
 734
 735 (defun tar-read-file-name (&optional prompt)
 736   "Read a file name with this line's entry as the default."
 737   (or prompt (setq prompt "Copy to: "))
 738   (let* ((default-file (expand-file-name
 739                         (tar-header-name (tar-desc-tokens
 740                                           (tar-current-descriptor)))))
 741          (target (expand-file-name
 742                   (read-file-name prompt
 743                                   (file-name-directory default-file)
 744                                   default-file nil))))
 745     (if (or (string= "" (file-name-nondirectory target))
 746             (file-directory-p target))
 747         (setq target (concat (if (string-match "/$" target)
 748                                  (substring target 0 (1- (match-end 0)))
 749                                  target)
 750                              "/"
 751                              (file-name-nondirectory default-file))))
 752     target))
 753
 754
 755 (defun tar-copy (&optional to-file)
 756   "*In Tar mode, extract this entry of the tar file into a file on disk.
 757 If TO-FILE is not supplied, it is prompted for, defaulting to the name of
 758 the current tar-entry."
 759   (interactive (list (tar-read-file-name)))
 760   (let* ((descriptor (tar-get-descriptor))
 761          (tokens (tar-desc-tokens descriptor))
 762          (name (tar-header-name tokens))
 763          (size (tar-header-size tokens))
 764          (start (+ (tar-desc-data-start descriptor) tar-header-offset -1))
 765          (end (+ start size)))
 766     (save-restriction
 767       (widen)
 768       (write-region start end to-file))
 769     (message "Copied tar entry %s to %s" name to-file)))
 770
 771 (defun tar-flag-deleted (p &optional unflag)
 772   "*In Tar mode, mark this sub-file to be deleted from the tar file.
 773 With a prefix argument, mark that many files."
 774   (interactive "p")
 775   (beginning-of-line)
 776   (tar-dotimes (i (if (< p 0) (- p) p))
 777     (if (tar-current-descriptor unflag) ; barf if we're not on an entry-line.
 778         (progn
 779           (delete-char 1)
 780           (insert (if unflag " " "D"))))
 781     (forward-line (if (< p 0) -1 1)))
 782   (if (eobp) nil (forward-char 36)))
 783
 784 (defun tar-unflag (p)
 785   "*In Tar mode, un-mark this sub-file if it is marked to be deleted.
 786 With a prefix argument, un-mark that many files forward."
 787   (interactive "p")
 788   (tar-flag-deleted p t))
 789
 790 (defun tar-unflag-backwards (p)
 791   "*In Tar mode, un-mark this sub-file if it is marked to be deleted.
 792 With a prefix argument, un-mark that many files backward."
 793   (interactive "p")
 794   (tar-flag-deleted (- p) t))
 795
 796
 797 (defun tar-expunge-internal ()
 798   "Expunge the tar-entry specified by the current line."
 799   (let* ((descriptor (tar-current-descriptor))
 800          (tokens (tar-desc-tokens descriptor))
 801          (line (tar-desc-data-start descriptor))
 802          (name (tar-header-name tokens))
 803          (size (tar-header-size tokens))
 804          (link-p (tar-header-link-type tokens))
 805          (start (tar-desc-data-start descriptor))
 806          (following-descs (cdr (memq descriptor tar-parse-info))))
 807     (if link-p (setq size 0)) ; size lies for hard-links.
 808     ;;
 809     ;; delete the current line...
 810     (beginning-of-line)
 811     (let ((line-start (point)))
 812       (end-of-line) (forward-char)
 813       (let ((line-len (- (point) line-start)))
 814         (delete-region line-start (point))
 815         ;;
 816         ;; decrement the header-pointer to be in synch...
 817         (setq tar-header-offset (- tar-header-offset line-len))))
 818     ;;
 819     ;; delete the data pointer...
 820     (setq tar-parse-info (delq descriptor tar-parse-info))
 821     ;;
 822     ;; delete the data from inside the file...
 823     (widen)
 824     (let* ((data-start (+ start tar-header-offset -513))
 825            (data-end (+ data-start 512 (ash (ash (+ size 511) -9) 9))))
 826       (delete-region data-start data-end)
 827       ;;
 828       ;; and finally, decrement the start-pointers of all following
 829       ;; entries in the archive.  This is a pig when deleting a bunch
 830       ;; of files at once - we could optimize this to only do the
 831       ;; iteration over the files that remain, or only iterate up to
 832       ;; the next file to be deleted.
 833       (let ((data-length (- data-end data-start)))
 834         (tar-dolist (desc following-descs)
 835           (tar-setf (tar-desc-data-start desc)
 836                     (- (tar-desc-data-start desc) data-length))))
 837       ))
 838   (narrow-to-region 1 tar-header-offset))
 839
 840
 841 (defun tar-expunge (&optional noconfirm)
 842   "*In Tar mode, delete all the archived files flagged for deletion.
 843 This does not modify the disk image; you must save the tar file itself
 844 for this to be permanent."
 845   (interactive)
 846   (if (or noconfirm
 847           (y-or-n-p "expunge files marked for deletion? "))
 848       (let ((n 0))
 849         (save-excursion
 850           (goto-char 0)
 851           (while (not (eobp))
 852             (if (looking-at "D")
 853                 (progn (tar-expunge-internal)
 854                        (setq n (1+ n)))
 855                 (forward-line 1)))
 856           ;; after doing the deletions, add any padding that may be necessary.
 857           (tar-pad-to-blocksize)
 858           (narrow-to-region 1 tar-header-offset)
 859           )
 860         (if (zerop n)
 861             (message "nothing to expunge.")
 862             (message "%s expunged.  Be sure to save this buffer." n)))))
 863
 864
 865 (defun tar-clear-modification-flags ()
 866   "Remove the stars at the beginning of each line."
 867   (save-excursion
 868     (goto-char 0)
 869     (while (< (point) tar-header-offset)
 870       (if (looking-at "*")
 871           (progn (delete-char 1) (insert " ")))
 872       (forward-line 1))))
 873
 874
 875 (defun tar-chown-entry (new-uid)
 876   "*Change the user-id associated with this entry in the tar file.
 877 If this tar file was written by GNU tar, then you will be able to edit
 878 the user id as a string; otherwise, you must edit it as a number.
 879 You can force editing as a number by calling this with a prefix arg.
 880 This does not modify the disk image; you must save the tar file itself
 881 for this to be permanent."
 882   (interactive (list
 883                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 884                    (if (or current-prefix-arg
 885                            (not (tar-header-magic tokens)))
 886                        (let (n)
 887                          (while (not (numberp (setq n (read-minibuffer
 888                                                         "New UID number: "
 889                                                         (format "%s" (tar-header-uid tokens)))))))
 890                          n)
 891                        (read-string "New UID string: " (tar-header-uname tokens))))))
 892   (cond ((stringp new-uid)
 893          (tar-setf (tar-header-uname (tar-desc-tokens (tar-current-descriptor)))
 894                    new-uid)
 895          (tar-alter-one-field tar-uname-offset (concat new-uid "\000")))
 896         (t
 897          (tar-setf (tar-header-uid (tar-desc-tokens (tar-current-descriptor)))
 898                    new-uid)
 899          (tar-alter-one-field tar-uid-offset
 900            (concat (substring (format "%6o" new-uid) 0 6) "\000 ")))))
 901
 902
 903 (defun tar-chgrp-entry (new-gid)
 904   "*Change the group-id associated with this entry in the tar file.
 905 If this tar file was written by GNU tar, then you will be able to edit
 906 the group id as a string; otherwise, you must edit it as a number.
 907 You can force editing as a number by calling this with a prefix arg.
 908 This does not modify the disk image; you must save the tar file itself
 909 for this to be permanent."
 910   (interactive (list
 911                  (let ((tokens (tar-desc-tokens (tar-current-descriptor))))
 912                    (if (or current-prefix-arg
 913                            (not (tar-header-magic tokens)))
 914                        (let (n)
 915                          (while (not (numberp (setq n (read-minibuffer
 916                                                         "New GID number: "
 917                                                         (format "%s" (tar-header-gid tokens)))))))
 918                          n)
 919                        (read-string "New GID string: " (tar-header-gname tokens))))))
 920   (cond ((stringp new-gid)
 921          (tar-setf (tar-header-gname (tar-desc-tokens (tar-current-descriptor)))
 922                    new-gid)
 923          (tar-alter-one-field tar-gname-offset
 924            (concat new-gid "\000")))
 925         (t
 926          (tar-setf (tar-header-gid (tar-desc-tokens (tar-current-descriptor)))
 927                    new-gid)
 928          (tar-alter-one-field tar-gid-offset
 929            (concat (substring (format "%6o" new-gid) 0 6) "\000 ")))))
 930
 931 (defun tar-rename-entry (new-name)
 932   "*Change the name associated with this entry in the tar file.
 933 This does not modify the disk image; you must save the tar file itself
 934 for this to be permanent."
 935   (interactive
 936     (list (read-string "New name: "
 937             (tar-header-name (tar-desc-tokens (tar-current-descriptor))))))
 938   (if (string= "" new-name) (error "zero length name"))
 939   (if (> (length new-name) 98) (error "name too long"))
 940   (tar-setf (tar-header-name (tar-desc-tokens (tar-current-descriptor)))
 941             new-name)
 942   (tar-alter-one-field 0
 943     (substring (concat new-name (make-string 99 0)) 0 99)))
 944
 945
 946 (defun tar-chmod-entry (new-mode)
 947   "*Change the protection bits associated with this entry in the tar file.
 948 This does not modify the disk image; you must save the tar file itself
 949 for this to be permanent."
 950   (interactive (list (tar-parse-octal-integer-safe
 951                        (read-string "New protection (octal): "))))
 952   (tar-setf (tar-header-mode (tar-desc-tokens (tar-current-descriptor)))
 953             new-mode)
 954   (tar-alter-one-field tar-mode-offset
 955     (concat (substring (format "%6o" new-mode) 0 6) "\000 ")))
 956
 957
 958 (defun tar-alter-one-field (data-position new-data-string)
 959   (let* ((descriptor (tar-current-descriptor))
 960          (tokens (tar-desc-tokens descriptor)))
 961     (unwind-protect
 962         (save-excursion
 963           ;;
 964           ;; update the header-line.
 965           (beginning-of-line)
 966           (let ((p (point)))
 967             (forward-line 1)
 968             (delete-region p (point))
 969             (insert (summarize-tar-header-block tokens) "\n")
 970             (setq tar-header-offset (point-max)))
 971
 972           (widen)
 973           (let* ((start (+ (tar-desc-data-start descriptor) tar-header-offset -513)))
 974             ;;
 975             ;; delete the old field and insert a new one.
 976             (goto-char (+ start data-position))
 977             (delete-region (point) (+ (point) (length new-data-string))) ; <--
 978             (insert new-data-string) ; <--
 979             ;;
 980             ;; compute a new checksum and insert it.
 981             (let ((chk (checksum-tar-header-block
 982                         (buffer-substring start (+ start 512)))))
 983               (goto-char (+ start tar-chk-offset))
 984               (delete-region (point) (+ (point) 8))
 985               (insert (format "%6o" chk))
 986               (insert 0)
 987               (insert ? )
 988               (tar-setf (tar-header-checksum tokens) chk)
 989               ;;
 990               ;; ok, make sure we didn't botch it.
 991               (check-tar-header-block-checksum
 992                 (buffer-substring start (+ start 512))
 993                 chk (tar-header-name tokens))
 994               )))
 995       (narrow-to-region 1 tar-header-offset))))
 996
 997
 998 (defun tar-octal-time (timeval)
 999   ;; Format a timestamp as 11 octal digits.  Ghod, I hope this works...
1000   (let ((hibits (car timeval)) (lobits (car (cdr timeval))))
1001     (insert (format "%05o%01o%05o"
1002                     (lsh hibits -2)
1003                     (logior (lsh (logand 3 hibits) 1) (> (logand lobits 32768) 0))
1004                     (logand 32767 lobits)
1005                     ))))
1006
1007 (defun tar-subfile-save-buffer ()
1008   "In tar subfile mode, save this buffer into its parent tar-file buffer.
1009 This doesn't write anything to disk; you must save the parent tar-file buffer
1010 to make your changes permanent."
1011   (interactive)
1012   (if (not (and (boundp 'tar-superior-buffer) tar-superior-buffer))
1013     (error "This buffer has no superior tar file buffer"))
1014   (if (not (and (boundp 'tar-superior-descriptor) tar-superior-descriptor))
1015     (error "This buffer doesn't have an index into its superior tar file!"))
1016   (save-excursion
1017   (let ((subfile (current-buffer))
1018         (subfile-size (buffer-size))
1019         (descriptor tar-superior-descriptor))
1020     (set-buffer tar-superior-buffer)
1021     (let* ((tokens (tar-desc-tokens descriptor))
1022            (start (tar-desc-data-start descriptor))
1023            (name (tar-header-name tokens))
1024            (size (tar-header-size tokens))
1025            (size-pad (ash (ash (+ size 511) -9) 9))
1026            (head (memq descriptor tar-parse-info))
1027            (following-descs (cdr head)))
1028       (if (not head)
1029         (error "Can't find this tar file entry in its parent tar file!"))
1030       (unwind-protect
1031        (save-excursion
1032         (widen)
1033         ;; delete the old data...
1034         (let* ((data-start (+ start tar-header-offset -1))
1035                (data-end (+ data-start (ash (ash (+ size 511) -9) 9))))
1036           (delete-region data-start data-end)
1037           ;; insert the new data...
1038           (goto-char data-start)
1039           (insert-buffer subfile)
1040           ;;
1041           ;; pad the new data out to a multiple of 512...
1042           (let ((subfile-size-pad (ash (ash (+ subfile-size 511) -9) 9)))
1043             (goto-char (+ data-start subfile-size))
1044             (insert (make-string (- subfile-size-pad subfile-size) 0))
1045             ;;
1046             ;; update the data pointer of this and all following files...
1047             (tar-setf (tar-header-size tokens) subfile-size)
1048             (let ((difference (- subfile-size-pad size-pad)))
1049               (tar-dolist (desc following-descs)
1050                 (tar-setf (tar-desc-data-start desc)
1051                           (+ (tar-desc-data-start desc) difference))))
1052             ;;
1053             ;; Update the size field in the header block.
1054             (let ((header-start (- data-start 512)))
1055               (goto-char (+ header-start tar-size-offset))
1056               (delete-region (point) (+ (point) 12))
1057               (insert (format "%11o" subfile-size))
1058               (insert ? )
1059               ;;
1060               ;; Maybe update the datestamp.
1061               (if (not tar-update-datestamp)
1062                   nil
1063                 (goto-char (+ header-start tar-time-offset))
1064                 (delete-region (point) (+ (point) 12))
1065                 (insert (tar-octal-time (current-time)))
1066                 (insert ? ))
1067               ;;
1068               ;; compute a new checksum and insert it.
1069               (let ((chk (checksum-tar-header-block
1070                           (buffer-substring header-start data-start))))
1071                 (goto-char (+ header-start tar-chk-offset))
1072                 (delete-region (point) (+ (point) 8))
1073                 (insert (format "%6o" chk))
1074                 (insert 0)
1075                 (insert ? )
1076                 (tar-setf (tar-header-checksum tokens) chk)))
1077             ;;
1078             ;; alter the descriptor-line...
1079             ;;
1080             (let ((position (- (length tar-parse-info) (length head))))
1081               (goto-char 1)
1082               (next-line position)
1083               (beginning-of-line)
1084               (let ((p (point))
1085                     (m (set-marker (make-marker) tar-header-offset)))
1086                 (forward-line 1)
1087                 (delete-region p (point))
1088                 (insert-before-markers (summarize-tar-header-block tokens t) "\n")
1089                 (setq tar-header-offset (marker-position m)))
1090               )))
1091         ;; after doing the insertion, add any final padding that may be necessary.
1092         (tar-pad-to-blocksize))
1093        (narrow-to-region 1 tar-header-offset)))
1094     (set-buffer-modified-p t)   ; mark the tar file as modified
1095     (set-buffer subfile)
1096     (set-buffer-modified-p nil) ; mark the tar subfile as unmodified
1097     (message "saved into tar-buffer \"%s\" - remember to save that buffer!"
1098              (buffer-name tar-superior-buffer))
1099     ;; Prevent ordinary saving from happening.
1100     t)))
1101
1102
1103 (defun tar-pad-to-blocksize ()
1104   "If we are being anal about tar file blocksizes, fix up the current buffer.
1105 Leaves the region wide."
1106   (if (null tar-anal-blocksize)
1107       nil
1108     (widen)
1109     (let* ((last-desc (nth (1- (length tar-parse-info)) tar-parse-info))
1110            (start (tar-desc-data-start last-desc))
1111            (tokens (tar-desc-tokens last-desc))
1112            (link-p (tar-header-link-type tokens))
1113            (size (if link-p 0 (tar-header-size tokens)))
1114            (data-end (+ start size))
1115            (bbytes (ash tar-anal-blocksize 9))
1116            (pad-to (+ bbytes (* bbytes (/ (1- data-end) bbytes))))
1117            (inhibit-read-only t) ; ##
1118            )
1119       ;; If the padding after the last data is too long, delete some;
1120       ;; else insert some until we are padded out to the right number of blocks.
1121       ;;
1122       (goto-char (+ (or tar-header-offset 0) data-end))
1123       (if (> (1+ (buffer-size)) (+ (or tar-header-offset 0) pad-to))
1124           (delete-region (+ (or tar-header-offset 0) pad-to) (1+ (buffer-size)))
1125           (insert (make-string (- (+ (or tar-header-offset 0) pad-to)
1126                                   (1+ (buffer-size)))
1127                                0)))
1128       )))
1129
1130
1131 ;; Used in write-file-hook to write tar-files out correctly.
1132 (defun tar-mode-maybe-write-tar-file ()
1133   ;;
1134   ;; If the current buffer is in Tar mode and has its header-offset set,
1135   ;; only write out the part of the file after the header-offset.
1136   ;;
1137   (if (and (eq major-mode 'tar-mode)
1138            (and (boundp 'tar-header-offset) tar-header-offset))
1139       (unwind-protect
1140         (save-excursion
1141           (tar-clear-modification-flags)
1142           (widen)
1143           ;; Doing this here confuses things - the region gets left too wide!
1144           ;; I suppose this is run in a context where changing the buffer is bad.
1145           ;; (tar-pad-to-blocksize)
1146           (write-region tar-header-offset (1+ (buffer-size)) buffer-file-name nil t)
1147           ;; return T because we've written the file.
1148           t)
1149         (narrow-to-region 1 tar-header-offset)
1150         t)
1151       ;; return NIL because we haven't.
1152       nil))
1153
1154 \f
1155 ;;; Patch it in.
1156
1157 (or (memq 'tar-mode-maybe-write-tar-file write-file-hooks)
1158     (setq write-file-hooks
1159           (cons 'tar-mode-maybe-write-tar-file write-file-hooks)))
1160
1161 (provide 'tar-mode)
1162
1163 ;;; tar-mode.el ends here