jka-compr.el 23.8 KB
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;;; jka-compr.el - reading/writing/loading compressed files.
;;; Copyright (C) 1993, 1994  Free Software Foundation, Inc.

;; Author: jka@ece.cmu.edu (Jay K. Adams)
;; Keywords: data

;;; Commentary: 

;;; This package implements low-level support for reading, writing,
;;; and loading compressed files.  It hooks into the low-level file
;;; I/O functions (including write-region and insert-file-contents) so
;;; that they automatically compress or uncompress a file if the file
;;; appears to need it (based on the extension of the file name).
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;;; Packages like Rmail, VM, GNUS, and Info should be able to work
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;;; with compressed files without modification.


;;; INSTRUCTIONS:
;;;
;;; To use jka-compr, simply load this package, and edit as usual.
;;; Its operation should be transparent to the user (except for
;;; messages appearing when a file is being compressed or
;;; uncompressed).
;;;
;;; The variable, jka-compr-compression-info-list can be used to
;;; customize jka-compr to work with other compression programs.
;;; The default value of this variable allows jka-compr to work with
;;; Unix compress and gzip.
;;;
;;; If you are concerned about the stderr output of gzip and other
;;; compression/decompression programs showing up in your buffers, you
;;; should set the discard-error flag in the compression-info-list.
;;; This will cause the stderr of all programs to be discarded.
;;; However, it also causes emacs to call compression/uncompression
;;; programs through a shell (which is specified by jka-compr-shell).
;;; This may be a drag if, on your system, starting up a shell is
;;; slow.
;;;
;;; If you don't want messages about compressing and decompressing
;;; to show up in the echo area, you can set the compress-name and
;;; decompress-name fields of the jka-compr-compression-info-list to
;;; nil.


;;; APPLICATION NOTES:
;;;
;;; crypt++
;;;   jka-compr can coexist with crpyt++ if you take all the decompression
;;;   entries out of the crypt-encoding-list.  Clearly problems will arise if
;;;   you have two programs trying to compress/decompress files.  jka-compr
;;;   will not "work with" crypt++ in the following sense: you won't be able to
;;;   decode encrypted compressed files--that is, files that have been
;;;   compressed then encrypted (in that order).  Theoretically, crypt++ and
;;;   jka-compr could properly handle a file that has been encrypted then
;;;   compressed, but there is little point in trying to compress an encrypted
;;;   file.
;;;


;;; ACKNOWLEDGMENTS
;;; 
;;; jka-compr is a V19 adaptation of jka-compr for V18 of Emacs.  Many people
;;; have made helpful suggestions, reported bugs, and even fixed bugs in 
;;; jka-compr.  I recall the following people as being particularly helpful.
;;;
;;;   Jean-loup Gailly
;;;   David Hughes
;;;   Richard Pieri
;;;   Daniel Quinlan
;;;   Chris P. Ross
;;;   Rick Sladkey
;;;
;;; Andy Norman's ange-ftp was the inspiration for the original jka-compr for
;;; Version 18 of Emacs.
;;;
;;; After I had made progress on the original jka-compr for V18, I learned of a
;;; package written by Kazushi Jam Marukawa, called jam-zcat, that did exactly
;;; what I was trying to do.  I looked over the jam-zcat source code and
;;; probably got some ideas from it.
;;;

;;; Code:

(defvar jka-compr-shell "sh"
  "*Shell to be used for calling compression programs.
The value of this variable only matters if you want to discard the
stderr of a compression/decompression program (see the documentation
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for `jka-compr-compression-info-list').")
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(defvar jka-compr-use-shell t)


;;; I have this defined so that .Z files are assumed to be in unix
;;; compress format; and .gz files, in gzip format.
(defvar jka-compr-compression-info-list
  ;;[regexp
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  ;; compr-message  compr-prog  compr-args
  ;; uncomp-message uncomp-prog uncomp-args
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  ;; can-append auto-mode-flag]
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  '(["\\.Z\\(~\\|\\.~[0-9]+~\\)?\\'"
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     "compressing"    "compress"     ("-c")
     "uncompressing"  "uncompress"   ("-c")
     nil t]
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    ["\\.tgz\\'"
     "zipping"        "gzip"         ("-c" "-q")
     "unzipping"      "gzip"         ("-c" "-q" "-d")
     t nil]
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    ["\\.gz\\(~\\|\\.~[0-9]+~\\)?\\'"
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     "zipping"        "gzip"         ("-c" "-q")
     "unzipping"      "gzip"         ("-c" "-q" "-d")
     t t])

  "List of vectors that describe available compression techniques.
Each element, which describes a compression technique, is a vector of
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the form [REGEXP COMPRESS-MSG COMPRESS-PROGRAM COMPRESS-ARGS
UNCOMPRESS-MSG UNCOMPRESS-PROGRAM UNCOMPRESS-ARGS
APPEND-FLAG EXTENSION], where:
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   regexp                is a regexp that matches filenames that are
                         compressed with this format

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   compress-msg          is the message to issue to the user when doing this
                         type of compression (nil means no message)

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   compress-program      is a program that performs this compression

   compress-args         is a list of args to pass to the compress program

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   uncompress-msg        is the message to issue to the user when doing this
                         type of uncompression (nil means no message)
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   uncompress-program    is a program that performs this compression

   uncompress-args       is a list of args to pass to the uncompress program

   append-flag           is non-nil if this compression technique can be
                         appended

   auto-mode flag        non-nil means strip the regexp from file names
                         before attempting to set the mode.

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Because of the way `call-process' is defined, discarding the stderr output of
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a program adds the overhead of starting a shell each time the program is
invoked.")

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(defvar jka-compr-mode-alist-additions
  (list (cons "\\.tgz\\'" 'tar-mode))
  "A list of pairs to add to auto-mode-alist when jka-compr is installed.")
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(defvar jka-compr-file-name-handler-entry
  nil
  "The entry in `file-name-handler-alist' used by the jka-compr I/O functions.")

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;;; Functions for accessing the return value of jka-get-compression-info
(defun jka-compr-info-regexp               (info)  (aref info 0))
(defun jka-compr-info-compress-message     (info)  (aref info 1))
(defun jka-compr-info-compress-program     (info)  (aref info 2))
(defun jka-compr-info-compress-args        (info)  (aref info 3))
(defun jka-compr-info-uncompress-message   (info)  (aref info 4))
(defun jka-compr-info-uncompress-program   (info)  (aref info 5))
(defun jka-compr-info-uncompress-args      (info)  (aref info 6))
(defun jka-compr-info-can-append           (info)  (aref info 7))
(defun jka-compr-info-strip-extension      (info)  (aref info 8))


(defun jka-compr-get-compression-info (filename)
  "Return information about the compression scheme of FILENAME.
The determination as to which compression scheme, if any, to use is
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based on the filename itself and `jka-compr-compression-info-list'."
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  (catch 'compression-info
    (let ((case-fold-search nil))
      (mapcar
       (function (lambda (x)
		   (and (string-match (jka-compr-info-regexp x) filename)
			(throw 'compression-info x))))
       jka-compr-compression-info-list)
      nil)))


(put 'compression-error 'error-conditions '(compression-error file-error error))


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(defvar jka-compr-acceptable-retval-list '(0 2 141))
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(defun jka-compr-error (prog args infile message &optional errfile)

  (let ((errbuf (get-buffer-create " *jka-compr-error*"))
	(curbuf (current-buffer)))
    (set-buffer errbuf)
    (widen) (erase-buffer)
    (insert (format "Error while executing \"%s %s < %s\"\n\n"
		     prog
		     (mapconcat 'identity args " ")
		     infile))

     (and errfile
	  (insert-file-contents errfile))

     (set-buffer curbuf)
     (display-buffer errbuf))

  (signal 'compression-error (list "Opening input file" (format "error %s" message) infile)))
			
   
(defvar jka-compr-dd-program
  "/bin/dd")


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(defvar jka-compr-dd-blocksize 256)
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(defun jka-compr-partial-uncompress (prog message args infile beg len)
  "Call program PROG with ARGS args taking input from INFILE.
Fourth and fifth args, BEG and LEN, specify which part of the output
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to keep: LEN chars starting BEG chars from the beginning."
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  (let* ((skip (/ beg jka-compr-dd-blocksize))
	 (prefix (- beg (* skip jka-compr-dd-blocksize)))
	 (count (and len (1+ (/ (+ len prefix) jka-compr-dd-blocksize))))
	 (start (point))
	 (err-file (jka-compr-make-temp-name))
	 (run-string (format "%s %s 2> %s | %s bs=%d skip=%d %s 2> /dev/null"
			     prog
			     (mapconcat 'identity args " ")
			     err-file
			     jka-compr-dd-program
			     jka-compr-dd-blocksize
			     skip
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			     ;; dd seems to be unreliable about
			     ;; providing the last block.  So, always
			     ;; read one more than you think you need.
			     (if count (concat "count=" (1+ count)) ""))))
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    (unwind-protect
	(or (memq (call-process jka-compr-shell
				infile t nil "-c"
				run-string)
		  jka-compr-acceptable-retval-list)
	    
	    (jka-compr-error prog args infile message err-file))

      (jka-compr-delete-temp-file err-file))

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    ;; Delete the stuff after what we want, if there is any.
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    (and
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     len
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     (< (+ start prefix len) (point))
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     (delete-region (+ start prefix len) (point)))
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    ;; Delete the stuff before what we want.
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    (delete-region start (+ start prefix))))


(defun jka-compr-call-process (prog message infile output temp args)
  (if jka-compr-use-shell

      (let ((err-file (jka-compr-make-temp-name)))
	    
	(unwind-protect

	    (or (memq
		 (call-process jka-compr-shell infile
			       (if (stringp output) nil output)
			       nil
			       "-c"
			       (format "%s %s 2> %s %s"
				       prog
				       (mapconcat 'identity args " ")
				       err-file
				       (if (stringp output)
					   (concat "> " output)
					 "")))
		 jka-compr-acceptable-retval-list)

		(jka-compr-error prog args infile message err-file))

	  (jka-compr-delete-temp-file err-file)))

    (or (zerop
	 (apply 'call-process
		prog
		infile
		(if (stringp output) temp output)
		nil
		args))
	(jka-compr-error prog args infile message))

    (and (stringp output)
	 (let ((cbuf (current-buffer)))
	   (set-buffer temp)
	   (write-region (point-min) (point-max) output)
	   (erase-buffer)
	   (set-buffer cbuf)))))


;;; Support for temp files.  Much of this was inspired if not lifted
;;; from ange-ftp.

(defvar jka-compr-temp-name-template
  "/tmp/jka-com"
  "Prefix added to all temp files created by jka-compr.
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There should be no more than seven characters after the final `/'")
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(defvar jka-compr-temp-name-table (make-vector 31 nil))

(defun jka-compr-make-temp-name (&optional local-copy)
  "This routine will return the name of a new file."
  (let* ((lastchar ?a)
	 (prevchar ?a)
	 (template (concat jka-compr-temp-name-template "aa"))
	 (lastpos (1- (length template)))
	 (not-done t)
	 file
	 entry)

    (while not-done
      (aset template lastpos lastchar)
      (setq file (concat (make-temp-name template) "#"))
      (setq entry (intern file jka-compr-temp-name-table))
      (if (or (get entry 'active)
	      (file-exists-p file))

	  (progn
	    (setq lastchar (1+ lastchar))
	    (if (> lastchar ?z)
		(progn
		  (setq prevchar (1+ prevchar))
		  (setq lastchar ?a)
		  (if (> prevchar ?z)
		      (error "Can't allocate temp file.")
		    (aset template (1- lastpos) prevchar)))))

	(put entry 'active (not local-copy))
	(setq not-done nil)))

    file))


(defun jka-compr-delete-temp-file (temp)

  (put (intern temp jka-compr-temp-name-table)
       'active nil)

  (condition-case ()
      (delete-file temp)
    (error nil)))


(defun jka-compr-write-region (start end file &optional append visit)
  (let* ((filename (expand-file-name file))
	 (visit-file (if (stringp visit) (expand-file-name visit) filename))
	 (info (jka-compr-get-compression-info visit-file)))
      
      (if info

	  (let ((can-append (jka-compr-info-can-append info))
		(compress-program (jka-compr-info-compress-program info))
		(compress-message (jka-compr-info-compress-message info))
		(uncompress-program (jka-compr-info-uncompress-program info))
		(uncompress-message (jka-compr-info-uncompress-message info))
		(compress-args (jka-compr-info-compress-args info))
		(uncompress-args (jka-compr-info-uncompress-args info))
		(base-name (file-name-nondirectory visit-file))
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		temp-file cbuf temp-buffer)
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	    (setq cbuf (current-buffer)
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		  temp-buffer (get-buffer-create " *jka-compr-wr-temp*"))
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	    (set-buffer temp-buffer)
	    (widen) (erase-buffer)
	    (set-buffer cbuf)

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	    (if (and append
		     (not can-append)
		     (file-exists-p filename))
		
		(let* ((local-copy (file-local-copy filename))
		       (local-file (or local-copy filename)))
		  
		  (setq temp-file local-file))

	      (setq temp-file (jka-compr-make-temp-name)))
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	    (and 
	     compress-message
	     (message "%s %s..." compress-message base-name))
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	    (jka-compr-run-real-handler 'write-region
					(list start end temp-file t 'dont))
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	    (jka-compr-call-process compress-program
				    (concat compress-message
					    " " base-name)
				    temp-file
				    temp-buffer
				    nil
				    compress-args)

	    (set-buffer temp-buffer)
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	    (jka-compr-run-real-handler 'write-region
					(list (point-min) (point-max)
					      filename
					      (and append can-append) 'dont))
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	    (erase-buffer)
	    (set-buffer cbuf)

	    (jka-compr-delete-temp-file temp-file)

	    (and
	     compress-message
	     (message "%s %s...done" compress-message base-name))

	    (cond
	     ((eq visit t)
	      (setq buffer-file-name filename)
	      (set-visited-file-modtime))
	     ((stringp visit)
	      (setq buffer-file-name visit)
	      (let ((buffer-file-name filename))
		(set-visited-file-modtime))))

	    (and (or (eq visit t)
		     (eq visit nil)
		     (stringp visit))
		 (message "Wrote %s" visit-file))

	    nil)
	      
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	(jka-compr-run-real-handler 'write-region
				    (list start end filename append visit)))))
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(defun jka-compr-insert-file-contents (file &optional visit beg end replace)
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  (barf-if-buffer-read-only)

  (and (or beg end)
       visit
       (error "Attempt to visit less than an entire file"))

  (let* ((filename (expand-file-name file))
	 (info (jka-compr-get-compression-info filename)))

    (if info

	(let ((uncompress-message (jka-compr-info-uncompress-message info))
	      (uncompress-program (jka-compr-info-uncompress-program info))
	      (uncompress-args (jka-compr-info-uncompress-args info))
	      (base-name (file-name-nondirectory filename))
	      (notfound nil)
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	      (local-copy
	       (jka-compr-run-real-handler 'file-local-copy (list filename)))
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	      local-file
	      size start)

	  (setq local-file (or local-copy filename))

	  (and
	   visit
	   (setq buffer-file-name filename))

	  (unwind-protect		; to make sure local-copy gets deleted

	      (progn
		  
		(and
		 uncompress-message
		 (message "%s %s..." uncompress-message base-name))

		(condition-case error-code

		    (progn
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		      (if replace
			  (goto-char (point-min)))
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		      (setq start (point))
		      (if (or beg end)
			  (jka-compr-partial-uncompress uncompress-program
							(concat uncompress-message
								" " base-name)
							uncompress-args
							local-file
							(or beg 0)
							(if (and beg end)
							    (- end beg)
							  end))
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			;; If visiting, bind off buffer-file-name so that
			;; file-locking will not ask whether we should
			;; really edit the buffer.
			(let ((buffer-file-name
			       (if visit nil buffer-file-name)))
			  (jka-compr-call-process uncompress-program
						  (concat uncompress-message
							  " " base-name)
						  local-file
						  t
						  nil
						  uncompress-args)))
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		      (setq size (- (point) start))
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		      (if replace
			  (let* ((del-beg (point))
				 (del-end (+ del-beg size)))
			    (delete-region del-beg
					   (min del-end (point-max)))))
		      (goto-char start))
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		  (error
		   (if (and (eq (car error-code) 'file-error)
			    (eq (nth 3 error-code) local-file))
		       (if visit
			   (setq notfound error-code)
			 (signal 'file-error 
				 (cons "Opening input file"
				       (nthcdr 2 error-code))))
		     (signal (car error-code) (cdr error-code))))))

	    (and
	     local-copy
	     (file-exists-p local-copy)
	     (delete-file local-copy)))

	  (and
	   visit
	   (progn
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	     (unlock-buffer)
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	     (setq buffer-file-name filename)
	     (set-visited-file-modtime)))
	    
	  (and
	   uncompress-message
	   (message "%s %s...done" uncompress-message base-name))

	  (and
	   visit
	   notfound
	   (signal 'file-error
		   (cons "Opening input file" (nth 2 notfound))))

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	  ;; Run the functions that insert-file-contents would.
	  (let ((p after-insert-file-functions)
		(insval size))
	    (while p
	      (setq insval (funcall (car p) size))
	      (if insval
		  (progn
		    (or (integerp insval)
			(signal 'wrong-type-argument
				(list 'integerp insval)))
		    (setq size insval)))
	      (setq p (cdr p))))

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	  (list filename size))

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      (jka-compr-run-real-handler 'insert-file-contents
				  (list file visit beg end replace)))))
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(defun jka-compr-file-local-copy (file)
  (let* ((filename (expand-file-name file))
	 (info (jka-compr-get-compression-info filename)))

    (if info

	(let ((uncompress-message (jka-compr-info-uncompress-message info))
	      (uncompress-program (jka-compr-info-uncompress-program info))
	      (uncompress-args (jka-compr-info-uncompress-args info))
	      (base-name (file-name-nondirectory filename))
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	      (local-copy
	       (jka-compr-run-real-handler 'file-local-copy (list filename)))
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	      (temp-file (jka-compr-make-temp-name t))
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	      (temp-buffer (get-buffer-create " *jka-compr-flc-temp*"))
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	      (notfound nil)
	      (cbuf (current-buffer))
	      local-file)

	  (setq local-file (or local-copy filename))

	  (unwind-protect

	      (progn
		  
		(and
		 uncompress-message
		 (message "%s %s..." uncompress-message base-name))

		(set-buffer temp-buffer)
		  
		(jka-compr-call-process uncompress-program
					(concat uncompress-message
						" " base-name)
					local-file
					t
					nil
					uncompress-args)

		(and
		 uncompress-message
		 (message "%s %s...done" uncompress-message base-name))

		(write-region
		 (point-min) (point-max) temp-file nil 'dont))

	    (and
	     local-copy
	     (file-exists-p local-copy)
	     (delete-file local-copy))

	    (set-buffer cbuf)
	    (kill-buffer temp-buffer))

	  temp-file)
	    
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      (jka-compr-run-real-handler 'file-local-copy (list filename)))))
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;;; Support for loading compressed files.
(defun jka-compr-load (file &optional noerror nomessage nosuffix)
  "Documented as original."

  (let* ((local-copy (jka-compr-file-local-copy file))
	 (load-file (or local-copy file)))

    (unwind-protect

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	(let (inhibit-file-name-operation
	      inhibit-file-name-handlers)
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	  (or nomessage
	      (message "Loading %s..." file))

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	  (let ((load-force-doc-strings t))
	    (load load-file noerror t t))
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	  (or nomessage
	      (message "Loading %s...done." file)))

      (jka-compr-delete-temp-file local-copy))

    t))
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(defun jka-compr-byte-compiler-base-file-name (file)
  (let ((info (jka-compr-get-compression-info file)))
    (if (and info (jka-compr-info-strip-extension info))
	(save-match-data
	  (substring file 0 (string-match (jka-compr-info-regexp info) file)))
      file)))
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(put 'write-region 'jka-compr 'jka-compr-write-region)
(put 'insert-file-contents 'jka-compr 'jka-compr-insert-file-contents)
(put 'file-local-copy 'jka-compr 'jka-compr-file-local-copy)
(put 'load 'jka-compr 'jka-compr-load)
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(put 'byte-compiler-base-file-name 'jka-compr
     'jka-compr-byte-compiler-base-file-name)
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(defun jka-compr-handler (operation &rest args)
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  (save-match-data
    (let ((jka-op (get operation 'jka-compr)))
      (if jka-op
	  (apply jka-op args)
	(jka-compr-run-real-handler operation args)))))
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;; If we are given an operation that we don't handle,
;; call the Emacs primitive for that operation,
;; and manipulate the inhibit variables
;; to prevent the primitive from calling our handler again.
(defun jka-compr-run-real-handler (operation args)
  (let ((inhibit-file-name-handlers
	 (cons 'jka-compr-handler
	       (and (eq inhibit-file-name-operation operation)
		    inhibit-file-name-handlers)))
	(inhibit-file-name-operation operation))
    (apply operation args)))

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(defun toggle-auto-compression (arg)
  "Toggle automatic file compression and decompression.
With prefix argument ARG, turn auto compression on if positive, else off.
Returns the new status of auto compression (non-nil means on)."
  (interactive "P")
  (let* ((installed (jka-compr-installed-p))
	 (flag (if (null arg)
		   (not installed)
		 (or (eq arg t) (listp arg) (and (integerp arg) (> arg 0))))))

    (cond
     ((and flag installed) t)		; already installed

     ((and (not flag) (not installed)) nil) ; already not installed

     (flag
      (jka-compr-install))

     (t
      (jka-compr-uninstall)))


    (and (interactive-p)
	 (if flag
	     (message "Automatic file (de)compression is now ON.")
	   (message "Automatic file (de)compression is now OFF.")))

    flag))


(defun jka-compr-build-file-regexp ()
  (concat
   "\\("
   (mapconcat
    'jka-compr-info-regexp
    jka-compr-compression-info-list
    "\\)\\|\\(")
   "\\)"))


(defun jka-compr-install ()
  "Install jka-compr.
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This adds entries to `file-name-handler-alist' and `auto-mode-alist'
and `inhibit-first-line-modes-suffixes'."
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  (setq jka-compr-file-name-handler-entry
	(cons (jka-compr-build-file-regexp) 'jka-compr-handler))

  (setq file-name-handler-alist (cons jka-compr-file-name-handler-entry
				      file-name-handler-alist))

  (mapcar
   (function (lambda (x)
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	       (and (jka-compr-info-strip-extension x)
		    ;; Make entries in auto-mode-alist so that modes
		    ;; are chosen right according to the file names
		    ;; sans `.gz'.
		    (setq auto-mode-alist
			  (cons (list (jka-compr-info-regexp x)
				      nil 'jka-compr)
				auto-mode-alist))
		    ;; Also add these regexps to
		    ;; inhibit-first-line-modes-suffixes, so that a
		    ;; -*- line in the first file of a compressed tar
		    ;; file doesn't override tar-mode.
		    (setq inhibit-first-line-modes-suffixes
			  (cons (jka-compr-info-regexp x)
				inhibit-first-line-modes-suffixes)))))
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   jka-compr-compression-info-list)
  (setq auto-mode-alist
	(append auto-mode-alist jka-compr-mode-alist-additions)))
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(defun jka-compr-uninstall ()
  "Uninstall jka-compr.
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This removes the entries in `file-name-handler-alist' and `auto-mode-alist'
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and `inhibit-first-line-modes-suffixes' that were added
by `jka-compr-installed'."
  ;; Delete from inhibit-first-line-modes-suffixes
  ;; what jka-compr-install added.
  (mapcar
     (function (lambda (x)
		 (and (jka-compr-info-strip-extension x)
		      (setq inhibit-first-line-modes-suffixes
			    (delete (jka-compr-info-regexp x)
				    inhibit-first-line-modes-suffixes)))))
     jka-compr-compression-info-list)
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  (let* ((fnha (cons nil file-name-handler-alist))
	 (last fnha))

    (while (cdr last)
      (if (eq (cdr (car (cdr last))) 'jka-compr-handler)
	  (setcdr last (cdr (cdr last)))
	(setq last (cdr last))))

    (setq file-name-handler-alist (cdr fnha)))

  (let* ((ama (cons nil auto-mode-alist))
	 (last ama)
	 entry)

    (while (cdr last)
      (setq entry (car (cdr last)))
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      (if (or (member entry jka-compr-mode-alist-additions)
	      (and (consp (cdr entry))
		   (eq (nth 2 entry) 'jka-compr)))
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	  (setcdr last (cdr (cdr last)))
	(setq last (cdr last))))
    
    (setq auto-mode-alist (cdr ama))))

      
(defun jka-compr-installed-p ()
  "Return non-nil if jka-compr is installed.
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The return value is the entry in `file-name-handler-alist' for jka-compr."
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  (let ((fnha file-name-handler-alist)
	(installed nil))

    (while (and fnha (not installed))
     (and (eq (cdr (car fnha)) 'jka-compr-handler)
	   (setq installed (car fnha)))
      (setq fnha (cdr fnha)))

    installed))


;;; Add the file I/O hook if it does not already exist.
;;; Make sure that jka-compr-file-name-handler-entry is eq to the
;;; entry for jka-compr in file-name-handler-alist.
(and (jka-compr-installed-p)
     (jka-compr-uninstall))

(jka-compr-install)


(provide 'jka-compr)

;; jka-compr.el ends here.