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;;; jka-compr.el --- reading/writing/loading compressed files

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;; Copyright (C) 1993, 1994, 1995, 1997, 1999, 2000, 2003, 2004  Free Software Foundation, Inc.
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;; Author: jka@ece.cmu.edu (Jay K. Adams)
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;; Maintainer: FSF
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;; Keywords: data

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;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; 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).
;; Packages like Rmail, VM, GNUS, and Info should be able to work
;; with compressed files without modification.


;; INSTRUCTIONS:
;;
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;; To use jka-compr, invoke the command `auto-compression-mode' (which
;; see), or customize the variable of the same name.  Its operation
;; should be transparent to the user (except for messages appearing when
;; a file is being compressed or uncompressed).
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;;
;; 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++
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;;   jka-compr can coexist with crypt++ if you take all the decompression
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;;   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
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;;
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;; jka-compr is a V19 adaptation of jka-compr for V18 of Emacs.  Many people
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;; have made helpful suggestions, reported bugs, and even fixed bugs in
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;; 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.
;;
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;;; Code:

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(defcustom jka-compr-shell "sh"
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  "*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')."
  :type 'string
  :group 'jka-compr)
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(defvar jka-compr-use-shell
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  (not (memq system-type '(ms-dos windows-nt))))
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(defvar jka-compr-really-do-compress nil
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  "Non-nil in a buffer whose visited file was uncompressed on visiting it.
This means compress the data on writing the file, even if the
data appears to be compressed already.")
(make-variable-buffer-local 'jka-compr-really-do-compress)
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(put 'jka-compr-really-do-compress 'permanent-local t)
120

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;;; Functions for accessing the return value of jka-compr-get-compression-info
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(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))
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(defun jka-compr-info-file-magic-bytes     (info)  (aref info 9))
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(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)))
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    (with-current-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)))
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     (display-buffer errbuf))

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  (signal 'compression-error
	  (list "Opening input file" (format "error %s" message) infile)))
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(defcustom jka-compr-dd-program "/bin/dd"
  "How to invoke `dd'."
  :type 'string
  :group 'jka-compr)
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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 ((start (point))
	(prefix beg))
    (if (and jka-compr-use-shell jka-compr-dd-program)
	;; Put the uncompression output through dd
	;; to discard the part we don't want.
	(let ((skip (/ beg jka-compr-dd-blocksize))
	      (err-file (jka-compr-make-temp-name))
	      count)
	  ;; Update PREFIX based on the text that we won't read in.
	  (setq prefix (- beg (* skip jka-compr-dd-blocksize))
		count (and len (1+ (/ (+ len prefix) jka-compr-dd-blocksize))))
	  (unwind-protect
	      (or (memq (call-process
			 jka-compr-shell infile t nil "-c"
			 (format
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			  "%s %s 2> %s | %s bs=%d skip=%d %s 2> %s"
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			  prog
			  (mapconcat 'identity args " ")
			  err-file
			  jka-compr-dd-program
			  jka-compr-dd-blocksize
			  skip
			  ;; dd seems to be unreliable about
			  ;; providing the last block.  So, always
			  ;; read one more than you think you need.
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			  (if count (format "count=%d" (1+ count)) "")
			  null-device))
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			jka-compr-acceptable-retval-list)
		  (jka-compr-error prog args infile message err-file))
	    (jka-compr-delete-temp-file err-file)))
      ;; Run the uncompression program directly.
      ;; We get the whole file and must delete what we don't want.
      (jka-compr-call-process prog message infile t nil args))
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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

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      (let ((err-file (jka-compr-make-temp-name))
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	    (coding-system-for-read (or coding-system-for-read 'undecided))
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            (coding-system-for-write 'no-conversion))
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	(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)))

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    (or (eq 0
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	 (apply 'call-process
		prog
		infile
		(if (stringp output) temp output)
		nil
		args))
	(jka-compr-error prog args infile message))

    (and (stringp output)
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	 (with-current-buffer temp
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	   (write-region (point-min) (point-max) output)
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	   (erase-buffer)))))
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;;; Support for temp files.  Much of this was inspired if not lifted
;;; from ange-ftp.

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(defcustom jka-compr-temp-name-template
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  (expand-file-name "jka-com" temporary-file-directory)
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  "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 `/'."
  :type 'string
  :group 'jka-compr)
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(defun jka-compr-make-temp-name (&optional local-copy)
  "This routine will return the name of a new file."
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  (make-temp-file jka-compr-temp-name-template))

(defalias 'jka-compr-delete-temp-file 'delete-file)
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(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))
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	 (info (jka-compr-get-compression-info visit-file))
	 (magic (and info (jka-compr-info-file-magic-bytes info))))

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    ;; If START is nil, use the whole buffer.
    (if (null start)
	(setq start 1 end (1+ (buffer-size))))

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    ;; If we uncompressed this file when visiting it,
    ;; then recompress it when writing it
    ;; even if the contents look compressed already.
    (if (and jka-compr-really-do-compress
	     (eq start 1)
	     (eq end (1+ (buffer-size))))
	(setq magic nil))

    (if (and info
	     ;; If the contents to be written out
	     ;; are properly compressed already,
	     ;; don't try to compress them over again.
	     (not (and magic
		       (equal (if (stringp start)
				  (substring start 0 (min (length start)
							  (length magic)))
				(buffer-substring start
						  (min end
						       (+ start (length magic)))))
			      magic))))
	(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))
	      (compress-args (jka-compr-info-compress-args info))
	      (base-name (file-name-nondirectory visit-file))
	      temp-file temp-buffer
	      ;; we need to leave `last-coding-system-used' set to its
	      ;; value after calling write-region the first time, so
	      ;; that `basic-save-buffer' sees the right value.
	      (coding-system-used last-coding-system-used))

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          (or compress-program
              (error "No compression program defined"))

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	  (setq temp-buffer (get-buffer-create " *jka-compr-wr-temp*"))
	  (with-current-buffer temp-buffer
	    (widen) (erase-buffer))

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

	  (jka-compr-run-real-handler 'write-region
				      (list start end temp-file t 'dont))
	  ;; save value used by the real write-region
	  (setq coding-system-used last-coding-system-used)

	  ;; Here we must read the output of compress program as is
	  ;; without any code conversion.
	  (let ((coding-system-for-read 'no-conversion))
	    (jka-compr-call-process compress-program
				    (concat compress-message
					    " " base-name)
				    temp-file
				    temp-buffer
				    nil
				    compress-args))

	  (with-current-buffer temp-buffer
	    (let ((coding-system-for-write 'no-conversion))
	      (if (memq system-type '(ms-dos windows-nt))
		  (setq buffer-file-type t) )
	      (jka-compr-run-real-handler 'write-region
					  (list (point-min) (point-max)
						filename
						(and append can-append) 'dont))
	      (erase-buffer)) )

	  (jka-compr-delete-temp-file temp-file)
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	  (and
	   compress-message
	   (message "%s %s...done" compress-message base-name))

	  (cond
	   ((eq visit t)
	    (setq buffer-file-name filename)
	    (setq jka-compr-really-do-compress t)
	    (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))

	  ;; ensure `last-coding-system-used' has an appropriate value
	  (setq last-coding-system-used coding-system-used)

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

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

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

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

		(condition-case error-code

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		    (let ((coding-system-for-read 'no-conversion))
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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
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			  (delete-region (point) (point-max)))
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		      (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)
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			 (signal 'file-error
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				 (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)))

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	  (unless notfound
	    (decode-coding-inserted-region
	     (point) (+ (point) size)
	     (jka-compr-byte-compiler-base-file-name file)
	     visit beg end replace))
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	  (and
	   visit
	   (progn
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	     (unlock-buffer)
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	     (setq buffer-file-name filename)
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	     (setq jka-compr-really-do-compress t)
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	     (set-visited-file-modtime)))
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	  (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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	  ;; This is done in insert-file-contents after we return.
	  ;; That is a little weird, but better to go along with it now
	  ;; than to change it now.

;;;	  ;; 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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          (or (jka-compr-info-compress-program info)
              (message "You can't save this buffer because compression program is not defined"))

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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)
	      local-file)

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

	  (unwind-protect

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	      (with-current-buffer temp-buffer
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		(and
		 uncompress-message
		 (message "%s %s..." uncompress-message base-name))
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		;; Here we must read the output of uncompress program
		;; and write it to TEMP-FILE without any code
		;; conversion.  An appropriate code conversion (if
		;; necessary) is done by the later I/O operation
		;; (e.g. load).
		(let ((coding-system-for-read 'no-conversion)
		      (coding-system-for-write 'no-conversion))

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

	    (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
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	      (message "Loading %s...done." file))
	  ;; Fix up the load history to point at the right library.
	  (let ((l (assoc load-file load-history)))
	    ;; Remove .gz and .elc?.
	    (while (file-name-extension file)
	      (setq file (file-name-sans-extension file)))
	    (setcar l file)))
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      (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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;;;###autoload
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(defvar jka-compr-inhibit nil
  "Non-nil means inhibit automatic uncompression temporarily.
Lisp programs can bind this to t to do that.
It is not recommended to set this variable permanently to anything but nil.")

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;;;###autoload
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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)))
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      (if (and jka-op (not jka-compr-inhibit))
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	  (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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;;;###autoload
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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))))
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    (setq auto-mode-alist (cdr ama)))

  (let* ((ama (cons nil file-coding-system-alist))
	 (last ama)
	 entry)

    (while (cdr last)
      (setq entry (car (cdr last)))
      (if (member entry jka-compr-added-to-file-coding-system-alist)
	  (setcdr last (cdr (cdr last)))
	(setq last (cdr last))))
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    (setq file-coding-system-alist (cdr ama)))

  ;; Remove the suffixes that were added by jka-compr.
  (let ((suffixes nil)
	(re (jka-compr-build-file-regexp)))
    (dolist (suffix load-suffixes)
      (unless (string-match re suffix)
	(push suffix suffixes)))
    (setq load-suffixes (nreverse suffixes))))
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(provide 'jka-compr)

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;;; arch-tag: 3f15b630-e9a7-46c4-a22a-94afdde86ebc
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;;; jka-compr.el ends here