Re: po file charset via auto-coding-functions

[Kenichi Handa <handa@m17n.org>]

In article <87k6g6e05k.fsf-monnier+emacs@gnu.org>, Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>  environment.  Hmmm, it seems that you are right.  There's no
>>  way to handle a tared/archived file in a function registered
>>  in file-coding-system-alist.

> Provide a file-name-handler for tar files and archives would work
> around that problem.

Maybe, but I'm not sure.  My gut feeling tells that it's not
easy to setup various handlers for an archive member already
setup in a (narrowed) buffer.  We don't know what kind of
file operation a function in file-coding-system-alist
performs.

By the way, while considering the possibility of using
file-name-handler, I got this idea.

The correct operation in a handler for insert-file-contents
will be to find a buffer pretending to visit the file, and
insert that buffer contents.  And, for that, we have to give
buffer-file-name (e.g. /home/handa/x.tgz!vi.po") not the
filename itself (e.g. vi.po) to
find-operation-coding-system.  I think such a change is safe
because, at least, all current entries in
file-coding-system-alist checks only the tail of a filename.

But, if we have such a change, with a fairly simple change
to po.el, we can fix the current problem.  So, I now propose
the attached change.

---
Kenichi Handa
handa@m17n.org


2005-10-24  Kenichi Handa  <handa@m17n.org>

	* arc-mode.el (archive-set-buffer-as-visiting-file): Give
	buffer-file-name to find-operation-coding-system.

	* tar-mode.el (tar-extract): Give buffer-file-name to
	find-operation-coding-system.

	* textmodes/po.el (po-find-charset): If there exists a buffer
	visiting filename, check the contents of that buffer.
	(po-find-file-coding-system-guts): Check if there exists a buffer
	visiting filename.

Index: arc-mode.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/arc-mode.el,v
retrieving revision 1.68
diff -c -r1.68 arc-mode.el
*** arc-mode.el	16 Oct 2005 17:05:23 -0000	1.68
--- arc-mode.el	24 Oct 2005 01:33:13 -0000
***************
*** 877,883 ****
  	       (let ((file-name-handler-alist
  		      '(("" . archive-file-name-handler))))
  		 (car (find-operation-coding-system 'insert-file-contents
! 						    filename t))))))
        (if (and (not coding-system-for-read)
  	       (not enable-multibyte-characters))
  	  (setq coding
--- 877,883 ----
  	       (let ((file-name-handler-alist
  		      '(("" . archive-file-name-handler))))
  		 (car (find-operation-coding-system 'insert-file-contents
! 						    buffer-file-name t))))))
        (if (and (not coding-system-for-read)
  	       (not enable-multibyte-characters))
  	  (setq coding
Index: tar-mode.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/tar-mode.el,v
retrieving revision 1.103
diff -c -r1.103 tar-mode.el
*** tar-mode.el	22 Oct 2005 01:24:38 -0000	1.103
--- tar-mode.el	24 Oct 2005 01:33:14 -0000
***************
*** 737,743 ****
  				    (funcall set-auto-coding-function
  					     name (- (point-max) (point)))))
  			     (car (find-operation-coding-system
! 				   'insert-file-contents name t))))
  			(multibyte enable-multibyte-characters)
  			(detected (detect-coding-region
  				   (point-min)
--- 737,743 ----
  				    (funcall set-auto-coding-function
  					     name (- (point-max) (point)))))
  			     (car (find-operation-coding-system
! 				   'insert-file-contents buffer-file-name t))))
  			(multibyte enable-multibyte-characters)
  			(detected (detect-coding-region
  				   (point-min)
Index: textmodes/po.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/textmodes/po.el,v
retrieving revision 1.12
diff -c -r1.12 po.el
*** textmodes/po.el	6 Aug 2005 17:41:15 -0000	1.12
--- textmodes/po.el	24 Oct 2005 01:33:14 -0000
***************
*** 44,55 ****
    "Return PO charset value for FILENAME."
    (let ((charset-regexp
  	 "^\"Content-Type:[ \t]*text/plain;[ \t]*charset=\\(.*\\)\\\\n\"")
  	(short-read nil))
      ;; Try the first 4096 bytes.  In case we cannot find the charset value
      ;; within the first 4096 bytes (the PO file might start with a long
      ;; comment) try the next 4096 bytes repeatedly until we'll know for sure
      ;; we've checked the empty header entry entirely.
!     (while (not (or short-read (re-search-forward "^msgid" nil t)))
        (save-excursion
          (goto-char (point-max))
  	(let ((pair (insert-file-contents-literally filename nil
--- 44,59 ----
    "Return PO charset value for FILENAME."
    (let ((charset-regexp
  	 "^\"Content-Type:[ \t]*text/plain;[ \t]*charset=\\(.*\\)\\\\n\"")
+ 	(buf (get-file-buffer filename))
  	(short-read nil))
+     (when buf
+       (set-buffer buf)
+       (goto-char (point-min)))
      ;; Try the first 4096 bytes.  In case we cannot find the charset value
      ;; within the first 4096 bytes (the PO file might start with a long
      ;; comment) try the next 4096 bytes repeatedly until we'll know for sure
      ;; we've checked the empty header entry entirely.
!     (while (not (or short-read (re-search-forward "^msgid" nil t) buf))
        (save-excursion
          (goto-char (point-max))
  	(let ((pair (insert-file-contents-literally filename nil
***************
*** 57,63 ****
  						    (1- (+ (point) 4096)))))
  	  (setq short-read (< (nth 1 pair) 4096)))))
      (cond ((re-search-forward charset-regexp nil t) (match-string 1))
! 	  (short-read nil)
  	  ;; We've found the first msgid; maybe, only a part of the msgstr
  	  ;; value was loaded.  Load the next 1024 bytes; if charset still
  	  ;; isn't available, give up.
--- 61,67 ----
  						    (1- (+ (point) 4096)))))
  	  (setq short-read (< (nth 1 pair) 4096)))))
      (cond ((re-search-forward charset-regexp nil t) (match-string 1))
! 	  ((or short-read buf) nil)
  	  ;; We've found the first msgid; maybe, only a part of the msgstr
  	  ;; value was loaded.  Load the next 1024 bytes; if charset still
  	  ;; isn't available, give up.
***************
*** 74,80 ****
  Do so according to FILENAME's declared charset."
    (and
     (eq operation 'insert-file-contents)
!    (file-exists-p filename)
     (with-temp-buffer
       (let* ((coding-system-for-read 'no-conversion)
  	    (charset (or (po-find-charset filename) "ascii"))
--- 78,84 ----
  Do so according to FILENAME's declared charset."
    (and
     (eq operation 'insert-file-contents)
!    (or (get-file-buffer filename) (file-exists-p filename))
     (with-temp-buffer
       (let* ((coding-system-for-read 'no-conversion)
  	    (charset (or (po-find-charset filename) "ascii"))