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;;; po.el --- basic support of PO translation files
;; Copyright (C) 1995-1998, 2000-2020 Free Software Foundation, Inc.
;; Authors: François Pinard <pinard@iro.umontreal.ca>,
;; Greg McGary <gkm@magilla.cichlid.com>,
;; Bruno Haible <bruno@clisp.org>.
;; Keywords: i18n, files
;; 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 3 of the License, 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
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; This package makes sure visiting PO files decodes them correctly,
;; according to the Charset= header in the PO file. For more support
;; for editing PO files, see po-mode.el.
;;; Code:
(defconst po-content-type-charset-alist
'(("ASCII" . undecided)
("ANSI_X3.4-1968" . undecided)
("US-ASCII" . undecided))
"Alist of coding system versus GNU libc/libiconv canonical charset name.
Contains canonical charset names that don't correspond to coding systems.")
(defun po-find-charset (filename)
"Return PO charset value for FILENAME.
If FILENAME is a cons cell, its CDR is a buffer that already contains
the PO file (but not yet decoded)."
(let ((charset-regexp
"^\"Content-Type:[ \t]*text/plain;[ \t]*charset=\\(.*\\)\\\\n\"")
(buf (and (consp filename) (cdr 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
(1- (point))
(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.
(t (save-excursion
(goto-char (point-max))
(insert-file-contents-literally filename nil
(1- (point))
(1- (+ (point) 1024))))
(if (re-search-forward charset-regexp nil t)
(match-string 1))))))
(defun po-find-file-coding-system-guts (operation filename)
"Return a (DECODING . ENCODING) pair for OPERATION on PO file FILENAME.
Do so according to FILENAME's declared charset.
FILENAME may be a cons (NAME . BUFFER). In that case, detect charset
in BUFFER."
(and
(eq operation 'insert-file-contents)
(or (if (consp filename) (buffer-live-p (cdr filename)))
(file-exists-p filename))
(with-temp-buffer
(let* ((coding-system-for-read 'no-conversion)
(charset (or (po-find-charset filename) "ascii"))
assoc)
(list (cond
((setq assoc
(assoc-string charset
po-content-type-charset-alist
t))
(cdr assoc))
((or (setq assoc (assoc-string charset coding-system-alist t))
(setq assoc
(assoc-string (subst-char-in-string ?_ ?-
charset)
coding-system-alist t)))
(intern (car assoc)))
;; In principle we should also check the `mime-charset'
;; property of everything in the base coding system
;; list, but there should always be a coding system
;; corresponding to the MIME name.
((featurep 'code-pages)
;; Give up.
'raw-text)
(t
;; Try again with code-pages loaded. Maybe it's best
;; to require it initially?
(require 'code-pages nil t)
(if (or
(setq assoc (assoc-string charset coding-system-alist t))
(setq assoc (assoc-string (subst-char-in-string
?_ ?- charset)
coding-system-alist t)))
(intern (car assoc))
'raw-text))))))))
;;;###autoload
(defun po-find-file-coding-system (arg-list)
"Return a (DECODING . ENCODING) pair, according to PO file's charset.
Called through `file-coding-system-alist', before the file is visited for real."
(po-find-file-coding-system-guts (car arg-list) (car (cdr arg-list))))
(provide 'po)
;;; po.el ends here
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