Add a NEWS entry.

[emacs.git] / lisp / gnus / mm-bodies.el

;;; mm-bodies.el --- Functions for decoding MIME things

;; Copyright (C) 1998-2016 Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;;      MORIOKA Tomohiko <morioka@jaist.ac.jp>
;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;;; Code:

(require 'mm-util)
(require 'rfc2047)
(require 'mm-encode)

(defvar mm-uu-yenc-decode-function)
(defvar mm-uu-decode-function)
(defvar mm-uu-binhex-decode-function)

;; 8bit treatment gets any char except: 0x32 - 0x7f, LF, TAB, BEL,
;; BS, vertical TAB, form feed, and ^_
;;
;; Note that CR is *not* included, as that would allow a non-paired CR
;; in the body contrary to RFC 2822:
;;
;;   - CR and LF MUST only occur together as CRLF; they MUST NOT
;;     appear independently in the body.

(defvar mm-7bit-chars "\x20-\x7f\n\t\x7\x8\xb\xc\x1f")

(defcustom mm-body-charset-encoding-alist
  '((iso-2022-jp . 7bit)
    (iso-2022-jp-2 . 7bit)
    ;; We MUST encode UTF-16 because it can contain \0's which is
    ;; known to break servers.
    ;; Note: UTF-16 variants are invalid for text parts [RFC 2781],
    ;; so this can't happen :-/.
    ;; PPS: Yes, it can happen if the user specifies UTF-16 in the MML
    ;; markup. - jh.
    (utf-16 . base64)
    (utf-16be . base64)
    (utf-16le . base64))
  "Alist of MIME charsets to encodings.
Valid encodings are `7bit', `8bit', `quoted-printable' and `base64'."
  :type '(repeat (cons (symbol :tag "charset")
                       (choice :tag "encoding"
                               (const 7bit)
                               (const 8bit)
                               (const quoted-printable)
                               (const base64))))
  :group 'mime)

(autoload 'message-options-get "message")
(declare-function message-options-set "message" (symbol value))

(defun mm-encode-body (&optional charset)
  "Encode a body.
Should be called narrowed to the body that is to be encoded.
If there is more than one non-ASCII MULE charset in the body, then the
list of MULE charsets found is returned.
If CHARSET is non-nil, it is used as the MIME charset to encode the body.
If successful, the MIME charset is returned.
If no encoding was done, nil is returned."
  (if (not (mm-multibyte-p))
      ;; In the non-Mule case, we search for non-ASCII chars and
      ;; return the value of `mail-parse-charset' if any are found.
      (or charset
          (save-excursion
            (goto-char (point-min))
            (if (re-search-forward "[^\x0-\x7f]" nil t)
                (or mail-parse-charset
                    (message-options-get 'mm-body-charset-encoding-alist)
                    (message-options-set
                     'mm-body-charset-encoding-alist
                     (read-coding-system "Charset used in the article: ")))
              ;; The logic in `mml-generate-mime-1' confirms that it's OK
              ;; to return nil here.
              nil)))
    (save-excursion
      (if charset
          (progn
            (encode-coding-region (point-min) (point-max)
                                  (mm-charset-to-coding-system charset))
            charset)
        (goto-char (point-min))
        (let ((charsets (mm-find-mime-charset-region (point-min) (point-max)
                                                     mm-hack-charsets)))
          (cond
           ;; No encoding.
           ((null charsets)
            nil)
           ;; Too many charsets.
           ((> (length charsets) 1)
            charsets)
           ;; We encode.
           (t
            (prog1
                (setq charset (car charsets))
              (encode-coding-region (point-min) (point-max)
                                    (mm-charset-to-coding-system charset))))
           ))))))

(defun mm-long-lines-p (length)
  "Say whether any of the lines in the buffer is longer than LENGTH."
  (save-excursion
    (goto-char (point-min))
    (end-of-line)
    (while (and (not (eobp))
                (not (> (current-column) length)))
      (forward-line 1)
      (end-of-line))
    (and (> (current-column) length)
         (current-column))))

(defvar message-posting-charset)

(defun mm-body-encoding (charset &optional encoding)
  "Do Content-Transfer-Encoding and return the encoding of the current buffer."
  (when (stringp encoding)
    (setq encoding (intern (downcase encoding))))
  (let ((bits (mm-body-7-or-8))
        (longp (mm-long-lines-p 1000)))
    (require 'message)
    (cond
     ((and (not longp)
           (not (and mm-use-ultra-safe-encoding
                     (or (save-excursion (re-search-forward " $" nil t))
                         (save-excursion (re-search-forward "^From " nil t)))))
           (eq bits '7bit))
      bits)
     ((and (not mm-use-ultra-safe-encoding)
           (not longp)
           (not (cdr (assq charset mm-body-charset-encoding-alist)))
           (or (eq t (cdr message-posting-charset))
               (memq charset (cdr message-posting-charset))
               (eq charset mail-parse-charset)))
      bits)
     (t
      (let ((encoding (or encoding
                          (cdr (assq charset mm-body-charset-encoding-alist))
                          (mm-qp-or-base64))))
        (when mm-use-ultra-safe-encoding
          (setq encoding (mm-safer-encoding encoding)))
        (mm-encode-content-transfer-encoding encoding "text/plain")
        encoding)))))

(defun mm-body-7-or-8 ()
  "Say whether the body is 7bit or 8bit."
  (if (save-excursion
        (goto-char (point-min))
        (skip-chars-forward mm-7bit-chars)
        (eobp))
      '7bit
    '8bit))

;;;
;;; Functions for decoding
;;;

(defun mm-decode-content-transfer-encoding (encoding &optional type)
  "Decodes buffer encoded with ENCODING, returning success status.
If TYPE is `text/plain' CRLF->LF translation may occur."
  (prog1
      (condition-case error
          (cond
           ((eq encoding 'quoted-printable)
            (quoted-printable-decode-region (point-min) (point-max))
            t)
           ((eq encoding 'base64)
            (base64-decode-region
             (point-min)
             ;; Some mailers insert whitespace
             ;; junk at the end which
             ;; base64-decode-region dislikes.
             ;; Also remove possible junk which could
             ;; have been added by mailing list software.
             (save-excursion
               (goto-char (point-min))
               (while (re-search-forward "^[\t ]*\r?\n" nil t)
                 (delete-region (match-beginning 0) (match-end 0)))
               (goto-char (point-max))
               (when (re-search-backward "^[\t ]*[A-Za-z0-9+/]+=*[\t ]*$"
                                         nil t)
                 (forward-line))
               (point))))
           ((memq encoding '(nil 7bit 8bit binary))
            ;; Do nothing.
            t)
           ((memq encoding '(x-uuencode x-uue))
            (require 'mm-uu)
            (funcall mm-uu-decode-function (point-min) (point-max))
            t)
           ((eq encoding 'x-binhex)
            (require 'mm-uu)
            (funcall mm-uu-binhex-decode-function (point-min) (point-max))
            t)
           ((eq encoding 'x-yenc)
            (require 'mm-uu)
            (funcall mm-uu-yenc-decode-function (point-min) (point-max))
            )
           ((functionp encoding)
            (funcall encoding (point-min) (point-max))
            t)
           (t
            (message "Unknown encoding %s; defaulting to 8bit" encoding)))
        (error
         (message "Error while decoding: %s" error)
         nil))
    (when (and
           type
           (memq encoding '(base64 x-uuencode x-uue x-binhex x-yenc))
           (string-match "\\`text/" type))
      (goto-char (point-min))
      (while (search-forward "\r\n" nil t)
        (replace-match "\n" t t)))))

(defun mm-decode-body (charset &optional encoding type)
  "Decode the current article that has been encoded with ENCODING to CHARSET.
ENCODING is a MIME content transfer encoding.
CHARSET is the MIME charset with which to decode the data after transfer
decoding.  If it is nil, default to `mail-parse-charset'."
  (when (stringp charset)
    (setq charset (intern (downcase charset))))
  (when (or (not charset)
            (eq 'gnus-all mail-parse-ignored-charsets)
            (memq 'gnus-all mail-parse-ignored-charsets)
            (memq charset mail-parse-ignored-charsets))
    (setq charset mail-parse-charset))
  (save-excursion
    (when encoding
      (mm-decode-content-transfer-encoding encoding type))
    (when (not (eq charset 'gnus-decoded))
      (let ((coding-system (mm-charset-to-coding-system
                            ;; Allow overwrite using
                            ;; `mm-charset-override-alist'.
                            charset nil t)))
        (if (and (not coding-system)
                 (listp mail-parse-ignored-charsets)
                 (memq 'gnus-unknown mail-parse-ignored-charsets))
            (setq coding-system
                  (mm-charset-to-coding-system mail-parse-charset)))
        (when (and charset coding-system
                   (mm-multibyte-p)
                   (or (not (eq coding-system 'ascii))
                       (setq coding-system mail-parse-charset)))
          (decode-coding-region (point-min) (point-max) coding-system))
        (setq buffer-file-coding-system last-coding-system-used)))))

(defun mm-decode-string (string charset)
  "Decode STRING with CHARSET."
  (when (stringp charset)
    (setq charset (intern (downcase charset))))
  (when (or (not charset)
            (eq 'gnus-all mail-parse-ignored-charsets)
            (memq 'gnus-all mail-parse-ignored-charsets)
            (memq charset mail-parse-ignored-charsets))
    (setq charset mail-parse-charset))
  (or
   (let ((coding-system (mm-charset-to-coding-system
                         charset
                         ;; Allow overwrite using
                         ;; `mm-charset-override-alist'.
                         nil t)))
     (if (and (not coding-system)
              (listp mail-parse-ignored-charsets)
              (memq 'gnus-unknown mail-parse-ignored-charsets))
         (setq coding-system
               (mm-charset-to-coding-system mail-parse-charset)))
     (when (and charset coding-system
                (mm-multibyte-p)
                (or (not (eq coding-system 'ascii))
                    (setq coding-system mail-parse-charset)))
       (decode-coding-string string coding-system)))
   string))

(provide 'mm-bodies)

;;; mm-bodies.el ends here