lisp/gnus/rfc2047.el

   1 ;;; rfc2047.el --- functions for encoding and decoding rfc2047 messages
   2
   3 ;; Copyright (C) 1998, 1999, 2000, 2002, 2003, 2004,
   4 ;;   2005, 2006 Free Software Foundation, Inc.
   5
   6 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   7 ;;      MORIOKA Tomohiko <morioka@jaist.ac.jp>
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  23 ;; Boston, MA 02110-1301, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; RFC 2047 is "MIME (Multipurpose Internet Mail Extensions) Part
  28 ;; Three:  Message Header Extensions for Non-ASCII Text".
  29
  30 ;;; Code:
  31
  32 (eval-when-compile
  33   (require 'cl)
  34   (defvar message-posting-charset)
  35   (unless (fboundp 'with-syntax-table)  ; not in Emacs 20
  36     (defmacro with-syntax-table (table &rest body)
  37       "Evaluate BODY with syntax table of current buffer set to TABLE.
  38 The syntax table of the current buffer is saved, BODY is evaluated, and the
  39 saved table is restored, even in case of an abnormal exit.
  40 Value is what BODY returns."
  41       (let ((old-table (make-symbol "table"))
  42             (old-buffer (make-symbol "buffer")))
  43         `(let ((,old-table (syntax-table))
  44                (,old-buffer (current-buffer)))
  45            (unwind-protect
  46                (progn
  47                  (set-syntax-table ,table)
  48                  ,@body)
  49              (save-current-buffer
  50                (set-buffer ,old-buffer)
  51                (set-syntax-table ,old-table))))))))
  52
  53 (require 'qp)
  54 (require 'mm-util)
  55 (require 'ietf-drums)
  56 ;; Fixme: Avoid this (used for mail-parse-charset) mm dependence on gnus.
  57 (require 'mail-prsvr)
  58 (require 'base64)
  59 (autoload 'mm-body-7-or-8 "mm-bodies")
  60
  61 (eval-and-compile
  62   ;; Avoid gnus-util for mm- code.
  63   (defalias 'rfc2047-point-at-bol
  64     (if (fboundp 'point-at-bol)
  65         'point-at-bol
  66       'line-beginning-position))
  67
  68   (defalias 'rfc2047-point-at-eol
  69     (if (fboundp 'point-at-eol)
  70         'point-at-eol
  71       'line-end-position)))
  72
  73 (defvar rfc2047-header-encoding-alist
  74   '(("Newsgroups" . nil)
  75     ("Followup-To" . nil)
  76     ("Message-ID" . nil)
  77     ("\\(Resent-\\)?\\(From\\|Cc\\|To\\|Bcc\\|\\(In-\\)?Reply-To\\|Sender\
  78 \\|Mail-Followup-To\\|Mail-Copies-To\\|Approved\\)" . address-mime)
  79     (t . mime))
  80   "*Header/encoding method alist.
  81 The list is traversed sequentially.  The keys can either be
  82 header regexps or t.
  83
  84 The values can be:
  85
  86 1) nil, in which case no encoding is done;
  87 2) `mime', in which case the header will be encoded according to RFC2047;
  88 3) `address-mime', like `mime', but takes account of the rules for address
  89    fields (where quoted strings and comments must be treated separately);
  90 4) a charset, in which case it will be encoded as that charset;
  91 5) `default', in which case the field will be encoded as the rest
  92    of the article.")
  93
  94 (defvar rfc2047-charset-encoding-alist
  95   '((us-ascii . nil)
  96     (iso-8859-1 . Q)
  97     (iso-8859-2 . Q)
  98     (iso-8859-3 . Q)
  99     (iso-8859-4 . Q)
 100     (iso-8859-5 . B)
 101     (koi8-r . B)
 102     (iso-8859-7 . B)
 103     (iso-8859-8 . B)
 104     (iso-8859-9 . Q)
 105     (iso-8859-14 . Q)
 106     (iso-8859-15 . Q)
 107     (iso-2022-jp . B)
 108     (iso-2022-kr . B)
 109     (gb2312 . B)
 110     (big5 . B)
 111     (cn-big5 . B)
 112     (cn-gb . B)
 113     (cn-gb-2312 . B)
 114     (euc-kr . B)
 115     (iso-2022-jp-2 . B)
 116     (iso-2022-int-1 . B)
 117     (viscii . Q))
 118   "Alist of MIME charsets to RFC2047 encodings.
 119 Valid encodings are nil, `Q' and `B'.  These indicate binary (no) encoding,
 120 quoted-printable and base64 respectively.")
 121
 122 (defvar rfc2047-encode-function-alist
 123   '((Q . rfc2047-q-encode-string)
 124     (B . rfc2047-b-encode-string)
 125     (nil . identity))
 126   "Alist of RFC2047 encodings to encoding functions.")
 127
 128 (defvar rfc2047-encode-encoded-words t
 129   "Whether encoded words should be encoded again.")
 130
 131 ;;;
 132 ;;; Functions for encoding RFC2047 messages
 133 ;;;
 134
 135 (defun rfc2047-qp-or-base64 ()
 136   "Return the type with which to encode the buffer.
 137 This is either `base64' or `quoted-printable'."
 138   (save-excursion
 139     (let ((limit (min (point-max) (+ 2000 (point-min))))
 140           (n8bit 0))
 141       (goto-char (point-min))
 142       (skip-chars-forward "\x20-\x7f\r\n\t" limit)
 143       (while (< (point) limit)
 144         (incf n8bit)
 145         (forward-char 1)
 146         (skip-chars-forward "\x20-\x7f\r\n\t" limit))
 147       (if (or (< (* 6 n8bit) (- limit (point-min)))
 148               ;; Don't base64, say, a short line with a single
 149               ;; non-ASCII char when splitting parts by charset.
 150               (= n8bit 1))
 151           'quoted-printable
 152         'base64))))
 153
 154 (defun rfc2047-narrow-to-field ()
 155   "Narrow the buffer to the header on the current line."
 156   (beginning-of-line)
 157   (narrow-to-region
 158    (point)
 159    (progn
 160      (forward-line 1)
 161      (if (re-search-forward "^[^ \n\t]" nil t)
 162          (rfc2047-point-at-bol)
 163        (point-max))))
 164   (goto-char (point-min)))
 165
 166 (defun rfc2047-field-value ()
 167   "Return the value of the field at point."
 168   (save-excursion
 169     (save-restriction
 170       (rfc2047-narrow-to-field)
 171       (re-search-forward ":[ \t\n]*" nil t)
 172       (buffer-substring-no-properties (point) (point-max)))))
 173
 174 (defun rfc2047-quote-special-characters-in-quoted-strings (&optional
 175                                                            encodable-regexp)
 176   "Quote special characters with `\\'s in quoted strings.
 177 Quoting will not be done in a quoted string if it contains characters
 178 matching ENCODABLE-REGEXP."
 179   (goto-char (point-min))
 180   (let ((tspecials (concat "[" ietf-drums-tspecials "]"))
 181         beg)
 182     (with-syntax-table (standard-syntax-table)
 183       (while (search-forward "\"" nil t)
 184         (unless (eq (char-before) ?\\)
 185           (setq beg (match-end 0))
 186           (goto-char (match-beginning 0))
 187           (condition-case nil
 188               (progn
 189                 (forward-sexp)
 190                 (save-restriction
 191                   (narrow-to-region beg (1- (point)))
 192                   (goto-char beg)
 193                   (unless (and encodable-regexp
 194                                (re-search-forward encodable-regexp nil t))
 195                     (while (re-search-forward tspecials nil 'move)
 196                       (unless (and (eq (char-before) ?\\) ;; Already quoted.
 197                                    (looking-at tspecials))
 198                         (goto-char (match-beginning 0))
 199                         (unless (or (eq (char-before) ?\\)
 200                                     (and rfc2047-encode-encoded-words
 201                                          (eq (char-after) ??)
 202                                          (eq (char-before) ?=)))
 203                           (insert "\\")))
 204                       (forward-char)))))
 205             (error
 206              (goto-char beg))))))))
 207
 208 (defvar rfc2047-encoding-type 'address-mime
 209   "The type of encoding done by `rfc2047-encode-region'.
 210 This should be dynamically bound around calls to
 211 `rfc2047-encode-region' to either `mime' or `address-mime'.  See
 212 `rfc2047-header-encoding-alist', for definitions.")
 213
 214 (defun rfc2047-encode-message-header ()
 215   "Encode the message header according to `rfc2047-header-encoding-alist'.
 216 Should be called narrowed to the head of the message."
 217   (interactive "*")
 218   (save-excursion
 219     (goto-char (point-min))
 220     (let (alist elem method)
 221       (while (not (eobp))
 222         (save-restriction
 223           (rfc2047-narrow-to-field)
 224           (setq method nil
 225                 alist rfc2047-header-encoding-alist)
 226           (while (setq elem (pop alist))
 227             (when (or (and (stringp (car elem))
 228                            (looking-at (car elem)))
 229                       (eq (car elem) t))
 230               (setq alist nil
 231                     method (cdr elem))))
 232           (if (not (rfc2047-encodable-p))
 233               (prog2
 234                   (when (eq method 'address-mime)
 235                     (rfc2047-quote-special-characters-in-quoted-strings))
 236                   (if (and (eq (mm-body-7-or-8) '8bit)
 237                            (mm-multibyte-p)
 238                            (mm-coding-system-p
 239                             (car message-posting-charset)))
 240                       ;; 8 bit must be decoded.
 241                       (mm-encode-coding-region
 242                        (point-min) (point-max)
 243                        (mm-charset-to-coding-system
 244                         (car message-posting-charset))))
 245                 ;; No encoding necessary, but folding is nice
 246                 (when nil
 247                   (rfc2047-fold-region
 248                    (save-excursion
 249                      (goto-char (point-min))
 250                      (skip-chars-forward "^:")
 251                      (when (looking-at ": ")
 252                        (forward-char 2))
 253                      (point))
 254                    (point-max))))
 255             ;; We found something that may perhaps be encoded.
 256             (re-search-forward "^[^:]+: *" nil t)
 257             (cond
 258              ((eq method 'address-mime)
 259               (rfc2047-encode-region (point) (point-max)))
 260              ((eq method 'mime)
 261               (let ((rfc2047-encoding-type 'mime))
 262                 (rfc2047-encode-region (point) (point-max))))
 263              ((eq method 'default)
 264               (if (and (featurep 'mule)
 265                        (if (boundp 'default-enable-multibyte-characters)
 266                            default-enable-multibyte-characters)
 267                        mail-parse-charset)
 268                   (mm-encode-coding-region (point) (point-max)
 269                                            mail-parse-charset)))
 270              ;; We get this when CC'ing messsages to newsgroups with
 271              ;; 8-bit names.  The group name mail copy just got
 272              ;; unconditionally encoded.  Previously, it would ask
 273              ;; whether to encode, which was quite confusing for the
 274              ;; user.  If the new behaviour is wrong, tell me. I have
 275              ;; left the old code commented out below.
 276              ;; -- Per Abrahamsen <abraham@dina.kvl.dk> Date: 2001-10-07.
 277              ;; Modified by Dave Love, with the commented-out code changed
 278              ;; in accordance with changes elsewhere.
 279              ((null method)
 280               (rfc2047-encode-region (point) (point-max)))
 281 ;;;          ((null method)
 282 ;;;           (if (or (message-options-get
 283 ;;;                    'rfc2047-encode-message-header-encode-any)
 284 ;;;                   (message-options-set
 285 ;;;                    'rfc2047-encode-message-header-encode-any
 286 ;;;                    (y-or-n-p
 287 ;;;                     "Some texts are not encoded. Encode anyway?")))
 288 ;;;               (rfc2047-encode-region (point-min) (point-max))
 289 ;;;             (error "Cannot send unencoded text")))
 290              ((mm-coding-system-p method)
 291               (if (and (featurep 'mule)
 292                        (if (boundp 'default-enable-multibyte-characters)
 293                            default-enable-multibyte-characters))
 294                   (mm-encode-coding-region (point) (point-max) method)))
 295              ;; Hm.
 296              (t)))
 297           (goto-char (point-max)))))))
 298
 299 ;; Fixme: This, and the require below may not be the Right Thing, but
 300 ;; should be safe just before release.  -- fx 2001-02-08
 301 (eval-when-compile (defvar message-posting-charset))
 302
 303 (defun rfc2047-encodable-p ()
 304   "Return non-nil if any characters in current buffer need encoding in headers.
 305 The buffer may be narrowed."
 306   (require 'message)                    ; for message-posting-charset
 307   (let ((charsets
 308          (mm-find-mime-charset-region (point-min) (point-max))))
 309     (goto-char (point-min))
 310     (or (and rfc2047-encode-encoded-words
 311              (prog1
 312                  (search-forward "=?" nil t)
 313                (goto-char (point-min))))
 314         (and charsets
 315              (not (equal charsets (list (car message-posting-charset))))))))
 316
 317 ;; Use this syntax table when parsing into regions that may need
 318 ;; encoding.  Double quotes are string delimiters, backslash is
 319 ;; character quoting, and all other RFC 2822 special characters are
 320 ;; treated as punctuation so we can use forward-sexp/forward-word to
 321 ;; skip to the end of regions appropriately.  Nb. ietf-drums does
 322 ;; things differently.
 323 (defconst rfc2047-syntax-table
 324   ;; (make-char-table 'syntax-table '(2)) only works in Emacs.
 325   (let ((table (make-syntax-table)))
 326     ;; The following is done to work for setting all elements of the table
 327     ;; in Emacs 21 and 22 and XEmacs; it appears to be the cleanest way.
 328     ;; Play safe and don't assume the form of the word syntax entry --
 329     ;; copy it from ?a.
 330     (if (fboundp 'set-char-table-range) ; Emacs
 331         (funcall (intern "set-char-table-range")
 332                  table t (aref (standard-syntax-table) ?a))
 333       (if (fboundp 'put-char-table)
 334           (if (fboundp 'get-char-table) ; warning avoidance
 335               (put-char-table t (get-char-table ?a (standard-syntax-table))
 336                               table))))
 337     (modify-syntax-entry ?\\ "\\" table)
 338     (modify-syntax-entry ?\" "\"" table)
 339     (modify-syntax-entry ?\( "(" table)
 340     (modify-syntax-entry ?\) ")" table)
 341     (modify-syntax-entry ?\< "." table)
 342     (modify-syntax-entry ?\> "." table)
 343     (modify-syntax-entry ?\[ "." table)
 344     (modify-syntax-entry ?\] "." table)
 345     (modify-syntax-entry ?: "." table)
 346     (modify-syntax-entry ?\; "." table)
 347     (modify-syntax-entry ?, "." table)
 348     (modify-syntax-entry ?@ "." table)
 349     table))
 350
 351 (defun rfc2047-encode-region (b e)
 352   "Encode words in region B to E that need encoding.
 353 By default, the region is treated as containing RFC2822 addresses.
 354 Dynamically bind `rfc2047-encoding-type' to change that."
 355   (save-restriction
 356     (narrow-to-region b e)
 357     (let ((encodable-regexp (if rfc2047-encode-encoded-words
 358                                 "[^\000-\177]+\\|=\\?"
 359                               "[^\000-\177]+"))
 360           start                         ; start of current token
 361           end begin csyntax
 362           ;; Whether there's an encoded word before the current token,
 363           ;; either immediately or separated by space.
 364           last-encoded
 365           (orig-text (buffer-substring-no-properties b e)))
 366       (if (eq 'mime rfc2047-encoding-type)
 367           ;; Simple case.  Continuous words in which all those contain
 368           ;; non-ASCII characters are encoded collectively.  Encoding
 369           ;; ASCII words, including `Re:' used in Subject headers, is
 370           ;; avoided for interoperability with non-MIME clients and
 371           ;; for making it easy to find keywords.
 372           (progn
 373             (goto-char (point-min))
 374             (while (progn (skip-chars-forward " \t\n")
 375                           (not (eobp)))
 376               (setq start (point))
 377               (while (and (looking-at "[ \t\n]*\\([^ \t\n]+\\)")
 378                           (progn
 379                             (setq end (match-end 0))
 380                             (re-search-forward encodable-regexp end t)))
 381                 (goto-char end))
 382               (if (> (point) start)
 383                   (rfc2047-encode start (point))
 384                 (goto-char end))))
 385         ;; `address-mime' case -- take care of quoted words, comments.
 386         (rfc2047-quote-special-characters-in-quoted-strings encodable-regexp)
 387         (with-syntax-table rfc2047-syntax-table
 388           (goto-char (point-min))
 389           (condition-case err           ; in case of unbalanced quotes
 390               ;; Look for rfc2822-style: sequences of atoms, quoted
 391               ;; strings, specials, whitespace.  (Specials mustn't be
 392               ;; encoded.)
 393               (while (not (eobp))
 394                 ;; Skip whitespace.
 395                 (skip-chars-forward " \t\n")
 396                 (setq start (point))
 397                 (cond
 398                  ((not (char-after)))   ; eob
 399                  ;; else token start
 400                  ((eq ?\" (setq csyntax (char-syntax (char-after))))
 401                   ;; Quoted word.
 402                   (forward-sexp)
 403                   (setq end (point))
 404                   ;; Does it need encoding?
 405                   (goto-char start)
 406                   (if (re-search-forward encodable-regexp end 'move)
 407                       ;; It needs encoding.  Strip the quotes first,
 408                       ;; since encoded words can't occur in quotes.
 409                       (progn
 410                         (goto-char end)
 411                         (delete-backward-char 1)
 412                         (goto-char start)
 413                         (delete-char 1)
 414                         (when last-encoded
 415                           ;; There was a preceding quoted word.  We need
 416                           ;; to include any separating whitespace in this
 417                           ;; word to avoid it getting lost.
 418                           (skip-chars-backward " \t")
 419                           ;; A space is needed between the encoded words.
 420                           (insert ? )
 421                           (setq start (point)
 422                                 end (1+ end)))
 423                         ;; Adjust the end position for the deleted quotes.
 424                         (rfc2047-encode start (- end 2))
 425                         (setq last-encoded t)) ; record that it was encoded
 426                     (setq last-encoded  nil)))
 427                  ((eq ?. csyntax)
 428                   ;; Skip other delimiters, but record that they've
 429                   ;; potentially separated quoted words.
 430                   (forward-char)
 431                   (setq last-encoded nil))
 432                  ((eq ?\) csyntax)
 433                   (error "Unbalanced parentheses"))
 434                  ((eq ?\( csyntax)
 435                   ;; Look for the end of parentheses.
 436                   (forward-list)
 437                   ;; Encode text as an unstructured field.
 438                   (let ((rfc2047-encoding-type 'mime))
 439                     (rfc2047-encode-region (1+ start) (1- (point))))
 440                   (skip-chars-forward ")"))
 441                  (t                 ; normal token/whitespace sequence
 442                   ;; Find the end.
 443                   ;; Skip one ASCII word, or encode continuous words
 444                   ;; in which all those contain non-ASCII characters.
 445                   (setq end nil)
 446                   (while (not (or end (eobp)))
 447                     (when (looking-at "[\000-\177]+")
 448                       (setq begin (point)
 449                             end (match-end 0))
 450                       (when (progn
 451                               (while (and (or (re-search-forward
 452                                                "[ \t\n]\\|\\Sw" end 'move)
 453                                               (setq end nil))
 454                                           (eq ?\\ (char-syntax (char-before))))
 455                                 ;; Skip backslash-quoted characters.
 456                                 (forward-char))
 457                               end)
 458                         (setq end (match-beginning 0))
 459                         (if rfc2047-encode-encoded-words
 460                             (progn
 461                               (goto-char begin)
 462                               (when (search-forward "=?" end 'move)
 463                                 (goto-char (match-beginning 0))
 464                                 (setq end nil)))
 465                           (goto-char end))))
 466                     ;; Where the value nil of `end' means there may be
 467                     ;; text to have to be encoded following the point.
 468                     ;; Otherwise, the point reached to the end of ASCII
 469                     ;; words separated by whitespace or a special char.
 470                     (unless end
 471                       (when (looking-at encodable-regexp)
 472                         (goto-char (setq begin (match-end 0)))
 473                         (while (and (looking-at "[ \t\n]+\\([^ \t\n]+\\)")
 474                                     (setq end (match-end 0))
 475                                     (progn
 476                                       (while (re-search-forward
 477                                               encodable-regexp end t))
 478                                       (< begin (point)))
 479                                     (goto-char begin)
 480                                     (or (not (re-search-forward "\\Sw" end t))
 481                                         (progn
 482                                           (goto-char (match-beginning 0))
 483                                           nil)))
 484                           (goto-char end))
 485                         (when (looking-at "[^ \t\n]+")
 486                           (setq end (match-end 0))
 487                           (if (re-search-forward "\\Sw+" end t)
 488                               ;; There are special characters better
 489                               ;; to be encoded so that MTAs may parse
 490                               ;; them safely.
 491                               (cond ((= end (point)))
 492                                     ((looking-at (concat "\\sw*\\("
 493                                                          encodable-regexp
 494                                                          "\\)"))
 495                                      (setq end nil))
 496                                     (t
 497                                      (goto-char (1- (match-end 0)))
 498                                      (unless (= (point) (match-beginning 0))
 499                                        ;; Separate encodable text and
 500                                        ;; delimiter.
 501                                        (insert " "))))
 502                             (goto-char end)
 503                             (skip-chars-forward " \t\n")
 504                             (if (and (looking-at "[^ \t\n]+")
 505                                      (string-match encodable-regexp
 506                                                    (match-string 0)))
 507                                 (setq end nil)
 508                               (goto-char end)))))))
 509                   (skip-chars-backward " \t\n")
 510                   (setq end (point))
 511                   (goto-char start)
 512                   (if (re-search-forward encodable-regexp end 'move)
 513                       (progn
 514                         (unless (memq (char-before start) '(nil ?\t ? ))
 515                           (if (progn
 516                                 (goto-char start)
 517                                 (skip-chars-backward "^ \t\n")
 518                                 (and (looking-at "\\Sw+")
 519                                      (= (match-end 0) start)))
 520                               ;; Also encode bogus delimiters.
 521                               (setq start (point))
 522                             ;; Separate encodable text and delimiter.
 523                             (goto-char start)
 524                             (insert " ")
 525                             (setq start (1+ start)
 526                                   end (1+ end))))
 527                         (rfc2047-encode start end)
 528                         (setq last-encoded t))
 529                     (setq last-encoded nil)))))
 530             (error
 531              (if (or debug-on-quit debug-on-error)
 532                  (signal (car err) (cdr err))
 533                (error "Invalid data for rfc2047 encoding: %s"
 534                       (mm-replace-in-string orig-text "[ \t\n]+" " "))))))))
 535     (rfc2047-fold-region b (point))
 536     (goto-char (point-max))))
 537
 538 (defun rfc2047-encode-string (string)
 539   "Encode words in STRING.
 540 By default, the string is treated as containing addresses (see
 541 `rfc2047-encoding-type')."
 542   (mm-with-multibyte-buffer
 543     (insert string)
 544     (rfc2047-encode-region (point-min) (point-max))
 545     (buffer-string)))
 546
 547 (defvar rfc2047-encode-max-chars 76
 548   "Maximum characters of each header line that contain encoded-words.
 549 If it is nil, encoded-words will not be folded.  Too small value may
 550 cause an error.  Don't change this for no particular reason.")
 551
 552 (defun rfc2047-encode-1 (column string cs encoder start crest tail
 553                                 &optional eword)
 554   "Subroutine used by `rfc2047-encode'."
 555   (cond ((string-equal string "")
 556          (or eword ""))
 557         ((not rfc2047-encode-max-chars)
 558          (concat start
 559                  (funcall encoder (if cs
 560                                       (mm-encode-coding-string string cs)
 561                                     string))
 562                  "?="))
 563         ((>= column rfc2047-encode-max-chars)
 564          (when eword
 565            (cond ((string-match "\n[ \t]+\\'" eword)
 566                   ;; Reomove a superfluous empty line.
 567                   (setq eword (substring eword 0 (match-beginning 0))))
 568                  ((string-match "(+\\'" eword)
 569                   ;; Break the line before the open parenthesis.
 570                   (setq crest (concat crest (match-string 0 eword))
 571                         eword (substring eword 0 (match-beginning 0))))))
 572          (rfc2047-encode-1 (length crest) string cs encoder start " " tail
 573                            (concat eword "\n" crest)))
 574         (t
 575          (let ((index 0)
 576                (limit (1- (length string)))
 577                (prev "")
 578                next len)
 579            (while (and prev
 580                        (<= index limit))
 581              (setq next (concat start
 582                                 (funcall encoder
 583                                          (if cs
 584                                              (mm-encode-coding-string
 585                                               (substring string 0 (1+ index))
 586                                               cs)
 587                                            (substring string 0 (1+ index))))
 588                                 "?=")
 589                    len (+ column (length next)))
 590              (if (> len rfc2047-encode-max-chars)
 591                  (setq next prev
 592                        prev nil)
 593                (if (or (< index limit)
 594                        (<= (+ len (or (string-match "\n" tail)
 595                                       (length tail)))
 596                            rfc2047-encode-max-chars))
 597                    (setq prev next
 598                          index (1+ index))
 599                  (if (string-match "\\`)+" tail)
 600                      ;; Break the line after the close parenthesis.
 601                      (setq tail (concat (substring tail 0 (match-end 0))
 602                                         "\n "
 603                                         (substring tail (match-end 0)))
 604                            prev next
 605                            index (1+ index))
 606                    (setq next prev
 607                          prev nil)))))
 608            (if (> index limit)
 609                (concat eword next tail)
 610              (if (= 0 index)
 611                  (if (and eword
 612                           (string-match "(+\\'" eword))
 613                      (setq crest (concat crest (match-string 0 eword))
 614                            eword (substring eword 0 (match-beginning 0)))
 615                    (setq eword (concat eword next)))
 616                (setq crest " "
 617                      eword (concat eword next)))
 618              (when (string-match "\n[ \t]+\\'" eword)
 619                ;; Reomove a superfluous empty line.
 620                (setq eword (substring eword 0 (match-beginning 0))))
 621              (rfc2047-encode-1 (length crest) (substring string index)
 622                                cs encoder start " " tail
 623                                (concat eword "\n" crest)))))))
 624
 625 (defun rfc2047-encode (b e)
 626   "Encode the word(s) in the region B to E.
 627 Point moves to the end of the region."
 628   (let ((mime-charset (or (mm-find-mime-charset-region b e) (list 'us-ascii)))
 629         cs encoding tail crest eword)
 630     (cond ((> (length mime-charset) 1)
 631            (error "Can't rfc2047-encode `%s'"
 632                   (buffer-substring-no-properties b e)))
 633           ((= (length mime-charset) 1)
 634            (setq mime-charset (car mime-charset)
 635                  cs (mm-charset-to-coding-system mime-charset))
 636            (unless (and (mm-multibyte-p)
 637                         (mm-coding-system-p cs))
 638              (setq cs nil))
 639            (save-restriction
 640              (narrow-to-region b e)
 641              (setq encoding
 642                    (or (cdr (assq mime-charset
 643                                   rfc2047-charset-encoding-alist))
 644                        ;; For the charsets that don't have a preferred
 645                        ;; encoding, choose the one that's shorter.
 646                        (if (eq (rfc2047-qp-or-base64) 'base64)
 647                            'B
 648                          'Q)))
 649              (widen)
 650              (goto-char e)
 651              (skip-chars-forward "^ \t\n")
 652              ;; `tail' may contain a close parenthesis.
 653              (setq tail (buffer-substring-no-properties e (point)))
 654              (goto-char b)
 655              (setq b (point-marker)
 656                    e (set-marker (make-marker) e))
 657              (rfc2047-fold-region (rfc2047-point-at-bol) b)
 658              (goto-char b)
 659              (skip-chars-backward "^ \t\n")
 660              (unless (= 0 (skip-chars-backward " \t"))
 661                ;; `crest' may contain whitespace and an open parenthesis.
 662                (setq crest (buffer-substring-no-properties (point) b)))
 663              (setq eword (rfc2047-encode-1
 664                           (- b (rfc2047-point-at-bol))
 665                           (mm-replace-in-string
 666                            (buffer-substring-no-properties b e)
 667                            "\n\\([ \t]?\\)" "\\1")
 668                           cs
 669                           (or (cdr (assq encoding
 670                                          rfc2047-encode-function-alist))
 671                               'identity)
 672                           (concat "=?" (downcase (symbol-name mime-charset))
 673                                   "?" (upcase (symbol-name encoding)) "?")
 674                           (or crest " ")
 675                           tail))
 676              (delete-region (if (eq (aref eword 0) ?\n)
 677                                 (if (bolp)
 678                                     ;; The line was folded before encoding.
 679                                     (1- (point))
 680                                   (point))
 681                               (goto-char b))
 682                             (+ e (length tail)))
 683              ;; `eword' contains `crest' and `tail'.
 684              (insert eword)
 685              (set-marker b nil)
 686              (set-marker e nil)
 687              (unless (or (/= 0 (length tail))
 688                          (eobp)
 689                          (looking-at "[ \t\n)]"))
 690                (insert " "))))
 691           (t
 692            (goto-char e)))))
 693
 694 (defun rfc2047-fold-field ()
 695   "Fold the current header field."
 696   (save-excursion
 697     (save-restriction
 698       (rfc2047-narrow-to-field)
 699       (rfc2047-fold-region (point-min) (point-max)))))
 700
 701 (defun rfc2047-fold-region (b e)
 702   "Fold long lines in region B to E."
 703   (save-restriction
 704     (narrow-to-region b e)
 705     (goto-char (point-min))
 706     (let ((break nil)
 707           (qword-break nil)
 708           (first t)
 709           (bol (save-restriction
 710                  (widen)
 711                  (rfc2047-point-at-bol))))
 712       (while (not (eobp))
 713         (when (and (or break qword-break)
 714                    (> (- (point) bol) 76))
 715           (goto-char (or break qword-break))
 716           (setq break nil
 717                 qword-break nil)
 718           (skip-chars-backward " \t")
 719           (if (looking-at "[ \t]")
 720               (insert ?\n)
 721             (insert "\n "))
 722           (setq bol (1- (point)))
 723           ;; Don't break before the first non-LWSP characters.
 724           (skip-chars-forward " \t")
 725           (unless (eobp)
 726             (forward-char 1)))
 727         (cond
 728          ((eq (char-after) ?\n)
 729           (forward-char 1)
 730           (setq bol (point)
 731                 break nil
 732                 qword-break nil)
 733           (skip-chars-forward " \t")
 734           (unless (or (eobp) (eq (char-after) ?\n))
 735             (forward-char 1)))
 736          ((eq (char-after) ?\r)
 737           (forward-char 1))
 738          ((memq (char-after) '(?  ?\t))
 739           (skip-chars-forward " \t")
 740           (unless first ;; Don't break just after the header name.
 741             (setq break (point))))
 742          ((not break)
 743           (if (not (looking-at "=\\?[^=]"))
 744               (if (eq (char-after) ?=)
 745                   (forward-char 1)
 746                 (skip-chars-forward "^ \t\n\r="))
 747             ;; Don't break at the start of the field.
 748             (unless (= (point) b)
 749               (setq qword-break (point)))
 750             (skip-chars-forward "^ \t\n\r")))
 751          (t
 752           (skip-chars-forward "^ \t\n\r")))
 753         (setq first nil))
 754       (when (and (or break qword-break)
 755                  (> (- (point) bol) 76))
 756         (goto-char (or break qword-break))
 757         (setq break nil
 758               qword-break nil)
 759         (if (or (> 0 (skip-chars-backward " \t"))
 760                 (looking-at "[ \t]"))
 761             (insert ?\n)
 762           (insert "\n "))
 763         (setq bol (1- (point)))
 764         ;; Don't break before the first non-LWSP characters.
 765         (skip-chars-forward " \t")
 766         (unless (eobp)
 767           (forward-char 1))))))
 768
 769 (defun rfc2047-unfold-field ()
 770   "Fold the current line."
 771   (save-excursion
 772     (save-restriction
 773       (rfc2047-narrow-to-field)
 774       (rfc2047-unfold-region (point-min) (point-max)))))
 775
 776 (defun rfc2047-unfold-region (b e)
 777   "Unfold lines in region B to E."
 778   (save-restriction
 779     (narrow-to-region b e)
 780     (goto-char (point-min))
 781     (let ((bol (save-restriction
 782                  (widen)
 783                  (rfc2047-point-at-bol)))
 784           (eol (rfc2047-point-at-eol)))
 785       (forward-line 1)
 786       (while (not (eobp))
 787         (if (and (looking-at "[ \t]")
 788                  (< (- (rfc2047-point-at-eol) bol) 76))
 789             (delete-region eol (progn
 790                                  (goto-char eol)
 791                                  (skip-chars-forward "\r\n")
 792                                  (point)))
 793           (setq bol (rfc2047-point-at-bol)))
 794         (setq eol (rfc2047-point-at-eol))
 795         (forward-line 1)))))
 796
 797 (defun rfc2047-b-encode-string (string)
 798   "Base64-encode the header contained in STRING."
 799   (base64-encode-string string t))
 800
 801 (defun rfc2047-q-encode-string (string)
 802   "Quoted-printable-encode the header in STRING."
 803   (mm-with-unibyte-buffer
 804     (insert string)
 805     (quoted-printable-encode-region
 806      (point-min) (point-max) nil
 807      ;; = (\075), _ (\137), ? (\077) are used in the encoded word.
 808      ;; Avoid using 8bit characters.
 809      ;; This list excludes `especials' (see the RFC2047 syntax),
 810      ;; meaning that some characters in non-structured fields will
 811      ;; get encoded when they con't need to be.  The following is
 812      ;; what it used to be.
 813      ;;;  ;; Equivalent to "^\000-\007\011\013\015-\037\200-\377=_?"
 814      ;;;  "\010\012\014\040-\074\076\100-\136\140-\177")
 815      "-\b\n\f !#-'*+0-9A-Z\\^`-~\d")
 816     (subst-char-in-region (point-min) (point-max) ?  ?_)
 817     (buffer-string)))
 818
 819 (defun rfc2047-encode-parameter (param value)
 820   "Return and PARAM=VALUE string encoded in the RFC2047-like style.
 821 This is a replacement for the `rfc2231-encode-string' function.
 822
 823 When attaching files as MIME parts, we should use the RFC2231 encoding
 824 to specify the file names containing non-ASCII characters.  However,
 825 many mail softwares don't support it in practice and recipients won't
 826 be able to extract files with correct names.  Instead, the RFC2047-like
 827 encoding is acceptable generally.  This function provides the very
 828 RFC2047-like encoding, resigning to such a regrettable trend.  To use
 829 it, put the following line in your ~/.gnus.el file:
 830
 831 \(defalias 'mail-header-encode-parameter 'rfc2047-encode-parameter)
 832 "
 833   (let* ((rfc2047-encoding-type 'mime)
 834          (rfc2047-encode-max-chars nil)
 835          (string (rfc2047-encode-string value)))
 836     (if (string-match (concat "[" ietf-drums-tspecials "]") string)
 837         (format "%s=%S" param string)
 838       (concat param "=" string))))
 839
 840 ;;;
 841 ;;; Functions for decoding RFC2047 messages
 842 ;;;
 843
 844 (eval-and-compile
 845   (defconst rfc2047-encoded-word-regexp
 846     "=\\?\\([^][\000-\040()<>@,\;:*\\\"/?.=]+\\)\\(\\*[^?]+\\)?\
 847 \\?\\(B\\|Q\\)\\?\\([!->@-~ ]*\\)\\?="))
 848
 849 (defvar rfc2047-quote-decoded-words-containing-tspecials nil
 850   "If non-nil, quote decoded words containing special characters.")
 851
 852 (defvar rfc2047-allow-incomplete-encoded-text t
 853   "*Non-nil means allow incomplete encoded-text in successive encoded-words.
 854 Dividing of encoded-text in the place other than character boundaries
 855 violates RFC2047 section 5, while we have a capability to decode it.
 856 If it is non-nil, the decoder will decode B- or Q-encoding in each
 857 encoded-word, concatenate them, and decode it by charset.  Otherwise,
 858 the decoder will fully decode each encoded-word before concatenating
 859 them.")
 860
 861 (defun rfc2047-strip-backslashes-in-quoted-strings ()
 862   "Strip backslashes in quoted strings.  `\\\"' and `\\\\' remain."
 863   (goto-char (point-min))
 864   (let (beg)
 865     (with-syntax-table (standard-syntax-table)
 866       (while (search-forward "\"" nil t)
 867         (unless (eq (char-before) ?\\)
 868           (setq beg (match-end 0))
 869           (goto-char (match-beginning 0))
 870           (condition-case nil
 871               (progn
 872                 (forward-sexp)
 873                 (save-restriction
 874                   (narrow-to-region beg (1- (point)))
 875                   (goto-char beg)
 876                   (while (search-forward "\\" nil 'move)
 877                     (unless (memq (char-after) '(?\" ?\\))
 878                       (delete-backward-char 1))
 879                     (forward-char)))
 880                 (forward-char))
 881             (error
 882              (goto-char beg))))))))
 883
 884 (defun rfc2047-charset-to-coding-system (charset)
 885   "Return coding-system corresponding to MIME CHARSET.
 886 If your Emacs implementation can't decode CHARSET, return nil."
 887   (when (stringp charset)
 888     (setq charset (intern (downcase charset))))
 889   (when (or (not charset)
 890             (eq 'gnus-all mail-parse-ignored-charsets)
 891             (memq 'gnus-all mail-parse-ignored-charsets)
 892             (memq charset mail-parse-ignored-charsets))
 893     (setq charset mail-parse-charset))
 894   (let ((cs (mm-charset-to-coding-system charset)))
 895     (cond ((eq cs 'ascii)
 896            (setq cs (or (mm-charset-to-coding-system mail-parse-charset)
 897                         'raw-text)))
 898           ((mm-coding-system-p cs))
 899           ((and charset
 900                 (listp mail-parse-ignored-charsets)
 901                 (memq 'gnus-unknown mail-parse-ignored-charsets))
 902            (setq cs (mm-charset-to-coding-system mail-parse-charset))))
 903     (if (eq cs 'ascii)
 904         'raw-text
 905       cs)))
 906
 907 (defun rfc2047-decode-encoded-words (words)
 908   "Decode successive encoded-words in WORDS and return a decoded string.
 909 Each element of WORDS looks like (CHARSET ENCODING ENCODED-TEXT
 910 ENCODED-WORD)."
 911   (let (word charset cs encoding text rest)
 912     (while words
 913       (setq word (pop words))
 914       (if (and (setq cs (rfc2047-charset-to-coding-system
 915                          (setq charset (car word))))
 916                (condition-case code
 917                    (cond ((char-equal ?B (nth 1 word))
 918                           (setq text (base64-decode-string
 919                                       (rfc2047-pad-base64 (nth 2 word)))))
 920                          ((char-equal ?Q (nth 1 word))
 921                           (setq text (quoted-printable-decode-string
 922                                       (mm-subst-char-in-string
 923                                        ?_ ?  (nth 2 word) t)))))
 924                  (error
 925                   (message "%s" (error-message-string code))
 926                   nil)))
 927           (if (and rfc2047-allow-incomplete-encoded-text
 928                    (eq cs (caar rest)))
 929               ;; Concatenate text of which the charset is the same.
 930               (setcdr (car rest) (concat (cdar rest) text))
 931             (push (cons cs text) rest))
 932         ;; Don't decode encoded-word.
 933         (push (cons nil (nth 3 word)) rest)))
 934     (while rest
 935       (setq words (concat
 936                    (or (and (setq cs (caar rest))
 937                             (condition-case code
 938                                 (mm-decode-coding-string (cdar rest) cs)
 939                               (error
 940                                (message "%s" (error-message-string code))
 941                                nil)))
 942                        (concat (when (cdr rest) " ")
 943                                (cdar rest)
 944                                (when (and words
 945                                           (not (eq (string-to-char words) ? )))
 946                                  " ")))
 947                    words)
 948             rest (cdr rest)))
 949     words))
 950
 951 ;; Fixme: This should decode in place, not cons intermediate strings.
 952 ;; Also check whether it needs to worry about delimiting fields like
 953 ;; encoding.
 954
 955 ;; In fact it's reported that (invalid) encoding of mailboxes in
 956 ;; addr-specs is in use, so delimiting fields might help.  Probably
 957 ;; not decoding a word which isn't properly delimited is good enough
 958 ;; and worthwhile (is it more correct or not?), e.g. something like
 959 ;; `=?iso-8859-1?q?foo?=@'.
 960
 961 (defun rfc2047-decode-region (start end &optional address-mime)
 962   "Decode MIME-encoded words in region between START and END.
 963 If ADDRESS-MIME is non-nil, strip backslashes which precede characters
 964 other than `\"' and `\\' in quoted strings."
 965   (interactive "r")
 966   (let ((case-fold-search t)
 967         (eword-regexp (eval-when-compile
 968                         ;; Ignore whitespace between encoded-words.
 969                         (concat "[\n\t ]*\\(" rfc2047-encoded-word-regexp
 970                                 "\\)")))
 971         b e match words)
 972     (save-excursion
 973       (save-restriction
 974         (narrow-to-region start end)
 975         (when address-mime
 976           (rfc2047-strip-backslashes-in-quoted-strings))
 977         (goto-char (setq b start))
 978         ;; Look for the encoded-words.
 979         (while (setq match (re-search-forward eword-regexp nil t))
 980           (setq e (match-beginning 1)
 981                 end (match-end 0)
 982                 words nil)
 983           (while match
 984             (push (list (match-string 2) ;; charset
 985                         (char-after (match-beginning 4)) ;; encoding
 986                         (match-string 5) ;; encoded-text
 987                         (match-string 1)) ;; encoded-word
 988                   words)
 989             ;; Look for the subsequent encoded-words.
 990             (when (setq match (looking-at eword-regexp))
 991               (goto-char (setq end (match-end 0)))))
 992           ;; Replace the encoded-words with the decoded one.
 993           (delete-region e end)
 994           (insert (rfc2047-decode-encoded-words (nreverse words)))
 995           (save-restriction
 996             (narrow-to-region e (point))
 997             (goto-char e)
 998             ;; Remove newlines between decoded words, though such
 999             ;; things essentially must not be there.
1000             (while (re-search-forward "[\n\r]+" nil t)
1001               (replace-match " "))
1002             ;; Quote decoded words if there are special characters
1003             ;; which might violate RFC2822.
1004             (when (and rfc2047-quote-decoded-words-containing-tspecials
1005                        (let ((regexp (car (rassq
1006                                            'address-mime
1007                                            rfc2047-header-encoding-alist))))
1008                          (when regexp
1009                            (save-restriction
1010                              (widen)
1011                              (beginning-of-line)
1012                              (while (and (memq (char-after) '(?  ?\t))
1013                                          (zerop (forward-line -1))))
1014                              (looking-at regexp)))))
1015               (let (quoted)
1016                 (goto-char e)
1017                 (skip-chars-forward " \t")
1018                 (setq start (point))
1019                 (setq quoted (eq (char-after) ?\"))
1020                 (goto-char (point-max))
1021                 (skip-chars-backward " \t")
1022                 (if (setq quoted (and quoted
1023                                       (> (point) (1+ start))
1024                                       (eq (char-before) ?\")))
1025                     (progn
1026                       (backward-char)
1027                       (setq start (1+ start)
1028                             end (point-marker)))
1029                   (setq end (point-marker)))
1030                 (goto-char start)
1031                 (while (search-forward "\"" end t)
1032                   (when (prog2
1033                             (backward-char)
1034                             (zerop (% (skip-chars-backward "\\\\") 2))
1035                           (goto-char (match-beginning 0)))
1036                     (insert "\\"))
1037                   (forward-char))
1038                 (when (and (not quoted)
1039                            (progn
1040                              (goto-char start)
1041                              (re-search-forward
1042                               (concat "[" ietf-drums-tspecials "]")
1043                               end t)))
1044                   (goto-char start)
1045                   (insert "\"")
1046                   (goto-char end)
1047                   (insert "\""))
1048                 (set-marker end nil)))
1049             (goto-char (point-max)))
1050           (when (and (mm-multibyte-p)
1051                      mail-parse-charset
1052                      (not (eq mail-parse-charset 'us-ascii))
1053                      (not (eq mail-parse-charset 'gnus-decoded)))
1054             (mm-decode-coding-region b e mail-parse-charset))
1055           (setq b (point)))
1056         (when (and (mm-multibyte-p)
1057                    mail-parse-charset
1058                    (not (eq mail-parse-charset 'us-ascii))
1059                    (not (eq mail-parse-charset 'gnus-decoded)))
1060           (mm-decode-coding-region b (point-max) mail-parse-charset))))))
1061
1062 (defun rfc2047-decode-address-region (start end)
1063   "Decode MIME-encoded words in region between START and END.
1064 Backslashes which precede characters other than `\"' and `\\' in quoted
1065 strings are stripped."
1066   (rfc2047-decode-region start end t))
1067
1068 (defun rfc2047-decode-string (string &optional address-mime)
1069   "Decode MIME-encoded STRING and return the result.
1070 If ADDRESS-MIME is non-nil, strip backslashes which precede characters
1071 other than `\"' and `\\' in quoted strings."
1072   (let ((m (mm-multibyte-p)))
1073     (if (string-match "=\\?" string)
1074         (with-temp-buffer
1075           ;; Fixme: This logic is wrong, but seems to be required by
1076           ;; Gnus summary buffer generation.  The value of `m' depends
1077           ;; on the current buffer, not global multibyteness or that
1078           ;; of the string.  Also the string returned should always be
1079           ;; multibyte in a multibyte session, i.e. the buffer should
1080           ;; be multibyte before `buffer-string' is called.
1081           (when m
1082             (mm-enable-multibyte))
1083           (insert string)
1084           (inline
1085             (rfc2047-decode-region (point-min) (point-max) address-mime))
1086           (buffer-string))
1087       (when address-mime
1088         (setq string
1089               (with-temp-buffer
1090                 (when (mm-multibyte-string-p string)
1091                   (mm-enable-multibyte))
1092                 (insert string)
1093                 (rfc2047-strip-backslashes-in-quoted-strings)
1094                 (buffer-string))))
1095       ;; Fixme: As above, `m' here is inappropriate.
1096       (if (and m
1097                mail-parse-charset
1098                (not (eq mail-parse-charset 'us-ascii))
1099                (not (eq mail-parse-charset 'gnus-decoded)))
1100           ;; `decode-coding-string' in Emacs offers a third optional
1101           ;; arg NOCOPY to avoid consing a new string if the decoding
1102           ;; is "trivial".  Unfortunately it currently doesn't
1103           ;; consider anything else than a `nil' coding system
1104           ;; trivial.
1105           ;; `rfc2047-decode-string' is called multiple times for each
1106           ;; article during summary buffer generation, and we really
1107           ;; want to avoid unnecessary consing.  So we bypass
1108           ;; `decode-coding-string' if the string is purely ASCII.
1109           (if (and (fboundp 'detect-coding-string)
1110                    ;; string is purely ASCII
1111                    (eq (detect-coding-string string t) 'undecided))
1112               string
1113             (mm-decode-coding-string string mail-parse-charset))
1114         (mm-string-as-multibyte string)))))
1115
1116 (defun rfc2047-decode-address-string (string)
1117   "Decode MIME-encoded STRING and return the result.
1118 Backslashes which precede characters other than `\"' and `\\' in quoted
1119 strings are stripped."
1120   (rfc2047-decode-string string t))
1121
1122 (defun rfc2047-pad-base64 (string)
1123   "Pad STRING to quartets."
1124   ;; Be more liberal to accept buggy base64 strings. If
1125   ;; base64-decode-string accepts buggy strings, this function could
1126   ;; be aliased to identity.
1127   (if (= 0 (mod (length string) 4))
1128       string
1129     (when (string-match "=+$" string)
1130       (setq string (substring string 0 (match-beginning 0))))
1131     (case (mod (length string) 4)
1132       (0 string)
1133       (1 string) ;; Error, don't pad it.
1134       (2 (concat string "=="))
1135       (3 (concat string "=")))))
1136
1137 (provide 'rfc2047)
1138
1139 ;;; arch-tag: a07fe3d4-22b5-4c4a-bd89-b1f82d5d36f6
1140 ;;; rfc2047.el ends here