;;; mm-encode.el --- Functions for encoding MIME things
;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
;; 2005, 2006 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <email@example.com>
;; MORIOKA Tomohiko <firstname.lastname@example.org>
;; 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
;; along with GNU Emacs; see the file COPYING. If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.
(eval-when-compile (require 'cl))
(autoload 'mm-body-7-or-8 "mm-bodies")
(autoload 'mm-long-lines-p "mm-bodies"))
"Alist of regexps that match MIME types and their encodings.
If the encoding is `qp-or-base64', then either quoted-printable
or base64 will be used, depending on what is more efficient.
`qp-or-base64' has another effect. It will fold long lines so that
MIME parts may not be broken by MTA. So do `quoted-printable' and
Note: It affects body encoding only when a part is a raw forwarded
message (which will be made by `gnus-summary-mail-forward' with the
arg 2 for example) or is neither the text/* type nor the message/*
type. Even though in those cases, you can use the `encoding' MML tag
to specify encoding of non-ASCII MIME parts."
:type '(repeat (list (regexp :tag "MIME type")
(choice :tag "encoding"
(defvar mm-use-ultra-safe-encoding nil
"If non-nil, use encodings aimed at Procrustean bed survival.
This means that textual parts are encoded as quoted-printable if they
contain lines longer than 76 characters or starting with \"From \" in
the body. Non-7bit encodings (8bit, binary) are generally disallowed.
This is to reduce the probability that a broken MTA or MDA changes the
This variable should never be set directly, but bound before a call to
`mml-generate-mime' or similar functions.")
(defun mm-insert-rfc822-headers (charset encoding)
"Insert text/plain headers with CHARSET and ENCODING."
(insert "MIME-Version: 1.0\n")
(insert "Content-Type: text/plain; charset="
(mail-quote-string (downcase (symbol-name charset))) "\n")
(insert "Content-Transfer-Encoding: "
(downcase (symbol-name encoding)) "\n"))
(defun mm-insert-multipart-headers ()
"Insert multipart/mixed headers."
(let ((boundary "=-=-="))
(insert "MIME-Version: 1.0\n")
(insert "Content-Type: multipart/mixed; boundary=\"" boundary "\"\n")
(defun mm-default-file-encoding (file)
"Return a default encoding for FILE."
(if (not (string-match "\\.[^.]+$" file))
(mailcap-extension-to-mime (match-string 0 file))))
(defun mm-safer-encoding (encoding)
"Return an encoding similar to ENCODING but safer than it."
((eq encoding '7bit) '7bit) ;; 7bit is considered safe.
((memq encoding '(8bit quoted-printable)) 'quoted-printable)
;; The remaining encodings are binary and base64 (and perhaps some
;; non-standard ones), which are both turned into base64.
(defun mm-encode-content-transfer-encoding (encoding &optional type)
"Encode the current buffer with ENCODING for MIME type TYPE.
ENCODING can be: nil (do nothing); one of `quoted-printable', `base64';
`7bit', `8bit' or `binary' (all do nothing); a function to do the encoding."
((eq encoding 'quoted-printable)
;; This used to try to make a multibyte buffer unibyte. That's
;; completely wrong, since you'd get QP-encoded emacs-mule. If
;; this gets run on multibyte text it's an error that needs
;; fixing, and the encoding function will signal an error.
;; Likewise base64 below.
(quoted-printable-encode-region (point-min) (point-max) t))
((eq encoding 'base64)
(when (string-match "\\`text/" type)
(while (search-forward "\n" nil t)
(replace-match "\r\n" t t)))
(base64-encode-region (point-min) (point-max)))
((memq encoding '(7bit 8bit binary))
;; Do nothing.
;; Do nothing.
;; Fixme: Ignoring errors here looks bogus.
(ignore-errors (funcall encoding (point-min) (point-max))))
(error "Unknown encoding %s" encoding))))
(defun mm-encode-buffer (type)
"Encode the buffer which contains data of MIME type TYPE.
TYPE is a string or a list of the components.
The encoding used is returned."
(let* ((mime-type (if (stringp type) type (car type)))
(or (and (listp type)
(cadr (assq 'encoding type)))
;; We force buffers that are 7bit to be unencoded, no matter
;; what the preferred encoding is.
;; Only if the buffers don't contain lone lines.
(when (and (eq bits '7bit) (not (mm-long-lines-p 76)))
(setq encoding bits))
(mm-encode-content-transfer-encoding encoding mime-type)
(defun mm-insert-headers (type encoding &optional file)
"Insert headers for TYPE."
(insert "Content-Type: " type)
(insert ";\n\tname=\"" (file-name-nondirectory file) "\""))
(insert (format "Content-Transfer-Encoding: %s\n" encoding))
(insert "Content-Disposition: inline")
(insert ";\n\tfilename=\"" (file-name-nondirectory file) "\""))
(defun mm-content-transfer-encoding (type)
"Return a CTE suitable for TYPE to encode the current buffer."
(let ((rules mm-content-transfer-encoding-defaults))
(when (string-match (caar rules) type)
(if (eq (cadr (car rules)) 'qp-or-base64)
(cadr (car rules)))))
(defun mm-qp-or-base64 ()
"Return the type with which to encode the buffer.
This is either `base64' or `quoted-printable'."
(if (equal mm-use-ultra-safe-encoding '(sign . "pgp"))
;; perhaps not always accurate?
(let ((limit (min (point-max) (+ 2000 (point-min))))
(skip-chars-forward "\x20-\x7f\r\n\t" limit)
(while (< (point) limit)
(skip-chars-forward "\x20-\x7f\r\n\t" limit))
(if (or (< (* 6 n8bit) (- limit (point-min)))
;; Don't base64, say, a short line with a single
;; non-ASCII char when splitting parts by charset.
(= n8bit 1))
;;; arch-tag: 7d01bba4-d469-4851-952b-dc863f84ed66
;;; mm-encode.el ends here