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213 lines
7.8 KiB
EmacsLisp
213 lines
7.8 KiB
EmacsLisp
;;; mm-encode.el --- Functions for encoding MIME things
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;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
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;; 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
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;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
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;; MORIOKA Tomohiko <morioka@jaist.ac.jp>
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:
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;;; Code:
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(eval-when-compile (require 'cl))
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(require 'mail-parse)
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(require 'mailcap)
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(autoload 'mm-body-7-or-8 "mm-bodies")
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(autoload 'mm-long-lines-p "mm-bodies")
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(defcustom mm-content-transfer-encoding-defaults
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'(("text/x-patch" 8bit)
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("text/.*" qp-or-base64)
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("message/rfc822" 8bit)
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("application/emacs-lisp" qp-or-base64)
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("application/x-emacs-lisp" qp-or-base64)
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("application/x-patch" qp-or-base64)
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(".*" base64))
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"Alist of regexps that match MIME types and their encodings.
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If the encoding is `qp-or-base64', then either quoted-printable
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or base64 will be used, depending on what is more efficient.
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`qp-or-base64' has another effect. It will fold long lines so that
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MIME parts may not be broken by MTA. So do `quoted-printable' and
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`base64'.
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Note: It affects body encoding only when a part is a raw forwarded
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message (which will be made by `gnus-summary-mail-forward' with the
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arg 2 for example) or is neither the text/* type nor the message/*
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type. Even though in those cases, you can use the `encoding' MML tag
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to specify encoding of non-ASCII MIME parts."
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:type '(repeat (list (regexp :tag "MIME type")
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(choice :tag "encoding"
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(const 7bit)
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(const 8bit)
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(const qp-or-base64)
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(const quoted-printable)
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(const base64))))
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:group 'mime)
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(defvar mm-use-ultra-safe-encoding nil
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"If non-nil, use encodings aimed at Procrustean bed survival.
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This means that textual parts are encoded as quoted-printable if they
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contain lines longer than 76 characters or starting with \"From \" in
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the body. Non-7bit encodings (8bit, binary) are generally disallowed.
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This is to reduce the probability that a broken MTA or MDA changes the
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message.
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This variable should never be set directly, but bound before a call to
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`mml-generate-mime' or similar functions.")
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(defun mm-insert-rfc822-headers (charset encoding)
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"Insert text/plain headers with CHARSET and ENCODING."
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(insert "MIME-Version: 1.0\n")
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(insert "Content-Type: text/plain; charset="
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(mail-quote-string (downcase (symbol-name charset))) "\n")
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(insert "Content-Transfer-Encoding: "
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(downcase (symbol-name encoding)) "\n"))
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(defun mm-insert-multipart-headers ()
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"Insert multipart/mixed headers."
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(let ((boundary "=-=-="))
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(insert "MIME-Version: 1.0\n")
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(insert "Content-Type: multipart/mixed; boundary=\"" boundary "\"\n")
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boundary))
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(defun mm-default-file-encoding (file)
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"Return a default encoding for FILE."
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(if (not (string-match "\\.[^.]+$" file))
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"application/octet-stream"
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(mailcap-extension-to-mime (match-string 0 file))))
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(defun mm-safer-encoding (encoding &optional type)
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"Return an encoding similar to ENCODING but safer than it."
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(cond
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((eq encoding '7bit) '7bit) ;; 7bit is considered safe.
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((memq encoding '(8bit quoted-printable))
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;; According to RFC2046, 5.2.1, RFC822 Subtype, "quoted-printable" is not
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;; a valid encoding for message/rfc822:
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;; No encoding other than "7bit", "8bit", or "binary" is permitted for the
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;; body of a "message/rfc822" entity.
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(if (string= type "message/rfc822") '8bit 'quoted-printable))
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;; The remaining encodings are binary and base64 (and perhaps some
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;; non-standard ones), which are both turned into base64.
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(t (if (string= type "message/rfc822") 'binary 'base64))))
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(defun mm-encode-content-transfer-encoding (encoding &optional type)
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"Encode the current buffer with ENCODING for MIME type TYPE.
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ENCODING can be: nil (do nothing); one of `quoted-printable', `base64';
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`7bit', `8bit' or `binary' (all do nothing); a function to do the encoding."
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(cond
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((eq encoding 'quoted-printable)
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;; This used to try to make a multibyte buffer unibyte. That's
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;; completely wrong, since you'd get QP-encoded emacs-mule. If
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;; this gets run on multibyte text it's an error that needs
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;; fixing, and the encoding function will signal an error.
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;; Likewise base64 below.
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(quoted-printable-encode-region (point-min) (point-max) t))
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((eq encoding 'base64)
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(when (string-match "\\`text/" type)
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(goto-char (point-min))
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(while (search-forward "\n" nil t)
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(replace-match "\r\n" t t)))
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(base64-encode-region (point-min) (point-max)))
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((memq encoding '(7bit 8bit binary))
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;; Do nothing.
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)
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((null encoding)
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;; Do nothing.
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)
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;; Fixme: Ignoring errors here looks bogus.
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((functionp encoding)
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(ignore-errors (funcall encoding (point-min) (point-max))))
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(t
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(error "Unknown encoding %s" encoding))))
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(defun mm-encode-buffer (type)
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"Encode the buffer which contains data of MIME type TYPE.
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TYPE is a string or a list of the components.
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The encoding used is returned."
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(let* ((mime-type (if (stringp type) type (car type)))
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(encoding
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(or (and (listp type)
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(cadr (assq 'encoding type)))
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(mm-content-transfer-encoding mime-type)))
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(bits (mm-body-7-or-8)))
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;; We force buffers that are 7bit to be unencoded, no matter
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;; what the preferred encoding is.
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;; Only if the buffers don't contain lone lines.
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(when (and (eq bits '7bit) (not (mm-long-lines-p 76)))
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(setq encoding bits))
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(mm-encode-content-transfer-encoding encoding mime-type)
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encoding))
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(defun mm-insert-headers (type encoding &optional file)
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"Insert headers for TYPE."
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(insert "Content-Type: " type)
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(when file
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(insert ";\n\tname=\"" (file-name-nondirectory file) "\""))
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(insert "\n")
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(insert (format "Content-Transfer-Encoding: %s\n" encoding))
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(insert "Content-Disposition: inline")
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(when file
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(insert ";\n\tfilename=\"" (file-name-nondirectory file) "\""))
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(insert "\n")
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(insert "\n"))
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(defun mm-content-transfer-encoding (type)
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"Return a CTE suitable for TYPE to encode the current buffer."
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(let ((rules mm-content-transfer-encoding-defaults))
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(catch 'found
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(while rules
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(when (string-match (caar rules) type)
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(throw 'found
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(let ((encoding
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(if (eq (cadr (car rules)) 'qp-or-base64)
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(mm-qp-or-base64)
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(cadr (car rules)))))
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(if mm-use-ultra-safe-encoding
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(mm-safer-encoding encoding type)
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encoding))))
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(pop rules)))))
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(defun mm-qp-or-base64 ()
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"Return the type with which to encode the buffer.
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This is either `base64' or `quoted-printable'."
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(if (equal mm-use-ultra-safe-encoding '(sign . "pgp"))
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;; perhaps not always accurate?
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'quoted-printable
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(save-excursion
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(let ((limit (min (point-max) (+ 2000 (point-min))))
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(n8bit 0))
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(goto-char (point-min))
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(skip-chars-forward "\x20-\x7f\r\n\t" limit)
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(while (< (point) limit)
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(incf n8bit)
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(forward-char 1)
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(skip-chars-forward "\x20-\x7f\r\n\t" limit))
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(if (or (< (* 6 n8bit) (- limit (point-min)))
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;; Don't base64, say, a short line with a single
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;; non-ASCII char when splitting parts by charset.
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(= n8bit 1))
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'quoted-printable
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'base64)))))
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(provide 'mm-encode)
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;; arch-tag: 7d01bba4-d469-4851-952b-dc863f84ed66
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;;; mm-encode.el ends here
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