1;;; utf7.el --- UTF-7 encoding/decoding for Emacs -*-coding: iso-8859-1;-*- 2 3;; Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 4;; 2005, 2006, 2007 Free Software Foundation, Inc. 5 6;; Author: Jon K Hellan <hellan@acm.org> 7;; Maintainer: bugs@gnus.org 8;; Keywords: mail 9 10;; This file is part of GNU Emacs. 11 12;; GNU Emacs is free software; you can redistribute it and/or modify 13;; it under the terms of the GNU General Public License as published by 14;; the Free Software Foundation; either version 2, or (at your option) 15;; any later version. 16 17;; GNU Emacs is distributed in the hope that it will be useful, 18;; but WITHOUT ANY WARRANTY; without even the implied warranty of 19;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20;; GNU General Public License for more details. 21 22;; You should have received a copy of the GNU General Public License 23;; along with GNU Emacs; see the file COPYING. If not, write to 24;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 25;; Boston, MA 02110-1301, USA. 26 27;;; Commentary: 28 29;; UTF-7 - A Mail-Safe Transformation Format of Unicode - RFC 2152 30;; This is a transformation format of Unicode that contains only 7-bit 31;; ASCII octets and is intended to be readable by humans in the limiting 32;; case that the document consists of characters from the US-ASCII 33;; repertoire. 34;; In short, runs of characters outside US-ASCII are encoded as base64 35;; inside delimiters. 36;; A variation of UTF-7 is specified in IMAP 4rev1 (RFC 2060) as the way 37;; to represent characters outside US-ASCII in mailbox names in IMAP. 38;; This library supports both variants, but the IMAP variation was the 39;; reason I wrote it. 40;; The routines convert UTF-7 -> UTF-16 (16 bit encoding of Unicode) 41;; -> current character set, and vice versa. 42;; However, until Emacs supports Unicode, the only Emacs character set 43;; supported here is ISO-8859.1, which can trivially be converted to/from 44;; Unicode. 45;; When decoding results in a character outside the Emacs character set, 46;; an error is thrown. It is up to the application to recover. 47 48;; UTF-7 should be done by providing a coding system. Mule-UCS does 49;; already, but I don't know if it does the IMAP version and it's not 50;; clear whether that should really be a coding system. The UTF-16 51;; part of the conversion can be done with coding systems available 52;; with Mule-UCS or some versions of Emacs. Unfortunately these were 53;; done wrongly (regarding handling of byte-order marks and how the 54;; variants were named), so we don't have a consistent name for the 55;; necessary coding system. The code below doesn't seem to DTRT 56;; generally. E.g.: 57;; 58;; (utf7-encode "a+�") 59;; => "a+ACsAow-" 60;; 61;; $ echo "a+�"|iconv -f iso-8859-1 -t utf-7 62;; a+-+AKM 63;; 64;; -- fx 65 66 67;;; Code: 68 69(require 'base64) 70(eval-when-compile (require 'cl)) 71(require 'mm-util) 72 73(defconst utf7-direct-encoding-chars " -%'-*,-[]-}" 74 "Character ranges which do not need escaping in UTF-7.") 75 76(defconst utf7-imap-direct-encoding-chars 77 (concat utf7-direct-encoding-chars "+\\~") 78 "Character ranges which do not need escaping in the IMAP variant of UTF-7.") 79 80(defconst utf7-utf-16-coding-system 81 (cond ((mm-coding-system-p 'utf-16-be-no-signature) ; Mule-UCS 82 'utf-16-be-no-signature) 83 ((and (mm-coding-system-p 'utf-16-be) ; Emacs 21.3, Emacs 22 84 ;; Avoid versions with BOM. 85 (= 2 (length (encode-coding-string "a" 'utf-16-be)))) 86 'utf-16-be) 87 ((mm-coding-system-p 'utf-16-be-nosig) ; ? 88 'utf-16-be-nosig)) 89 "Coding system which encodes big endian UTF-16 without a BOM signature.") 90 91(defsubst utf7-imap-get-pad-length (len modulus) 92 "Return required length of padding for IMAP modified base64 fragment." 93 (mod (- len) modulus)) 94 95(defun utf7-encode-internal (&optional for-imap) 96 "Encode text in (temporary) buffer as UTF-7. 97Use IMAP modification if FOR-IMAP is non-nil." 98 (let ((start (point-min)) 99 (end (point-max))) 100 (narrow-to-region start end) 101 (goto-char start) 102 (let* ((esc-char (if for-imap ?& ?+)) 103 (direct-encoding-chars 104 (if for-imap utf7-imap-direct-encoding-chars 105 utf7-direct-encoding-chars)) 106 (not-direct-encoding-chars (concat "^" direct-encoding-chars))) 107 (while (not (eobp)) 108 (skip-chars-forward direct-encoding-chars) 109 (unless (eobp) 110 (insert esc-char) 111 (let ((p (point)) 112 (fc (following-char)) 113 (run-length 114 (skip-chars-forward not-direct-encoding-chars))) 115 (if (and (= fc esc-char) 116 (= run-length 1)) ; Lone esc-char? 117 (delete-backward-char 1) ; Now there's one too many 118 (utf7-fragment-encode p (point) for-imap)) 119 (insert "-"))))))) 120 121(defun utf7-fragment-encode (start end &optional for-imap) 122 "Encode text from START to END in buffer as UTF-7 escape fragment. 123Use IMAP modification if FOR-IMAP is non-nil." 124 (save-restriction 125 (narrow-to-region start end) 126 (funcall (utf7-get-u16char-converter 'to-utf-16)) 127 (mm-with-unibyte-current-buffer 128 (base64-encode-region start (point-max))) 129 (goto-char start) 130 (let ((pm (point-max))) 131 (when for-imap 132 (while (search-forward "/" nil t) 133 (replace-match ","))) 134 (skip-chars-forward "^= \t\n" pm) 135 (delete-region (point) pm)))) 136 137(defun utf7-decode-internal (&optional for-imap) 138 "Decode UTF-7 text in (temporary) buffer. 139Use IMAP modification if FOR-IMAP is non-nil." 140 (let ((start (point-min)) 141 (end (point-max))) 142 (goto-char start) 143 (let* ((esc-pattern (concat "^" (char-to-string (if for-imap ?& ?+)))) 144 (base64-chars (concat "A-Za-z0-9+" 145 (char-to-string (if for-imap ?, ?/))))) 146 (while (not (eobp)) 147 (skip-chars-forward esc-pattern) 148 (unless (eobp) 149 (forward-char) 150 (let ((p (point)) 151 (run-length (skip-chars-forward base64-chars))) 152 (when (and (not (eobp)) (= (following-char) ?-)) 153 (delete-char 1)) 154 (unless (= run-length 0) ; Encoded lone esc-char? 155 (save-excursion 156 (utf7-fragment-decode p (point) for-imap) 157 (goto-char p) 158 (delete-backward-char 1))))))))) 159 160(defun utf7-fragment-decode (start end &optional for-imap) 161 "Decode base64 encoded fragment from START to END of UTF-7 text in buffer. 162Use IMAP modification if FOR-IMAP is non-nil." 163 (save-restriction 164 (narrow-to-region start end) 165 (when for-imap 166 (goto-char start) 167 (while (search-forward "," nil 'move-to-end) (replace-match "/"))) 168 (let ((pl (utf7-imap-get-pad-length (- end start) 4))) 169 (insert (make-string pl ?=)) 170 (base64-decode-region start (+ end pl))) 171 (funcall (utf7-get-u16char-converter 'from-utf-16)))) 172 173(defun utf7-get-u16char-converter (which-way) 174 "Return a function to convert between UTF-16 and current character set." 175 (if utf7-utf-16-coding-system 176 (if (eq which-way 'to-utf-16) 177 (lambda () 178 (encode-coding-region (point-min) (point-max) 179 utf7-utf-16-coding-system)) 180 (lambda () 181 (decode-coding-region (point-min) (point-max) 182 utf7-utf-16-coding-system))) 183 ;; Add test to check if we are really Latin-1. 184 (if (eq which-way 'to-utf-16) 185 'utf7-latin1-u16-char-converter 186 'utf7-u16-latin1-char-converter))) 187 188(defun utf7-latin1-u16-char-converter () 189 "Convert latin 1 (ISO-8859.1) characters to 16 bit Unicode. 190Characters are converted to raw byte pairs in narrowed buffer." 191 (mm-encode-coding-region (point-min) (point-max) 'iso-8859-1) 192 (mm-disable-multibyte) 193 (goto-char (point-min)) 194 (while (not (eobp)) 195 (insert 0) 196 (forward-char))) 197 198(defun utf7-u16-latin1-char-converter () 199 "Convert 16 bit Unicode characters to latin 1 (ISO-8859.1). 200Characters are in raw byte pairs in narrowed buffer." 201 (goto-char (point-min)) 202 (while (not (eobp)) 203 (if (= 0 (following-char)) 204 (delete-char 1) 205 (error "Unable to convert from Unicode")) 206 (forward-char)) 207 (mm-decode-coding-region (point-min) (point-max) 'iso-8859-1) 208 (mm-enable-multibyte)) 209 210(defun utf7-encode (string &optional for-imap) 211 "Encode UTF-7 STRING. Use IMAP modification if FOR-IMAP is non-nil." 212 (let ((default-enable-multibyte-characters t)) 213 (with-temp-buffer 214 (insert string) 215 (utf7-encode-internal for-imap) 216 (buffer-string)))) 217 218(defun utf7-decode (string &optional for-imap) 219 "Decode UTF-7 STRING. Use IMAP modification if FOR-IMAP is non-nil." 220 (let ((default-enable-multibyte-characters nil)) 221 (with-temp-buffer 222 (insert string) 223 (utf7-decode-internal for-imap) 224 (mm-enable-multibyte) 225 (buffer-string)))) 226 227(provide 'utf7) 228 229;;; arch-tag: 96078b55-85c7-4161-aed2-932c24b282c7 230;;; utf7.el ends here 231