-;;; utf7.el --- UTF-7 encoding/decoding for Emacs
-;; Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+;;; utf7.el --- UTF-7 encoding/decoding for Emacs -*-coding: iso-8859-1;-*-
+;; Copyright (C) 1999, 2000, 2003 Free Software Foundation, Inc.
;; Author: Jon K Hellan <hellan@acm.org>
+;; Maintainer: bugs@gnus.org
;; Keywords: mail
;; This file is part of GNU Emacs.
;; Boston, MA 02111-1307, USA.
;;; Commentary:
-;;; UTF-7 - A Mail-Safe Transformation Format of Unicode - RFC 2152
-;;; This is a transformation format of Unicode that contains only 7-bit
-;;; ASCII octets and is intended to be readable by humans in the limiting
-;;; case that the document consists of characters from the US-ASCII
-;;; repertoire.
-;;; In short, runs of characters outside US-ASCII are encoded as base64
-;;; inside delimiters.
-;;; A variation of UTF-7 is specified in IMAP 4rev1 (RFC 2060) as the way
-;;; to represent characters outside US-ASCII in mailbox names in IMAP.
-;;; This library supports both variants, but the IMAP variation was the
-;;; reason I wrote it.
-;;; The routines convert UTF-7 -> UTF-16 (16 bit encoding of Unicode)
-;;; -> current character set, and vice versa.
-;;; However, until Emacs supports Unicode, the only Emacs character set
-;;; supported here is ISO-8859.1, which can trivially be converted to/from
-;;; Unicode.
-;;; When decoding results in a character outside the Emacs character set,
-;;; an error is thrown. It is up to the application to recover.
+
+;; UTF-7 - A Mail-Safe Transformation Format of Unicode - RFC 2152
+;; This is a transformation format of Unicode that contains only 7-bit
+;; ASCII octets and is intended to be readable by humans in the limiting
+;; case that the document consists of characters from the US-ASCII
+;; repertoire.
+;; In short, runs of characters outside US-ASCII are encoded as base64
+;; inside delimiters.
+;; A variation of UTF-7 is specified in IMAP 4rev1 (RFC 2060) as the way
+;; to represent characters outside US-ASCII in mailbox names in IMAP.
+;; This library supports both variants, but the IMAP variation was the
+;; reason I wrote it.
+;; The routines convert UTF-7 -> UTF-16 (16 bit encoding of Unicode)
+;; -> current character set, and vice versa.
+;; However, until Emacs supports Unicode, the only Emacs character set
+;; supported here is ISO-8859.1, which can trivially be converted to/from
+;; Unicode.
+;; When decoding results in a character outside the Emacs character set,
+;; an error is thrown. It is up to the application to recover.
+
+;; UTF-7 should be done by providing a coding system. Mule-UCS does
+;; already, but I don't know if it does the IMAP version and it's not
+;; clear whether that should really be a coding system. The UTF-16
+;; part of the conversion can be done with coding systems available
+;; with Mule-UCS or some versions of Emacs. Unfortunately these were
+;; done wrongly (regarding handling of byte-order marks and how the
+;; variants were named), so we don't have a consistent name for the
+;; necessary coding system. The code below doesn't seem to DTRT
+;; generally. E.g.:
+;;
+;; (utf7-encode "a+£")
+;; => "a+ACsAow-"
+;;
+;; $ echo "a+£"|iconv -f iso-8859-1 -t utf-7
+;; a+-+AKM
+;;
+;; -- fx
+
;;; Code:
(require 'base64)
(eval-when-compile (require 'cl))
+(require 'mm-util)
-(defvar utf7-direct-encoding-chars " -%'-*,-[]-}"
+(defconst utf7-direct-encoding-chars " -%'-*,-[]-}"
"Character ranges which do not need escaping in UTF-7.")
-(defvar utf7-imap-direct-encoding-chars
+(defconst utf7-imap-direct-encoding-chars
(concat utf7-direct-encoding-chars "+\\~")
"Character ranges which do not need escaping in the IMAP variant of UTF-7.")
+(defconst utf7-utf-16-coding-system
+ (cond ((mm-coding-system-p 'utf-16-be-no-signature) ; Mule-UCS
+ 'utf-16-be-no-signature)
+ ((and (mm-coding-system-p 'utf-16-be) ; Emacs 21.4 (?), Emacs 22
+ ;; Avoid versions with BOM.
+ (= 2 (length (encode-coding-string "a" 'utf-16-be))))
+ 'utf-16-be)
+ ((mm-coding-system-p 'utf-16-be-nosig) ; ?
+ 'utf-16-be-nosig))
+ "Coding system which encodes big endian UTF-16 without a BOM signature.")
+
(defsubst utf7-imap-get-pad-length (len modulus)
"Return required length of padding for IMAP modified base64 fragment."
(mod (- len) modulus))
(end (point-max)))
(narrow-to-region start end)
(goto-char start)
- (let ((esc-char (if for-imap ?& ?+))
- (direct-encoding-chars
- (if for-imap utf7-imap-direct-encoding-chars
- utf7-direct-encoding-chars)))
+ (let* ((esc-char (if for-imap ?& ?+))
+ (direct-encoding-chars
+ (if for-imap utf7-imap-direct-encoding-chars
+ utf7-direct-encoding-chars))
+ (not-direct-encoding-chars (concat "^" direct-encoding-chars)))
(while (not (eobp))
(skip-chars-forward direct-encoding-chars)
(unless (eobp)
(let ((p (point))
(fc (following-char))
(run-length
- (skip-chars-forward (concat "^" direct-encoding-chars))))
+ (skip-chars-forward not-direct-encoding-chars)))
(if (and (= fc esc-char)
(= run-length 1)) ; Lone esc-char?
(delete-backward-char 1) ; Now there's one too many
(save-restriction
(narrow-to-region start end)
(funcall (utf7-get-u16char-converter 'to-utf-16))
- (base64-encode-region start (point-max))
+ (mm-with-unibyte-current-buffer
+ (base64-encode-region start (point-max)))
(goto-char start)
(let ((pm (point-max)))
(when for-imap
(defun utf7-get-u16char-converter (which-way)
"Return a function to convert between UTF-16 and current character set."
- ;; Add test to check if we are really Latin-1.
- ;; Support other character sets once Emacs groks Unicode.
- (if (eq which-way 'to-utf-16)
- 'utf7-latin1-u16-char-converter
- 'utf7-u16-latin1-char-converter))
+ (if utf7-utf-16-coding-system
+ (if (eq which-way 'to-utf-16)
+ (lambda ()
+ (encode-coding-region (point-min) (point-max)
+ utf7-utf-16-coding-system))
+ (lambda ()
+ (decode-coding-region (point-min) (point-max)
+ utf7-utf-16-coding-system)))
+ ;; Add test to check if we are really Latin-1.
+ (if (eq which-way 'to-utf-16)
+ 'utf7-latin1-u16-char-converter
+ 'utf7-u16-latin1-char-converter)))
(defun utf7-latin1-u16-char-converter ()
"Convert latin 1 (ISO-8859.1) characters to 16 bit Unicode.
Characters are converted to raw byte pairs in narrowed buffer."
+ (mm-encode-coding-region (point-min) (point-max) 'iso-8859-1)
+ (mm-disable-multibyte)
(goto-char (point-min))
(while (not (eobp))
(insert 0)
(if (= 0 (following-char))
(delete-char 1)
(error "Unable to convert from Unicode"))
- (forward-char)))
+ (forward-char))
+ (mm-decode-coding-region (point-min) (point-max) 'iso-8859-1)
+ (mm-enable-multibyte))
(defun utf7-encode (string &optional for-imap)
"Encode UTF-7 STRING. Use IMAP modification if FOR-IMAP is non-nil."
- (let ((default-enable-multibyte-characters nil))
+ (let ((default-enable-multibyte-characters t))
(with-temp-buffer
(insert string)
(utf7-encode-internal for-imap)
(with-temp-buffer
(insert string)
(utf7-decode-internal for-imap)
+ (mm-enable-multibyte)
(buffer-string))))
(provide 'utf7)
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