;;; mel-q.el: Quoted-Printable and Q-encoding encoder/decoder for GNU Emacs

;; Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.

;; Author: MORIOKA Tomohiko <morioka@jaist.ac.jp>
;; Created: 1995/6/25
;; Keywords: MIME, Quoted-Printable, Q-encoding

;; This file is part of MEL (MIME Encoding Library).

;; This program 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.

;; This program 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., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Code:

(require 'emu)
(require 'mime-def)


;;; @ Quoted-Printable encoder
;;;

(defsubst quoted-printable-quote-char (character)
  (concat
   "="
   (char-to-string (aref quoted-printable-hex-chars (ash character -4)))
   (char-to-string (aref quoted-printable-hex-chars (logand character 15)))
   ))

(defun quoted-printable-internal-encode-region (start end)
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char start)
      (let ((col 0))
	(while (< (point)(point-max))
	  (cond ((>= col 75)
		 (insert "=\n")
		 (setq col 0)
		 )
		((looking-at-as-unibyte "^From ")
		 (replace-match "=46rom ")
		 (backward-char 1)
		 (setq col (+ col 6))
		 )
		((looking-at-as-unibyte "[ \t]\n")
		 (forward-char 1)
		 (insert "=\n")
		 (forward-char 1)
		 (setq col 0)
		 )
		(t
		 (let ((chr (char-after (point))))
		   (cond ((= chr ?\n)
			  (forward-char 1)
			  (setq col 0)
			  )
			 ((or (= chr ?\t)
			      (and (<= 32 chr)(/= chr ?=)(< chr 127))
			      )
			  (forward-char 1)
			  (setq col (1+ col))
			  )
			 ((>= col 73)
			  (insert "=\n")
			  (setq col 0)
			  )
			 (t
			  (delete-char 1)
			  (insert (quoted-printable-quote-char chr))
			  (setq col (+ col 3))
			  ))
		   )))
	  )))))


(defvar quoted-printable-external-encoder '("mmencode" "-q")
  "*list of quoted-printable encoder program name and its arguments.")

(defun quoted-printable-external-encode-region (start end)
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (as-binary-process
       (apply (function call-process-region)
	      start end (car quoted-printable-external-encoder)
	      t t nil (cdr quoted-printable-external-encoder))
       )
      ;; for OS/2
      ;;   regularize line break code
      (goto-char (point-min))
      (while (re-search-forward "\r$" nil t)
	(replace-match "")
	)
      )))


(defvar quoted-printable-internal-encoding-limit
  (if (and (featurep 'xemacs)(featurep 'mule))
      0
    (require 'path-util)
    (if (exec-installed-p "mmencode")
	1000
      (message "Don't found external encoder for Quoted-Printable!")
      nil))
  "*limit size to use internal quoted-printable encoder.
If size of input to encode is larger than this limit,
external encoder is called.")

(defun quoted-printable-encode-region (start end)
  "Encode current region by quoted-printable.
START and END are buffer positions.
This function calls internal quoted-printable encoder if size of
region is smaller than `quoted-printable-internal-encoding-limit',
otherwise it calls external quoted-printable encoder specified by
`quoted-printable-external-encoder'.  In this case, you must install
the program (maybe mmencode included in metamail or XEmacs package)."
  (interactive "r")
  (if (and quoted-printable-internal-encoding-limit
	   (> (- end start) quoted-printable-internal-encoding-limit))
      (quoted-printable-external-encode-region start end)
    (quoted-printable-internal-encode-region start end)
    ))


(defun quoted-printable-encode-string (string)
  "Encode STRING to quoted-printable, and return the result."
  (with-temp-buffer
    (insert string)
    (quoted-printable-encode-region (point-min)(point-max))
    (buffer-string)
    ))


(defun quoted-printable-insert-encoded-file (filename)
  "Encode contents of file FILENAME to quoted-printable, and insert the result.
It calls external quoted-printable encoder specified by
`quoted-printable-external-encoder'.  So you must install the program
\(maybe mmencode included in metamail or XEmacs package)."
  (interactive (list (read-file-name "Insert encoded file: ")))
  (apply (function call-process) (car quoted-printable-external-encoder)
	 filename t nil (cdr quoted-printable-external-encoder))
  )


;;; @ Quoted-Printable decoder
;;;

(defsubst quoted-printable-hex-char-to-num (chr)
  (cond ((<= ?a chr) (+ (- chr ?a) 10))
	((<= ?A chr) (+ (- chr ?A) 10))
	((<= ?0 chr) (- chr ?0))
	))

(defun quoted-printable-internal-decode-region (start end)
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char (point-min))
      (while (search-forward "=" nil t)
	(let ((beg (match-beginning 0)))
	  (cond ((looking-at "\n")
		 (delete-region beg (match-end 0))
		 )
		((looking-at
		  `,(concat "[" quoted-printable-hex-chars
			    "][" quoted-printable-hex-chars "]"))
		 (let* ((end (match-end 0))
			(hex (buffer-substring (match-beginning 0) end)))
		   (delete-region beg end)
		   (insert
		    (logior
		     (ash (quoted-printable-hex-char-to-num (aref hex 0)) 4)
		     (quoted-printable-hex-char-to-num (aref hex 1))))
		   ))
		(t
		 ;; invalid
		 ))
	  )))))

(defvar quoted-printable-external-decoder '("mmencode" "-q" "-u")
  "*list of quoted-printable decoder program name and its arguments.")

(defun quoted-printable-external-decode-region (start end)
  (save-excursion
    (as-binary-process
     (apply (function call-process-region)
	    start end (car quoted-printable-external-decoder)
	    t t nil (cdr quoted-printable-external-decoder))
     )))


(defvar quoted-printable-internal-decoding-limit nil
  "*limit size to use internal quoted-printable decoder.
If size of input to decode is larger than this limit,
external decoder is called.")

(defun quoted-printable-decode-region (start end)
  "Decode current region by quoted-printable.
START and END are buffer positions.
This function calls internal quoted-printable decoder if size of
region is smaller than `quoted-printable-internal-decoding-limit',
otherwise it calls external quoted-printable decoder specified by
`quoted-printable-external-decoder'.  In this case, you must install
the program (maybe mmencode included in metamail or XEmacs package)."
  (interactive "r")
  (if (and quoted-printable-internal-decoding-limit
	   (> (- end start) quoted-printable-internal-decoding-limit))
      (quoted-printable-external-decode-region start end)
    (quoted-printable-internal-decode-region start end)
    ))

(defun quoted-printable-decode-string (string)
  "Decode STRING which is encoded in quoted-printable, and return the result."
  (with-temp-buffer
    (insert string)
    (quoted-printable-decode-region (point-min)(point-max))
    (buffer-string)))


(defvar quoted-printable-external-decoder-option-to-specify-file '("-o")
  "*list of options of quoted-printable decoder program to specify file.")

(defun quoted-printable-write-decoded-region (start end filename)
  "Decode and write current region encoded by quoted-printable into FILENAME.
START and END are buffer positions."
  (interactive
   (list (region-beginning) (region-end)
	 (read-file-name "Write decoded region to file: ")))
  (as-binary-process
   (apply (function call-process-region)
	  start end (car quoted-printable-external-decoder)
	  nil nil nil
	  (append (cdr quoted-printable-external-decoder)
		  quoted-printable-external-decoder-option-to-specify-file
		  (list filename))
	  )))


;;; @ Q-encoding encode/decode string
;;;

(defconst q-encoding-special-chars-alist
  '((text	?= ?? ?_)
    (comment	?= ?? ?_ ?\( ?\) ?\\)
    (phrase	?= ?? ?_ ?\( ?\) ?\\ ?\" ?# ?$ ?% ?& ?' ?, ?. ?/
		?: ?\; ?< ?> ?@ ?\[ ?\] ?^ ?` ?{ ?| ?} ?~)
    ))

(defun q-encoding-encode-string (string &optional mode)
  "Encode STRING to Q-encoding of encoded-word, and return the result.
MODE allows `text', `comment', `phrase' or nil.  Default value is
`phrase'."
  (let ((specials (cdr (or (assq mode q-encoding-special-chars-alist)
			   (assq 'phrase q-encoding-special-chars-alist)
			   ))))
    (mapconcat (function
		(lambda (chr)
		  (cond ((eq chr ? ) "_")
			((or (< chr 32) (< 126 chr)
			     (memq chr specials)
			     )
			 (quoted-printable-quote-char chr)
			 )
			(t
			 (char-to-string chr)
			 ))
		  ))
	       string "")
    ))

(defun q-encoding-decode-string (string)
  "Decode STRING which is encoded in Q-encoding and return the result."
  (let (q h l)
    (mapconcat (function
		(lambda (chr)
		  (cond ((eq chr ?_) " ")
			((eq chr ?=)
			 (setq q t)
			 "")
			(q (setq h (quoted-printable-hex-char-to-num chr))
			   (setq q nil)
			   "")
			(h (setq l (quoted-printable-hex-char-to-num chr))
			   (prog1
			       (char-to-string (logior (ash h 4) l))
			     (setq h nil)
			     )
			   )
			(t (char-to-string chr))
			)))
	       string "")))


;;; @@ etc
;;;

(defun q-encoding-printable-char-p (chr mode)
  (and (not (memq chr '(?= ?? ?_)))
       (<= ?\   chr)(<= chr ?~)
       (cond ((eq mode 'text) t)
	     ((eq mode 'comment)
	      (not (memq chr '(?\( ?\) ?\\)))
	      )
	     (t
	      (string-match "[A-Za-z0-9!*+/=_---]" (char-to-string chr))
	      ))))

(defun q-encoding-encoded-length (string &optional mode)
  (let ((l 0)(i 0)(len (length string)) chr)
    (while (< i len)
      (setq chr (elt string i))
      (if (q-encoding-printable-char-p chr mode)
	  (setq l (+ l 1))
	(setq l (+ l 3))
	)
      (setq i (+ i 1)) )
    l))


;;; @ end
;;;

(provide 'mel-q)

;;; mel-q.el ends here