lisp/language/china-util.el

   1 ;;; china-util.el --- utilities for Chinese  -*- coding: utf-8 -*-
   2
   3 ;; Copyright (C) 1995, 2001-2017 Free Software Foundation, Inc.
   4 ;; Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   5 ;;   2005, 2006, 2007, 2008, 2009, 2010, 2011
   6 ;;   National Institute of Advanced Industrial Science and Technology (AIST)
   7 ;;   Registration Number H14PRO021
   8 ;; Copyright (C) 2003
   9 ;;   National Institute of Advanced Industrial Science and Technology (AIST)
  10 ;;   Registration Number H13PRO009
  11
  12 ;; Keywords: mule, multilingual, Chinese
  13
  14 ;; This file is part of GNU Emacs.
  15
  16 ;; GNU Emacs is free software: you can redistribute it and/or modify
  17 ;; it under the terms of the GNU General Public License as published by
  18 ;; the Free Software Foundation, either version 3 of the License, or
  19 ;; (at your option) any later version.
  20
  21 ;; GNU Emacs is distributed in the hope that it will be useful,
  22 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  23 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24 ;; GNU General Public License for more details.
  25
  26 ;; You should have received a copy of the GNU General Public License
  27 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  28
  29 ;;; Commentary:
  30
  31 ;;; Code:
  32
  33 ;; Hz/ZW/EUC-TW encoding stuff
  34
  35 ;; HZ is an encoding method for Chinese character set GB2312 used
  36 ;; widely in Internet.  It is very similar to 7-bit environment of
  37 ;; ISO-2022.  The difference is that HZ uses the sequence "~{" and
  38 ;; "~}" for designating GB2312 and ASCII respectively, hence, it
  39 ;; doesn't uses ESC (0x1B) code.
  40
  41 ;; ZW is another encoding method for Chinese character set GB2312.  It
  42 ;; encodes Chinese characters line by line by starting each line with
  43 ;; the sequence "zW".  It also uses only 7-bit as HZ.
  44
  45 ;; EUC-TW is similar to EUC-KS or EUC-JP.  Its main character set is
  46 ;; plane 1 of CNS 11643; characters of planes 2 to 7 are accessed with
  47 ;; a single shift escape followed by three bytes: the first gives the
  48 ;; plane, the second and third the character code.  Note that characters
  49 ;; of plane 1 are (redundantly) accessible with a single shift escape
  50 ;; also.
  51
  52 ;; ISO-2022 escape sequence to designate GB2312.
  53 (defvar iso2022-gb-designation "\e$A")
  54 ;; HZ escape sequence to designate GB2312.
  55 (defvar hz-gb-designation "~{")
  56 ;; ISO-2022 escape sequence to designate ASCII.
  57 (defvar iso2022-ascii-designation "\e(B")
  58 ;; HZ escape sequence to designate ASCII.
  59 (defvar hz-ascii-designation "~}")
  60 ;; Regexp of ZW sequence to start GB2312.
  61 (defvar zw-start-gb "^zW")
  62 ;; Regexp for start of GB2312 in an encoding mixture of HZ and ZW.
  63 (defvar hz/zw-start-gb
  64   (concat hz-gb-designation "\\|" zw-start-gb "\\|[^\0-\177]"))
  65
  66 (defvar decode-hz-line-continuation nil
  67   "Flag to tell if we should care line continuation convention of Hz.")
  68
  69 (defconst hz-set-msb-table
  70   (eval-when-compile
  71     (let ((chars nil)
  72           (i 0))
  73       (while (< i 33)
  74         (push i chars)
  75         (setq i (1+ i)))
  76       (while (< i 127)
  77         (push (decode-char 'eight-bit (+ i 128)) chars)
  78         (setq i (1+ i)))
  79       (apply 'string (nreverse chars)))))
  80
  81 ;;;###autoload
  82 (defun decode-hz-region (beg end)
  83   "Decode HZ/ZW encoded text in the current region.
  84 Return the length of resulting text."
  85   (interactive "r")
  86   (save-excursion
  87     (save-restriction
  88       (let (pos ch)
  89         (narrow-to-region beg end)
  90
  91         ;; We, at first, convert HZ/ZW to `iso-2022-7bit',
  92         ;; then decode it.
  93
  94         ;; "~\n" -> "", "~~" -> "~"
  95         (goto-char (point-min))
  96         (while (search-forward "~" nil t)
  97           (setq ch (following-char))
  98           (cond ((= ch ?{)
  99                  (delete-region (1- (point)) (1+ (point)))
 100                  (setq pos (point))
 101                  (insert iso2022-gb-designation)
 102                  (if (looking-at "\\([!-}][!-~]\\)*")
 103                      (goto-char (match-end 0)))
 104                  (if (looking-at hz-ascii-designation)
 105                      (delete-region (match-beginning 0) (match-end 0)))
 106                  (insert iso2022-ascii-designation)
 107                  (decode-coding-region pos (point) 'iso-2022-7bit))
 108
 109                 ((= ch ?~)
 110                  (delete-char 1))
 111
 112                 ((and (= ch ?\n)
 113                       decode-hz-line-continuation)
 114                  (delete-region (1- (point)) (1+ (point))))
 115
 116                 (t
 117                  (forward-char 1)))))
 118
 119       (- (point-max) (point-min)))))
 120
 121 ;;;###autoload
 122 (defun decode-hz-buffer ()
 123   "Decode HZ/ZW encoded text in the current buffer."
 124   (interactive)
 125   (decode-hz-region (point-min) (point-max)))
 126
 127 (defvar hz-category-table nil)
 128
 129 ;;;###autoload
 130 (defun encode-hz-region (beg end)
 131   "Encode the text in the current region to HZ.
 132 Return the length of resulting text."
 133   (interactive "r")
 134   (unless hz-category-table
 135     (setq hz-category-table (make-category-table))
 136     (with-category-table hz-category-table
 137       (define-category ?c "hz encodable")
 138       (map-charset-chars #'modify-category-entry 'ascii ?c)
 139       (map-charset-chars #'modify-category-entry 'chinese-gb2312 ?c)))
 140   (save-excursion
 141     (save-restriction
 142       (narrow-to-region beg end)
 143       (with-category-table hz-category-table
 144         ;; ~ -> ~~
 145         (goto-char (point-min))
 146         (while (search-forward "~" nil t) (insert ?~))
 147
 148         ;; ESC -> ESC ESC
 149         (goto-char (point-min))
 150         (while (search-forward "\e" nil t) (insert ?\e))
 151
 152         ;; Non-ASCII-GB2312 -> \uXXXX
 153         (goto-char (point-min))
 154         (while (re-search-forward "\\Cc" nil t)
 155           (let ((ch (preceding-char)))
 156             (delete-char -1)
 157             (insert (format (if (< ch #x10000) "\\u%04X" "\\U%08X") ch))))
 158
 159         ;; Prefer chinese-gb2312 for Chinese characters.
 160         (put-text-property (point-min) (point-max) 'charset 'chinese-gb2312)
 161         (encode-coding-region (point-min) (point-max) 'iso-2022-7bit)
 162
 163         ;; ESC $ B ... ESC ( B  -> ~{ ... ~}
 164         ;; ESC ESC -> ESC
 165         (goto-char (point-min))
 166         (while (search-forward "\e" nil t)
 167           (if (= (following-char) ?\e)
 168               ;; ESC ESC -> ESC
 169               (delete-char 1)
 170             (forward-char -1)
 171             (if (looking-at iso2022-gb-designation)
 172                 (progn
 173                   (delete-region (match-beginning 0) (match-end 0))
 174                   (insert hz-gb-designation)
 175                   (search-forward iso2022-ascii-designation nil 'move)
 176                   (delete-region (match-beginning 0) (match-end 0))
 177                   (insert hz-ascii-designation))))))
 178       (- (point-max) (point-min)))))
 179
 180 ;;;###autoload
 181 (defun encode-hz-buffer ()
 182   "Encode the text in the current buffer to HZ."
 183   (interactive)
 184   (encode-hz-region (point-min) (point-max)))
 185
 186 ;;;###autoload
 187 (defun post-read-decode-hz (len)
 188   (let ((pos (point))
 189         (buffer-modified-p (buffer-modified-p))
 190         last-coding-system-used)
 191     (prog1
 192         (decode-hz-region pos (+ pos len))
 193       (set-buffer-modified-p buffer-modified-p))))
 194
 195 ;;;###autoload
 196 (defun pre-write-encode-hz (from to)
 197   (let ((buf (current-buffer)))
 198     (set-buffer (generate-new-buffer " *temp*"))
 199     (if (stringp from)
 200         (insert from)
 201       (insert-buffer-substring buf from to))
 202     (let (last-coding-system-used)
 203       (encode-hz-region 1 (point-max)))
 204     nil))
 205 ;;
 206 (provide 'china-util)
 207
 208 ;;; china-util.el ends here