lisp/language/china-util.el

   1 ;;; china-util.el --- utilities for Chinese
   2
   3 ;; Copyright (C) 1995 Electrotechnical Laboratory, JAPAN.
   4 ;; Licensed to the Free Software Foundation.
   5
   6 ;; Keywords: mule, multilingual, Chinese
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;;; Code:
  28
  29 ;; Hz/ZW encoding stuffs
  30
  31 ;; HZ is an encoding method for Chinese character set GB2312 used
  32 ;; widely in Internet.  It is very similar to 7-bit environment of
  33 ;; ISO-2022.  The difference is that HZ uses the sequence "~{" and
  34 ;; "~}" for designating GB2312 and ASCII respectively, hence, it
  35 ;; doesn't uses ESC (0x1B) code.
  36
  37 ;; ZW is another encoding method for Chinese character set GB2312.  It
  38 ;; encodes Chinese characters line by line by starting each line with
  39 ;; the sequence "zW".  It also uses only 7-bit as HZ.
  40
  41 ;; ISO-2022 escape sequence to designate GB2312.
  42 (defvar iso2022-gb-designation "\e$A")
  43 ;; HZ escape sequence to designate GB2312.
  44 (defvar hz-gb-designnation "~{")
  45 ;; ISO-2022 escape sequence to designate ASCII.
  46 (defvar iso2022-ascii-designation "\e(B")
  47 ;; HZ escape sequence to designate ASCII.
  48 (defvar hz-ascii-designnation "~}")
  49 ;; Regexp of ZW sequence to start GB2312.
  50 (defvar zw-start-gb "^zW")
  51 ;; Regexp for start of GB2312 in an encoding mixture of HZ and ZW.
  52 (defvar hz/zw-start-gb
  53   (concat hz-gb-designnation "\\|" zw-start-gb "\\|[^\0-\177]"))
  54
  55 (defvar decode-hz-line-continuation nil
  56   "Flag to tell if we should care line continuation convention of Hz.")
  57
  58 (defconst hz-set-msb-table
  59   (let ((str (make-string 127 0))
  60         (i 0))
  61     (while (< i 33)
  62       (aset str i i)
  63       (setq i (1+ i)))
  64     (while (< i 127)
  65       (aset str i (+ i 128))
  66       (setq i (1+ i)))
  67     str))
  68
  69 ;;;###autoload
  70 (defun decode-hz-region (beg end)
  71   "Decode HZ/ZW encoded text in the current region.
  72 Return the length of resulting text."
  73   (interactive "r")
  74   (save-excursion
  75     (save-restriction
  76       (let (pos ch)
  77         (narrow-to-region beg end)
  78
  79         ;; We, at first, convert HZ/ZW to `euc-china',
  80         ;; then decode it.
  81
  82         ;; "~\n" -> "\n", "~~" -> "~"
  83         (goto-char (point-min))
  84         (while (search-forward "~" nil t)
  85           (setq ch (following-char))
  86           (if (or (= ch ?\n) (= ch ?~)) (delete-char -1)))
  87
  88         ;; "^zW...\n" -> Chinese GB2312
  89         ;; "~{...~}"  -> Chinese GB2312
  90         (goto-char (point-min))
  91         (setq beg nil)
  92         (while (re-search-forward hz/zw-start-gb nil t)
  93           (setq pos (match-beginning 0)
  94                 ch (char-after pos))
  95           ;; Record the first position to start conversion.
  96           (or beg (setq beg pos))
  97           (end-of-line)
  98           (setq end (point))
  99           (if (>= ch 128)               ; 8bit GB2312
 100               nil
 101             (goto-char pos)
 102             (delete-char 2)
 103             (setq end (- end 2))
 104             (if (= ch ?z)                       ; ZW -> euc-china
 105                 (progn
 106                   (translate-region (point) end hz-set-msb-table)
 107                   (goto-char end))
 108               (if (search-forward hz-ascii-designnation
 109                                   (if decode-hz-line-continuation nil end)
 110                                   t)
 111                   (delete-char -2))
 112               (setq end (point))
 113               (translate-region pos (point) hz-set-msb-table))))
 114         (if beg
 115             (decode-coding-region beg end 'euc-china)))
 116       (- (point-max) (point-min)))))
 117
 118 ;;;###autoload
 119 (defun decode-hz-buffer ()
 120   "Decode HZ/ZW encoded text in the current buffer."
 121   (interactive)
 122   (decode-hz-region (point-min) (point-max)))
 123
 124 ;;;###autoload
 125 (defun encode-hz-region (beg end)
 126   "Encode the text in the current region to HZ.
 127 Return the length of resulting text."
 128   (interactive "r")
 129   (save-excursion
 130     (save-restriction
 131       (narrow-to-region beg end)
 132
 133       ;; "~" -> "~~"
 134       (goto-char (point-min))
 135       (while (search-forward "~" nil t) (insert ?~))
 136
 137       ;; Chinese GB2312 -> "~{...~}"
 138       (goto-char (point-min))
 139       (if (re-search-forward "\\cc" nil t)
 140           (let (pos)
 141             (goto-char (setq pos (match-beginning 0)))
 142             (encode-coding-region pos (point-max) 'iso-2022-7bit)
 143             (goto-char pos)
 144             (while (search-forward iso2022-gb-designation nil t)
 145               (delete-char -3)
 146               (insert hz-gb-designnation))
 147             (goto-char pos)
 148             (while (search-forward iso2022-ascii-designation nil t)
 149               (delete-char -3)
 150               (insert hz-ascii-designnation))))
 151       (- (point-max) (point-min)))))
 152
 153 ;;;###autoload
 154 (defun encode-hz-buffer ()
 155   "Encode the text in the current buffer to HZ."
 156   (interactive)
 157   (encode-hz-region (point-min) (point-max)))
 158
 159 ;;
 160 (provide 'china-util)
 161
 162 ;;; china-util.el ends here