lisp/language/china-util.el

   1 ;;; china-util.el --- utilities for Chinese  -*- coding: utf-8 -*-
   2
   3 ;; Copyright (C) 1995, 2001-2014 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 <http://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-designnation "~{")
  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-designnation "~}")
  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-designnation "\\|" 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 `euc-china',
  92         ;; then decode it.
  93
  94         ;; "~\n" -> "\n", "~~" -> "~"
  95         (goto-char (point-min))
  96         (while (search-forward "~" nil t)
  97           (setq ch (following-char))
  98           (if (or (= ch ?\n) (= ch ?~)) (delete-char -1)))
  99
 100         ;; "^zW...\n" -> Chinese GB2312
 101         ;; "~{...~}"  -> Chinese GB2312
 102         (goto-char (point-min))
 103         (setq beg nil)
 104         (while (re-search-forward hz/zw-start-gb nil t)
 105           (setq pos (match-beginning 0)
 106                 ch (char-after pos))
 107           ;; Record the first position to start conversion.
 108           (or beg (setq beg pos))
 109           (end-of-line)
 110           (setq end (point))
 111           (if (>= ch 128)               ; 8bit GB2312
 112               nil
 113             (goto-char pos)
 114             (delete-char 2)
 115             (setq end (- end 2))
 116             (if (= ch ?z)                       ; ZW -> euc-china
 117                 (progn
 118                   (translate-region (point) end hz-set-msb-table)
 119                   (goto-char end))
 120               (if (search-forward hz-ascii-designnation
 121                                   (if decode-hz-line-continuation nil end)
 122                                   t)
 123                   (delete-char -2))
 124               (setq end (point))
 125               (translate-region pos (point) hz-set-msb-table))))
 126         (if beg
 127             (decode-coding-region beg end 'euc-china)))
 128       (- (point-max) (point-min)))))
 129
 130 ;;;###autoload
 131 (defun decode-hz-buffer ()
 132   "Decode HZ/ZW encoded text in the current buffer."
 133   (interactive)
 134   (decode-hz-region (point-min) (point-max)))
 135
 136 ;;;###autoload
 137 (defun encode-hz-region (beg end)
 138   "Encode the text in the current region to HZ.
 139 Return the length of resulting text."
 140   (interactive "r")
 141   (save-excursion
 142     (save-restriction
 143       (narrow-to-region beg end)
 144
 145       ;; "~" -> "~~"
 146       (goto-char (point-min))
 147       (while (search-forward "~" nil t) (insert ?~))
 148
 149       ;; Chinese GB2312 -> "~{...~}"
 150       (goto-char (point-min))
 151       (if (re-search-forward "\\cc" nil t)
 152           (let (pos)
 153             (goto-char (setq pos (match-beginning 0)))
 154             (encode-coding-region pos (point-max) 'iso-2022-7bit)
 155             (goto-char pos)
 156             (while (search-forward iso2022-gb-designation nil t)
 157               (delete-char -3)
 158               (insert hz-gb-designnation))
 159             (goto-char pos)
 160             (while (search-forward iso2022-ascii-designation nil t)
 161               (delete-char -3)
 162               (insert hz-ascii-designnation))))
 163       (- (point-max) (point-min)))))
 164
 165 ;;;###autoload
 166 (defun encode-hz-buffer ()
 167   "Encode the text in the current buffer to HZ."
 168   (interactive)
 169   (encode-hz-region (point-min) (point-max)))
 170
 171 ;;;###autoload
 172 (defun post-read-decode-hz (len)
 173   (let ((pos (point))
 174         (buffer-modified-p (buffer-modified-p))
 175         last-coding-system-used)
 176     (prog1
 177         (decode-hz-region pos (+ pos len))
 178       (set-buffer-modified-p buffer-modified-p))))
 179
 180 ;;;###autoload
 181 (defun pre-write-encode-hz (from to)
 182   (let ((buf (current-buffer)))
 183     (set-buffer (generate-new-buffer " *temp*"))
 184     (if (stringp from)
 185         (insert from)
 186       (insert-buffer-substring buf from to))
 187     (let (last-coding-system-used)
 188       (encode-hz-region 1 (point-max)))
 189     nil))
 190 ;;
 191 (provide 'china-util)
 192
 193 ;;; china-util.el ends here