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+;;; codepage.el --- MS-DOS specific coding systems.
+
+;; Copyright (C) 1998 Free Software Foundation, Inc.
+
+;; Author: Eli Zaretskii
+;; Maintainer: FSF
+;; Keywords: i18n ms-dos codepage
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs 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.
+
+;; GNU Emacs 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.
+
+;;; Commentary:
+
+;; Special coding systems for DOS codepage support.
+;;
+;; These coding systems perform conversion from the DOS codepage encoding
+;; to one of the ISO-8859 character sets.  Each codepage has its corresponding
+;; ISO-8859 charset, chosen so as to be able to convert all (or most) of the
+;; characters.  The idea is that Emacs internally works with the usual MULE
+;; charsets, and the conversion to and from the DOS codepage is performed
+;; on I/O only.
+;; See term/internal.el for the complementary setup of the DOS terminal
+;; display and input methods.
+;;
+;; Thanks to Ken'ichi Handa <handa@etl.go.jp> for writing the CCL
+;; encoders/decoders, and for help in debugging this code. 
+
+;;; Code:
+
+(defun cp-coding-system-for-codepage-1 (coding mnemonic iso-name
+                                               decoder encoder)
+  "Make coding system CODING for a DOS codepage using translation tables.
+MNEMONIC is a character to be displayed on mode line for the coding system.
+ISO-NAME is the name of the ISO-8859 charset which corresponds to this
+codepage.
+DECODER is a translation table for converting characters in the DOS codepage
+encoding to Emacs multibyte characters.
+ENCODER is a translation table for encoding Emacs multibyte characters into
+external DOS codepage codes.
+
+Note that the coding systems created by this function don't support
+automatic detection of the EOL format.  Use explicit -dos or -unix variants
+as appropriate (Mac EOL style is not supported, as it doesn't make sense for
+these coding systems).
+
+If the coding system's name ends with \"-dos\", this function automatically
+creates a coding system which converts from and to DOS EOL format; otherwise
+the created coding system assumes Unix-style EOL (i.e., it doesn't perform
+any EOL conversions)."
+  (save-match-data
+    (let* ((coding-name (symbol-name coding))
+           (eol-type (string-match "-\\(dos\\|unix\\)\\'" coding-name))
+           (dos-p
+            (and eol-type
+                 (string= "-dos" (substring coding-name eol-type))))
+           (coding-sans-eol
+            (if eol-type (substring coding-name 0 eol-type) coding-name))
+           (ccl-decoder
+            (if dos-p
+                (ccl-compile
+                 `(4 (loop (read r1)
+                           (if (r1 != ?\r)
+                               (if (r1 >= 128)
+                                   ((r0 = ,(charset-id 'ascii))
+                                    (translate-character ,decoder r0 r1)
+                                    (if (r0 == ,(charset-id 'ascii))
+                                        (write r1)
+                                      (write-multibyte-character r0 r1)))
+                                 (write r1)))
+                           (repeat))))
+              (ccl-compile
+               `(4 (loop (read r1)
+                         (if (r1 >= 128)
+                             ((r0 = ,(charset-id 'ascii))
+                              (translate-character ,decoder r0 r1)
+                              (if (r0 == ,(charset-id 'ascii))
+                                  (write r1)
+                                (write-multibyte-character r0 r1)))
+                           (write r1))
+                         (repeat))))))
+           (ccl-encoder
+            (if dos-p
+                (ccl-compile
+                 `(1 (loop (read-multibyte-character r0 r1)
+                           (if (r1 == ?\n)
+                               (write ?\r)
+                             (if (r0 != ,(charset-id 'ascii))
+                                 ((translate-character ,encoder r0 r1)
+                                  (if (r0 == ,(charset-id 'japanese-jisx0208))
+                                      ((r1 = ??)
+                                       (write r1))))))
+                           (write-repeat r1))))
+              (ccl-compile
+               `(1 (loop (read-multibyte-character r0 r1)
+                         (if (r0 != ,(charset-id 'ascii))
+                             ((translate-character ,encoder r0 r1)
+                              (if (r0 == ,(charset-id 'japanese-jisx0208))
+                                  ((r1 = ??)
+                                   (write r1)))))
+                         (write-repeat r1)))))))
+      (if (memq coding coding-system-list)
+          (setq coding-system-list (delq coding coding-system-list)))
+      (make-coding-system
+       coding 4 mnemonic
+       (concat "8-bit encoding of " (symbol-name iso-name)
+               " characters using IBM codepage " (substring coding-sans-eol 2))
+       (cons ccl-decoder ccl-encoder)
+       `((safe-charsets ascii ,iso-name)))
+      (put coding 'eol-type (if dos-p 1 0)))))
+
+(defun cp-decoding-vector-for-codepage (table charset offset)
+  "Create a vector for decoding IBM PC characters using conversion table
+TABLE into an ISO-8859 character set CHARSET whose first non-ASCII
+character' is generated by (make-char CHARSET OFFSET)."
+  (let* ((len (length table))
+         (undefined-char
+          (if (eq system-type 'ms-dos)
+              (if dos-unsupported-char-glyph
+                  (logand dos-unsupported-char-glyph 255)
+                127)
+            32))
+         (vec1 (make-vector 256 undefined-char))
+         (i 0))
+    (while (< i offset)
+      (aset vec1 i i)
+      (setq i (1+ i)))
+    (setq i 0)
+    (while (< i len)
+      (if (aref table i)
+          (aset vec1 (aref table i) (make-char charset (+ i offset))))
+      (setq i (1+ i)))
+    vec1))
+
+;;; You don't think I created all these tables below by hand, do you?
+;;; The following Awk script will create the table for cp850-to-Latin-1
+;;; conversion from the RFC 1345 file (the other tables are left as an
+;;; excercise):
+;;; BEGIN { n_pages = 11;
+;;;         pn["IBM437"] = 0; pn["IBM850"] = 1; pn["IBM851"] = 2;
+;;;         pn["IBM852"] = 3; pn["IBM855"] = 4; pn["IBM860"] = 5;
+;;;         pn["IBM861"] = 6; pn["IBM862"] = 7; pn["IBM863"] = 8;
+;;;         pn["IBM864"] = 9; pn["IBM865"] = 10;
+;;;       }
+;;; $1 == "&charset" { charset = $2; }
+;;; $1 == "&code"    { code = $2; }
+;;; /^  [^&]/  {
+;;;   if ((charset ~ /^IBM(437|8(5[0125]|6[0-5]))$/) || (charset ~ /^ISO_8859-1/))
+;;;     {
+;;;       for (i = 1; i <= NF; i++)
+;;;         chars[charset,code++] = $i;
+;;;     }
+;;;   }
+;;;
+;;; END {
+;;;   for (i = 160; i < 256; i++)
+;;;     {
+;;;       c =  chars["ISO_8859-1:1987",i];
+;;;       if (c == "??")        # skip unused positions
+;;;         {
+;;;           printf " nil";
+;;;           if ((i - 159)%16 == 0)
+;;;             printf "\n";
+;;;           continue;
+;;;         }
+;;;       found = 0;
+;;;       for (j in pn)
+;;;         map[j] = "nil";
+;;;       for (combined in chars)
+;;;         {
+;;;           candidate = chars[combined];
+;;;           split (combined, separate, SUBSEP);
+;;;           if (separate[1] == "IBM850" && candidate == c)
+;;;             {
+;;;               found = 1;
+;;;               map[separate[1]] = separate[2];
+;;;             }
+;;;         }
+;;;       printf " %s", map["IBM850"];
+;;;       if ((i - 159)%16 == 0)
+;;;         printf "\n";
+;;;     }
+;;; }
+
+;;; WARNING WARNING WARNING!!!
+;;;
+;;; If you want to get fancy with these tables, remember that the inverse
+;;; tables, created by `cp-decoding-vector-for-codepage' above, are installed
+;;; on MS-DOS as nonascii-translation-table (see `dos-codepage-setup' on
+;;; internal.el).  Therefore, you should NOT put any codes below 128 in
+;;; these tables!  Otherwise, various Emacs commands and functions will
+;;; mysteriously fail!  For example, a typical screwup is to map the Latin-N
+;;; acute accent character to the apostrophe, and have all regexps which
+;;; end with "\\'" begin to fail (e.g., the automatic setting of the major
+;;; mode by file name extension will stop working).
+;;;
+;;; You HAVE BEEN warned!
+
+;; US/English/PC-8/IBM-2.  This doesn't support Latin-1 characters very
+;; well, but why not use what we can salvage?
+(defvar cp437-decode-table
+  ;; Nth element is the code of a cp437 glyph for the multibyte
+  ;; character created by (make-char 'latin-iso8859-1 (+ N 160)).
+  ;; The element nil means there's no corresponding cp850 glyph.
+  [
+   255 173 155 156 nil 157 179 nil nil nil 166 174 170 196 nil nil
+   248 241 253 nil nil nil nil 249 nil nil 167 175 172 171 nil 168
+   nil nil nil nil 142 143 146 128 nil 144 nil nil nil nil nil nil
+   nil 165 nil nil nil nil 153 nil nil nil nil nil 154 nil nil 225
+   133 160 131 nil 132 134 145 135 138 130 136 137 141 161 140 139
+   nil 164 149 162 147 nil 148 246 nil 151 163 150 129 nil nil 152]
+  "Table for converting ISO-8859-1 characters into codepage 437 glyphs.")
+(setplist 'cp437-decode-table
+          '(charset latin-iso8859-1 language "Latin-1" offset 160))
+
+;; Multilingual (Latin-1)
+(defvar cp850-decode-table
+  ;; Nth element is the code of a cp850 glyph for the multibyte
+  ;; character created by (make-char 'latin-iso8859-1 (+ N 160)).
+  ;; The element nil means there's no corresponding cp850 glyph.
+  [
+   255 173 189 156 207 190 221 245 249 184 166 174 170 240 169 nil
+   248 241 253 252 239 nil 244 nil nil 251 167 175 172 171 243 168
+   183 181 182 199 142 143 146 128 212 144 210 211 222 214 215 216
+   209 165 227 224 226 229 153 158 157 235 233 234 154 237 231 225
+   133 160 131 198 132 134 145 135 138 130 136 137 141 161 140 139
+   208 164 149 162 147 228 148 246 155 151 163 150 129 236 232 152]
+  "Table for converting ISO-8859-1 characters into codepage 850 glyphs.")
+(setplist 'cp850-decode-table
+          '(charset latin-iso8859-1 language "Latin-1" offset 160))
+
+;; Greek
+(defvar cp851-decode-table
+  [
+   255 nil nil 156 nil nil nil 245 249 nil nil 174 nil 240 nil nil
+   248 241 nil nil 239 nil 134 nil 141 143 144 175 146 171 149 152
+   161 164 165 166 167 168 169 170 172 173 181 182 184 183 189 190
+   198 199 nil 207 208 209 210 211 212 213 nil nil 155 157 158 159
+   252 214 215 216 221 222 224 225 226 227 228 229 230 231 232 233
+   234 235 237 236 238 242 243 244 246 250 160 251 162 163 253 nil]
+  "Table for converting ISO-8859-7 characters into codepage 851 glyphs.")
+(setplist 'cp851-decode-table
+          '(charset greek-iso8859-7 language "Greek" offset 160))
+
+;; Slavic/Eastern Europe (Latin-2)
+(defvar cp852-decode-table
+  [
+   255 164 244 157 207 149 151 245 249 230 184 155 141 240 166 189
+   248 165 247 136 239 150 152 243 242 231 173 156 171 241 167 190
+   232 181 182 198 142 145 143 128 172 144 168 211 183 214 nil 210
+   209 227 213 224 226 138 153 158 252 222 233 235 154 237 221 225
+   234 160 131 199 132 146 134 135 159 130 169 137 216 161 140 212
+   208 228 229 162 147 139 148 246 253 133 163 251 129 236 238 250]
+  "Table for converting ISO-8859-2 characters into codepage 852 glyphs.")
+(setplist 'cp852-decode-table
+          '(charset latin-iso8859-2 language "Latin-2" offset 160))
+
+;; Russian
+(defvar cp855-decode-table
+  [
+   255 133 129 131 135 137 139 141 143 145 147 nil 151 240 153 155
+   161 163 236 173 167 169 234 244 184 190 199 209 211 213 215 221
+   226 228 230 232 171 182 165 252 246 250 159 242 238 248 157 224
+   160 162 235 172 166 168 233 243 183 189 198 208 210 212 214 216
+   225 227 229 231 170 181 164 251 245 249 158 241 237 247 156 222
+   nil 132 128 130 134 136 138 140 142 144 146 148 150 nil 152 154]
+  "Table for converting ISO-8859-5 characters into codepage 855 glyphs.")
+(setplist 'cp855-decode-table
+          '(charset cyrillic-iso8859-5 language "Cyrillic-ISO" offset 160))
+
+;; Turkish
+(defvar cp857-decode-table
+  [
+   255 nil nil 156 207 nil 245 249 152 158 166 nil 240 nil
+   248 nil 253 252 239 nil nil nil nil 141 159 167 nil 171 nil
+   183 181 182 142 nil nil 128 212 144 210 211 222 214 215 216
+   165 227 224 226 nil 153 232 nil 235 233 234 154 nil nil 225
+   133 160 131 132 nil nil 135 138 130 136 137 236 161 140 139
+   164 149 162 147 nil 148 246 nil 151 163 150 129 nil nil 250]
+  "Table for converting ISO-8859-3 characters into codepage 857 glyphs.")
+(setplist 'cp857-decode-table
+          '(charset latin-iso8859-3 language "Latin-3" offset 160))
+
+;; Portuguese
+(defvar cp860-decode-table
+  [
+   255 173 155 156 nil nil 179 nil nil nil 166 174 170 nil nil nil
+   nil 241 253 nil nil nil nil 249 nil nil 167 175 172 171 nil 168
+   145 134 143 142 nil nil nil 128 146 144 137 nil 152 nil 139 nil
+   nil 165 159 169 140 153 nil nil nil 157 150 nil 154 nil nil nil
+   133 160 131 132 nil nil nil 135 138 130 136 nil 141 161 nil nil
+   nil 164 149 162 147 148 nil 246 nil 151 163 nil 129 nil nil nil]
+  "Table for converting ISO-8859-1 characters into codepage 860 glyphs.")
+(setplist 'cp860-decode-table
+          '(charset latin-iso8859-1 language "Latin-1" offset 160))
+
+;; Icelandic
+(defvar cp861-decode-table
+  [
+   255 173 nil 156 nil nil nil nil nil nil nil 174 170 nil nil nil
+   nil 241 253 nil nil nil nil 249 nil nil nil 175 172 171 nil 168
+   nil 164 nil nil 142 143 146 128 nil 144 nil nil nil 165 nil nil
+   139 nil 159 166 nil nil 153 nil 157 nil 167 nil 154 151 141 nil
+   133 160 131 nil 132 134 145 135 138 130 136 137 nil 161 nil nil
+   140 nil nil 162 147 nil 148 246 155 nil 163 150 129 152 149 nil]
+  "Table for converting ISO-8859-1 characters into codepage 861 glyphs.")
+(setplist 'cp861-decode-table
+          '(charset latin-iso8859-1 language "Latin-1" offset 160))
+
+;; Hebrew
+(defvar cp862-decode-table
+  ;; Nth element is the code of a cp862 glyph for the multibyte
+  ;; character created by (make-char 'hebrew-iso8859-8 (+ N 160)).
+  ;; The element nil means there's no corresponding cp850 glyph.
+  [
+   255 173 155 156 nil 157 179 nil nil nil nil 174 170 196 nil nil
+   248 241 253 nil nil 230 nil 249 nil nil 246 175 172 171 nil nil
+   nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil
+   nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil 205
+   128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
+   144 145 146 147 148 149 150 151 152 153 154 nil nil nil nil nil]
+  "Table for converting ISO-8859-8 characters into codepage 862 glyphs.")
+(setplist 'cp862-decode-table
+          '(charset hebrew-iso8859-8 language "Hebrew" offset 160))
+
+;; French Canadian
+(defvar cp863-decode-table
+  [
+   255 nil 155 156 152 nil 160 143 164 nil nil 174 170 nil nil 167
+   nil 241 253 166 161 nil 134 249 165 nil nil 175 172 171 173 nil
+   142 nil 132 nil nil nil nil 128 145 144 146 148 nil nil 168 149
+   nil nil nil nil 153 nil nil nil nil 157 nil 158 154 nil nil nil
+   133 nil 131 nil nil nil nil 135 138 130 136 137 141 nil 140 139
+   nil nil nil 162 147 nil nil 246 nil 151 163 150 129 nil nil nil]
+  "Table for converting ISO-8859-1 characters into codepage 863 glyphs.")
+(setplist 'cp863-decode-table
+          '(charset latin-iso8859-1 language "Latin-1" offset 160))
+
+;; Arabic
+;; FIXME: Emacs doesn't seem to support the "Arabic" language
+;; environment yet.  So this is only partially usable, for now
+(defvar cp864-decode-table
+  [
+   255 nil nil nil 164 nil nil nil nil nil nil nil 172 161 nil nil
+   nil nil nil nil nil nil nil nil nil nil nil 187 nil nil nil 191
+   nil 193 194 195 196 nil 198 199 169 201 170 171 173 174 175 207
+   208 209 210 188 189 190 235 215 216 223 238 nil nil nil nil nil
+   224 247 248 252 251 239 242 243 232 233 253 nil nil nil nil nil
+   nil 241 nil nil nil nil nil nil nil nil nil nil nil nil nil nil]
+  "Table for converting ISO-8859-1 characters into codepage 863 glyphs.")
+(setplist 'cp864-decode-table
+          '(charset arabic-iso8859-6 language nil offset 160))
+
+;; Nordic (Norwegian/Danish)
+(defvar cp865-decode-table
+  [
+   255 173 nil 156 nil nil nil nil nil nil 166 174 170 nil nil nil
+   nil 241 253 nil nil nil nil 249 nil nil 167 175 172 171 nil 168
+   nil nil nil nil 142 143 146 128 nil 144 nil nil nil nil nil nil
+   nil 165 nil nil nil nil 153 nil 157 nil nil nil 154 nil nil nil
+   133 160 131 nil 132 134 145 135 138 130 136 137 141 161 140 139
+   nil 164 149 162 147 nil 148 246 155 151 163 150 129 nil nil 152]
+  "Table for converting ISO-8859-1 characters into codepage 865 glyphs.")
+(setplist 'cp865-decode-table
+          '(charset latin-iso8859-1 language "Latin-1" offset 160))
+
+;; Greek (yes, another one!)
+(defvar cp869-decode-table
+  [
+   255 139 140 156 nil nil 138 245 249 151 nil 174 137 240 nil 142
+   248 241 153 154 239 247 134 136 141 143 144 175 146 171 149 152
+   161 164 165 166 167 168 169 170 172 173 181 182 183 184 189 190
+   198 199 nil 207 208 209 210 211 212 213 145 150 155 157 158 159
+   252 214 215 216 221 222 224 225 226 227 228 229 230 231 232 233
+   234 235 237 236 238 242 243 244 246 250 160 251 162 163 253 nil]
+  "Table for converting ISO-8859-7 characters into codepage 869 glyphs.")
+(setplist 'cp869-decode-table
+          '(charset greek-iso8859-7 language "Greek" offset 160))
+
+;; Conversion from codepage 775 to Latin-4 for Baltic countries.
+(defvar cp775-decode-table
+  [
+   255 181 nil 138 150 nil 234 245 166 190 237 149 173 240 207 nil
+   248 208 nil 139 239 nil 235 nil nil 213 137 133 nil nil 216 nil
+   160 nil nil nil 142 143 146 189 182 144 183 nil 184 nil nil 161
+   nil 238 226 232 nil 229 153 158 157 198 nil nil 154 nil 199 225
+   131 nil nil nil 132 134 145 212 209 130 210 nil 211 nil nil 140
+   nil 236 147 233 nil 228 148 nil 155 214 nil nil 129 nil 215 nil]
+  "Table for converting ISO-8859-4 characters into codepage 775 glyphs.")
+(setplist 'cp775-decode-table
+          '(charset latin-iso8859-4 language "Latin-4" offset 160))
+
+;;;###autoload
+(defun cp-make-coding-systems-for-codepage (codepage iso-name offset)
+  "Create 2 coding systems to convert IBM CODEPAGE into charset ISO-NAME
+whose first character is at offset OFFSET from the beginning of 8-bit
+ASCII table.
+
+The two coding systems are identical except for the EOL conversion: one
+of them decodes DOS-style EOLs, the other assumes Unix style and doesn't
+perform any EOL conversions."
+  (let* ((decode-table (intern (format "%s-decode-table" codepage)))
+         (nonascii-table
+          (intern (format "%s-nonascii-translation-table" codepage)))
+         (decode-translation
+          (intern (format "%s-decode-translation-table" codepage)))
+         (encode-translation
+          (intern (format "%s-encode-translation-table" codepage)))
+         (codepage-dos
+          (intern (format "%s-dos" codepage)))
+         (codepage-unix
+          (intern (format "%s-unix" codepage))))
+    (set nonascii-table
+         (make-translation-table-from-vector
+          (cp-decoding-vector-for-codepage
+           (symbol-value decode-table) iso-name offset)))
+    (define-translation-table encode-translation
+      (char-table-extra-slot (symbol-value nonascii-table) 0))
+    ;; For charsets other than ascii and ISO-NAME, set `?' for
+    ;; one-column charsets, and some Japanese character for
+    ;; wide-column charsets.  CCL encoder convert that Japanese
+    ;; character to "??".
+    (let ((tbl (char-table-extra-slot (symbol-value nonascii-table) 0))
+          (charsets (delq 'ascii (delq iso-name
+                                       (copy-sequence charset-list))))
+          (wide-column-char (make-char 'japanese-jisx0208 32 32)))
+      (while charsets
+        (aset tbl (make-char (car charsets))
+              (if (= (charset-width (car charsets)) 1) ?? wide-column-char))
+        (setq charsets (cdr charsets))))
+    (define-translation-table decode-translation
+      (symbol-value nonascii-table))
+    (cp-coding-system-for-codepage-1
+     codepage-dos ?D iso-name decode-translation encode-translation)
+    (cp-coding-system-for-codepage-1
+     codepage-unix ?D iso-name decode-translation encode-translation)))
+
+(defun cp-codepage-decoder (codepage)
+  "If CODEPAGE is the name of a supported codepage, return its decode table;
+otherwise return nil."
+  (let ((cp (if (symbolp codepage) (symbol-name codepage) codepage)))
+    (cond
+     ((stringp cp)
+      (intern-soft (format "%s-decode-table" cp)))
+     (t nil))))
+
+;;;###autoload
+(defun cp-charset-for-codepage (codepage)
+  "Return the charset for which there is a translation table to DOS CODEPAGE.
+CODEPAGE must be the name of a DOS codepage, a string."
+  (let ((cp-decoder (cp-codepage-decoder codepage)))
+    (if (null cp-decoder)
+        (error "Unsupported codepage %s" codepage)
+      (get cp-decoder 'charset))))
+
+;;;###autoload
+(defun cp-language-for-codepage (codepage)
+  "Return the name of the MULE language environment for CODEPAGE.
+CODEPAGE must be the name of a DOS codepage, a string."
+  (let ((cp-decoder (cp-codepage-decoder codepage)))
+    (if (null cp-decoder)
+        (error "Unsupported codepage %s" codepage)
+      (get cp-decoder 'language))))
+
+;;;###autoload
+(defun cp-offset-for-codepage (codepage)
+  "Return the offset to be used in setting up coding systems for CODEPAGE.
+CODEPAGE must be the name of a DOS codepage, a string."
+  (let ((cp-decoder (cp-codepage-decoder codepage)))
+    (if (null cp-decoder)
+        (error "Unsupported codepage %s" codepage)
+      (get cp-decoder 'offset))))
+
+;;;###autoload
+(defun cp-supported-codepages ()
+  "Return an alist of supported codepages.
+
+Each association in the alist has the form (NNN . CHARSET), where NNN is the
+codepage number, and CHARSET is the MULE charset which is the closest match
+for the character set supported by that codepage.
+
+A codepage NNN is supported if a variable called `cpNNN-decode-table' exists,
+is a vector, and has a charset property."
+  (save-match-data
+    (let (alist chset sname)
+      (mapatoms
+       (function
+        (lambda (sym)
+          (if (and (boundp sym)
+                   (string-match "\\`cp\\([1-9][0-9][0-9]\\)-decode-table\\'"
+                                 (setq sname (symbol-name sym)))
+                   (vectorp (symbol-value sym))
+                   (setq chset (get sym 'charset)))
+              (setq alist
+                    (cons (cons (match-string 1 sname) chset) alist))))))
+      alist)))
+
+;;;###autoload
+(defun codepage-setup (codepage)
+  "Create 2 coding systems for codepage CODEPAGE: cpCODEPAGE-dos and
+cpCODEPAGE-unix.
+
+These coding systems are meant for encoding and decoding 8-bit non-ASCII
+characters used by the IBM codepages, typically in conjunction with files
+read/written by MS-DOS software, or for display on MS-DOS terminal."
+  (interactive
+   (let ((completion-ignore-case t)
+         (candidates (cp-supported-codepages)))
+     (list (completing-read "Setup DOS Codepage: (default 437) " candidates
+                            nil t nil nil "437"))))
+  (let ((cp (format "cp%s" codepage)))
+    (cp-make-coding-systems-for-codepage
+     cp (cp-charset-for-codepage cp) (cp-offset-for-codepage cp))))
+
+(provide 'codepage)
+
+;; codepage.el ends here