--- /dev/null
+;;; yenc.el --- elisp native yenc decoder
+
+;; Copyright (C) 2002-2016 Free Software Foundation, Inc.
+
+;; Author: Jesper Harder <harder@ifa.au.dk>
+;; Keywords: yenc news
+
+;; 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 3 of the License, 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. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Functions for decoding yenc encoded messages.
+;;
+;; Limitations:
+;;
+;; * Does not handle multipart messages.
+;; * No support for external decoders.
+;; * Doesn't check the crc32 checksum (if present).
+
+;;; Code:
+
+(eval-when-compile (require 'cl))
+
+(defconst yenc-begin-line
+ "^=ybegin.*$")
+
+(defconst yenc-decoding-vector
+ [214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230
+ 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247
+ 248 249 250 251 252 253 254 255 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+ 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
+ 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
+ 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84
+ 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105
+ 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122
+ 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139
+ 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156
+ 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173
+ 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190
+ 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207
+ 208 209 210 211 212 213])
+
+(defun yenc-first-part-p ()
+ "Say whether the buffer contains the first part of a yEnc file."
+ (save-excursion
+ (goto-char (point-min))
+ (re-search-forward "^=ybegin part=1 " nil t)))
+
+(defun yenc-last-part-p ()
+ "Say whether the buffer contains the last part of a yEnc file."
+ (save-excursion
+ (goto-char (point-min))
+ (let (total-size end-size)
+ (when (re-search-forward "^=ybegin.*size=\\([0-9]+\\)" nil t)
+ (setq total-size (match-string 1)))
+ (when (re-search-forward "^=ypart.*end=\\([0-9]+\\)" nil t)
+ (setq end-size (match-string 1)))
+ (and total-size
+ end-size
+ (string= total-size end-size)))))
+
+;;;###autoload
+(defun yenc-decode-region (start end)
+ "Yenc decode region between START and END using an internal decoder."
+ (interactive "r")
+ (let (work-buffer)
+ (unwind-protect
+ (save-excursion
+ (goto-char start)
+ (when (re-search-forward yenc-begin-line end t)
+ (let ((first (match-end 0))
+ (header-alist (yenc-parse-line (match-string 0)))
+ bytes last footer-alist char)
+ (when (re-search-forward "^=ypart.*$" end t)
+ (setq first (match-end 0)))
+ (when (re-search-forward "^=yend.*$" end t)
+ (setq last (match-beginning 0))
+ (setq footer-alist (yenc-parse-line (match-string 0)))
+ (setq work-buffer (generate-new-buffer " *yenc-work*"))
+ (unless (featurep 'xemacs)
+ (with-current-buffer work-buffer (set-buffer-multibyte nil)))
+ (while (< first last)
+ (setq char (char-after first))
+ (cond ((or (eq char ?\r)
+ (eq char ?\n)))
+ ((eq char ?=)
+ (setq char (char-after (incf first)))
+ (with-current-buffer work-buffer
+ (insert-char (mod (- char 106) 256) 1)))
+ (t
+ (with-current-buffer work-buffer
+ ;;(insert-char (mod (- char 42) 256) 1)
+ (insert-char (aref yenc-decoding-vector char) 1))))
+ (incf first))
+ (setq bytes (buffer-size work-buffer))
+ (unless (and (= (cdr (assq 'size header-alist)) bytes)
+ (= (cdr (assq 'size footer-alist)) bytes))
+ (message "Warning: Size mismatch while decoding."))
+ (goto-char start)
+ (delete-region start end)
+ (insert-buffer-substring work-buffer))))
+ (and work-buffer (kill-buffer work-buffer))))))
+
+;;;###autoload
+(defun yenc-extract-filename ()
+ "Extract file name from an yenc header."
+ (save-excursion
+ (when (re-search-forward yenc-begin-line nil t)
+ (cdr (assoc 'name (yenc-parse-line (match-string 0)))))))
+
+(defun yenc-parse-line (str)
+ "Extract file name and size from STR."
+ (let (result name)
+ (when (string-match "^=y.*size=\\([0-9]+\\)" str)
+ (push (cons 'size (string-to-number (match-string 1 str))) result))
+ (when (string-match "^=y.*name=\\(.*\\)$" str)
+ (setq name (match-string 1 str))
+ ;; Remove trailing white space
+ (when (string-match " +$" name)
+ (setq name (substring name 0 (match-beginning 0))))
+ (push (cons 'name name) result))
+ result))
+
+(provide 'yenc)
+
+;;; yenc.el ends here
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