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[emacs.git] / lisp / gnus / rfc2231.el

;;; rfc2231.el --- Functions for decoding rfc2231 headers

;; Copyright (C) 1998-2015 Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; 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:

;;; Code:

(eval-when-compile (require 'cl))
(require 'ietf-drums)
(require 'rfc2047)
(autoload 'mm-encode-body "mm-bodies")
(autoload 'mail-header-remove-whitespace "mail-parse")
(autoload 'mail-header-remove-comments "mail-parse")

(defun rfc2231-get-value (ct attribute)
  "Return the value of ATTRIBUTE from CT."
  (cdr (assq attribute (cdr ct))))

(defun rfc2231-parse-qp-string (string)
  "Parse QP-encoded string using `rfc2231-parse-string'.
N.B.  This is in violation with RFC2047, but it seem to be in common use."
  (rfc2231-parse-string (rfc2047-decode-string string)))

(defun rfc2231-parse-string (string &optional signal-error)
  "Parse STRING and return a list.
The list will be on the form
 `(name (attribute . value) (attribute . value)...)'.

If the optional SIGNAL-ERROR is non-nil, signal an error when this
function fails in parsing of parameters.  Otherwise, this function
must never cause a Lisp error."
  (with-temp-buffer
    (let ((ttoken (ietf-drums-token-to-list ietf-drums-text-token))
          (stoken (ietf-drums-token-to-list ietf-drums-tspecials))
          (ntoken (ietf-drums-token-to-list "0-9"))
          c type attribute encoded number parameters value)
      (ietf-drums-init
       (condition-case nil
           (mail-header-remove-whitespace
            (mail-header-remove-comments string))
         ;; The most likely cause of an error is unbalanced parentheses
         ;; or double-quotes.  If all parentheses and double-quotes are
         ;; quoted meaninglessly with backslashes, removing them might
         ;; make it parsable.  Let's try...
         (error
          (let (mod)
            (when (and (string-match "\\\\\"" string)
                       (not (string-match "\\`\"\\|[^\\]\"" string)))
              (setq string (mm-replace-in-string string "\\\\\"" "\"")
                    mod t))
            (when (and (string-match "\\\\(" string)
                       (string-match "\\\\)" string)
                       (not (string-match "\\`(\\|[^\\][()]" string)))
              (setq string (mm-replace-in-string string "\\\\\\([()]\\)" "\\1")
                    mod t))
            (or (and mod
                     (ignore-errors
                       (mail-header-remove-whitespace
                        (mail-header-remove-comments string))))
                ;; Finally, attempt to extract only type.
                (if (string-match
                     (concat "\\`[\t\n ]*\\([^" ietf-drums-tspecials "\t\n ]+"
                             "\\(?:/[^" ietf-drums-tspecials
                             "\t\n ]+\\)?\\)\\(?:[\t\n ;]\\|\\'\\)")
                     string)
                    (match-string 1 string)
                  ""))))))
      (let ((table (copy-syntax-table ietf-drums-syntax-table)))
        (modify-syntax-entry ?\' "w" table)
        (modify-syntax-entry ?* " " table)
        (modify-syntax-entry ?\; " " table)
        (modify-syntax-entry ?= " " table)
        ;; The following isn't valid, but one should be liberal
        ;; in what one receives.
        (modify-syntax-entry ?\: "w" table)
        (set-syntax-table table))
      (setq c (char-after))
      (when (and (memq c ttoken)
                 (not (memq c stoken))
                 (setq type (ignore-errors
                              (downcase
                               (buffer-substring (point) (progn
                                                           (forward-sexp 1)
                                                           (point)))))))
        ;; Do the params
        (condition-case err
            (progn
              (while (not (eobp))
                (setq c (char-after))
                (unless (eq c ?\;)
                  (error "Invalid header: %s" string))
                (forward-char 1)
                ;; If c in nil, then this is an invalid header, but
                ;; since elm generates invalid headers on this form,
                ;; we allow it.
                (when (setq c (char-after))
                  (if (and (memq c ttoken)
                           (not (memq c stoken)))
                      (setq attribute
                            (intern
                             (downcase
                              (buffer-substring
                               (point) (progn (forward-sexp 1) (point))))))
                    (error "Invalid header: %s" string))
                  (setq c (char-after))
                  (if (eq c ?*)
                      (progn
                        (forward-char 1)
                        (setq c (char-after))
                        (if (not (memq c ntoken))
                            (setq encoded t
                                  number nil)
                          (setq number
                                (string-to-number
                                 (buffer-substring
                                  (point) (progn (forward-sexp 1) (point)))))
                          (setq c (char-after))
                          (when (eq c ?*)
                            (setq encoded t)
                            (forward-char 1)
                            (setq c (char-after)))))
                    (setq number nil
                          encoded nil))
                  (unless (eq c ?=)
                    (error "Invalid header: %s" string))
                  (forward-char 1)
                  (setq c (char-after))
                  (cond
                   ((eq c ?\")
                    (setq value (buffer-substring (1+ (point))
                                                  (progn
                                                    (forward-sexp 1)
                                                    (1- (point)))))
                    (when encoded
                      (setq value (mapconcat (lambda (c) (format "%%%02x" c))
                                             value ""))))
                   ((and (or (memq c ttoken)
                             ;; EXTENSION: Support non-ascii chars.
                             (> c ?\177))
                         (not (memq c stoken)))
                    (setq value
                          (buffer-substring
                           (point)
                           (progn
                             ;; Jump over asterisk, non-ASCII
                             ;; and non-boundary characters.
                             (while (and c
                                         (or (eq c ?*)
                                             (> c ?\177)
                                             (not (eq (char-syntax c) ? ))))
                               (forward-char 1)
                               (setq c (char-after)))
                             (point)))))
                   (t
                    (error "Invalid header: %s" string)))
                  (push (list attribute value number encoded)
                        parameters))))
          (error
           (setq parameters nil)
           (when signal-error
             (signal (car err) (cdr err)))))

        ;; Now collect and concatenate continuation parameters.
        (let ((cparams nil)
              elem)
          (loop for (attribute value part encoded)
                in (sort parameters (lambda (e1 e2)
                                      (< (or (caddr e1) 0)
                                         (or (caddr e2) 0))))
                do (cond
                    ;; First part.
                    ((or (not (setq elem (assq attribute cparams)))
                         (and (numberp part)
                              (zerop part)))
                     (push (list attribute value encoded) cparams))
                    ;; Repetition of a part; do nothing.
                    ((and elem
                          (null number))
                     )
                    ;; Concatenate continuation parts.
                    (t
                     (setcar (cdr elem) (concat (cadr elem) value)))))
          ;; Finally decode encoded values.
          (cons type (mapcar
                      (lambda (elem)
                        (cons (car elem)
                              (if (nth 2 elem)
                                  (rfc2231-decode-encoded-string (nth 1 elem))
                                (nth 1 elem))))
                      (nreverse cparams))))))))

(defun rfc2231-decode-encoded-string (string)
  "Decode an RFC2231-encoded string.
These look like:
 \"us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A\",
 \"us-ascii''This%20is%20%2A%2A%2Afun%2A%2A%2A\",
 \"'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A\",
 \"''This%20is%20%2A%2A%2Afun%2A%2A%2A\", or
 \"This is ***fun***\"."
  (string-match "\\`\\(?:\\([^']+\\)?'\\([^']+\\)?'\\)?\\(.+\\)" string)
  (let ((coding-system (mm-charset-to-coding-system
                        (match-string 1 string) nil t))
        ;;(language (match-string 2 string))
        (value (match-string 3 string)))
    (mm-with-unibyte-buffer
      (insert value)
      (goto-char (point-min))
      (while (re-search-forward "%\\([0-9A-Fa-f][0-9A-Fa-f]\\)" nil t)
        (insert
         (prog1
             (string-to-number (match-string 1) 16)
           (delete-region (match-beginning 0) (match-end 0)))))
      ;; Decode using the charset, if any.
      (if (memq coding-system '(nil ascii))
          (buffer-string)
        (mm-decode-coding-string (buffer-string) coding-system)))))

(defun rfc2231-encode-string (param value)
  "Return and PARAM=VALUE string encoded according to RFC2231.
Use `mml-insert-parameter' or `mml-insert-parameter-string' to insert
the result of this function."
  (let ((control (ietf-drums-token-to-list ietf-drums-no-ws-ctl-token))
        (tspecial (ietf-drums-token-to-list ietf-drums-tspecials))
        (special (ietf-drums-token-to-list "*'%\n\t"))
        (ascii (ietf-drums-token-to-list ietf-drums-text-token))
        (num -1)
        ;; Don't make lines exceeding 76 column.
        (limit (- 74 (length param)))
        spacep encodep charsetp charset broken)
    (mm-with-multibyte-buffer
      (insert value)
      (goto-char (point-min))
      (while (not (eobp))
        (cond
         ((or (memq (following-char) control)
              (memq (following-char) tspecial)
              (memq (following-char) special))
          (setq encodep t))
         ((eq (following-char) ? )
          (setq spacep t))
         ((not (memq (following-char) ascii))
          (setq charsetp t)))
        (forward-char 1))
      (when charsetp
        (setq charset (mm-encode-body)))
      (mm-disable-multibyte)
      (cond
       ((or encodep charsetp
            (progn
              (end-of-line)
              (> (current-column) (if spacep (- limit 2) limit))))
        (setq limit (- limit 6))
        (goto-char (point-min))
        (insert (symbol-name (or charset 'us-ascii)) "''")
        (while (not (eobp))
          (if (or (not (memq (following-char) ascii))
                  (memq (following-char) control)
                  (memq (following-char) tspecial)
                  (memq (following-char) special)
                  (eq (following-char) ? ))
              (progn
                (when (>= (current-column) (1- limit))
                  (insert ";\n")
                  (setq broken t))
                (insert "%" (format "%02x" (following-char)))
                (delete-char 1))
            (when (> (current-column) limit)
              (insert ";\n")
              (setq broken t))
            (forward-char 1)))
        (goto-char (point-min))
        (if (not broken)
            (insert param "*=")
          (while (not (eobp))
            (insert (if (>= num 0) " " "")
                    param "*" (format "%d" (incf num)) "*=")
            (forward-line 1))))
       (spacep
        (goto-char (point-min))
        (insert param "=\"")
        (goto-char (point-max))
        (insert "\""))
       (t
        (goto-char (point-min))
        (insert param "=")))
      (buffer-string))))

(provide 'rfc2231)

;;; rfc2231.el ends here