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|
;;; rfc2231.el --- Functions for decoding rfc2231 headers -*- lexical-binding:t -*-
;; Copyright (C) 1998-2025 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 <https://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
(eval-when-compile (require 'cl-lib))
(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-search "\\\"" string)
(not (string-match "\\`\"\\|[^\\]\"" string)))
(setq string (string-replace "\\\"" "\"" string)
mod t))
(when (and (string-search "\\(" string)
(string-search "\\)" string)
(not (string-match "\\`(\\|[^\\][()]" string)))
(setq string (replace-regexp-in-string
"\\\\\\([()]\\)" "\\1" string)
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)
(cl-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 part))
)
;; 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***\"."
(if (not (string-match "\\`\\(?:\\([^']+\\)?'\\([^']+\\)?'\\)?\\(.+\\)\\'"
string))
(error "Unrecognized RFC2231 format: %S" string)
(let ((value (match-string 3 string))
;;(language (match-string 2 string))
(coding-system (mm-charset-to-coding-system
(match-string 1 string) nil t)))
(mm-with-unibyte-buffer
(insert value)
(goto-char (point-min))
(while (re-search-forward "%\\([[:xdigit:]][[:xdigit:]]\\)" 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)
(decode-coding-string (buffer-string) coding-system))))))
(defun rfc2231-encode-string (param value)
"Return a 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" (cl-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
|
