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[emacs.git] / lisp / gnus / mm-decode.el

;;; mm-decode.el --- Functions for decoding MIME things

;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
;;   2005 Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;;      MORIOKA Tomohiko <morioka@jaist.ac.jp>
;; 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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;;; Code:

(require 'mail-parse)
(require 'mailcap)
(require 'mm-bodies)
(eval-when-compile (require 'cl)
                   (require 'term))

(eval-and-compile
  (autoload 'executable-find "executable")
  (autoload 'mm-inline-partial "mm-partial")
  (autoload 'mm-inline-external-body "mm-extern")
  (autoload 'mm-insert-inline "mm-view"))

(defvar gnus-current-window-configuration)

(add-hook 'gnus-exit-gnus-hook 'mm-destroy-postponed-undisplay-list)

(defgroup mime-display ()
  "Display of MIME in mail and news articles."
  :link '(custom-manual "(emacs-mime)Display Customization")
  :version "21.1"
  :group 'mail
  :group 'news
  :group 'multimedia)

(defgroup mime-security ()
  "MIME security in mail and news articles."
  :link '(custom-manual "(emacs-mime)Display Customization")
  :group 'mail
  :group 'news
  :group 'multimedia)

;;; Convenience macros.

(defmacro mm-handle-buffer (handle)
  `(nth 0 ,handle))
(defmacro mm-handle-type (handle)
  `(nth 1 ,handle))
(defsubst mm-handle-media-type (handle)
  (if (stringp (car handle))
      (car handle)
    (car (mm-handle-type handle))))
(defsubst mm-handle-media-supertype (handle)
  (car (split-string (mm-handle-media-type handle) "/")))
(defsubst mm-handle-media-subtype (handle)
  (cadr (split-string (mm-handle-media-type handle) "/")))
(defmacro mm-handle-encoding (handle)
  `(nth 2 ,handle))
(defmacro mm-handle-undisplayer (handle)
  `(nth 3 ,handle))
(defmacro mm-handle-set-undisplayer (handle function)
  `(setcar (nthcdr 3 ,handle) ,function))
(defmacro mm-handle-disposition (handle)
  `(nth 4 ,handle))
(defmacro mm-handle-description (handle)
  `(nth 5 ,handle))
(defmacro mm-handle-cache (handle)
  `(nth 6 ,handle))
(defmacro mm-handle-set-cache (handle contents)
  `(setcar (nthcdr 6 ,handle) ,contents))
(defmacro mm-handle-id (handle)
  `(nth 7 ,handle))
(defmacro mm-handle-multipart-original-buffer (handle)
  `(get-text-property 0 'buffer (car ,handle)))
(defmacro mm-handle-multipart-from (handle)
  `(get-text-property 0 'from (car ,handle)))
(defmacro mm-handle-multipart-ctl-parameter (handle parameter)
  `(get-text-property 0 ,parameter (car ,handle)))

(defmacro mm-make-handle (&optional buffer type encoding undisplayer
                                    disposition description cache
                                    id)
  `(list ,buffer ,type ,encoding ,undisplayer
         ,disposition ,description ,cache ,id))

(defcustom mm-text-html-renderer
  (cond ((locate-library "w3") 'w3)
        ((executable-find "w3m") (if (locate-library "w3m")
                                     'w3m
                                   'w3m-standalone))
        ((executable-find "links") 'links)
        ((executable-find "lynx") 'lynx)
        (t 'html2text))
  "Render of HTML contents.
It is one of defined renderer types, or a rendering function.
The defined renderer types are:
`w3'   : use Emacs/W3;
`w3m'  : use emacs-w3m;
`w3m-standalone': use w3m;
`links': use links;
`lynx' : use lynx;
`html2text' : use html2text;
nil    : use external viewer."
  :version "22.1"
  :type '(choice (const w3)
                 (const w3m)
                 (const w3m-standalone)
                 (const links)
                 (const lynx)
                 (const html2text)
                 (const nil)
                 (function))
  :group 'mime-display)

(defvar mm-inline-text-html-renderer nil
  "Function used for rendering inline HTML contents.
It is suggested to customize `mm-text-html-renderer' instead.")

(defcustom mm-inline-text-html-with-images nil
  "If non-nil, Gnus will allow retrieving images in HTML contents with
the <img> tags.  It has no effect on Emacs/w3.  See also the
documentation for the `mm-w3m-safe-url-regexp' variable."
  :version "22.1"
  :type 'boolean
  :group 'mime-display)

(defcustom mm-w3m-safe-url-regexp "\\`cid:"
  "Regexp matching URLs which are considered to be safe.
Some HTML mails might contain a nasty trick used by spammers, using
the <img> tag which is far more evil than the [Click Here!] button.
It is most likely intended to check whether the ominous spam mail has
reached your eyes or not, in which case the spammer knows for sure
that your email address is valid.  It is done by embedding an
identifier string into a URL that you might automatically retrieve
when displaying the image.  The default value is \"\\\\`cid:\" which only
matches parts embedded to the Multipart/Related type MIME contents and
Gnus will never connect to the spammer's site arbitrarily.  You may
set this variable to nil if you consider all urls to be safe."
  :version "22.1"
  :type '(choice (regexp :tag "Regexp")
                 (const :tag "All URLs are safe" nil))
  :group 'mime-display)

(defcustom mm-inline-text-html-with-w3m-keymap t
  "If non-nil, use emacs-w3m command keys in the article buffer."
  :version "22.1"
  :type 'boolean
  :group 'mime-display)

(defcustom mm-enable-external t
  "Indicate whether external MIME handlers should be used.

If t, all defined external MIME handlers are used.  If nil, files are saved by
`mailcap-save-binary-file'.  If it is the symbol `ask', you are prompted
before the external MIME handler is invoked."
  :version "22.1"
  :type '(choice (const :tag "Always" t)
                 (const :tag "Never" nil)
                 (const :tag "Ask" ask))
  :group 'mime-display)

(defcustom mm-inline-media-tests
  '(("image/p?jpeg"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'jpeg handle)))
    ("image/png"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'png handle)))
    ("image/gif"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'gif handle)))
    ("image/tiff"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'tiff handle)) )
    ("image/xbm"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'xbm handle)))
    ("image/x-xbitmap"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'xbm handle)))
    ("image/xpm"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'xpm handle)))
    ("image/x-xpixmap"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'xpm handle)))
    ("image/bmp"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'bmp handle)))
    ("image/x-portable-bitmap"
     mm-inline-image
     (lambda (handle)
       (mm-valid-and-fit-image-p 'pbm handle)))
    ("text/plain" mm-inline-text identity)
    ("text/enriched" mm-inline-text identity)
    ("text/richtext" mm-inline-text identity)
    ("text/x-patch" mm-display-patch-inline
     (lambda (handle)
       ;; If the diff-mode.el package is installed, the function is
       ;; autoloaded.  Checking (locate-library "diff-mode") would be trying
       ;; to cater to broken installations.  OTOH checking the function
       ;; makes it possible to install another package which provides an
       ;; alternative implementation of diff-mode.  --Stef
       (fboundp 'diff-mode)))
    ("application/emacs-lisp" mm-display-elisp-inline identity)
    ("application/x-emacs-lisp" mm-display-elisp-inline identity)
    ("text/html"
     mm-inline-text-html
     (lambda (handle)
       (or mm-inline-text-html-renderer
           mm-text-html-renderer)))
    ("text/x-vcard"
     mm-inline-text-vcard
     (lambda (handle)
       (or (featurep 'vcard)
           (locate-library "vcard"))))
    ("message/delivery-status" mm-inline-text identity)
    ("message/rfc822" mm-inline-message identity)
    ("message/partial" mm-inline-partial identity)
    ("message/external-body" mm-inline-external-body identity)
    ("text/.*" mm-inline-text identity)
    ("audio/wav" mm-inline-audio
     (lambda (handle)
       (and (or (featurep 'nas-sound) (featurep 'native-sound))
            (device-sound-enabled-p))))
    ("audio/au"
     mm-inline-audio
     (lambda (handle)
       (and (or (featurep 'nas-sound) (featurep 'native-sound))
            (device-sound-enabled-p))))
    ("application/pgp-signature" ignore identity)
    ("application/x-pkcs7-signature" ignore identity)
    ("application/pkcs7-signature" ignore identity)
    ("application/x-pkcs7-mime" ignore identity)
    ("application/pkcs7-mime" ignore identity)
    ("multipart/alternative" ignore identity)
    ("multipart/mixed" ignore identity)
    ("multipart/related" ignore identity)
    ;; Disable audio and image
    ("audio/.*" ignore ignore)
    ("image/.*" ignore ignore)
    ;; Default to displaying as text
    (".*" mm-inline-text mm-readable-p))
  "Alist of media types/tests saying whether types can be displayed inline."
  :type '(repeat (list (regexp :tag "MIME type")
                       (function :tag "Display function")
                       (function :tag "Display test")))
  :group 'mime-display)

(defcustom mm-inlined-types
  '("image/.*" "text/.*" "message/delivery-status" "message/rfc822"
    "message/partial" "message/external-body" "application/emacs-lisp"
    "application/x-emacs-lisp"
    "application/pgp-signature" "application/x-pkcs7-signature"
    "application/pkcs7-signature" "application/x-pkcs7-mime"
    "application/pkcs7-mime")
  "List of media types that are to be displayed inline.
See also `mm-inline-media-tests', which says how to display a media
type inline."
  :type '(repeat string)
  :group 'mime-display)

(defcustom mm-keep-viewer-alive-types
  '("application/postscript" "application/msword" "application/vnd.ms-excel"
    "application/pdf" "application/x-dvi")
  "List of media types for which the external viewer will not be killed
when selecting a different article."
  :version "22.1"
  :type '(repeat string)
  :group 'mime-display)

(defcustom mm-automatic-display
  '("text/plain" "text/enriched" "text/richtext" "text/html"
    "text/x-vcard" "image/.*" "message/delivery-status" "multipart/.*"
    "message/rfc822" "text/x-patch" "application/pgp-signature"
    "application/emacs-lisp" "application/x-emacs-lisp"
    "application/x-pkcs7-signature"
    "application/pkcs7-signature" "application/x-pkcs7-mime"
    "application/pkcs7-mime")
  "A list of MIME types to be displayed automatically."
  :type '(repeat string)
  :group 'mime-display)

(defcustom mm-attachment-override-types '("text/x-vcard"
                                          "application/pkcs7-mime"
                                          "application/x-pkcs7-mime"
                                          "application/pkcs7-signature"
                                          "application/x-pkcs7-signature")
  "Types to have \"attachment\" ignored if they can be displayed inline."
  :type '(repeat string)
  :group 'mime-display)

(defcustom mm-inline-override-types nil
  "Types to be treated as attachments even if they can be displayed inline."
  :type '(repeat string)
  :group 'mime-display)

(defcustom mm-automatic-external-display nil
  "List of MIME type regexps that will be displayed externally automatically."
  :type '(repeat string)
  :group 'mime-display)

(defcustom mm-discouraged-alternatives nil
  "List of MIME types that are discouraged when viewing multipart/alternative.
Viewing agents are supposed to view the last possible part of a message,
as that is supposed to be the richest.  However, users may prefer other
types instead, and this list says what types are most unwanted.  If,
for instance, text/html parts are very unwanted, and text/richtext are
somewhat unwanted, then the value of this variable should be set
to:

 (\"text/html\" \"text/richtext\")

Adding \"image/.*\" might also be useful.  Spammers use it as the
prefered part of multipart/alternative messages."
  :type '(repeat regexp) ;; See `mm-preferred-alternative-precedence'.
  :group 'mime-display)

(defcustom mm-tmp-directory
  (if (fboundp 'temp-directory)
      (temp-directory)
    (if (boundp 'temporary-file-directory)
        temporary-file-directory
      "/tmp/"))
  "Where mm will store its temporary files."
  :type 'directory
  :group 'mime-display)

(defcustom mm-inline-large-images nil
  "If non-nil, then all images fit in the buffer."
  :type 'boolean
  :group 'mime-display)

(defvar mm-file-name-rewrite-functions
  '(mm-file-name-delete-control mm-file-name-delete-gotchas)
  "*List of functions used for rewriting file names of MIME parts.
Each function takes a file name as input and returns a file name.

Ready-made functions include
`mm-file-name-delete-control'
`mm-file-name-delete-gotchas'
`mm-file-name-delete-whitespace',
`mm-file-name-trim-whitespace',
`mm-file-name-collapse-whitespace',
`mm-file-name-replace-whitespace',
`capitalize', `downcase', `upcase', and
`upcase-initials'.")

(defvar mm-path-name-rewrite-functions nil
  "*List of functions for rewriting the full file names of MIME parts.
This is used when viewing parts externally, and is meant for
transforming the absolute name so that non-compliant programs can find
the file where it's saved.

Each function takes a file name as input and returns a file name.")

(defvar mm-file-name-replace-whitespace nil
  "String used for replacing whitespace characters; default is `\"_\"'.")

(defcustom mm-default-directory nil
  "The default directory where mm will save files.
If not set, `default-directory' will be used."
  :type '(choice directory (const :tag "Default" nil))
  :group 'mime-display)

(defcustom mm-attachment-file-modes 384
  "Set the mode bits of saved attachments to this integer."
  :version "22.1"
  :type 'integer
  :group 'mime-display)

(defcustom mm-external-terminal-program "xterm"
  "The program to start an external terminal."
  :version "22.1"
  :type 'string
  :group 'mime-display)

;;; Internal variables.

(defvar mm-last-shell-command "")
(defvar mm-content-id-alist nil)
(defvar mm-postponed-undisplay-list nil)

;; According to RFC2046, in particular, in a digest, the default
;; Content-Type value for a body part is changed from "text/plain" to
;; "message/rfc822".
(defvar mm-dissect-default-type "text/plain")

(autoload 'mml2015-verify "mml2015")
(autoload 'mml2015-verify-test "mml2015")
(autoload 'mml-smime-verify "mml-smime")
(autoload 'mml-smime-verify-test "mml-smime")

(defvar mm-verify-function-alist
  '(("application/pgp-signature" mml2015-verify "PGP" mml2015-verify-test)
    ("application/x-gnus-pgp-signature" mm-uu-pgp-signed-extract-1 "PGP"
     mm-uu-pgp-signed-test)
    ("application/pkcs7-signature" mml-smime-verify "S/MIME"
     mml-smime-verify-test)
    ("application/x-pkcs7-signature" mml-smime-verify "S/MIME"
     mml-smime-verify-test)))

(defcustom mm-verify-option 'never
  "Option of verifying signed parts.
`never', not verify; `always', always verify;
`known', only verify known protocols.  Otherwise, ask user."
  :version "22.1"
  :type '(choice (item always)
                 (item never)
                 (item :tag "only known protocols" known)
                 (item :tag "ask" nil))
  :group 'mime-security)

(autoload 'mml2015-decrypt "mml2015")
(autoload 'mml2015-decrypt-test "mml2015")

(defvar mm-decrypt-function-alist
  '(("application/pgp-encrypted" mml2015-decrypt "PGP" mml2015-decrypt-test)
    ("application/x-gnus-pgp-encrypted" mm-uu-pgp-encrypted-extract-1 "PGP"
     mm-uu-pgp-encrypted-test)))

(defcustom mm-decrypt-option nil
  "Option of decrypting encrypted parts.
`never', not decrypt; `always', always decrypt;
`known', only decrypt known protocols.  Otherwise, ask user."
  :version "22.1"
  :type '(choice (item always)
                 (item never)
                 (item :tag "only known protocols" known)
                 (item :tag "ask" nil))
  :group 'mime-security)

(defvar mm-viewer-completion-map
  (let ((map (make-sparse-keymap 'mm-viewer-completion-map)))
    (set-keymap-parent map minibuffer-local-completion-map)
    ;; Should we bind other key to minibuffer-complete-word?
    (define-key map " " 'self-insert-command)
    map)
  "Keymap for input viewer with completion.")

(defvar mm-viewer-completion-map
  (let ((map (make-sparse-keymap 'mm-viewer-completion-map)))
    (set-keymap-parent map minibuffer-local-completion-map)
    ;; Should we bind other key to minibuffer-complete-word?
    (define-key map " " 'self-insert-command)
    map)
  "Keymap for input viewer with completion.")

;;; The functions.

(defun mm-alist-to-plist (alist)
  "Convert association list ALIST into the equivalent property-list form.
The plist is returned.  This converts from

\((a . 1) (b . 2) (c . 3))

into

\(a 1 b 2 c 3)

The original alist is not modified.  See also `destructive-alist-to-plist'."
  (let (plist)
    (while alist
      (let ((el (car alist)))
        (setq plist (cons (cdr el) (cons (car el) plist))))
      (setq alist (cdr alist)))
    (nreverse plist)))

(defun mm-keep-viewer-alive-p (handle)
  "Say whether external viewer for HANDLE should stay alive."
  (let ((types mm-keep-viewer-alive-types)
        (type (mm-handle-media-type handle))
        ty)
    (catch 'found
      (while (setq ty (pop types))
        (when (string-match ty type)
          (throw 'found t))))))

(defun mm-handle-set-external-undisplayer (handle function)
  "Set the undisplayer for HANDLE to FUNCTION.
Postpone undisplaying of viewers for types in
`mm-keep-viewer-alive-types'."
  (if (mm-keep-viewer-alive-p handle)
      (let ((new-handle (copy-sequence handle)))
        (mm-handle-set-undisplayer new-handle function)
        (mm-handle-set-undisplayer handle nil)
        (push new-handle mm-postponed-undisplay-list))
    (mm-handle-set-undisplayer handle function)))

(defun mm-destroy-postponed-undisplay-list ()
  (when mm-postponed-undisplay-list
    (message "Destroying external MIME viewers")
    (mm-destroy-parts mm-postponed-undisplay-list)))

(defun mm-dissect-buffer (&optional no-strict-mime loose-mime from)
  "Dissect the current buffer and return a list of MIME handles."
  (save-excursion
    (let (ct ctl type subtype cte cd description id result)
      (save-restriction
        (mail-narrow-to-head)
        (when (or no-strict-mime
                  loose-mime
                  (mail-fetch-field "mime-version"))
          (setq ct (mail-fetch-field "content-type")
                ctl (ignore-errors (mail-header-parse-content-type ct))
                cte (mail-fetch-field "content-transfer-encoding")
                cd (mail-fetch-field "content-disposition")
                description (mail-fetch-field "content-description")
                id (mail-fetch-field "content-id"))
          (unless from
                (setq from (mail-fetch-field "from")))
          ;; FIXME: In some circumstances, this code is running within
          ;; an unibyte macro.  mail-extract-address-components
          ;; creates unibyte buffers. This `if', though not a perfect
          ;; solution, avoids most of them.
          (if from
              (setq from (cadr (mail-extract-address-components from))))))
      (when cte
        (setq cte (mail-header-strip cte)))
      (if (or (not ctl)
              (not (string-match "/" (car ctl))))
          (mm-dissect-singlepart
           (list mm-dissect-default-type)
           (and cte (intern (downcase (mail-header-remove-whitespace
                                       (mail-header-remove-comments
                                        cte)))))
           no-strict-mime
           (and cd (ignore-errors (mail-header-parse-content-disposition cd)))
           description)
        (setq type (split-string (car ctl) "/"))
        (setq subtype (cadr type)
              type (pop type))
        (setq
         result
         (cond
          ((equal type "multipart")
           (let ((mm-dissect-default-type (if (equal subtype "digest")
                                              "message/rfc822"
                                            "text/plain"))
                 (start (cdr (assq 'start (cdr ctl)))))
             (add-text-properties 0 (length (car ctl))
                                  (mm-alist-to-plist (cdr ctl)) (car ctl))

             ;; what really needs to be done here is a way to link a
             ;; MIME handle back to it's parent MIME handle (in a multilevel
             ;; MIME article).  That would probably require changing
             ;; the mm-handle API so we simply store the multipart buffer
             ;; name as a text property of the "multipart/whatever" string.
             (add-text-properties 0 (length (car ctl))
                                  (list 'buffer (mm-copy-to-buffer)
                                        'from from
                                        'start start)
                                  (car ctl))
             (cons (car ctl) (mm-dissect-multipart ctl from))))
          (t
           (mm-possibly-verify-or-decrypt
            (mm-dissect-singlepart
             ctl
             (and cte (intern (downcase (mail-header-remove-whitespace
                                         (mail-header-remove-comments
                                          cte)))))
             no-strict-mime
             (and cd (ignore-errors
                       (mail-header-parse-content-disposition cd)))
             description id)
            ctl))))
        (when id
          (when (string-match " *<\\(.*\\)> *" id)
            (setq id (match-string 1 id)))
          (push (cons id result) mm-content-id-alist))
        result))))

(defun mm-dissect-singlepart (ctl cte &optional force cdl description id)
  (when (or force
            (if (equal "text/plain" (car ctl))
                (assoc 'format ctl)
              t))
    (mm-make-handle
     (mm-copy-to-buffer) ctl cte nil cdl description nil id)))

(defun mm-dissect-multipart (ctl from)
  (goto-char (point-min))
  (let* ((boundary (concat "\n--" (mail-content-type-get ctl 'boundary)))
         (close-delimiter (concat (regexp-quote boundary) "--[ \t]*$"))
         start parts
         (end (save-excursion
                (goto-char (point-max))
                (if (re-search-backward close-delimiter nil t)
                    (match-beginning 0)
                  (point-max)))))
    (setq boundary (concat (regexp-quote boundary) "[ \t]*$"))
    (while (and (< (point) end) (re-search-forward boundary end t))
      (goto-char (match-beginning 0))
      (when start
        (save-excursion
          (save-restriction
            (narrow-to-region start (point))
            (setq parts (nconc (list (mm-dissect-buffer t nil from)) parts)))))
      (end-of-line 2)
      (or (looking-at boundary)
          (forward-line 1))
      (setq start (point)))
    (when (and start (< start end))
      (save-excursion
        (save-restriction
          (narrow-to-region start end)
          (setq parts (nconc (list (mm-dissect-buffer t nil from)) parts)))))
    (mm-possibly-verify-or-decrypt (nreverse parts) ctl)))

(defun mm-copy-to-buffer ()
  "Copy the contents of the current buffer to a fresh buffer."
  (save-excursion
    (let ((obuf (current-buffer))
          beg)
      (goto-char (point-min))
      (search-forward-regexp "^\n" nil t)
      (setq beg (point))
      (set-buffer
       ;; Preserve the data's unibyteness (for url-insert-file-contents).
       (let ((default-enable-multibyte-characters (mm-multibyte-p)))
         (generate-new-buffer " *mm*")))
      (insert-buffer-substring obuf beg)
      (current-buffer))))

(defun mm-display-parts (handle &optional no-default)
  (if (stringp (car handle))
      (mapcar 'mm-display-parts (cdr handle))
    (if (bufferp (car handle))
        (save-restriction
          (narrow-to-region (point) (point))
          (mm-display-part handle)
          (goto-char (point-max)))
      (mapcar 'mm-display-parts handle))))

(defun mm-display-part (handle &optional no-default)
  "Display the MIME part represented by HANDLE.
Returns nil if the part is removed; inline if displayed inline;
external if displayed external."
  (save-excursion
    (mailcap-parse-mailcaps)
    (if (mm-handle-displayed-p handle)
        (mm-remove-part handle)
      (let* ((type (mm-handle-media-type handle))
             (method (mailcap-mime-info type))
             (filename (or (mail-content-type-get
                            (mm-handle-disposition handle) 'filename)
                           (mail-content-type-get
                            (mm-handle-type handle) 'name)
                           "<file>"))
             (external mm-enable-external))
        (if (and (mm-inlinable-p handle)
                 (mm-inlined-p handle))
            (progn
              (forward-line 1)
              (mm-display-inline handle)
              'inline)
          (when (or method
                    (not no-default))
            (if (and (not method)
                     (equal "text" (car (split-string type))))
                (progn
                  (forward-line 1)
                  (mm-insert-inline handle (mm-get-part handle))
                  'inline)
              (if (and method ;; If nil, we always use "save".
                       (stringp method) ;; 'mailcap-save-binary-file
                       (or (eq mm-enable-external t)
                           (and (eq mm-enable-external 'ask)
                                (y-or-n-p
                                 (concat
                                  "Display part (" type
                                  ") using external program"
                                  ;; Can non-string method ever happen?
                                  (if (stringp method)
                                      (concat
                                       " \"" (format method filename) "\"")
                                    "")
                                  "? ")))))
                  (setq external t)
                (setq external nil))
              (if external
                  (mm-display-external
                   handle (or method 'mailcap-save-binary-file))
                (mm-display-external
                 handle 'mailcap-save-binary-file)))))))))

(defun mm-display-external (handle method)
  "Display HANDLE using METHOD."
  (let ((outbuf (current-buffer)))
    (mm-with-unibyte-buffer
      (if (functionp method)
          (let ((cur (current-buffer)))
            (if (eq method 'mailcap-save-binary-file)
                (progn
                  (set-buffer (generate-new-buffer " *mm*"))
                  (setq method nil))
              (mm-insert-part handle)
              (let ((win (get-buffer-window cur t)))
                (when win
                  (select-window win)))
              (switch-to-buffer (generate-new-buffer " *mm*")))
            (buffer-disable-undo)
            (mm-set-buffer-file-coding-system mm-binary-coding-system)
            (insert-buffer-substring cur)
            (goto-char (point-min))
            (when method
              (message "Viewing with %s" method))
            (let ((mm (current-buffer))
                  (non-viewer (assq 'non-viewer
                                    (mailcap-mime-info
                                     (mm-handle-media-type handle) t))))
              (unwind-protect
                  (if method
                      (funcall method)
                    (mm-save-part handle))
                (when (and (not non-viewer)
                           method)
                  (mm-handle-set-undisplayer handle mm)))))
        ;; The function is a string to be executed.
        (mm-insert-part handle)
        (let* ((dir (mm-make-temp-file
                     (expand-file-name "emm." mm-tmp-directory) 'dir))
               (filename (or
                          (mail-content-type-get
                           (mm-handle-disposition handle) 'filename)
                          (mail-content-type-get
                           (mm-handle-type handle) 'name)))
               (mime-info (mailcap-mime-info
                           (mm-handle-media-type handle) t))
               (needsterm (or (assoc "needsterm" mime-info)
                              (assoc "needsterminal" mime-info)))
               (copiousoutput (assoc "copiousoutput" mime-info))
               file buffer)
          ;; We create a private sub-directory where we store our files.
          (set-file-modes dir 448)
          (if filename
              (setq file (expand-file-name
                          (gnus-map-function mm-file-name-rewrite-functions
                                             (file-name-nondirectory filename))
                          dir))
            (setq file (mm-make-temp-file (expand-file-name "mm." dir)))
            (let ((newname
                   ;; Use nametemplate (defined in RFC1524) if it is
                   ;; specified in mailcap.
                   (if (assoc "nametemplate" mime-info)
                       (format (assoc "nametemplate" mime-info) file)
                     ;; Add a suffix according to `mailcap-mime-extensions'.
                     (concat file (car (rassoc (mm-handle-media-type handle)
                                               mailcap-mime-extensions))))))
              (unless (string-equal file newname)
                (when (file-exists-p file)
                  (rename-file file newname))
                (setq file newname))))
          (let ((coding-system-for-write mm-binary-coding-system))
            (write-region (point-min) (point-max) file nil 'nomesg))
          (message "Viewing with %s" method)
          (cond
           (needsterm
            (let ((command (mm-mailcap-command
                            method file (mm-handle-type handle))))
              (unwind-protect
                  (if window-system
                      (start-process "*display*" nil
                                     mm-external-terminal-program
                                     "-e" shell-file-name
                                     shell-command-switch command)
                    (require 'term)
                    (require 'gnus-win)
                    (set-buffer
                     (setq buffer
                           (make-term "display"
                                      shell-file-name
                                      nil
                                      shell-command-switch command)))
                    (term-mode)
                    (term-char-mode)
                    (set-process-sentinel
                     (get-buffer-process buffer)
                     `(lambda (process state)
                        (if (eq 'exit (process-status process))
                            (gnus-configure-windows
                             ',gnus-current-window-configuration))))
                    (gnus-configure-windows 'display-term))
                (mm-handle-set-external-undisplayer handle (cons file buffer)))
              (message "Displaying %s..." command))
            'external)
           (copiousoutput
            (with-current-buffer outbuf
              (forward-line 1)
              (mm-insert-inline
               handle
               (unwind-protect
                   (progn
                     (call-process shell-file-name nil
                                   (setq buffer
                                         (generate-new-buffer " *mm*"))
                                   nil
                                   shell-command-switch
                                   (mm-mailcap-command
                                    method file (mm-handle-type handle)))
                     (if (buffer-live-p buffer)
                         (with-current-buffer buffer
                           (buffer-string))))
                 (progn
                   (ignore-errors (delete-file file))
                   (ignore-errors (delete-directory
                                   (file-name-directory file)))
                   (ignore-errors (kill-buffer buffer))))))
            'inline)
           (t
            ;; Deleting the temp file should be postponed for some wrappers,
            ;; shell scripts, and so on, which might exit right after having
            ;; started a viewer command as a background job.
            (let ((command (mm-mailcap-command
                            method file (mm-handle-type handle))))
              (unwind-protect
                  (progn
                    (start-process "*display*"
                                   (setq buffer
                                         (generate-new-buffer " *mm*"))
                                   shell-file-name
                                   shell-command-switch command)
                    (set-process-sentinel
                     (get-buffer-process buffer)
                     (lexical-let ;; Don't use `let'.
                         ;; Function used to remove temp file and directory.
                         ((fn `(lambda nil
                                 ;; Don't use `ignore-errors'.
                                 (condition-case nil
                                     (delete-file ,file)
                                   (error))
                                 (condition-case nil
                                     (delete-directory
                                      ,(file-name-directory file))
                                   (error))))
                          ;; Form uses to kill the process buffer and
                          ;; remove the undisplayer.
                          (fm `(progn
                                 (kill-buffer ,buffer)
                                 ,(macroexpand
                                   (list 'mm-handle-set-undisplayer
                                         (list 'quote handle)
                                         nil))))
                          ;; Message to be issued when the process exits.
                          (done (format "Displaying %s...done" command))
                          ;; In particular, the timer object (which is
                          ;; a vector in Emacs but is a list in XEmacs)
                          ;; requires that it is lexically scoped.
                          (timer (run-at-time 2.0 nil 'ignore)))
                       (lambda (process state)
                         (when (eq 'exit (process-status process))
                           (if (memq timer timer-list)
                               (timer-set-function timer fn)
                             (funcall fn))
                           (ignore-errors (eval fm))
                           (message "%s" done))))))
                (mm-handle-set-external-undisplayer
                 handle (cons file buffer)))
              (message "Displaying %s..." command))
            'external)))))))

(defun mm-mailcap-command (method file type-list)
  (let ((ctl (cdr type-list))
        (beg 0)
        (uses-stdin t)
        out sub total)
    (while (string-match "%{\\([^}]+\\)}\\|'%s'\\|\"%s\"\\|%s\\|%t\\|%%"
                         method beg)
      (push (substring method beg (match-beginning 0)) out)
      (setq beg (match-end 0)
            total (match-string 0 method)
            sub (match-string 1 method))
      (cond
       ((string= total "%%")
        (push "%" out))
       ((or (string= total "%s")
            ;; We do our own quoting.
            (string= total "'%s'")
            (string= total "\"%s\""))
        (setq uses-stdin nil)
        (push (mm-quote-arg
               (gnus-map-function mm-path-name-rewrite-functions file)) out))
       ((string= total "%t")
        (push (mm-quote-arg (car type-list)) out))
       (t
        (push (mm-quote-arg (or (cdr (assq (intern sub) ctl)) "")) out))))
    (push (substring method beg (length method)) out)
    (when uses-stdin
      (push "<" out)
      (push (mm-quote-arg
             (gnus-map-function mm-path-name-rewrite-functions file))
            out))
    (mapconcat 'identity (nreverse out) "")))

(defun mm-remove-parts (handles)
  "Remove the displayed MIME parts represented by HANDLES."
  (if (and (listp handles)
           (bufferp (car handles)))
      (mm-remove-part handles)
    (let (handle)
      (while (setq handle (pop handles))
        (cond
         ((stringp handle)
          (when (buffer-live-p (get-text-property 0 'buffer handle))
            (kill-buffer (get-text-property 0 'buffer handle))))
         ((and (listp handle)
               (stringp (car handle)))
          (mm-remove-parts (cdr handle)))
         (t
          (mm-remove-part handle)))))))

(defun mm-destroy-parts (handles)
  "Remove the displayed MIME parts represented by HANDLES."
  (if (and (listp handles)
           (bufferp (car handles)))
      (mm-destroy-part handles)
    (let (handle)
      (while (setq handle (pop handles))
        (cond
         ((stringp handle)
          (when (buffer-live-p (get-text-property 0 'buffer handle))
            (kill-buffer (get-text-property 0 'buffer handle))))
         ((and (listp handle)
               (stringp (car handle)))
          (mm-destroy-parts handle))
         (t
          (mm-destroy-part handle)))))))

(defun mm-remove-part (handle)
  "Remove the displayed MIME part represented by HANDLE."
  (when (listp handle)
    (let ((object (mm-handle-undisplayer handle)))
      (ignore-errors
        (cond
         ;; Internally displayed part.
         ((mm-annotationp object)
          (delete-annotation object))
         ((or (functionp object)
              (and (listp object)
                   (eq (car object) 'lambda)))
          (funcall object))
         ;; Externally displayed part.
         ((consp object)
          (condition-case ()
              (while (get-buffer-process (cdr object))
                (interrupt-process (get-buffer-process (cdr object)))
                (message "Waiting for external displayer to die...")
                (sit-for 1))
            (quit)
            (error))
          (ignore-errors (and (cdr object) (kill-buffer (cdr object))))
          (message "Waiting for external displayer to die...done")
          (ignore-errors (delete-file (car object)))
          (ignore-errors (delete-directory (file-name-directory
                                            (car object)))))
         ((bufferp object)
          (when (buffer-live-p object)
            (kill-buffer object)))))
      (mm-handle-set-undisplayer handle nil))))

(defun mm-display-inline (handle)
  (let* ((type (mm-handle-media-type handle))
         (function (cadr (mm-assoc-string-match mm-inline-media-tests type))))
    (funcall function handle)
    (goto-char (point-min))))

(defun mm-assoc-string-match (alist type)
  (dolist (elem alist)
    (when (string-match (car elem) type)
      (return elem))))

(defun mm-automatic-display-p (handle)
  "Say whether the user wants HANDLE to be displayed automatically."
  (let ((methods mm-automatic-display)
        (type (mm-handle-media-type handle))
        method result)
    (while (setq method (pop methods))
      (when (and (not (mm-inline-override-p handle))
                 (string-match method type))
        (setq result t
              methods nil)))
    result))

(defun mm-inlinable-p (handle)
  "Say whether HANDLE can be displayed inline."
  (let ((alist mm-inline-media-tests)
        (type (mm-handle-media-type handle))
        test)
    (while alist
      (when (string-match (caar alist) type)
        (setq test (caddar alist)
              alist nil)
        (setq test (funcall test handle)))
      (pop alist))
    test))

(defun mm-inlined-p (handle)
  "Say whether the user wants HANDLE to be displayed inline."
  (let ((methods mm-inlined-types)
        (type (mm-handle-media-type handle))
        method result)
    (while (setq method (pop methods))
      (when (and (not (mm-inline-override-p handle))
                 (string-match method type))
        (setq result t
              methods nil)))
    result))

(defun mm-attachment-override-p (handle)
  "Say whether HANDLE should have attachment behavior overridden."
  (let ((types mm-attachment-override-types)
        (type (mm-handle-media-type handle))
        ty)
    (catch 'found
      (while (setq ty (pop types))
        (when (and (string-match ty type)
                   (mm-inlinable-p handle))
          (throw 'found t))))))

(defun mm-inline-override-p (handle)
  "Say whether HANDLE should have inline behavior overridden."
  (let ((types mm-inline-override-types)
        (type (mm-handle-media-type handle))
        ty)
    (catch 'found
      (while (setq ty (pop types))
        (when (string-match ty type)
          (throw 'found t))))))

(defun mm-automatic-external-display-p (type)
  "Return the user-defined method for TYPE."
  (let ((methods mm-automatic-external-display)
        method result)
    (while (setq method (pop methods))
      (when (string-match method type)
        (setq result t
              methods nil)))
    result))

(defun mm-destroy-part (handle)
  "Destroy the data structures connected to HANDLE."
  (when (listp handle)
    (mm-remove-part handle)
    (when (buffer-live-p (mm-handle-buffer handle))
      (kill-buffer (mm-handle-buffer handle)))))

(defun mm-handle-displayed-p (handle)
  "Say whether HANDLE is displayed or not."
  (mm-handle-undisplayer handle))

;;;
;;; Functions for outputting parts
;;;

(defun mm-get-part (handle)
  "Return the contents of HANDLE as a string."
  (mm-with-unibyte-buffer
    (insert (with-current-buffer (mm-handle-buffer handle)
              (mm-with-unibyte-current-buffer
                (buffer-string))))
    (mm-decode-content-transfer-encoding
     (mm-handle-encoding handle)
     (mm-handle-media-type handle))
    (buffer-string)))

(defun mm-insert-part (handle)
  "Insert the contents of HANDLE in the current buffer."
  (save-excursion
    (insert
     (cond ((eq (mail-content-type-get (mm-handle-type handle) 'charset)
                'gnus-decoded)
            (with-current-buffer (mm-handle-buffer handle)
              (buffer-string)))
           ((mm-multibyte-p)
            (mm-string-as-multibyte (mm-get-part handle)))
           (t
            (mm-get-part handle))))))

(defun mm-file-name-delete-whitespace (file-name)
  "Remove all whitespace characters from FILE-NAME."
  (while (string-match "\\s-+" file-name)
    (setq file-name (replace-match "" t t file-name)))
  file-name)

(defun mm-file-name-trim-whitespace (file-name)
  "Remove leading and trailing whitespace characters from FILE-NAME."
  (when (string-match "\\`\\s-+" file-name)
    (setq file-name (substring file-name (match-end 0))))
  (when (string-match "\\s-+\\'" file-name)
    (setq file-name (substring file-name 0 (match-beginning 0))))
  file-name)

(defun mm-file-name-collapse-whitespace (file-name)
  "Collapse multiple whitespace characters in FILE-NAME."
  (while (string-match "\\s-\\s-+" file-name)
    (setq file-name (replace-match " " t t file-name)))
  file-name)

(defun mm-file-name-replace-whitespace (file-name)
  "Replace whitespace characters in FILE-NAME with underscores.
Set the option `mm-file-name-replace-whitespace' to any other
string if you do not like underscores."
  (let ((s (or mm-file-name-replace-whitespace "_")))
    (while (string-match "\\s-" file-name)
      (setq file-name (replace-match s t t file-name))))
  file-name)

(defun mm-file-name-delete-control (filename)
  "Delete control characters from FILENAME."
  (gnus-replace-in-string filename "[\x00-\x1f\x7f]" ""))

(defun mm-file-name-delete-gotchas (filename)
  "Delete shell gotchas from FILENAME."
  (setq filename (gnus-replace-in-string filename "[<>|]" ""))
  (gnus-replace-in-string filename "^[.-]+" ""))

(defun mm-save-part (handle)
  "Write HANDLE to a file."
  (let* ((name (mail-content-type-get (mm-handle-type handle) 'name))
         (filename (mail-content-type-get
                    (mm-handle-disposition handle) 'filename))
         file)
    (when filename
      (setq filename (gnus-map-function mm-file-name-rewrite-functions
                                        (file-name-nondirectory filename))))
    (setq file
          (mm-with-multibyte
            (read-file-name "Save MIME part to: "
                            (or mm-default-directory default-directory)
                            nil nil (or filename name ""))))
    (setq mm-default-directory (file-name-directory file))
    (and (or (not (file-exists-p file))
             (yes-or-no-p (format "File %s already exists; overwrite? "
                                  file)))
         (progn
           (mm-save-part-to-file handle file)
           file))))

(defun mm-save-part-to-file (handle file)
  (mm-with-unibyte-buffer
    (mm-insert-part handle)
    (let ((coding-system-for-write 'binary)
          (current-file-modes (default-file-modes))
          ;; Don't re-compress .gz & al.  Arguably we should make
          ;; `file-name-handler-alist' nil, but that would chop
          ;; ange-ftp, which is reasonable to use here.
          (inhibit-file-name-operation 'write-region)
          (inhibit-file-name-handlers
           (cons 'jka-compr-handler inhibit-file-name-handlers)))
      (set-default-file-modes mm-attachment-file-modes)
      (unwind-protect
          (write-region (point-min) (point-max) file)
        (set-default-file-modes current-file-modes)))))

(defun mm-pipe-part (handle)
  "Pipe HANDLE to a process."
  (let* ((name (mail-content-type-get (mm-handle-type handle) 'name))
         (command
          (read-string "Shell command on MIME part: " mm-last-shell-command)))
    (mm-with-unibyte-buffer
      (mm-insert-part handle)
      (let ((coding-system-for-write 'binary))
        (shell-command-on-region (point-min) (point-max) command nil)))))

(defun mm-interactively-view-part (handle)
  "Display HANDLE using METHOD."
  (let* ((type (mm-handle-media-type handle))
         (methods
          (mapcar (lambda (i) (list (cdr (assoc 'viewer i))))
                  (mailcap-mime-info type 'all)))
         (method (let ((minibuffer-local-completion-map
                        mm-viewer-completion-map))
                   (completing-read "Viewer: " methods))))
    (when (string= method "")
      (error "No method given"))
    (if (string-match "^[^% \t]+$" method)
        (setq method (concat method " %s")))
    (mm-display-external handle method)))

(defun mm-preferred-alternative (handles &optional preferred)
  "Say which of HANDLES are preferred."
  (let ((prec (if preferred (list preferred)
                (mm-preferred-alternative-precedence handles)))
        p h result type handle)
    (while (setq p (pop prec))
      (setq h handles)
      (while h
        (setq handle (car h))
        (setq type (mm-handle-media-type handle))
        (when (and (equal p type)
                   (mm-automatic-display-p handle)
                   (or (stringp (car handle))
                       (not (mm-handle-disposition handle))
                       (equal (car (mm-handle-disposition handle))
                              "inline")))
          (setq result handle
                h nil
                prec nil))
        (pop h)))
    result))

(defun mm-preferred-alternative-precedence (handles)
  "Return the precedence based on HANDLES and `mm-discouraged-alternatives'."
  (let ((seq (nreverse (mapcar #'mm-handle-media-type
                               handles))))
    (dolist (disc (reverse mm-discouraged-alternatives))
      (dolist (elem (copy-sequence seq))
        (when (string-match disc elem)
          (setq seq (nconc (delete elem seq) (list elem))))))
    seq))

(defun mm-get-content-id (id)
  "Return the handle(s) referred to by ID."
  (cdr (assoc id mm-content-id-alist)))

(defconst mm-image-type-regexps
  '(("/\\*.*XPM.\\*/" . xpm)
    ("P[1-6]" . pbm)
    ("GIF8" . gif)
    ("\377\330" . jpeg)
    ("\211PNG\r\n" . png)
    ("#define" . xbm)
    ("\\(MM\0\\*\\)\\|\\(II\\*\0\\)" . tiff)
    ("%!PS" . postscript))
  "Alist of (REGEXP . IMAGE-TYPE) pairs used to auto-detect image types.
When the first bytes of an image file match REGEXP, it is assumed to
be of image type IMAGE-TYPE.")

;; Steal from image.el. image-type-from-data suffers multi-line matching bug.
(defun mm-image-type-from-buffer ()
  "Determine the image type from data in the current buffer.
Value is a symbol specifying the image type or nil if type cannot
be determined."
  (let ((types mm-image-type-regexps)
        type)
    (goto-char (point-min))
    (while (and types (null type))
      (let ((regexp (car (car types)))
            (image-type (cdr (car types))))
        (when (looking-at regexp)
          (setq type image-type))
        (setq types (cdr types))))
    type))

(defun mm-get-image (handle)
  "Return an image instance based on HANDLE."
  (let ((type (mm-handle-media-subtype handle))
        spec)
    ;; Allow some common translations.
    (setq type
          (cond
           ((equal type "x-pixmap")
            "xpm")
           ((equal type "x-xbitmap")
            "xbm")
           ((equal type "x-portable-bitmap")
            "pbm")
           (t type)))
    (or (mm-handle-cache handle)
        (mm-with-unibyte-buffer
          (mm-insert-part handle)
          (prog1
              (setq spec
                    (ignore-errors
                      ;; Avoid testing `make-glyph' since W3 may define
                      ;; a bogus version of it.
                      (if (fboundp 'create-image)
                          (create-image (buffer-string)
                                        (or (mm-image-type-from-buffer)
                                            (intern type))
                                        'data-p)
                        (mm-create-image-xemacs type))))
            (mm-handle-set-cache handle spec))))))

(defun mm-create-image-xemacs (type)
  (cond
   ((equal type "xbm")
    ;; xbm images require special handling, since
    ;; the only way to create glyphs from these
    ;; (without a ton of work) is to write them
    ;; out to a file, and then create a file
    ;; specifier.
    (let ((file (mm-make-temp-file
                 (expand-file-name "emm.xbm"
                                   mm-tmp-directory))))
      (unwind-protect
          (progn
            (write-region (point-min) (point-max) file)
            (make-glyph (list (cons 'x file))))
        (ignore-errors
          (delete-file file)))))
   (t
    (make-glyph
     (vector
      (or (mm-image-type-from-buffer)
          (intern type))
      :data (buffer-string))))))

(defun mm-image-fit-p (handle)
  "Say whether the image in HANDLE will fit the current window."
  (let ((image (mm-get-image handle)))
    (if (fboundp 'glyph-width)
        ;; XEmacs' glyphs can actually tell us about their width, so
        ;; lets be nice and smart about them.
        (or mm-inline-large-images
            (and (< (glyph-width image) (window-pixel-width))
                 (< (glyph-height image) (window-pixel-height))))
      (let* ((size (image-size image))
             (w (car size))
             (h (cdr size)))
        (or mm-inline-large-images
            (and (< h (1- (window-height))) ; Don't include mode line.
                 (< w (window-width))))))))

(defun mm-valid-image-format-p (format)
  "Say whether FORMAT can be displayed natively by Emacs."
  (cond
   ;; Handle XEmacs
   ((fboundp 'valid-image-instantiator-format-p)
    (valid-image-instantiator-format-p format))
   ;; Handle Emacs 21
   ((fboundp 'image-type-available-p)
    (and (display-graphic-p)
         (image-type-available-p format)))
   ;; Nobody else can do images yet.
   (t
    nil)))

(defun mm-valid-and-fit-image-p (format handle)
  "Say whether FORMAT can be displayed natively and HANDLE fits the window."
  (and (mm-valid-image-format-p format)
       (mm-image-fit-p handle)))

(defun mm-find-part-by-type (handles type &optional notp recursive)
  "Search in HANDLES for part with TYPE.
If NOTP, returns first non-matching part.
If RECURSIVE, search recursively."
  (let (handle)
    (while handles
      (if (and recursive (stringp (caar handles)))
          (if (setq handle (mm-find-part-by-type (cdar handles) type
                                                 notp recursive))
              (setq handles nil))
        (if (if notp
                (not (equal (mm-handle-media-type (car handles)) type))
              (equal (mm-handle-media-type (car handles)) type))
            (setq handle (car handles)
                  handles nil)))
      (setq handles (cdr handles)))
    handle))

(defun mm-find-raw-part-by-type (ctl type &optional notp)
  (goto-char (point-min))
  (let* ((boundary (concat "--" (mm-handle-multipart-ctl-parameter ctl
                                                                   'boundary)))
         (close-delimiter (concat "^" (regexp-quote boundary) "--[ \t]*$"))
         start
         (end (save-excursion
                (goto-char (point-max))
                (if (re-search-backward close-delimiter nil t)
                    (match-beginning 0)
                  (point-max))))
         result)
    (setq boundary (concat "^" (regexp-quote boundary) "[ \t]*$"))
    (while (and (not result)
                (re-search-forward boundary end t))
      (goto-char (match-beginning 0))
      (when start
        (save-excursion
          (save-restriction
            (narrow-to-region start (1- (point)))
            (when (let ((ctl (ignore-errors
                               (mail-header-parse-content-type
                                (mail-fetch-field "content-type")))))
                    (if notp
                        (not (equal (car ctl) type))
                      (equal (car ctl) type)))
              (setq result (buffer-string))))))
      (forward-line 1)
      (setq start (point)))
    (when (and (not result) start)
      (save-excursion
        (save-restriction
          (narrow-to-region start end)
          (when (let ((ctl (ignore-errors
                             (mail-header-parse-content-type
                              (mail-fetch-field "content-type")))))
                  (if notp
                      (not (equal (car ctl) type))
                    (equal (car ctl) type)))
            (setq result (buffer-string))))))
    result))

(defvar mm-security-handle nil)

(defsubst mm-set-handle-multipart-parameter (handle parameter value)
  ;; HANDLE could be a CTL.
  (when handle
    (put-text-property 0 (length (car handle)) parameter value
                       (car handle))))

(defun mm-possibly-verify-or-decrypt (parts ctl)
  (let ((type (car ctl))
        (subtype (cadr (split-string (car ctl) "/")))
        (mm-security-handle ctl) ;; (car CTL) is the type.
        protocol func functest)
    (cond
     ((or (equal type "application/x-pkcs7-mime")
          (equal type "application/pkcs7-mime"))
      (with-temp-buffer
        (when (and (cond
                    ((eq mm-decrypt-option 'never) nil)
                    ((eq mm-decrypt-option 'always) t)
                    ((eq mm-decrypt-option 'known) t)
                    (t (y-or-n-p
                        (format "Decrypt (S/MIME) part? "))))
                   (mm-view-pkcs7 parts))
          (setq parts (mm-dissect-buffer t)))))
     ((equal subtype "signed")
      (unless (and (setq protocol
                         (mm-handle-multipart-ctl-parameter ctl 'protocol))
                   (not (equal protocol "multipart/mixed")))
        ;; The message is broken or draft-ietf-openpgp-multsig-01.
        (let ((protocols mm-verify-function-alist))
          (while protocols
            (if (and (or (not (setq functest (nth 3 (car protocols))))
                         (funcall functest parts ctl))
                     (mm-find-part-by-type parts (caar protocols) nil t))
                (setq protocol (caar protocols)
                      protocols nil)
              (setq protocols (cdr protocols))))))
      (setq func (nth 1 (assoc protocol mm-verify-function-alist)))
      (when (cond
             ((eq mm-verify-option 'never) nil)
             ((eq mm-verify-option 'always) t)
             ((eq mm-verify-option 'known)
              (and func
                   (or (not (setq functest
                                  (nth 3 (assoc protocol
                                                mm-verify-function-alist))))
                       (funcall functest parts ctl))))
             (t
              (y-or-n-p
               (format "Verify signed (%s) part? "
                       (or (nth 2 (assoc protocol mm-verify-function-alist))
                           (format "protocol=%s" protocol))))))
        (save-excursion
          (if func
              (funcall func parts ctl)
            (mm-set-handle-multipart-parameter
             mm-security-handle 'gnus-details
             (format "Unknown sign protocol (%s)" protocol))))))
     ((equal subtype "encrypted")
      (unless (setq protocol
                    (mm-handle-multipart-ctl-parameter ctl 'protocol))
        ;; The message is broken.
        (let ((parts parts))
          (while parts
            (if (assoc (mm-handle-media-type (car parts))
                       mm-decrypt-function-alist)
                (setq protocol (mm-handle-media-type (car parts))
                      parts nil)
              (setq parts (cdr parts))))))
      (setq func (nth 1 (assoc protocol mm-decrypt-function-alist)))
      (when (cond
             ((eq mm-decrypt-option 'never) nil)
             ((eq mm-decrypt-option 'always) t)
             ((eq mm-decrypt-option 'known)
              (and func
                   (or (not (setq functest
                                  (nth 3 (assoc protocol
                                                mm-decrypt-function-alist))))
                       (funcall functest parts ctl))))
             (t
              (y-or-n-p
               (format "Decrypt (%s) part? "
                       (or (nth 2 (assoc protocol mm-decrypt-function-alist))
                           (format "protocol=%s" protocol))))))
        (save-excursion
          (if func
              (setq parts (funcall func parts ctl))
            (mm-set-handle-multipart-parameter
             mm-security-handle 'gnus-details
             (format "Unknown encrypt protocol (%s)" protocol))))))
     (t nil))
    parts))

(defun mm-multiple-handles (handles)
  (and (listp handles)
       (> (length handles) 1)
       (or (listp (car handles))
           (stringp (car handles)))))

(defun mm-complicated-handles (handles)
  (and (listp (car handles))
       (> (length handles) 1)))

(defun mm-merge-handles (handles1 handles2)
  (append
   (if (listp (car handles1))
       handles1
     (list handles1))
   (if (listp (car handles2))
       handles2
     (list handles2))))

(defun mm-readable-p (handle)
  "Say whether the content of HANDLE is readable."
  (and (< (with-current-buffer (mm-handle-buffer handle)
            (buffer-size)) 10000)
       (mm-with-unibyte-buffer
         (mm-insert-part handle)
         (and (eq (mm-body-7-or-8) '7bit)
              (not (mm-long-lines-p 76))))))

(provide 'mm-decode)

;; arch-tag: 4f35d360-56b8-4030-9388-3ed82d359b9b
;;; mm-decode.el ends here