privacy function for deleting cookies, history, etc. [SNIPPET INCLUDED]

[Boruch Baum <boruch_baum@xxxxxxx>]

For a long time, I've wanted something for emacs-w3m similar to what
pretty much all other browsers have - a straightforward way to delete
personal information and browsing history. I plan to submit the attached
snippet as git pull request, but since the github repo is new, only has
two other watchers, and doesn't yet send email to the list, I thought to
first share it here and ask for feedback.

-- 
hkp://keys.gnupg.net
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(defvar w3m-scrub-command-list
  '(("/usr/bin/shred" "-fuz") ("/bin/rm" "-f"))
  "List of methods to use for attempting to securely delete temporary files.

Function `w3m-scrub-command' uses the first entry on the list
that it finds available on the host OS; if none are found, it
will use the insecure emacs function `delete-file'.")

(defun w3m-history-scrub ()
  "Initializes history, cache, cookies, and temp files.

The method used to delete files is configurable to your personal
level of paranoia, via `w3m-scrub-command-list'.

Note that some operations performed by this function may impact
operation of the external w3m browser. Also, be advised that
other emacs features outside the scope of `emacs-w3m' may
independantly be saving varibles, for example in order to restore
a crashed emacs session."
  ; TODO:
  ; + Use a defcustom or other user-friendly mechanism to allow
  ;   fine-grained customization of what to scrub.
  ; + When invoked with a prefix arg, allow the scrub to be limited to a
  ;   timeframe, for elements that store timestamp information.
  (interactive)
  (let* ((w3m-fb-mode nil)
         (w3m-message-silent t)
         (stdout-buf (generate-new-buffer "*w3m-scrub-history*"))
         (cookie-buf (get-buffer " *w3m-cookie-parse-temp*"))
         (bufs (w3m-list-buffers t))
         (cmds w3m-scrub-command-list)
         (cmd (progn
                (while (and (setq cmd (pop cmds))
                            (not (file-executable-p (car cmd)))))
                cmd))
         (cmd-string (if cmd
                       (format "%s %s" (car cmd) (cdr cmd))
                      "emacs' delete-file"))
         (file "")
         (files (append
                  (list w3m-arrived-file w3m-cookie-file)
                  w3m-form-textarea-post-files
                  w3m-form-textarea-files
                  (directory-files
                    (file-chase-links (expand-file-name w3m-form-textarea-directory))
                    'full "[^.]" 'nosort)
                  (directory-files w3m-profile-directory 'full
                    "^w3m\\(cache\\|cookie\\|el\\|src\\|tmp\\)" 'nosort))))
   (switch-to-buffer stdout-buf)
   (insert "Beginning emacs-w3m history scrub "
           (format-time-string "%Y-%m-%d %H:%M")
           "\n\nDeleting files ...\n")
   (if cmd
     (while files
       (setq file (pop files))
       (insert (format "  %s %s\n" cmd-string file))
       (call-process (car cmd) nil t t (cadr cmd) file))
    (while files
      (setq file (pop files))
      (insert (format "  %s %s\n" cmd-string file))
      (delete-file file)))
   (insert "Deleting files ... Complete.\n\nInitializing memory cache ...")
   (w3m-cache-shutdown)
   (insert " Complete.\nInitializing cookies from memory ...")
   (setq w3m-cookies nil)
   (when cookie-buf
     (kill-buffer cookie-buf))
   (insert " Complete.\nInitializing global history from memory ...")
   (setq w3m-arrived-db nil)
   (insert " Complete.\nInitializing individual buffer histories and forms ...")
   (dolist (buf bufs)
     (with-current-buffer buf
       (setq w3m-history nil)
       (setq w3m-history-flat nil)
       (cond
        ((or (string-match "^about://\\(cookie\\|history\\|db-history\\)/"  w3m-current-url)
             w3m-form-input-textarea-mode
             (eq major-mode 'w3m-form-input-select-mode)
             (eq major-mode 'w3m-form-input-map-mode))
         (w3m-reload-this-page nil t))

        ((string-match "*w3m-session select*" (buffer-name))
         (kill-buffer buf))
        (t nil))))
   (insert " Complete.\nScrubbing selected sessions from session database ...")
   (let ((sessions (w3m-load-list w3m-session-file)))
     (dolist (session sessions sessions)
       (cond
        ((string-match
           "^\\(Removed\\|Automatic saved\\|Crash recovery\\) sessions"
           (nth 0 session))
         (insert "\n  Deleting session named: " (nth 0 session))
         (setq sessions (delq session sessions)))
        (t
         (insert "\n  Examining session named: " (nth 0 session))
         (dolist (tab (nth 2 session))
           (when (nth 2 tab)
             (insert "\n    Removing history from tab: " (nth 3 tab))
             (setf (nth 2 tab) nil))))))
     (insert "\nScrubbing selected sessions from session database ... Complete\n")
     ; NOTE: Each saved session may have form or post data. These wil
     ; be represented as properties `:forms' and `:post-data', but so
     ; far I've only seen them in history elements, which are already
     ; being deleted.
     (insert "Updating session database on disk ...")
     (w3m-save-list w3m-session-file sessions))
   (insert " Complete.\n"
           (format-time-string "%Y-%m-%d %H:%M"))))