--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lisp/gnus/gnus-dup.el	Mon Aug 13 08:49:20 2007 +0200
@@ -0,0 +1,157 @@
+;;; gnus-dup.el --- suppression of duplicate articles in Gnus
+;; Copyright (C) 1996,97 Free Software Foundation, Inc.
+
+;; Author: Lars Magne Ingebrigtsen <larsi@ifi.uio.no>
+;; Keywords: 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 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., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; This package tries to mark articles as read the second time the
+;; user reads a copy.  This is useful if the server doesn't support
+;; Xref properly, or if the user reads the same group from several
+;; servers.
+
+;;; Code:
+
+(require 'gnus)
+(require 'gnus-art)
+
+(defgroup gnus-duplicate nil
+  "Suppression of duplicate articles."
+  :group 'gnus)
+
+(defcustom gnus-save-duplicate-list nil
+  "*If non-nil, save the duplicate list when shutting down Gnus.
+If nil, duplicate suppression will only work on duplicates
+seen in the same session."
+  :group 'gnus-duplicate
+  :type 'boolean)
+
+(defcustom gnus-duplicate-list-length 10000
+  "*The number of Message-IDs to keep in the duplicate suppression list."
+  :group 'gnus-duplicate
+  :type 'integer)
+
+(defcustom gnus-duplicate-file (nnheader-concat gnus-directory "suppression")
+  "*The name of the file to store the duplicate suppression list."
+  :group 'gnus-duplicate
+  :type 'file)
+
+;;; Internal variables
+
+(defvar gnus-dup-list nil)
+(defvar gnus-dup-hashtb nil)
+
+(defvar gnus-dup-list-dirty nil)
+
+;;;
+;;; Starting and stopping
+;;;
+
+(gnus-add-shutdown 'gnus-dup-close 'gnus)
+
+(defun gnus-dup-close ()
+  "Possibly save the duplicate suppression list and shut down the subsystem."
+  (gnus-dup-save)
+  (setq gnus-dup-list nil
+	gnus-dup-hashtb nil
+	gnus-dup-list-dirty nil))
+
+(defun gnus-dup-open ()
+  "Possibly read the duplicate suppression list and start the subsystem."
+  (if gnus-save-duplicate-list
+      (gnus-dup-read)
+    (setq gnus-dup-list nil))
+  (setq gnus-dup-hashtb (gnus-make-hashtable gnus-duplicate-list-length))
+  ;; Enter all Message-IDs into the hash table.
+  (let ((list gnus-dup-list)
+	(obarray gnus-dup-hashtb))
+    (while list 
+      (intern (pop list)))))
+
+(defun gnus-dup-read ()
+  "Read the duplicate suppression list."
+  (setq gnus-dup-list nil)
+  (when (file-exists-p gnus-duplicate-file)
+    (load gnus-duplicate-file t t t)))
+
+(defun gnus-dup-save ()
+  "Save the duplicate suppression list."
+  (when (and gnus-save-duplicate-list
+	     gnus-dup-list-dirty)
+    (nnheader-temp-write gnus-duplicate-file
+      (gnus-prin1 `(setq gnus-dup-list ',gnus-dup-list))))
+  (setq gnus-dup-list-dirty nil))
+
+;;;
+;;; Interface functions
+;;;
+
+(defun gnus-dup-enter-articles ()
+  "Enter articles from the current group for future duplicate suppression."
+  (unless gnus-dup-list
+    (gnus-dup-open))
+  (setq gnus-dup-list-dirty t)		; mark list for saving
+  (let ((data gnus-newsgroup-data)
+ 	datum msgid)
+    ;; Enter the Message-IDs of all read articles into the list
+    ;; and hash table.
+    (while (setq datum (pop data))
+      (when (and (not (gnus-data-pseudo-p datum))
+		 (> (gnus-data-number datum) 0)
+		 (gnus-data-read-p datum)
+ 		 (setq msgid (mail-header-id (gnus-data-header datum)))
+ 		 (not (nnheader-fake-message-id-p msgid))
+ 		 (not (intern-soft msgid gnus-dup-hashtb)))
+	(push msgid gnus-dup-list)
+ 	(intern msgid gnus-dup-hashtb))))
+  ;; Chop off excess Message-IDs from the list.
+  (let ((end (nthcdr gnus-duplicate-list-length gnus-dup-list)))
+    (when end 
+      (setcdr end nil))))
+
+(defun gnus-dup-suppress-articles ()
+  "Mark duplicate articles as read."
+  (unless gnus-dup-list
+    (gnus-dup-open))
+  (gnus-message 6 "Suppressing duplicates...")
+  (let ((headers gnus-newsgroup-headers)
+	number header)
+    (while (setq header (pop headers))
+      (when (and (intern-soft (mail-header-id header) gnus-dup-hashtb)
+		 (gnus-summary-article-unread-p (mail-header-number header)))
+	(setq gnus-newsgroup-unreads 
+	      (delq (setq number (mail-header-number header))
+		    gnus-newsgroup-unreads))
+	(push (cons number gnus-duplicate-mark)
+	      gnus-newsgroup-reads))))
+  (gnus-message 6 "Suppressing duplicates...done"))
+
+(defun gnus-dup-unsuppress-article (article)
+  "Stop suppression of ARTICLE."
+  (let ((id (mail-header-id (gnus-data-header (gnus-data-find article)))))
+    (when id
+      (setq gnus-dup-list-dirty t)
+      (setq gnus-dup-list (delete id gnus-dup-list))
+      (unintern id gnus-dup-hashtb))))
+
+(provide 'gnus-dup)
+
+;;; gnus-dup.el ends here