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+;;; gnus-cache.el --- cache interface for Gnus
+;; Copyright (C) 1995 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, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'gnus)
+
+(defvar gnus-cache-directory (concat gnus-article-save-directory "cache/")
+  "*The directory where cached articles will be stored.")
+
+(defvar gnus-cache-enter-articles '(ticked dormant)
+  "*Classes of articles to enter into the cache.")
+
+(defvar gnus-cache-remove-articles '(read)
+  "*Classes of articles to remove from the cache.")
+
+
+
+(defvar gnus-cache-buffer nil)
+
+
+
+(defun gnus-cache-change-buffer (group)
+  (and gnus-cache-buffer
+       ;; see if the current group's overview cache has been loaded 
+       (or (string= group (car gnus-cache-buffer))
+	   ;; another overview cache is current, save it
+	   (gnus-cache-save-buffers)))
+  ;; if gnus-cache buffer is nil, create it
+  (or gnus-cache-buffer
+      ;; create cache buffer
+      (save-excursion
+	(setq gnus-cache-buffer
+	      (cons group
+		    (set-buffer (get-buffer-create " *gnus-cache-overview*"))))
+	(buffer-disable-undo (current-buffer))
+	;; insert the contents of this groups cache overview
+	(erase-buffer)
+	(let ((file (gnus-cache-file-name group ".overview")))
+	  (and (file-exists-p file)
+	       (insert-file-contents file)))
+	;; we have a fresh (empty/just loaded) buffer, 
+	;; mark it as unmodified to save a redundant write later.
+	(set-buffer-modified-p nil))))
+
+
+(defun gnus-cache-save-buffers ()
+  ;; save the overview buffer if it exists and has been modified
+  ;; delete empty cache subdirectories
+  (if (null gnus-cache-buffer)
+      ()
+    (let ((buffer (cdr gnus-cache-buffer))
+	  (overview-file (gnus-cache-file-name
+			  (car gnus-cache-buffer) ".overview")))
+      ;; write the overview only if it was modified
+      (if (buffer-modified-p buffer)
+	  (save-excursion
+	    (set-buffer buffer)
+	    (if (> (buffer-size) 0)
+		;; non-empty overview, write it out
+		(progn
+		  (gnus-make-directory (file-name-directory overview-file))
+		  (write-region (point-min) (point-max)
+				overview-file nil 'quietly))
+	      ;; empty overview file, remove it
+	      (and (file-exists-p overview-file)
+		   (delete-file overview-file))
+	      ;; if possible, remove group's cache subdirectory
+	      (condition-case nil
+		  ;; FIXME: we can detect the error type and warn the user
+		  ;; of any inconsistencies (articles w/o nov entries?).
+		  ;; for now, just be conservative...delete only if safe -- sj
+		  (delete-directory (file-name-directory overview-file))
+		(error nil)))))
+      ;; kill the buffer, it's either unmodified or saved
+      (gnus-kill-buffer buffer)
+      (setq gnus-cache-buffer nil))))
+
+
+;; Return whether an article is a member of a class.
+(defun gnus-cache-member-of-class (class ticked dormant unread)
+  (or (and ticked (memq 'ticked class))
+      (and dormant (memq 'dormant class))
+      (and unread (memq 'unread class))
+      (and (not unread) (memq 'read class))))
+
+(defun gnus-cache-file-name (group article)
+  (concat (file-name-as-directory gnus-cache-directory)
+	  (if (gnus-use-long-file-name 'not-cache)
+	      group 
+	    (let ((group (concat group "")))
+	      (if (string-match ":" group)
+		  (aset group (match-beginning 0) ?/))
+	      (gnus-replace-chars-in-string group ?. ?/)))
+	  "/" (if (stringp article) article (int-to-string article))))
+
+(defun gnus-cache-possibly-enter-article 
+  (group article headers ticked dormant unread)
+  (let ((number (mail-header-number headers))
+	file dir)
+    (if (or (not (vectorp headers))	; This might be a dummy article.
+	    (< number 0)		; Reffed article from other group.
+	    (not (gnus-cache-member-of-class
+		  gnus-cache-enter-articles ticked dormant unread))
+	    (file-exists-p (setq file (gnus-cache-file-name group article))))
+	()				; Do nothing.
+      ;; Possibly create the cache directory.
+      (or (file-exists-p (setq dir (file-name-directory file)))
+	  (gnus-make-directory dir))
+      ;; Save the article in the cache.
+      (if (file-exists-p file)
+	  t				; The article already is saved, so we end here.
+	(let ((gnus-use-cache nil))
+	  (gnus-summary-select-article))
+	(save-excursion
+	  (set-buffer gnus-article-buffer)
+	  (save-restriction
+	    (widen)
+	    (write-region (point-min) (point-max) file nil 'quiet))
+	  (gnus-cache-change-buffer group)
+	  (set-buffer (cdr gnus-cache-buffer))
+	  (goto-char (point-max))
+	  (forward-line -1)
+	  (while (condition-case ()
+		     (and (not (bobp))
+			  (> (read (current-buffer)) number))
+		   (error
+		    ;; The line was malformed, so we just remove it!!
+		    (gnus-delete-line)
+		    t))
+	    (forward-line -1))
+	  (if (bobp) 
+	      (if (not (eobp))
+		  (progn
+		    (beginning-of-line)
+		    (if (< (read (current-buffer)) number)
+			(forward-line 1)))
+		(beginning-of-line))
+	    (forward-line 1))
+	  (beginning-of-line)
+	  ;; [number subject from date id references chars lines xref]
+	  (insert (format "%s\t%s\t%s\t%s\t%s\t%s\t%s\t%s\t%s\t\n"
+			  (mail-header-number headers)
+			  (mail-header-subject headers)
+			  (mail-header-from headers)
+			  (mail-header-date headers)
+			  (mail-header-id headers)
+			  (or (mail-header-references headers) "")
+			  (or (mail-header-chars headers) "")
+			  (or (mail-header-lines headers) "")
+			  (or (mail-header-xref headers) ""))))
+	t))))
+
+(defun gnus-cache-enter-remove-article (article)
+  (setq gnus-cache-removeable-articles
+	(cons article gnus-cache-removeable-articles)))
+
+(defsubst gnus-cache-possibly-remove-article 
+  (article ticked dormant unread)
+  (let ((file (gnus-cache-file-name gnus-newsgroup-name article)))
+    (if (or (not (file-exists-p file))
+	    (not (gnus-cache-member-of-class
+		  gnus-cache-remove-articles ticked dormant unread)))
+	nil
+      (save-excursion
+	(delete-file file)
+	(set-buffer (cdr gnus-cache-buffer))
+	(goto-char (point-min))
+	(if (or (looking-at (concat (int-to-string article) "\t"))
+		(search-forward (concat "\n" (int-to-string article) "\t")
+				(point-max) t))
+	    (delete-region (progn (beginning-of-line) (point))
+			   (progn (forward-line 1) (point))))))))
+
+(defun gnus-cache-possibly-remove-articles ()
+  (let ((articles gnus-cache-removeable-articles)
+	(cache-articles (gnus-cache-articles-in-group gnus-newsgroup-name))
+	article)
+    (gnus-cache-change-buffer gnus-newsgroup-name)
+    (while articles
+      (setq article (car articles)
+	    articles (cdr articles))
+      (if (memq article cache-articles)
+	  ;; The article was in the cache, so we see whether we are
+	  ;; supposed to remove it from the cache.
+	  (gnus-cache-possibly-remove-article
+	   article (memq article gnus-newsgroup-marked)
+	   (memq article gnus-newsgroup-dormant)
+	   (or (memq article gnus-newsgroup-unreads)
+	       (memq article gnus-newsgroup-unselected))))))
+  ;; the overview file might have been modified, save it
+  ;; safe because we're only called at group exit anyway
+  (gnus-cache-save-buffers))
+
+
+(defun gnus-cache-request-article (article group)
+  (let ((file (gnus-cache-file-name group article)))
+    (if (not (file-exists-p file))
+	()
+      (erase-buffer)
+      ;; There may be some overlays that we have to kill...
+      (insert "i")
+      (let ((overlays (overlays-at (point-min))))
+	(while overlays
+	  (delete-overlay (car overlays))
+	  (setq overlays (cdr overlays))))
+      (erase-buffer)	  
+      (insert-file-contents file)
+      t)))
+
+(defun gnus-cache-articles-in-group (group)
+  (let ((dir (file-name-directory (gnus-cache-file-name group 1)))
+	articles)
+    (if (not (file-exists-p dir))
+	nil
+      (setq articles (directory-files dir nil "^[0-9]+$" t))
+      (if (not articles)
+	  nil
+	(sort (mapcar (function (lambda (name)
+				  (string-to-int name))) 
+		      articles)
+	      '<)))))
+
+(defun gnus-cache-active-articles (group)
+  (let ((articles (gnus-cache-articles-in-group group)))
+    (and articles
+	 (cons (car articles) (gnus-last-element articles)))))
+
+(defun gnus-cache-possibly-alter-active (group active)
+  (let ((cache-active (gnus-cache-active-articles group)))
+    (and cache-active (< (car cache-active) (car active))
+	 (setcar active (car cache-active)))
+    (and cache-active (> (cdr cache-active) (cdr active))
+	 (setcdr active (cdr cache-active)))))
+
+(defun gnus-cache-retrieve-headers (articles group)
+  (let* ((cached (gnus-cache-articles-in-group group))
+	 (articles (gnus-sorted-complement articles cached))
+	 (cache-file (gnus-cache-file-name group ".overview"))
+	 type)
+    (let ((gnus-use-cache nil))
+      (setq type (and articles (gnus-retrieve-headers articles group))))
+    (gnus-cache-save-buffers)
+    (save-excursion
+      (cond ((not (file-exists-p cache-file))
+	     type)
+	    ((null type)
+	     (set-buffer nntp-server-buffer)
+	     (erase-buffer)
+	     (insert-file-contents cache-file)
+	     'nov)
+	    ((eq type 'nov)
+	     (gnus-cache-braid-nov group cached)
+	     type)
+	    (t
+	     (gnus-cache-braid-heads group cached)
+	     type)))))
+
+(defun gnus-cache-braid-nov (group cached)
+  (let ((cache-buf (get-buffer-create " *gnus-cache*"))
+	beg end)
+    (gnus-cache-save-buffers)
+    (save-excursion
+      (set-buffer cache-buf)
+      (buffer-disable-undo (current-buffer))
+      (erase-buffer)
+      (insert-file-contents (gnus-cache-file-name group ".overview"))
+      (goto-char (point-min))
+      (insert "\n")
+      (goto-char (point-min)))
+    (set-buffer nntp-server-buffer)
+    (goto-char (point-min))
+    (while cached
+      (while (and (not (eobp))
+		  (< (read (current-buffer)) (car cached)))
+	(forward-line 1))
+      (beginning-of-line)
+      (save-excursion
+	(set-buffer cache-buf)
+	(if (search-forward (concat "\n" (int-to-string (car cached)) "\t")
+			    nil t)
+	    (setq beg (progn (beginning-of-line) (point))
+		  end (progn (end-of-line) (point)))
+	  (setq beg nil)))
+      (if beg (progn (insert-buffer-substring cache-buf beg end)
+		     (insert "\n")))
+      (setq cached (cdr cached)))
+    (kill-buffer cache-buf)))
+
+(defun gnus-cache-braid-heads (group cached)
+  (let ((cache-buf (get-buffer-create " *gnus-cache*")))
+    (save-excursion
+      (set-buffer cache-buf)
+      (buffer-disable-undo (current-buffer))
+      (erase-buffer))
+    (set-buffer nntp-server-buffer)
+    (goto-char (point-min))
+    (while cached
+      (while (and (not (eobp))
+		  (looking-at "2.. +\\([0-9]+\\) ")
+		  (< (progn (goto-char (match-beginning 1))
+			    (read (current-buffer)))
+		     (car cached)))
+	(search-forward "\n.\n" nil 'move))
+      (beginning-of-line)
+      (save-excursion
+	(set-buffer cache-buf)
+	(erase-buffer)
+	(insert-file-contents (gnus-cache-file-name group (car cached)))
+	(goto-char (point-min))
+	(insert "220 " (int-to-string (car cached)) " Article retrieved.\n")
+	(search-forward "\n\n" nil 'move)
+	(delete-region (point) (point-max))
+	(forward-char -1)
+	(insert "."))
+      (insert-buffer-substring cache-buf)
+      (setq cached (cdr cached)))
+    (kill-buffer cache-buf)))
+
+(defun gnus-jog-cache ()
+  "Go through all groups and put the articles into the cache."
+  (interactive)
+  (let ((newsrc (cdr gnus-newsrc-alist))
+	(gnus-cache-enter-articles '(unread))
+	(gnus-mark-article-hook nil)
+	(gnus-expert-user t)
+	(gnus-large-newsgroup nil))
+    (while newsrc
+      (gnus-summary-read-group (car (car newsrc)))
+      (if (not (eq major-mode 'gnus-summary-mode))
+	  ()
+	(while gnus-newsgroup-unreads
+	  (gnus-summary-select-article t t nil (car gnus-newsgroup-unreads))
+	  (setq gnus-newsgroup-unreads (cdr gnus-newsgroup-unreads)))
+	(kill-buffer (current-buffer)))
+      (setq newsrc (cdr newsrc)))))
+
+(provide 'gnus-cache)
+	      
+;;; gnus-cache.el ends here