lisp/gnus/gnus-async.el

   1 ;;; gnus-async.el --- asynchronous support for Gnus
   2
   3 ;; Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   4 ;;   2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   5
   6 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   7 ;; Keywords: news
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 3, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27
  28 ;;; Code:
  29
  30 (eval-when-compile (require 'cl))
  31
  32 (require 'gnus)
  33 (require 'gnus-sum)
  34 (require 'nntp)
  35
  36 (defgroup gnus-asynchronous nil
  37   "Support for asynchronous operations."
  38   :group 'gnus)
  39
  40 (defcustom gnus-use-article-prefetch 30
  41   "*If non-nil, prefetch articles in groups that allow this.
  42 If a number, prefetch only that many articles forward;
  43 if t, prefetch as many articles as possible."
  44   :group 'gnus-asynchronous
  45   :type '(choice (const :tag "off" nil)
  46                  (const :tag "all" t)
  47                  (integer :tag "some" 0)))
  48
  49 (defcustom gnus-asynchronous nil
  50   "*If nil, inhibit all Gnus asynchronicity.
  51 If non-nil, let the other asynch variables be heeded."
  52   :group 'gnus-asynchronous
  53   :type 'boolean)
  54
  55 (defcustom gnus-prefetched-article-deletion-strategy '(read exit)
  56   "List of symbols that say when to remove articles from the prefetch buffer.
  57 Possible values in this list are `read', which means that
  58 articles are removed as they are read, and `exit', which means
  59 that all articles belonging to a group are removed on exit
  60 from that group."
  61   :group 'gnus-asynchronous
  62   :type '(set (const read) (const exit)))
  63
  64 (defcustom gnus-use-header-prefetch nil
  65   "*If non-nil, prefetch the headers to the next group."
  66   :group 'gnus-asynchronous
  67   :type 'boolean)
  68
  69 (defcustom gnus-async-prefetch-article-p 'gnus-async-unread-p
  70   "Function called to say whether an article should be prefetched or not.
  71 The function is called with one parameter -- the article data.
  72 It should return non-nil if the article is to be prefetched."
  73   :group 'gnus-asynchronous
  74   :type 'function)
  75
  76 ;;; Internal variables.
  77
  78 (defvar gnus-async-prefetch-article-buffer " *Async Prefetch Article*")
  79 (defvar gnus-async-article-alist nil)
  80 (defvar gnus-async-article-semaphore '(nil))
  81 (defvar gnus-async-fetch-list nil)
  82 (defvar gnus-async-hashtb nil)
  83 (defvar gnus-async-current-prefetch-group nil)
  84 (defvar gnus-async-current-prefetch-article nil)
  85 (defvar gnus-async-timer nil)
  86
  87 (defvar gnus-async-prefetch-headers-buffer " *Async Prefetch Headers*")
  88 (defvar gnus-async-header-prefetched nil)
  89
  90 ;;; Utility functions.
  91
  92 (defun gnus-group-asynchronous-p (group)
  93   "Say whether GROUP is fetched from a server that supports asynchronicity."
  94   (gnus-asynchronous-p (gnus-find-method-for-group group)))
  95
  96 ;;; Somewhat bogus semaphores.
  97
  98 (defun gnus-async-get-semaphore (semaphore)
  99   "Wait until SEMAPHORE is released."
 100   (while (/= (length (nconc (symbol-value semaphore) (list nil))) 2)
 101     (sleep-for 1)))
 102
 103 (defun gnus-async-release-semaphore (semaphore)
 104   "Release SEMAPHORE."
 105   (setcdr (symbol-value semaphore) nil))
 106
 107 (defmacro gnus-async-with-semaphore (&rest forms)
 108   `(unwind-protect
 109        (progn
 110          (gnus-async-get-semaphore 'gnus-async-article-semaphore)
 111          ,@forms)
 112      (gnus-async-release-semaphore 'gnus-async-article-semaphore)))
 113
 114 (put 'gnus-async-with-semaphore 'lisp-indent-function 0)
 115 (put 'gnus-async-with-semaphore 'edebug-form-spec '(body))
 116
 117 ;;;
 118 ;;; Article prefetch
 119 ;;;
 120
 121 (gnus-add-shutdown 'gnus-async-close 'gnus)
 122 (defun gnus-async-close ()
 123   (gnus-kill-buffer gnus-async-prefetch-article-buffer)
 124   (gnus-kill-buffer gnus-async-prefetch-headers-buffer)
 125   (setq gnus-async-hashtb nil
 126         gnus-async-article-alist nil
 127         gnus-async-header-prefetched nil))
 128
 129 (defun gnus-async-set-buffer ()
 130   (nnheader-set-temp-buffer gnus-async-prefetch-article-buffer t)
 131   (unless gnus-async-hashtb
 132     (setq gnus-async-hashtb (gnus-make-hashtable 1023))))
 133
 134 (defun gnus-async-halt-prefetch ()
 135   "Stop prefetching."
 136   (setq gnus-async-fetch-list nil))
 137
 138 (defun gnus-async-prefetch-next (group article summary)
 139   "Possibly prefetch several articles starting with the article after ARTICLE."
 140   (when (and (gnus-buffer-live-p summary)
 141              gnus-asynchronous
 142              (gnus-group-asynchronous-p group))
 143     (save-excursion
 144       (set-buffer gnus-summary-buffer)
 145       (let ((next (caadr (gnus-data-find-list article))))
 146         (when next
 147           (if (not (fboundp 'run-with-idle-timer))
 148               ;; This is either an older Emacs or XEmacs, so we
 149               ;; do this, which leads to slightly slower article
 150               ;; buffer display.
 151               (gnus-async-prefetch-article group next summary)
 152             (when gnus-async-timer
 153               (ignore-errors
 154                 (nnheader-cancel-timer 'gnus-async-timer)))
 155             (setq gnus-async-timer
 156                   (run-with-idle-timer
 157                    0.1 nil 'gnus-async-prefetch-article
 158                    group next summary))))))))
 159
 160 (defun gnus-async-prefetch-article (group article summary &optional next)
 161   "Possibly prefetch several articles starting with ARTICLE."
 162   (if (not (gnus-buffer-live-p summary))
 163       (gnus-async-with-semaphore
 164         (setq gnus-async-fetch-list nil))
 165     (when (and gnus-asynchronous
 166                (gnus-alive-p))
 167       (when next
 168         (gnus-async-with-semaphore
 169           (pop gnus-async-fetch-list)))
 170       (let ((do-fetch next)
 171             (do-message t))             ;(eq major-mode 'gnus-summary-mode)))
 172         (when (and (gnus-group-asynchronous-p group)
 173                    (gnus-buffer-live-p summary)
 174                    (or (not next)
 175                        gnus-async-fetch-list))
 176           (gnus-async-with-semaphore
 177             (unless next
 178               (setq do-fetch (not gnus-async-fetch-list))
 179               ;; Nix out any outstanding requests.
 180               (setq gnus-async-fetch-list nil)
 181               ;; Fill in the new list.
 182               (let ((n gnus-use-article-prefetch)
 183                     (data (gnus-data-find-list article))
 184                     d)
 185                 (while (and (setq d (pop data))
 186                             (if (numberp n)
 187                                 (natnump (decf n))
 188                               n))
 189                   (unless (or (gnus-async-prefetched-article-entry
 190                                group (setq article (gnus-data-number d)))
 191                               (not (natnump article))
 192                               (not (funcall gnus-async-prefetch-article-p d)))
 193                     ;; Not already fetched -- so we add it to the list.
 194                     (push article gnus-async-fetch-list)))
 195                 (setq gnus-async-fetch-list
 196                       (nreverse gnus-async-fetch-list))))
 197
 198             (when do-fetch
 199               (setq article (car gnus-async-fetch-list))))
 200
 201           (when (and do-fetch article)
 202             ;; We want to fetch some more articles.
 203             (save-excursion
 204               (set-buffer summary)
 205               (let (mark)
 206                 (gnus-async-set-buffer)
 207                 (goto-char (point-max))
 208                 (setq mark (point-marker))
 209                 (let ((nnheader-callback-function
 210                        (gnus-make-async-article-function
 211                         group article mark summary next))
 212                       (nntp-server-buffer
 213                        (get-buffer gnus-async-prefetch-article-buffer)))
 214                   (when do-message
 215                     (gnus-message 9 "Prefetching article %d in group %s"
 216                                   article group))
 217                   (setq gnus-async-current-prefetch-group group)
 218                   (setq gnus-async-current-prefetch-article article)
 219                   (gnus-request-article article group))))))))))
 220
 221 (defun gnus-make-async-article-function (group article mark summary next)
 222   "Return a callback function."
 223   `(lambda (arg)
 224      (gnus-async-article-callback arg ,group ,article ,mark ,summary ,next)))
 225
 226 (defun gnus-async-article-callback (arg group article mark summary next)
 227   "Function called when an async article is done being fetched."
 228   (save-excursion
 229     (setq gnus-async-current-prefetch-article nil)
 230     (when arg
 231       (gnus-async-set-buffer)
 232       (gnus-async-with-semaphore
 233         (setq
 234          gnus-async-article-alist
 235          (cons (list (intern (format "%s-%d" group article)
 236                              gnus-async-hashtb)
 237                      mark (set-marker (make-marker) (point-max))
 238                      group article)
 239                gnus-async-article-alist))))
 240     (if (not (gnus-buffer-live-p summary))
 241         (gnus-async-with-semaphore
 242           (setq gnus-async-fetch-list nil))
 243       (gnus-async-prefetch-article group next summary t))))
 244
 245 (defun gnus-async-unread-p (data)
 246   "Return non-nil if DATA represents an unread article."
 247   (gnus-data-unread-p data))
 248
 249 (defun gnus-async-request-fetched-article (group article buffer)
 250   "See whether we have ARTICLE from GROUP and put it in BUFFER."
 251   (when (numberp article)
 252     (when (and (equal group gnus-async-current-prefetch-group)
 253                (eq article gnus-async-current-prefetch-article))
 254       (gnus-async-wait-for-article article))
 255     (let ((entry (gnus-async-prefetched-article-entry group article)))
 256       (when entry
 257         (save-excursion
 258           (gnus-async-set-buffer)
 259           (copy-to-buffer buffer (cadr entry) (caddr entry))
 260           ;; Remove the read article from the prefetch buffer.
 261           (when (memq 'read gnus-prefetched-article-deletion-strategy)
 262             (gnus-async-delete-prefetched-entry entry))
 263           t)))))
 264
 265 (defun gnus-async-wait-for-article (article)
 266   "Wait until ARTICLE is no longer the currently-being-fetched article."
 267   (save-excursion
 268     (gnus-async-set-buffer)
 269     (let ((proc (nntp-find-connection (current-buffer)))
 270           (nntp-server-buffer (current-buffer))
 271           (nntp-have-messaged nil)
 272           (tries 0))
 273       (when proc
 274         (condition-case nil
 275             ;; FIXME: we could stop waiting after some
 276             ;; timeout, but this is the wrong place to do it.
 277             ;; rather than checking time-spent-waiting, we
 278             ;; should check time-since-last-output, which
 279             ;; needs to be done in nntp.el.
 280             (while (eq article gnus-async-current-prefetch-article)
 281               (incf tries)
 282               (when (nntp-accept-process-output proc)
 283                 (setq tries 0))
 284               (when (and (not nntp-have-messaged)
 285                          (= tries 3))
 286                 (gnus-message 5 "Waiting for async article...")
 287                 (setq nntp-have-messaged t)))
 288           (quit
 289            ;; if the user interrupted on a slow/hung connection,
 290            ;; do something friendly.
 291            (when (> tries 3)
 292              (setq gnus-async-current-prefetch-article nil))
 293            (signal 'quit nil)))
 294         (when nntp-have-messaged
 295           (gnus-message 5 ""))))))
 296
 297 (defun gnus-async-delete-prefetched-entry (entry)
 298   "Delete ENTRY from buffer and alist."
 299   (ignore-errors
 300     (delete-region (cadr entry) (caddr entry))
 301     (set-marker (cadr entry) nil)
 302     (set-marker (caddr entry) nil))
 303   (gnus-async-with-semaphore
 304     (setq gnus-async-article-alist
 305           (delq entry gnus-async-article-alist))))
 306
 307 (defun gnus-async-prefetch-remove-group (group)
 308   "Remove all articles belonging to GROUP from the prefetch buffer."
 309   (when (and (gnus-group-asynchronous-p group)
 310              (memq 'exit gnus-prefetched-article-deletion-strategy))
 311     (save-excursion
 312       (gnus-async-set-buffer)
 313       (dolist (entry gnus-async-article-alist)
 314         (when (equal group (nth 3 entry))
 315           (gnus-async-delete-prefetched-entry entry))))))
 316
 317 (defun gnus-async-prefetched-article-entry (group article)
 318   "Return the entry for ARTICLE in GROUP if it has been prefetched."
 319   (let ((entry (save-excursion
 320                  (gnus-async-set-buffer)
 321                  (assq (intern (format "%s-%d" group article)
 322                                gnus-async-hashtb)
 323                        gnus-async-article-alist))))
 324     ;; Perhaps something has emptied the buffer?
 325     (if (and entry
 326              (= (cadr entry) (caddr entry)))
 327         (progn
 328           (ignore-errors
 329             (set-marker (cadr entry) nil)
 330             (set-marker (caddr entry) nil))
 331           (setq gnus-async-article-alist
 332                 (delq entry gnus-async-article-alist))
 333           nil)
 334       entry)))
 335
 336 ;;;
 337 ;;; Header prefetch
 338 ;;;
 339
 340 (defun gnus-async-prefetch-headers (group)
 341   "Prefetch the headers for group GROUP."
 342   (save-excursion
 343     (let (unread)
 344       (when (and gnus-use-header-prefetch
 345                  gnus-asynchronous
 346                  (gnus-group-asynchronous-p group)
 347                  (listp gnus-async-header-prefetched)
 348                  (setq unread (gnus-list-of-unread-articles group)))
 349         ;; Mark that a fetch is in progress.
 350         (setq gnus-async-header-prefetched t)
 351         (nnheader-set-temp-buffer gnus-async-prefetch-headers-buffer t)
 352         (erase-buffer)
 353         (let ((nntp-server-buffer (current-buffer))
 354               (nnheader-callback-function
 355                `(lambda (arg)
 356                   (setq gnus-async-header-prefetched
 357                         ,(cons group unread)))))
 358           (gnus-retrieve-headers unread group gnus-fetch-old-headers))))))
 359
 360 (defun gnus-async-retrieve-fetched-headers (articles group)
 361   "See whether we have prefetched headers."
 362   (when (and gnus-use-header-prefetch
 363              (gnus-group-asynchronous-p group)
 364              (listp gnus-async-header-prefetched)
 365              (equal group (car gnus-async-header-prefetched))
 366              (equal articles (cdr gnus-async-header-prefetched)))
 367     (save-excursion
 368       (nnheader-set-temp-buffer gnus-async-prefetch-headers-buffer t)
 369       (nntp-decode-text)
 370       (copy-to-buffer nntp-server-buffer (point-min) (point-max))
 371       (erase-buffer)
 372       (setq gnus-async-header-prefetched nil)
 373       t)))
 374
 375 (provide 'gnus-async)
 376
 377 ;; arch-tag: fee61de5-3ea2-4de6-8578-2f90ce89391d
 378 ;;; gnus-async.el ends here