lisp/gnus/gnus-async.el

   1 ;;; gnus-async.el --- asynchronous support for Gnus
   2
   3 ;; Copyright (C) 1996-2011 Free Software Foundation, Inc.
   4
   5 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   6 ;; Keywords: news
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24
  25 ;;; Code:
  26
  27 (eval-when-compile (require 'cl))
  28
  29 (require 'gnus)
  30 (require 'gnus-sum)
  31 (require 'nntp)
  32
  33 (defgroup gnus-asynchronous nil
  34   "Support for asynchronous operations."
  35   :group 'gnus)
  36
  37 (defcustom gnus-use-article-prefetch 30
  38   "*If non-nil, prefetch articles in groups that allow this.
  39 If a number, prefetch only that many articles forward;
  40 if t, prefetch as many articles as possible."
  41   :group 'gnus-asynchronous
  42   :type '(choice (const :tag "off" nil)
  43                  (const :tag "all" t)
  44                  (integer :tag "some" 0)))
  45
  46 (defcustom gnus-asynchronous nil
  47   "*If nil, inhibit all Gnus asynchronicity.
  48 If non-nil, let the other asynch variables be heeded."
  49   :group 'gnus-asynchronous
  50   :type 'boolean)
  51
  52 (defcustom gnus-prefetched-article-deletion-strategy '(read exit)
  53   "List of symbols that say when to remove articles from the prefetch buffer.
  54 Possible values in this list are `read', which means that
  55 articles are removed as they are read, and `exit', which means
  56 that all articles belonging to a group are removed on exit
  57 from that group."
  58   :group 'gnus-asynchronous
  59   :type '(set (const read) (const exit)))
  60
  61 (defcustom gnus-use-header-prefetch nil
  62   "*If non-nil, prefetch the headers to the next group."
  63   :group 'gnus-asynchronous
  64   :type 'boolean)
  65
  66 (defcustom gnus-async-prefetch-article-p 'gnus-async-unread-p
  67   "Function called to say whether an article should be prefetched or not.
  68 The function is called with one parameter -- the article data.
  69 It should return non-nil if the article is to be prefetched."
  70   :group 'gnus-asynchronous
  71   :type 'function)
  72
  73 (defcustom gnus-async-post-fetch-function nil
  74   "Function called after an article has been prefetched.
  75 The function will be called narrowed to the region of the article
  76 that was fetched."
  77   :group 'gnus-asynchronous
  78   :type 'function)
  79
  80 ;;; Internal variables.
  81
  82 (defvar gnus-async-prefetch-article-buffer " *Async Prefetch Article*")
  83 (defvar gnus-async-article-alist nil)
  84 (defvar gnus-async-article-semaphore '(nil))
  85 (defvar gnus-async-fetch-list nil)
  86 (defvar gnus-async-hashtb nil)
  87 (defvar gnus-async-current-prefetch-group nil)
  88 (defvar gnus-async-current-prefetch-article nil)
  89 (defvar gnus-async-timer nil)
  90
  91 (defvar gnus-async-prefetch-headers-buffer " *Async Prefetch Headers*")
  92 (defvar gnus-async-header-prefetched nil)
  93
  94 ;;; Utility functions.
  95
  96 (defun gnus-group-asynchronous-p (group)
  97   "Say whether GROUP is fetched from a server that supports asynchronicity."
  98   (gnus-asynchronous-p (gnus-find-method-for-group group)))
  99
 100 ;;; Somewhat bogus semaphores.
 101
 102 (defun gnus-async-get-semaphore (semaphore)
 103   "Wait until SEMAPHORE is released."
 104   (while (/= (length (nconc (symbol-value semaphore) (list nil))) 2)
 105     (sleep-for 1)))
 106
 107 (defun gnus-async-release-semaphore (semaphore)
 108   "Release SEMAPHORE."
 109   (setcdr (symbol-value semaphore) nil))
 110
 111 (defmacro gnus-async-with-semaphore (&rest forms)
 112   `(unwind-protect
 113        (progn
 114          (gnus-async-get-semaphore 'gnus-async-article-semaphore)
 115          ,@forms)
 116      (gnus-async-release-semaphore 'gnus-async-article-semaphore)))
 117
 118 (put 'gnus-async-with-semaphore 'lisp-indent-function 0)
 119 (put 'gnus-async-with-semaphore 'edebug-form-spec '(body))
 120
 121 ;;;
 122 ;;; Article prefetch
 123 ;;;
 124
 125 (gnus-add-shutdown 'gnus-async-close 'gnus)
 126 (defun gnus-async-close ()
 127   (gnus-kill-buffer gnus-async-prefetch-article-buffer)
 128   (gnus-kill-buffer gnus-async-prefetch-headers-buffer)
 129   (setq gnus-async-hashtb nil
 130         gnus-async-article-alist nil
 131         gnus-async-header-prefetched nil))
 132
 133 (defun gnus-async-set-buffer ()
 134   (nnheader-set-temp-buffer gnus-async-prefetch-article-buffer t)
 135   (unless gnus-async-hashtb
 136     (setq gnus-async-hashtb (gnus-make-hashtable 1023))))
 137
 138 (defun gnus-async-halt-prefetch ()
 139   "Stop prefetching."
 140   (setq gnus-async-fetch-list nil))
 141
 142 (defun gnus-async-prefetch-next (group article summary)
 143   "Possibly prefetch several articles starting with the article after ARTICLE."
 144   (when (and (gnus-buffer-live-p summary)
 145              gnus-asynchronous
 146              (gnus-group-asynchronous-p group))
 147     (with-current-buffer gnus-summary-buffer
 148       (let ((next (caadr (gnus-data-find-list article))))
 149         (when next
 150           (if (not (fboundp 'run-with-idle-timer))
 151               ;; This is either an older Emacs or XEmacs, so we
 152               ;; do this, which leads to slightly slower article
 153               ;; buffer display.
 154               (gnus-async-prefetch-article group next summary)
 155             (when gnus-async-timer
 156               (ignore-errors
 157                 (nnheader-cancel-timer 'gnus-async-timer)))
 158             (setq gnus-async-timer
 159                   (run-with-idle-timer
 160                    0.1 nil 'gnus-async-prefetch-article
 161                    group next summary))))))))
 162
 163 (defun gnus-async-prefetch-article (group article summary &optional next)
 164   "Possibly prefetch several articles starting with ARTICLE."
 165   (if (not (gnus-buffer-live-p summary))
 166       (gnus-async-with-semaphore
 167         (setq gnus-async-fetch-list nil))
 168     (when (and gnus-asynchronous
 169                (gnus-alive-p))
 170       (when next
 171         (gnus-async-with-semaphore
 172           (pop gnus-async-fetch-list)))
 173       (let ((do-fetch next)
 174             (do-message t))             ;(eq major-mode 'gnus-summary-mode)))
 175         (when (and (gnus-group-asynchronous-p group)
 176                    (gnus-buffer-live-p summary)
 177                    (or (not next)
 178                        gnus-async-fetch-list))
 179           (gnus-async-with-semaphore
 180             (unless next
 181               (setq do-fetch (not gnus-async-fetch-list))
 182               ;; Nix out any outstanding requests.
 183               (setq gnus-async-fetch-list nil)
 184               ;; Fill in the new list.
 185               (let ((n gnus-use-article-prefetch)
 186                     (data (gnus-data-find-list article))
 187                     d)
 188                 (while (and (setq d (pop data))
 189                             (if (numberp n)
 190                                 (natnump (decf n))
 191                               n))
 192                   (unless (or (gnus-async-prefetched-article-entry
 193                                group (setq article (gnus-data-number d)))
 194                               (not (natnump article))
 195                               (not (funcall gnus-async-prefetch-article-p d)))
 196                     ;; Not already fetched -- so we add it to the list.
 197                     (push article gnus-async-fetch-list)))
 198                 (setq gnus-async-fetch-list
 199                       (nreverse gnus-async-fetch-list))))
 200
 201             (when do-fetch
 202               (setq article (car gnus-async-fetch-list))))
 203
 204           (when (and do-fetch article)
 205             ;; We want to fetch some more articles.
 206             (with-current-buffer summary
 207               (let (mark)
 208                 (gnus-async-set-buffer)
 209                 (goto-char (point-max))
 210                 (setq mark (point-marker))
 211                 (let ((nnheader-callback-function
 212                        (gnus-make-async-article-function
 213                         group article mark summary next))
 214                       (nntp-server-buffer
 215                        (get-buffer gnus-async-prefetch-article-buffer)))
 216                   (when do-message
 217                     (gnus-message 9 "Prefetching article %d in group %s"
 218                                   article group))
 219                   (setq gnus-async-current-prefetch-group group)
 220                   (setq gnus-async-current-prefetch-article article)
 221                   (gnus-request-article article group))))))))))
 222
 223 (defun gnus-make-async-article-function (group article mark summary next)
 224   "Return a callback function."
 225   `(lambda (arg)
 226      (gnus-async-article-callback arg ,group ,article ,mark ,summary ,next)))
 227
 228 (eval-when-compile
 229   (autoload 'gnus-html-prefetch-images "gnus-html"))
 230
 231 (defun gnus-async-article-callback (arg group article mark summary next)
 232   "Function called when an async article is done being fetched."
 233   (save-excursion
 234     (setq gnus-async-current-prefetch-article nil)
 235     (when arg
 236       (gnus-async-set-buffer)
 237       (save-excursion
 238         (save-restriction
 239           (narrow-to-region mark (point-max))
 240           ;; Put the articles into the agent, if they aren't already.
 241           (when (and gnus-agent
 242                      (gnus-agent-group-covered-p group))
 243             (save-restriction
 244               (narrow-to-region mark (point-max))
 245               (gnus-agent-store-article article group)))
 246           ;; Prefetch images for the groups that want that.
 247           (when (fboundp 'gnus-html-prefetch-images)
 248             (gnus-html-prefetch-images summary))
 249           (when gnus-async-post-fetch-function
 250             (funcall gnus-async-post-fetch-function summary))))
 251       (gnus-async-with-semaphore
 252         (setq
 253          gnus-async-article-alist
 254          (cons (list (intern (format "%s-%d" group article)
 255                              gnus-async-hashtb)
 256                      mark (set-marker (make-marker) (point-max))
 257                      group article)
 258                gnus-async-article-alist))))
 259     (if (not (gnus-buffer-live-p summary))
 260         (gnus-async-with-semaphore
 261           (setq gnus-async-fetch-list nil))
 262       (gnus-async-prefetch-article group next summary t))))
 263
 264 (defun gnus-async-unread-p (data)
 265   "Return non-nil if DATA represents an unread article."
 266   (gnus-data-unread-p data))
 267
 268 (defun gnus-async-request-fetched-article (group article buffer)
 269   "See whether we have ARTICLE from GROUP and put it in BUFFER."
 270   (when (numberp article)
 271     (when (and (equal group gnus-async-current-prefetch-group)
 272                (eq article gnus-async-current-prefetch-article))
 273       (gnus-async-wait-for-article article))
 274     (let ((entry (gnus-async-prefetched-article-entry group article)))
 275       (when entry
 276         (save-excursion
 277           (gnus-async-set-buffer)
 278           (copy-to-buffer buffer (cadr entry) (caddr entry))
 279           ;; Remove the read article from the prefetch buffer.
 280           (when (memq 'read gnus-prefetched-article-deletion-strategy)
 281             (gnus-async-delete-prefetched-entry entry))
 282           t)))))
 283
 284 (defun gnus-async-wait-for-article (article)
 285   "Wait until ARTICLE is no longer the currently-being-fetched article."
 286   (save-excursion
 287     (gnus-async-set-buffer)
 288     (let ((proc (nntp-find-connection (current-buffer)))
 289           (nntp-server-buffer (current-buffer))
 290           (nntp-have-messaged nil)
 291           (tries 0))
 292       (when proc
 293         (condition-case nil
 294             ;; FIXME: we could stop waiting after some
 295             ;; timeout, but this is the wrong place to do it.
 296             ;; rather than checking time-spent-waiting, we
 297             ;; should check time-since-last-output, which
 298             ;; needs to be done in nntp.el.
 299             (while (eq article gnus-async-current-prefetch-article)
 300               (incf tries)
 301               (when (nntp-accept-process-output proc)
 302                 (setq tries 0))
 303               (when (and (not nntp-have-messaged)
 304                          (= tries 3))
 305                 (gnus-message 5 "Waiting for async article...")
 306                 (setq nntp-have-messaged t)))
 307           (quit
 308            ;; if the user interrupted on a slow/hung connection,
 309            ;; do something friendly.
 310            (when (> tries 3)
 311              (setq gnus-async-current-prefetch-article nil))
 312            (signal 'quit nil)))
 313         (when nntp-have-messaged
 314           (gnus-message 5 ""))))))
 315
 316 (defun gnus-async-delete-prefetched-entry (entry)
 317   "Delete ENTRY from buffer and alist."
 318   (ignore-errors
 319     (delete-region (cadr entry) (caddr entry))
 320     (set-marker (cadr entry) nil)
 321     (set-marker (caddr entry) nil))
 322   (gnus-async-with-semaphore
 323     (setq gnus-async-article-alist
 324           (delq entry gnus-async-article-alist))
 325     (unintern (car entry) gnus-async-hashtb)))
 326
 327 (defun gnus-async-prefetch-remove-group (group)
 328   "Remove all articles belonging to GROUP from the prefetch buffer."
 329   (when (and (gnus-group-asynchronous-p group)
 330              (memq 'exit gnus-prefetched-article-deletion-strategy))
 331     (save-excursion
 332       (gnus-async-set-buffer)
 333       (dolist (entry gnus-async-article-alist)
 334         (when (equal group (nth 3 entry))
 335           (gnus-async-delete-prefetched-entry entry))))))
 336
 337 (defun gnus-async-prefetched-article-entry (group article)
 338   "Return the entry for ARTICLE in GROUP if it has been prefetched."
 339   (let ((entry (save-excursion
 340                  (gnus-async-set-buffer)
 341                  (assq (intern-soft (format "%s-%d" group article)
 342                                     gnus-async-hashtb)
 343                        gnus-async-article-alist))))
 344     ;; Perhaps something has emptied the buffer?
 345     (if (and entry
 346              (= (cadr entry) (caddr entry)))
 347         (progn
 348           (ignore-errors
 349             (set-marker (cadr entry) nil)
 350             (set-marker (caddr entry) nil))
 351           (setq gnus-async-article-alist
 352                 (delq entry gnus-async-article-alist))
 353           nil)
 354       entry)))
 355
 356 ;;;
 357 ;;; Header prefetch
 358 ;;;
 359
 360 (defun gnus-async-prefetch-headers (group)
 361   "Prefetch the headers for group GROUP."
 362   (save-excursion
 363     (let (unread)
 364       (when (and gnus-use-header-prefetch
 365                  gnus-asynchronous
 366                  (gnus-group-asynchronous-p group)
 367                  (listp gnus-async-header-prefetched)
 368                  (setq unread (gnus-list-of-unread-articles group)))
 369         ;; Mark that a fetch is in progress.
 370         (setq gnus-async-header-prefetched t)
 371         (nnheader-set-temp-buffer gnus-async-prefetch-headers-buffer t)
 372         (erase-buffer)
 373         (let ((nntp-server-buffer (current-buffer))
 374               (nnheader-callback-function
 375                `(lambda (arg)
 376                   (setq gnus-async-header-prefetched
 377                         ,(cons group unread)))))
 378           (gnus-retrieve-headers unread group gnus-fetch-old-headers))))))
 379
 380 (defun gnus-async-retrieve-fetched-headers (articles group)
 381   "See whether we have prefetched headers."
 382   (when (and gnus-use-header-prefetch
 383              (gnus-group-asynchronous-p group)
 384              (listp gnus-async-header-prefetched)
 385              (equal group (car gnus-async-header-prefetched))
 386              (equal articles (cdr gnus-async-header-prefetched)))
 387     (save-excursion
 388       (nnheader-set-temp-buffer gnus-async-prefetch-headers-buffer t)
 389       (nntp-decode-text)
 390       (copy-to-buffer nntp-server-buffer (point-min) (point-max))
 391       (erase-buffer)
 392       (setq gnus-async-header-prefetched nil)
 393       t)))
 394
 395 (provide 'gnus-async)
 396
 397 ;;; gnus-async.el ends here