lisp/gnus/gnus-async.el

   1 ;;; gnus-async.el --- asynchronous support for Gnus
   2
   3 ;; Copyright (C) 1996-2012 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   :version "24.1"
  78   :group 'gnus-asynchronous
  79   :type 'function)
  80
  81 ;;; Internal variables.
  82
  83 (defvar gnus-async-prefetch-article-buffer " *Async Prefetch Article*")
  84 (defvar gnus-async-article-alist nil)
  85 (defvar gnus-async-article-semaphore '(nil))
  86 (defvar gnus-async-fetch-list nil)
  87 (defvar gnus-async-hashtb nil)
  88 (defvar gnus-async-current-prefetch-group nil)
  89 (defvar gnus-async-current-prefetch-article nil)
  90 (defvar gnus-async-timer nil)
  91
  92 (defvar gnus-async-prefetch-headers-buffer " *Async Prefetch Headers*")
  93 (defvar gnus-async-header-prefetched nil)
  94
  95 ;;; Utility functions.
  96
  97 (defun gnus-group-asynchronous-p (group)
  98   "Say whether GROUP is fetched from a server that supports asynchronicity."
  99   (gnus-asynchronous-p (gnus-find-method-for-group group)))
 100
 101 ;;; Somewhat bogus semaphores.
 102
 103 (defun gnus-async-get-semaphore (semaphore)
 104   "Wait until SEMAPHORE is released."
 105   (while (/= (length (nconc (symbol-value semaphore) (list nil))) 2)
 106     (sleep-for 1)))
 107
 108 (defun gnus-async-release-semaphore (semaphore)
 109   "Release SEMAPHORE."
 110   (setcdr (symbol-value semaphore) nil))
 111
 112 (defmacro gnus-async-with-semaphore (&rest forms)
 113   `(unwind-protect
 114        (progn
 115          (gnus-async-get-semaphore 'gnus-async-article-semaphore)
 116          ,@forms)
 117      (gnus-async-release-semaphore 'gnus-async-article-semaphore)))
 118
 119 (put 'gnus-async-with-semaphore 'lisp-indent-function 0)
 120 (put 'gnus-async-with-semaphore 'edebug-form-spec '(body))
 121
 122 ;;;
 123 ;;; Article prefetch
 124 ;;;
 125
 126 (gnus-add-shutdown 'gnus-async-close 'gnus)
 127 (defun gnus-async-close ()
 128   (gnus-kill-buffer gnus-async-prefetch-article-buffer)
 129   (gnus-kill-buffer gnus-async-prefetch-headers-buffer)
 130   (setq gnus-async-hashtb nil
 131         gnus-async-article-alist nil
 132         gnus-async-header-prefetched nil))
 133
 134 (defun gnus-async-set-buffer ()
 135   (nnheader-set-temp-buffer gnus-async-prefetch-article-buffer t)
 136   (unless gnus-async-hashtb
 137     (setq gnus-async-hashtb (gnus-make-hashtable 1023))))
 138
 139 (defun gnus-async-halt-prefetch ()
 140   "Stop prefetching."
 141   (setq gnus-async-fetch-list nil))
 142
 143 (defun gnus-async-prefetch-next (group article summary)
 144   "Possibly prefetch several articles starting with the article after ARTICLE."
 145   (when (and (gnus-buffer-live-p summary)
 146              gnus-asynchronous
 147              (gnus-group-asynchronous-p group))
 148     (with-current-buffer gnus-summary-buffer
 149       (let ((next (caadr (gnus-data-find-list article))))
 150         (when next
 151           (if (not (fboundp 'run-with-idle-timer))
 152               ;; This is either an older Emacs or XEmacs, so we
 153               ;; do this, which leads to slightly slower article
 154               ;; buffer display.
 155               (gnus-async-prefetch-article group next summary)
 156             (when gnus-async-timer
 157               (ignore-errors
 158                 (nnheader-cancel-timer 'gnus-async-timer)))
 159             (setq gnus-async-timer
 160                   (run-with-idle-timer
 161                    0.1 nil 'gnus-async-prefetch-article
 162                    group next summary))))))))
 163
 164 (defun gnus-async-prefetch-article (group article summary &optional next)
 165   "Possibly prefetch several articles starting with ARTICLE."
 166   (if (not (gnus-buffer-live-p summary))
 167       (gnus-async-with-semaphore
 168         (setq gnus-async-fetch-list nil))
 169     (when (and gnus-asynchronous
 170                (gnus-alive-p))
 171       (when next
 172         (gnus-async-with-semaphore
 173           (pop gnus-async-fetch-list)))
 174       (let ((do-fetch next)
 175             (do-message t))             ;(eq major-mode 'gnus-summary-mode)))
 176         (when (and (gnus-group-asynchronous-p group)
 177                    (gnus-buffer-live-p summary)
 178                    (or (not next)
 179                        gnus-async-fetch-list))
 180           (gnus-async-with-semaphore
 181             (unless next
 182               (setq do-fetch (not gnus-async-fetch-list))
 183               ;; Nix out any outstanding requests.
 184               (setq gnus-async-fetch-list nil)
 185               ;; Fill in the new list.
 186               (let ((n gnus-use-article-prefetch)
 187                     (data (gnus-data-find-list article))
 188                     d)
 189                 (while (and (setq d (pop data))
 190                             (if (numberp n)
 191                                 (natnump (decf n))
 192                               n))
 193                   (unless (or (gnus-async-prefetched-article-entry
 194                                group (setq article (gnus-data-number d)))
 195                               (not (natnump article))
 196                               (not (funcall gnus-async-prefetch-article-p d)))
 197                     ;; Not already fetched -- so we add it to the list.
 198                     (push article gnus-async-fetch-list)))
 199                 (setq gnus-async-fetch-list
 200                       (nreverse gnus-async-fetch-list))))
 201
 202             (when do-fetch
 203               (setq article (car gnus-async-fetch-list))))
 204
 205           (when (and do-fetch article)
 206             ;; We want to fetch some more articles.
 207             (with-current-buffer summary
 208               (let (mark)
 209                 (gnus-async-set-buffer)
 210                 (goto-char (point-max))
 211                 (setq mark (point-marker))
 212                 (let ((nnheader-callback-function
 213                        (gnus-make-async-article-function
 214                         group article mark summary next))
 215                       (nntp-server-buffer
 216                        (get-buffer gnus-async-prefetch-article-buffer)))
 217                   (when do-message
 218                     (gnus-message 9 "Prefetching article %d in group %s"
 219                                   article group))
 220                   (setq gnus-async-current-prefetch-group group)
 221                   (setq gnus-async-current-prefetch-article article)
 222                   (gnus-request-article article group))))))))))
 223
 224 (defun gnus-make-async-article-function (group article mark summary next)
 225   "Return a callback function."
 226   `(lambda (arg)
 227      (gnus-async-article-callback arg ,group ,article ,mark ,summary ,next)))
 228
 229 (eval-when-compile
 230   (autoload 'gnus-html-prefetch-images "gnus-html"))
 231
 232 (defun gnus-async-article-callback (arg group article mark summary next)
 233   "Function called when an async article is done being fetched."
 234   (save-excursion
 235     (setq gnus-async-current-prefetch-article nil)
 236     (when arg
 237       (gnus-async-set-buffer)
 238       (save-excursion
 239         (save-restriction
 240           (narrow-to-region mark (point-max))
 241           ;; Put the articles into the agent, if they aren't already.
 242           (when (and gnus-agent
 243                      (gnus-agent-group-covered-p group))
 244             (save-restriction
 245               (narrow-to-region mark (point-max))
 246               (gnus-agent-store-article article group)))
 247           ;; Prefetch images for the groups that want that.
 248           (when (fboundp 'gnus-html-prefetch-images)
 249             (gnus-html-prefetch-images summary))
 250           (when gnus-async-post-fetch-function
 251             (funcall gnus-async-post-fetch-function summary))))
 252       (gnus-async-with-semaphore
 253         (setq
 254          gnus-async-article-alist
 255          (cons (list (intern (format "%s-%d" group article)
 256                              gnus-async-hashtb)
 257                      mark (set-marker (make-marker) (point-max))
 258                      group article)
 259                gnus-async-article-alist))))
 260     (if (not (gnus-buffer-live-p summary))
 261         (gnus-async-with-semaphore
 262           (setq gnus-async-fetch-list nil))
 263       (gnus-async-prefetch-article group next summary t))))
 264
 265 (defun gnus-async-unread-p (data)
 266   "Return non-nil if DATA represents an unread article."
 267   (gnus-data-unread-p data))
 268
 269 (defun gnus-async-request-fetched-article (group article buffer)
 270   "See whether we have ARTICLE from GROUP and put it in BUFFER."
 271   (when (numberp article)
 272     (when (and (equal group gnus-async-current-prefetch-group)
 273                (eq article gnus-async-current-prefetch-article))
 274       (gnus-async-wait-for-article article))
 275     (let ((entry (gnus-async-prefetched-article-entry group article)))
 276       (when entry
 277         (save-excursion
 278           (gnus-async-set-buffer)
 279           (copy-to-buffer buffer (cadr entry) (caddr entry))
 280           ;; Remove the read article from the prefetch buffer.
 281           (when (memq 'read gnus-prefetched-article-deletion-strategy)
 282             (gnus-async-delete-prefetched-entry entry))
 283           t)))))
 284
 285 (defun gnus-async-wait-for-article (article)
 286   "Wait until ARTICLE is no longer the currently-being-fetched article."
 287   (save-excursion
 288     (gnus-async-set-buffer)
 289     (let ((proc (nntp-find-connection (current-buffer)))
 290           (nntp-server-buffer (current-buffer))
 291           (nntp-have-messaged nil)
 292           (tries 0))
 293       (when proc
 294         (condition-case nil
 295             ;; FIXME: we could stop waiting after some
 296             ;; timeout, but this is the wrong place to do it.
 297             ;; rather than checking time-spent-waiting, we
 298             ;; should check time-since-last-output, which
 299             ;; needs to be done in nntp.el.
 300             (while (eq article gnus-async-current-prefetch-article)
 301               (incf tries)
 302               (when (nntp-accept-process-output proc)
 303                 (setq tries 0))
 304               (when (and (not nntp-have-messaged)
 305                          (= tries 3))
 306                 (gnus-message 5 "Waiting for async article...")
 307                 (setq nntp-have-messaged t)))
 308           (quit
 309            ;; if the user interrupted on a slow/hung connection,
 310            ;; do something friendly.
 311            (when (> tries 3)
 312              (setq gnus-async-current-prefetch-article nil))
 313            (signal 'quit nil)))
 314         (when nntp-have-messaged
 315           (gnus-message 5 ""))))))
 316
 317 (defun gnus-async-delete-prefetched-entry (entry)
 318   "Delete ENTRY from buffer and alist."
 319   (ignore-errors
 320     (delete-region (cadr entry) (caddr entry))
 321     (set-marker (cadr entry) nil)
 322     (set-marker (caddr entry) nil))
 323   (gnus-async-with-semaphore
 324     (setq gnus-async-article-alist
 325           (delq entry gnus-async-article-alist))
 326     (unintern (car entry) gnus-async-hashtb)))
 327
 328 (defun gnus-async-prefetch-remove-group (group)
 329   "Remove all articles belonging to GROUP from the prefetch buffer."
 330   (when (and (gnus-group-asynchronous-p group)
 331              (memq 'exit gnus-prefetched-article-deletion-strategy))
 332     (save-excursion
 333       (gnus-async-set-buffer)
 334       (dolist (entry gnus-async-article-alist)
 335         (when (equal group (nth 3 entry))
 336           (gnus-async-delete-prefetched-entry entry))))))
 337
 338 (defun gnus-async-prefetched-article-entry (group article)
 339   "Return the entry for ARTICLE in GROUP if it has been prefetched."
 340   (let ((entry (save-excursion
 341                  (gnus-async-set-buffer)
 342                  (assq (intern-soft (format "%s-%d" group article)
 343                                     gnus-async-hashtb)
 344                        gnus-async-article-alist))))
 345     ;; Perhaps something has emptied the buffer?
 346     (if (and entry
 347              (= (cadr entry) (caddr entry)))
 348         (progn
 349           (ignore-errors
 350             (set-marker (cadr entry) nil)
 351             (set-marker (caddr entry) nil))
 352           (setq gnus-async-article-alist
 353                 (delq entry gnus-async-article-alist))
 354           nil)
 355       entry)))
 356
 357 ;;;
 358 ;;; Header prefetch
 359 ;;;
 360
 361 (defun gnus-async-prefetch-headers (group)
 362   "Prefetch the headers for group GROUP."
 363   (save-excursion
 364     (let (unread)
 365       (when (and gnus-use-header-prefetch
 366                  gnus-asynchronous
 367                  (gnus-group-asynchronous-p group)
 368                  (listp gnus-async-header-prefetched)
 369                  (setq unread (gnus-list-of-unread-articles group)))
 370         ;; Mark that a fetch is in progress.
 371         (setq gnus-async-header-prefetched t)
 372         (nnheader-set-temp-buffer gnus-async-prefetch-headers-buffer t)
 373         (erase-buffer)
 374         (let ((nntp-server-buffer (current-buffer))
 375               (nnheader-callback-function
 376                `(lambda (arg)
 377                   (setq gnus-async-header-prefetched
 378                         ,(cons group unread)))))
 379           (gnus-retrieve-headers unread group gnus-fetch-old-headers))))))
 380
 381 (defun gnus-async-retrieve-fetched-headers (articles group)
 382   "See whether we have prefetched headers."
 383   (when (and gnus-use-header-prefetch
 384              (gnus-group-asynchronous-p group)
 385              (listp gnus-async-header-prefetched)
 386              (equal group (car gnus-async-header-prefetched))
 387              (equal articles (cdr gnus-async-header-prefetched)))
 388     (save-excursion
 389       (nnheader-set-temp-buffer gnus-async-prefetch-headers-buffer t)
 390       (nntp-decode-text)
 391       (copy-to-buffer nntp-server-buffer (point-min) (point-max))
 392       (erase-buffer)
 393       (setq gnus-async-header-prefetched nil)
 394       t)))
 395
 396 (provide 'gnus-async)
 397
 398 ;;; gnus-async.el ends here