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;;; sx-cache.el --- caching -*- lexical-binding: t; -*-
;; Copyright (C) 2014 Sean Allred
;; Author: Sean Allred <code@seanallred.com>
;; This program 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 3 of the License, or
;; (at your option) any later version.
;; This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; This file handles the cache system. All caches are retrieved and
;; set using symbols. The symbol should be the sub-package that is
;; using the cache. For example, `sx-pkg' would use
;;
;; `(sx-cache-get 'pkg)'
;;
;; This symbol is then converted into a filename within
;; `sx-cache-directory' using `sx-cache-get-file-name'.
;;
;; Currently, the cache is written at every `sx-cache-set', but this
;; write will eventually be done by some write-all function which will
;; be set on an idle timer.
;;; Code:
(defcustom sx-cache-directory (locate-user-emacs-file ".sx")
"Directory containing cached data."
:type 'directory
:group 'sx)
(defun sx-cache--ensure-sx-cache-directory-exists ()
"Ensure `sx-cache-directory' exists."
(unless (file-exists-p sx-cache-directory)
(mkdir sx-cache-directory)))
(defun sx-cache-get-file-name (filename)
"Expand FILENAME in the context of `sx-cache-directory'."
(expand-file-name
(concat (symbol-name filename) ".el")
sx-cache-directory))
(defun sx-cache-get (cache &optional form)
"Return the data within CACHE.
If CACHE does not exist, use `sx-cache-set' to set CACHE to the
result of evaluating FORM.
CACHE is resolved to a file name by `sx-cache-get-file-name'."
(sx-cache--ensure-sx-cache-directory-exists)
(let ((file (sx-cache-get-file-name cache)))
;; If the file exists, return the data it contains
(if (file-exists-p file)
(with-temp-buffer
(insert-file-contents (sx-cache-get-file-name cache))
(read (buffer-string)))
;; Otherwise, set CACHE to the evaluation of FORM.
;; `sx-cache-set' returns the data that CACHE was set to.
(sx-cache-set cache (eval form)))))
(defun sx-cache-set (cache data)
"Set the content of CACHE to DATA and save.
DATA will be written as returned by `prin1'.
CACHE is resolved to a file name by `sx-cache-get-file-name'."
(sx-cache--ensure-sx-cache-directory-exists)
(let (print-length print-level)
(write-region (prin1-to-string data) nil
(sx-cache-get-file-name cache)))
data)
(defun sx-cache--invalidate (cache &optional vars init-method)
"Set cache CACHE to nil.
VARS is a list of variables to unbind to ensure cache is cleared.
If INIT-METHOD is defined, call it after all invalidation to
re-initialize the cache."
(let ((file (sx-cache-get-file-name cache)))
(delete-file file))
(mapc #'makunbound vars)
(when init-method
(funcall init-method)))
(defun sx-cache-invalidate-all (&optional save-auth)
"Invalidate all caches using `sx-cache--invalidate'.
Afterwards reinitialize caches using `sx-initialize'. If
SAVE-AUTH is non-nil, do not clear AUTH cache.
Interactively only clear AUTH cache if prefix arg was given.
Note: This will also remove read/unread status of questions as well
as delete the list of hidden questions."
(interactive (list (not current-prefix-arg)))
(let* ((default-directory sx-cache-directory)
(caches (file-expand-wildcards "*.el")))
(when save-auth
(setq caches (cl-remove-if (lambda (x)
(string= x "auth.el")) caches)))
(lwarn 'sx :debug "Invalidating: %S" caches)
(mapc #'delete-file caches)
(sx-initialize 'force)))
(provide 'sx-cache)
;;; sx-cache.el ends here
;; Local Variables:
;; indent-tabs-mode: nil
;; End:
|
