refactor caching code into emms-cache.el

* caching support is now provided via two function vars in emms.el,
  emms-cache-get-function and emms-cache-set-function
* (emms-standard) or above will enable caching support
* you'll need to remove .emms-cache or s/emms-info-cache/emms-cache-db/

darcs-hash:20060607125345-4e3e3-7d9ad8d243a395f2f2a5eea004e58ac9e239855b.gz

1 files changed, 79 insertions, 0 deletions

diff --git a/emms-cache.el b/emms-cache.el
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+++ b/emms-cache.el
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+;;; emms-cache.el --- persistence for emms-track
+
+;; Copyright (C) 2006  Damien Elmes <resolve@repose.cx>
+
+;; Author: Damien Elmes <damien@repose.cx>
+;; Keywords: emms, mp3, mpeg, multimedia
+
+;; This file 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.
+
+;; This file 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, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; The cache is a mapping of a full path name to information, and so
+;; it is invalidated when you rename or move files about. It also does
+;; not differentiate between file or uri tracks.
+
+;; Because cache lookups are much faster than disk access, this works
+;; much better with a later-do-interval of something like 0.001. Also
+;; consider using synchronous mode, as it's quite fast now.
+
+;; This code is activated by (emms-standard) and above.
+
+;;; Code:
+
+(define-hash-table-test 'string-hash 'string= 'sxhash)
+(defvar emms-cache-db (make-hash-table :test 'string-hash)
+  "A mapping of paths to file info.
+This is used to cache over emacs sessions.")
+
+(defvar emms-cache-file "~/.emms-cache"
+  "A file used to store cached file info information over sessions")
+
+(defvar emms-cache-dirty nil
+  "True if the cache has been updated since init.")
+
+(defun emms-cache-get (path)
+  "Return a cache element for PATH, or nil."
+  (gethash path emms-cache-db))
+
+(defun emms-cache-set (path track)
+  "Set PATH to TRACK in the cache."
+  (puthash path track emms-cache-db)
+  (setq emms-cache-dirty t))
+
+(defun emms-cache-save ()
+  "Save the track cache to a file."
+  (when emms-cache-dirty
+    (message "Saving emms track cache...")
+    (set-buffer (get-buffer-create " emms-cache "))
+    (erase-buffer)
+    (maphash (lambda (k v)
+               (insert (format
+                        "(puthash %S '%S emms-cache-db)\n" k v)))
+             emms-cache-db)
+    (set-buffer-file-coding-system 'mule-utf-8)
+    (write-region (point-min) (point-max) emms-cache-file)
+    (kill-buffer (current-buffer))
+    (message "Saving emms track cache...done")
+    (setq emms-cache-dirty nil)))
+
+(defun emms-cache-restore ()
+  "Restore the track cache from a file."
+  (load emms-cache-file t nil t)
+  (setq emms-cache-dirty nil))
+
+(provide 'emms-cache)
+;;; emms-cache.el ends here