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

4 files changed, 113 insertions, 82 deletions

diff --git a/emms-cache.el b/emms-cache.el
new file mode 100644
index 0000000..dcda390
--- /dev/null
+++ b/emms-cache.el
@@ -0,0 +1,79 @@
+;;; 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
diff --git a/emms-info.el b/emms-info.el
index c4533bd..0edeb85 100644
--- a/emms-info.el
+++ b/emms-info.el
@@ -67,33 +67,6 @@ Each is called with a track as argument."
 (defvar emms-info-asynchronous-tracks 0
   "Number of tracks we're waiting for to be done.")
 
-;; cache support (break into a separate file and make
-;; emms-info-really-initialize-track into a variable controlling which
-;; function to use)?
-
-;; The cache is invalidated when track names are changed. It also does
-;; not differenciate between file or uri tracks, and relies on the
-;; uniqueness of the name.
-
-;; usage - in your .emacs
-
-;; (add-hook 'after-init-hook 'emms-info-cache-restore)
-;; (add-hook 'kill-emacs-hook 'emms-info-cache-save)
-
-;; this is works much better with a later-do-interval of something
-;; like 0.001
-
-(define-hash-table-test 'string-hash 'string= 'sxhash)
-(defvar emms-info-cache (make-hash-table :test 'string-hash)
-  "A mapping of paths to file info.
-This is used to cache file info over emacs sessions.")
-
-(defvar emms-info-cache-file "~/.emms-cache"
-  "A file used to store cached file info information over sessions")
-
-(defvar emms-info-cache-dirty nil
-  "True if the cache has been updated since init.")
-
 (defun emms-info-initialize-track (track)
   "Initialize TRACK with emms-info information.
 This is a suitable value for `emms-track-initialize-functions'."
@@ -107,34 +80,18 @@ This is a suitable value for `emms-track-initialize-functions'."
 Return t when the track got changed."
   (let ((file-mtime (when emms-info-auto-update
                       (emms-info-track-file-mtime track)))
-        (name (emms-track-get track 'name))
-        cached-track
-        updated)
-
-    (when (setq cached-track (gethash name emms-info-cache))
-      ;; We need to modify TRACK. This way we lose information already
-      ;; present in TRACK, which is not necessarily what we want, but
-      ;; it's efficient.
-      (setcar track (car cached-track))
-      (setcdr track (cdr cached-track)))
-
-    ;; if uncached, or cached and the time has changed
-    (when (or (not cached-track)
-              (and cached-track
-               emms-info-auto-update
-               (let ((info-mtime (emms-track-get track 'info-mtime)))
-                 (or (not (consp info-mtime))
-                     (emms-time-less-p info-mtime file-mtime)))))
-      (setq updated t)
-      (run-hook-with-args 'emms-info-functions track))
-
-    (emms-track-set track 'info-mtime file-mtime)
-    (emms-track-updated track)
-
-    (when (or (not cached-track)
-            updated)
-        (puthash name track emms-info-cache)
-        (setq emms-info-cache-dirty t))
+        (info-mtime (emms-track-get track 'info-mtime))
+        (name (emms-track-get track 'name)))
+
+    ;; if the file's been modified or is new
+    (when (or (not info-mtime)
+              (emms-time-less-p
+               info-mtime file-mtime))
+      (run-hook-with-args 'emms-info-functions track)
+      ;; not set by info functions
+      (emms-track-set track 'info-mtime file-mtime)
+      (funcall emms-cache-set-function name track)
+      (emms-track-updated track))
 
     (when emms-info-asynchronously
       (setq emms-info-asynchronous-tracks (1- emms-info-asynchronous-tracks))
@@ -142,27 +99,6 @@ Return t when the track got changed."
         (message "EMMS: All track information loaded.")))
     t))
 
-(defun emms-info-cache-save ()
-  "Save the info cache to a file."
-  (when emms-info-cache-dirty
-    (message "Saving emms info cache...")
-    (set-buffer (get-buffer-create " emms-info-cache "))
-    (erase-buffer)
-    (maphash (lambda (k v)
-               (insert (format
-                        "(puthash %S '%S emms-info-cache)\n" k v)))
-             emms-info-cache)
-    (set-buffer-file-coding-system 'mule-utf-8)
-    (write-region (point-min) (point-max) emms-info-cache-file)
-    (kill-buffer (current-buffer))
-    (message "Saving emms info cache...done")
-    (setq emms-info-cache-dirty nil)))
-
-(defun emms-info-cache-restore ()
-  "Restore the info cache from a file."
-  (load emms-info-cache-file t nil t)
-  (setq emms-info-cache-dirty nil))
-
 (defun emms-info-track-file-mtime (track)
   "Return the mtime of the file of TRACK, if any.
 Return zero otherwise."
diff --git a/emms-setup.el b/emms-setup.el
index b6fbd1d..b6fd534 100644
--- a/emms-setup.el
+++ b/emms-setup.el
@@ -64,8 +64,8 @@ Invisible playlists and all the basics for playing media."
 (defun emms-standard ()
   "An Emms setup script.
 Everything included in the `emms-minimalistic' setup, the Emms
-interactive playlist mode and reading information from tagged
-audio files."
+interactive playlist mode, reading information from tagged
+audio files, and a metadata cache."
   ;; include
   (emms-minimalistic)
   ;; define
@@ -73,12 +73,17 @@ audio files."
   (require 'emms-info)
   (require 'emms-info-mp3info)
   (require 'emms-info-ogginfo)
+  (require 'emms-cache)
   ;; setup
   (setq emms-playlist-default-major-mode 'emms-playlist-mode)
   (add-to-list 'emms-track-initialize-functions 'emms-info-initialize-track)
   (add-to-list 'emms-info-functions 'emms-info-mp3info)
   (add-to-list 'emms-info-functions 'emms-info-ogginfo)
-  (setq emms-track-description-function 'emms-info-track-description))
+  (setq emms-track-description-function 'emms-info-track-description)
+  (add-hook 'after-init-hook 'emms-cache-restore)
+  (add-hook 'kill-emacs-hook 'emms-cache-save)
+  (setq emms-cache-get-function 'emms-cache-get)
+  (setq emms-cache-set-function 'emms-cache-set))
 
 (defun emms-all ()
   "An Emms setup script.
diff --git a/emms.el b/emms.el
index 42f5f8f..1070b23 100644
--- a/emms.el
+++ b/emms.el
@@ -223,6 +223,11 @@ seconds the player did seek."
 This can be used if the source depends on the current buffer not
 being the playlist buffer.")
 
+(defvar emms-cache-get-function (lambda (path))
+  "A function to retrieve a track entry from the cache.")
+(defvar emms-cache-set-function (lambda (path track))
+  "A function to add/set a track entry from the cache.")
+
 
 ;;; User Interface
 
@@ -453,9 +458,15 @@ whenever possible."
 
 (defun emms-track (type name)
   "Create an EMMS track with type TYPE and name NAME."
-  (let ((track (emms-dictionary '*track*)))
-    (emms-track-set track 'type type)
-    (emms-track-set track 'name name)
+  (let (track)
+    ;; we assume that name is unique across types, so type is not used
+    ;; if we find name in the cache
+    (unless (setq track (funcall emms-cache-get-function name))
+      (setq track (emms-dictionary '*track*))
+      (emms-track-set track 'type type)
+      (emms-track-set track 'name name))
+    ;; run any hooks regardless of a cache hit, as the entry may be
+    ;; old
     (run-hook-with-args 'emms-track-initialize-functions track)
     track))