Clarified commentary.

[elpher.git] / elpher.el

diff --git a/elpher.el b/elpher.el
index a8f8edd..d4c582a 100644 (file)
--- a/elpher.el
+++ b/elpher.el
@@ -36,9 +36,8 @@
 ;; - (m)enu key support, similar to Emacs' info browser,
 ;; - clickable web and gopher links in plain text.
 
-;; The caching mechanism works by maintaining a hierarchy of visited
-;; pages rather than a linear history, meaning that it is quick and
-;; easy to navigate this history.
+;; Visited pages are stored as a hierarchy rather than a linear history,
+;; meaning that navigation between these pages is quick and easy.
 
 ;; To launch Elpher, simply use 'M-x elpher'.  This will open a start
 ;; page containing information on key bindings and suggested starting
@@ -164,8 +163,7 @@ Otherwise, use the system browser via the BROWSE-URL function."
   :type '(boolean))
 
 (defcustom elpher-buttonify-urls-in-directories nil
-  "If non-nil, turns URLs matched in \"i\" item types in directories
-into clickable buttons."
+  "If non-nil, turns URLs matched in directories into clickable buttons."
   :type '(boolean))
 
 (defcustom elpher-cache-images nil
@@ -201,6 +199,9 @@ use as the start page."
 
 ;; Node
 
+(defvar elpher-seen-nodes (make-hash-table :test 'equal)
+  "Table mapping addresses to existing (seen) node objects.")
+
 (defun elpher-make-node (parent address getter &optional content pos)
   "Create a node in the gopher page hierarchy.
 
@@ -209,8 +210,16 @@ the gopher page, GETTER provides the getter function used to obtain this
 page.
 
 The optional arguments CONTENT and POS can be used to fill the cached
-content and cursor position fields of the node."
-  (list parent address getter content pos))
+content and cursor position fields of the node.
+
+If the hash table `elpher-seen-nodes' contains a key equal to ADDRESS,
+the node contained as its value will be returned instead."
+  (let ((existing-node (gethash address elpher-seen-nodes)))
+    (if existing-node
+        existing-node
+      (let ((new-node (list parent address getter content pos)))
+        (puthash address new-node elpher-seen-nodes)
+        new-node))))
 
 (defun elpher-node-parent (node)
   "Retrieve the parent node of NODE."