Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.512
diff -u -p -r1.512 common.inc
--- includes/common.inc	29 Jan 2006 07:36:29 -0000	1.512
+++ includes/common.inc	3 Feb 2006 23:42:33 -0000
@@ -1035,6 +1035,8 @@ function drupal_page_footer() {
   }
 
   module_invoke_all('exit');
+  // write path alias cache
+  drupal_put_path_map();
 }
 
 /**
Index: includes/path.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/path.inc,v
retrieving revision 1.3
diff -u -p -r1.3 path.inc
--- includes/path.inc	24 Jan 2006 08:18:26 -0000	1.3
+++ includes/path.inc	3 Feb 2006 23:42:33 -0000
@@ -22,6 +22,43 @@ function drupal_init_path() {
   }
 }
 
+function &drupal_get_path_map() {
+  static $map = NULL;
+  static $loaded = false;
+  if (!$loaded) {
+    $data = cache_get('url_alias');
+    $map = unserialize($data->data);
+    $loaded = true;
+
+    if (!is_array($map->dest)) {
+      $map->dest = array();
+    }
+    if (!is_array($map->lasthit)) {
+      $map->lasthit = array();
+    }
+  }
+  return $map;
+}
+
+function drupal_put_path_map() {
+  $map = drupal_get_path_map();
+  if (!$map) {
+    return;
+  }
+  
+  $max = variable_get('url_alias_max_cache', 500);
+  $total = count($map->dest);
+  if ($count > $max) {
+    // prune
+    asort($map->lasthit);
+    for ($i = $total; $i > $max; $i--) {
+      $dest = array_shift($map->lasthit);
+      unset($map->dest[$dest]);
+    }
+  }
+  cache_set('url_alias', serialize($map));
+}
+
 /**
  * Given an alias, return its Drupal system URL if one exists. Given a Drupal
  * system URL return its alias if one exists.
@@ -39,36 +76,39 @@ function drupal_init_path() {
  *   found.
  */
 function drupal_lookup_path($action, $path = '') {
-  static $map = array();
-  static $count = NULL;
+  $cache = &drupal_get_path_map();
 
-  if ($count === NULL) {
-    $count = db_result(db_query('SELECT COUNT(pid) FROM {url_alias}'));
+  if ($cache->count === NULL) {
+    $cache->count = db_result(db_query('SELECT COUNT(pid) FROM {url_alias}'));
   }
 
   if ($action == 'wipe') {
-    $map = array();
+    $cache->dest = array();
+    $cache->lasthit = array();
   }
-  elseif ($count > 0 && $path != '') {
+  elseif ($cache->count > 0 && $path != '') {
     if ($action == 'alias') {
-      if (isset($map[$path])) {
-        return $map[$path];
+      if (isset($cache->dest[$path])) {
+        return $cache->dest[$path];
       }
       if ($alias = db_result(db_query("SELECT dst FROM {url_alias} WHERE src = '%s'", $path))) {
-        $map[$path] = $alias;
+        $cache->dest[$path] = $alias;
+        $cache->lasthit[$path] = time();
         return $alias;
       }
       else {
-        $map[$path] = $path;
+        $cache->dest[$path] = $path;
+        $cache->lasthit[$path] = time();
       }
     }
     elseif ($action == 'source') {
-      if ($alias = array_search($path, $map)) {
+      if ($alias = array_search($path, $cache->dest)) {
         return $alias;
       }
-      if (!isset($map[$path])) {
+      if (!isset($cache->dest[$path])) {
         if ($src = db_result(db_query("SELECT src FROM {url_alias} WHERE dst = '%s'", $path))) {
-          $map[$src] = $path;
+          $cache->dest[$src] = $path;
+          $cache->lasthit[$src] = time();
           return $src;
         }
       }