Member optimisation.

Member.php

diff --git a/security/Member.php b/security/Member.php
index 6fe8278..05f5d14 100644
--- a/security/Member.php
+++ b/security/Member.php
@@ -163,6 +163,9 @@ class Member extends DataObject implements TemplateGlobalProvider {
         */
        private static $session_regenerate_id = true;
 
+       private static $_cached_current_member_id;
+       private static $_cached_current_member;
+
        /**
         * @deprecated 3.2 Use the "Member.session_regenerate_id" config setting instead
         */
@@ -659,9 +662,26 @@ class Member extends DataObject implements TemplateGlobalProvider {
        public static function currentUser() {
                $id = Member::currentUserID();
 
-         if($id) {
-                 return Member::get()->byId($id);
+               if(!$id) {
+                       return null;
+               }
+
+               if($id !== self::$_cached_current_member_id) {
+                       self::$_cached_current_member = null;
+                       self::$_cached_current_member_id = $id;
                }
+           
+               if(is_null(self::$_cached_current_member)) {
+                       $member = Member::get()->byId($id);
+
+                       if($member) {
+                               self::$_cached_current_member = $member;
+                       } else {
+                               self::$_cached_current_member = false;
+                       }
+               }
+
+               return (self::$_cached_current_member) ? self::$_cached_current_member : null;
        }
        
        /**
@@ -717,6 +737,9 @@ class Member extends DataObject implements TemplateGlobalProvider {
         * Event handler called before writing to the database.
         */
        public function onBeforeWrite() {
+               self::$_cached_current_member_id = null;
+               self::$_cached_current_member = null;
+
                if($this->SetPassword) $this->Password = $this->SetPassword;
 
                // If a member with the same "unique identifier" already exists with a different ID, don't allow merging.