Index: includes/session.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/session.inc,v
retrieving revision 1.31
diff -u -F^f -r1.31 session.inc
--- includes/session.inc	21 Aug 2006 06:25:49 -0000	1.31
+++ includes/session.inc	31 Aug 2006 15:02:22 -0000
@@ -79,8 +79,52 @@ function sess_write($key, $value) {
   return TRUE;
 }
 
-function sess_destroy($key) {
-  db_query("DELETE FROM {sessions} WHERE sid = '%s'", $key);
+/**
+ * Called when an anonymous user becomes authenticated or vice-versa.
+ */
+function sess_regenerate() {
+  $old_session_id = session_id();
+  session_regenerate_id();
+  db_query("UPDATE {sessions} SET sid = '%s' WHERE sid = '%s'", session_id(), $old_session_id);
+}
+
+/**
+ * Counts how many users have sessions. Can count either anonymous sessions, authenticated sessions, or both.
+ *
+ * @param int $timestamp
+ *   A Unix timestamp representing a point of time in the past.
+ *   The default is 0, which counts all existing sessions.
+ * @param int $anonymous
+ *   TRUE counts only anonymous users.
+ *   FALSE counts only authenticated users.
+ *   Any other value will return the count of both authenticated and anonymous users.
+ * @return  int
+ *   The number of users with sessions.
+ */
+function sess_count($timestamp = 0, $anonymous = true) {
+  $query = $anonymous ? ' AND uid = 0' : ' AND uid > 0';
+  $result = db_fetch_object(db_query('SELECT COUNT(sid) AS count FROM {sessions} WHERE timestamp >= %d'. $query, $timestamp));
+  return $result->count;
+}
+
+/**
+ * Called by PHP session handling with the PHP session ID to end a user's session.
+ * Can also be called directly, either with the PHP session ID or another identifier
+ * such as uid to end a specific user's session.
+ *
+ * @param  string $key
+ * @param  string $type
+ *   Possible values:
+ *     sid (default): the PHP session id
+ *     uid: the Drupal user id
+ *     hostname: a hostname (usually an IP address)
+ */
+function sess_destroy($key, $type = 'sid') {
+  // validate $type strictly to avoid all chance of SQL injection
+  if (!in_array($type, array('sid', 'uid', 'hostname'))) {
+    $type = 'sid';
+  }
+  db_query('DELETE FROM {sessions} WHERE '. $type. " = '%s'", $key);
 }
 
 function sess_gc($lifetime) {
Index: modules/throttle/throttle.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/throttle/throttle.module,v
retrieving revision 1.65
diff -u -F^f -r1.65 throttle.module
--- modules/throttle/throttle.module	18 Aug 2006 18:58:46 -0000	1.65
+++ modules/throttle/throttle.module	31 Aug 2006 15:02:22 -0000
@@ -63,13 +63,13 @@ function throttle_exit() {
     $throttle = module_invoke('throttle', 'status');
 
     if ($max_guests = variable_get('throttle_anonymous', 0)) {
-      $guests = db_result(db_query('SELECT COUNT(sid) AS count FROM {sessions} WHERE timestamp >= %d AND uid = 0', time() - $time_period));
+      $guests = sess_count(time()-$time_period, TRUE);
     }
     else {
       $guests = 0;
     }
     if ($max_users = variable_get('throttle_user', 0)) {
-      $users = db_result(db_query('SELECT COUNT(DISTINCT(uid)) AS count FROM {sessions} WHERE timestamp >= %d AND uid != 0', time() - $time_period));
+      $users = sess_count(time()-$time_period, FALSE);
     }
     else {
       $users = 0;
Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.665
diff -u -F^f -r1.665 user.module
--- modules/user/user.module	30 Aug 2006 08:46:17 -0000	1.665
+++ modules/user/user.module	31 Aug 2006 15:02:24 -0000
@@ -148,7 +148,7 @@ function user_save($account, $array = ar
 
     // Delete a blocked user's sessions to kick them if they are online.
     if (isset($array['status']) && $array['status'] == 0) {
-      db_query('DELETE FROM {sessions} WHERE uid = %d', $account->uid);
+      sess_destroy($account->uid, 'uid');
     }
 
     // Refresh user object
@@ -560,24 +560,23 @@ function user_block($op = 'list', $delta
       case 3:
         if (user_access('access content')) {
           // Count users with activity in the past defined period.
-          $time_period = variable_get('user_block_seconds_online', 900);
+          $time_period = time() - variable_get('user_block_seconds_online', 900);
 
           // Perform database queries to gather online user lists.
-          $guests = db_fetch_object(db_query('SELECT COUNT(sid) AS count FROM {sessions} WHERE timestamp >= %d AND uid = 0', time() - $time_period));
-          $users = db_query('SELECT uid, name, access FROM {users} WHERE access >= %d AND uid != 0 ORDER BY access DESC', time() - $time_period);
-          $total_users = db_num_rows($users);
+          $anonymous = sess_count($time_period);
+          $authenticated = sess_count($time_period, false);
 
           // Format the output with proper grammar.
-          if ($total_users == 1 && $guests->count == 1) {
-            $output = t('There is currently %members and %visitors online.', array('%members' => format_plural($total_users, '1 user', '@count users'), '%visitors' => format_plural($guests->count, '1 guest', '@count guests')));
+          if ($anonymous == 1 && $authenticated == 1) {
+            $output = t('There is currently %members and %visitors online.', array('%members' => format_plural($authenticated, '1 user', '@count users'), '%visitors' => format_plural($anonymous, '1 guest', '@count guests')));
           }
           else {
-            $output = t('There are currently %members and %visitors online.', array('%members' => format_plural($total_users, '1 user', '@count users'), '%visitors' => format_plural($guests->count, '1 guest', '@count guests')));
+            $output = t('There are currently %members and %visitors online.', array('%members' => format_plural($authenticated, '1 user', '@count users'), '%visitors' => format_plural($anonymous, '1 guest', '@count guests')));
           }
 
           // Display a list of currently online users.
           $max_users = variable_get('user_block_max_list_count', 10);
-          if ($total_users && $max_users) {
+          if ($authenticated && $max_users) {
             $items = array();
 
             while ($max_users-- && $account = db_fetch_object($users)) {
@@ -929,10 +928,7 @@ function user_login_submit($form_id, $fo
 
     user_module_invoke('login', $form_values, $user);
 
-    $old_session_id = session_id();
-    session_regenerate_id();
-    db_query("UPDATE {sessions} SET sid = '%s' WHERE sid = '%s'", session_id(), $old_session_id);
-
+    sess_regenerate();
   }
 }
 
@@ -1433,8 +1429,8 @@ function user_confirm_delete($name, $uid
  */
 function user_delete($edit, $uid) {
   $account = user_load(array('uid' => $uid));
+  sess_destroy($uid, 'uid');
   db_query('DELETE FROM {users} WHERE uid = %d', $uid);
-  db_query('DELETE FROM {sessions} WHERE uid = %d', $uid);
   db_query('DELETE FROM {users_roles} WHERE uid = %d', $uid);
   db_query('DELETE FROM {authmap} WHERE uid = %d', $uid);
   $array = array('%name' => $account->name, '%email' => '<'. $account->mail .'>');