mutex.php

   1 <?php
   2
   3 function mutex_lock ($name, $duration) {
   4         while (true) {
   5                 $now = time();
   6                 $deleted_obsoletes = false;
   7                 db_insert('wfpl_mutexes', 'name,expires', $name, $now + $duration);
   8                 $id = db_auto_id();
   9                 $rows = db_get_assocs('wfpl_mutexes', 'id,name,expires', 'order by id');
  10                 $first_match = true;
  11                 foreach ($rows as $row) {
  12                         if ($row['expires'] < $now) {
  13                                 if (!$deleted_obsoletes) {
  14                                         db_delete('wfpl_mutexes', 'where expires < %i', $now);
  15                                         $deleted_obsoletes = true;
  16                                 }
  17                         } elseif ($row['name'] === $name) {
  18                                 if ($row['id'] == $id) {
  19                                         return $id;
  20                                 } else {
  21                                         break;
  22                                 }
  23                         }
  24                 }
  25                 # not first
  26                 db_delete('wfpl_mutexes', 'where id=%i', $id);
  27                 sleep(1);
  28         }
  29 }
  30
  31 function mutex_unlock ($id) {
  32         db_delete('wfpl_mutexes', 'where id=%i', $id);
  33 }