vichan/inc/lock.php

<?php
class Lock {
  function __construct($key) { global $config;
    if ($config['lock']['enabled'] == 'fs') {
      $key = str_replace('/', '::', $key);
      $key = str_replace("\0", '', $key);

      $this->f = fopen("tmp/locks/$key", "w");
    }
  }

  // Get a shared lock
  function get($nonblock = false) { global $config;
    if ($config['lock']['enabled'] == 'fs') {
      $wouldblock = false;
      flock($this->f, LOCK_SH | ($nonblock ? LOCK_NB : 0), $wouldblock);
      if ($nonblock && $wouldblock) return false;
    }
    return $this;
  }

  // Get an exclusive lock
  function get_ex($nonblock = false) { global $config;
    if ($config['lock']['enabled'] == 'fs') {
      $wouldblock = false;
      flock($this->f, LOCK_EX | ($nonblock ? LOCK_NB : 0), $wouldblock);
      if ($nonblock && $wouldblock) return false;
    }
    return $this;
  }

  // Free a lock
  function free() { global $config;
    if ($config['lock']['enabled'] == 'fs') {
      flock($this->f, LOCK_UN);
    }
    return $this;
  }
}